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Verfaillie G, Rutten J, D'Asseler Y, Bacher K. Accuracy of patient-specific CT organ doses from Monte Carlo simulations: influence of CT-based voxel models. Phys Eng Sci Med 2024:10.1007/s13246-024-01422-z. [PMID: 38634980 DOI: 10.1007/s13246-024-01422-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 04/01/2024] [Indexed: 04/19/2024]
Abstract
Monte Carlo simulations using patient CT images as input are the gold standard to perform patient-specific dosimetry. However, in standard clinical practice patient's CT images are limited to the reconstructed CT scan range. In this study, organ dose calculations were performed with ImpactMC for chest and cardiac CT using whole-body and anatomy-specific voxel models to estimate the accuracy of CT organ doses based on the latter model. When the 3D patient model is limited to the CT scan range, CT organ doses from Monte Carlo simulations are the most accurate for organs entirely in the field of view. For these organs only the radiation dose related to scatter from the rest of the body is not incorporated. For organs lying partially outside the field of view organ doses are overestimated by not accounting for the non-irradiated tissue mass. This overestimation depends strongly on the amount of the organ volume located outside the field of view. To get a more accurate estimation of the radiation dose to these organs, the ICRP reference organ masses and densities could form a solution. Except for the breast, good agreement in dose was found for most organs. Voxel models generated from clinical CT examinations do not include the overscan in the z-direction. The availability of whole-body voxel models allowed to study this influence as well. As expected, overscan induces slightly higher organ doses.
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Affiliation(s)
- Gwenny Verfaillie
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium.
| | - Jeff Rutten
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Yves D'Asseler
- Department of Nuclear Medicine, Ghent University Hospital, Ghent, Belgium
- Department of Diagnostic Sciences, Ghent University, Ghent, Belgium
| | - Klaus Bacher
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium
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2
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Development and verification of a novel system for computed tomography scanner model construction in Monte Carlo simulations. NUCLEAR ENGINEERING AND TECHNOLOGY 2022. [DOI: 10.1016/j.net.2022.07.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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3
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Fujii K, Nomura K, Muramatsu Y, Ota H. PATIENT-SPECIFIC ORGAN DOSE EVALUATION BASED ON MONTE CARLO SIMULATION AND DOSE METRICS IN PAEDIATRIC CHEST-ABDOMEN-PELVIS CT EXAMINATIONS. RADIATION PROTECTION DOSIMETRY 2021; 197:46-53. [PMID: 34726759 DOI: 10.1093/rpd/ncab157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 10/04/2021] [Accepted: 10/07/2021] [Indexed: 06/13/2023]
Abstract
This study aimed to determine organ doses based on Monte Carlo (MC) simulations for individual paediatric patients undergoing chest-abdomen-pelvis computed tomography (CT) examinations and to evaluate correlations of organ doses with dose metrics. MC simulations were performed by inputting detailed descriptions of a CT scanner, scanning parameters and CT images of 51 paediatric patients aged from 0 to 10 years into the simulation software. Organ doses for six radiosensitive organs were determined from dose distribution images obtained as the simulation results. The correlations of organ doses with dose metrics such as volume CT dose index, size-specific dose estimates (SSDEs), and organ-specific SSDEs were evaluated from the corresponding coefficients of determination. Organ doses for ages of 0-1 and 1-5 years were 22%-32% lower than those for ages of 5-10 years. Organ doses exhibited higher linear correlations with SSDEs and organ-specific SSDEs, and can be easily estimated using the linear regression.
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Affiliation(s)
- Keisuke Fujii
- Nagoya University Graduate School of Medicine, Department of Integrated Health Sciences, 1-1-20 Daiko-Minami, Higashi-ku, Nagoya, Aichi 461-8673, Japan
- National Cancer Center Hospital East, Department of Radiological Technology, 6-5-1 Kashiwanoha, Kashiwa, Chiba 277-8577, Japan
| | - Keiichi Nomura
- National Cancer Center Hospital East, Department of Radiological Technology, 6-5-1 Kashiwanoha, Kashiwa, Chiba 277-8577, Japan
| | - Yoshihisa Muramatsu
- National Cancer Center Hospital East, Department of Radiological Technology, 6-5-1 Kashiwanoha, Kashiwa, Chiba 277-8577, Japan
| | - Hiroyuki Ota
- National Cancer Center Hospital East, Department of Radiological Technology, 6-5-1 Kashiwanoha, Kashiwa, Chiba 277-8577, Japan
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4
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Hardy AJ, Bostani M, Kim GHJ, Cagnon CH, Zankl MA, McNitt-Gray M. Evaluating Size-Specific Dose Estimate (SSDE) as an estimate of organ doses from routine CT exams derived from Monte Carlo simulations. Med Phys 2021; 48:6160-6173. [PMID: 34309040 DOI: 10.1002/mp.15128] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Revised: 06/11/2021] [Accepted: 07/09/2021] [Indexed: 11/10/2022] Open
Abstract
PURPOSE Size-specific dose estimate (SSDE) is a metric that adjusts CTDIvol to account for patient size. While not intended to be an estimate of organ dose, AAPM Report 204 notes the difference between the patient organ dose and SSDE is expected to be 10-20%. The purpose of this work was therefore to evaluate SSDE against estimates of organ dose obtained using Monte Carlo (MC) simulation techniques applied to routine exams across a wide range of patient sizes. MATERIALS AND METHODS Size-specific dose estimate was evaluated with respect to organ dose based on three routine protocols taken from Siemens scanners: (a) brain parenchyma dose in routine head exams, (b) lung and breast dose in routine chest exams, and (c) liver, kidney, and spleen dose in routine abdomen/pelvis exams. For each exam, voxelized phantom models were created from existing models or derived from clinical patient scans. For routine head exams, 15 patient models were used which consisted of 10 GSF/ICRP voxelized phantom models and five pediatric voxelized patient models created from CT image data. For all exams, the size metric used was water equivalent diameter (Dw ). For the routine chest exams, data from 161 patients were collected with a Dw range of ~16-44 cm. For the routine abdomen/pelvis exams, data from 107 patients were collected with a range of Dw from ~16 to 44 cm. Image data from these patients were segmented to generate voxelized patient models. For routine head exams, fixed tube current (FTC) was used while tube current modulation (TCM) data for body exams were extracted from raw projection data. The voxelized patient models and tube current information were used in detailed MC simulations for organ dose estimation. Organ doses from MC simulation were normalized by CTDIvol and parameterized as a function of Dw . For each patient scan, the SSDE was obtained using Dw and CTDIvol values of each scan, according to AAPM Report 220 for body scans and Report 293 for head scans. For each protocol and each patient, normalized organ doses were compared with SSDE. A one-sided tolerance limit covering 95% (P = 0.95) of the population with 95% confidence (α = 0.05) was used to assess the upper tolerance limit (TU ) between SSDE and normalized organ dose. RESULTS For head exams, the TU between SSDE and brain parenchyma dose was observed to be 12.5%. For routine chest exams, the TU between SSDE and lung and breast dose was observed to be 35.6% and 68.3%, respectively. For routine abdomen/pelvis exams, the TU between SSDE and liver, spleen, and kidney dose was observed to be 30.7%, 33.2%, and 33.0%, respectively. CONCLUSIONS The TU of 20% between SSDE and organ dose was found to be insufficient to cover 95% of the sampled population with 95% confidence for all of the organs and protocols investigated, except for brain parenchyma dose. For the routine body exams, excluding the breasts, a wider threshold difference of ~30-36% would be needed. These results are, however, specific to Siemens scanners.
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Affiliation(s)
- Anthony James Hardy
- Materials Engineering Division/Non-destructive Evaluation Group, Livermore National Laboratory, Livermore, California, USA
| | - Maryam Bostani
- Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, Livermore, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - Grace Hyun J Kim
- Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, Livermore, USA
| | - Christopher H Cagnon
- Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, Livermore, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - Maria Agnes Zankl
- Institute of Radiation Medicine, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH, Neuherberg, Germany
| | - Michael McNitt-Gray
- Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, Livermore, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
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5
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Andersson J, Bednarek DR, Bolch W, Boltz T, Bosmans H, Gislason-Lee AJ, Granberg C, Hellstrom M, Kanal K, McDonagh E, Paden R, Pavlicek W, Khodadadegan Y, Torresin A, Trianni A, Zamora D. Estimation of patient skin dose in fluoroscopy: summary of a joint report by AAPM TG357 and EFOMP. Med Phys 2021; 48:e671-e696. [PMID: 33930183 DOI: 10.1002/mp.14910] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Revised: 04/04/2021] [Accepted: 04/23/2021] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND Physicians use fixed C-arm fluoroscopy equipment with many interventional radiological and cardiological procedures. The associated effective dose to a patient is generally considered low risk, as the benefit-risk ratio is almost certainly highly favorable. However, X-ray-induced skin injuries may occur due to high absorbed patient skin doses from complex fluoroscopically guided interventions (FGI). Suitable action levels for patient-specific follow-up could improve the clinical practice. There is a need for a refined metric regarding follow-up of X-ray-induced patient injuries and the knowledge gap regarding skin dose-related patient information from fluoroscopy devices must be filled. The most useful metric to indicate a risk of erythema, epilation or greater skin injury that also includes actionable information is the peak skin dose, that is, the largest dose to a region of skin. MATERIALS AND METHODS The report is based on a comprehensive review of best practices and methods to estimate peak skin dose found in the scientific literature and situates the importance of the Digital Imaging and Communication in Medicine (DICOM) standard detailing pertinent information contained in the Radiation Dose Structured Report (RDSR) and DICOM image headers for FGI devices. Furthermore, the expertise of the task group members and consultants have been used to bridge and discuss different methods and associated available DICOM information for peak skin dose estimation. RESULTS The report contributes an extensive summary and discussion of the current state of the art in estimating peak skin dose with FGI procedures with regard to methodology and DICOM information. Improvements in skin dose estimation efforts with more refined DICOM information are suggested and discussed. CONCLUSIONS The endeavor of skin dose estimation is greatly aided by the continuing efforts of the scientific medical physics community, the numerous technology enhancements, the dose-controlling features provided by the FGI device manufacturers, and the emergence and greater availability of the DICOM RDSR. Refined and new dosimetry systems continue to evolve and form the infrastructure for further improvements in accuracy. Dose-related content and information systems capable of handling big data are emerging for patient dose monitoring and quality assurance tools for large-scale multihospital enterprises.
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Affiliation(s)
- Jonas Andersson
- Department of Radiation Sciences, Radiation Physics, Umeå University, SE-901 85, Umeå, Sweden
| | - Daniel R Bednarek
- State University of New York, 875 Ellicott St, Buffalo, NY, 14203-1070, USA
| | - Wesley Bolch
- University of Florida, 1275 Center Drive, Gainesville, FL, 32611-6131, USA
| | - Thomas Boltz
- Orange Factor Imaging Physicists, 4035 E Captain Dreyfus Ave, Phoenix, AZ, 85032, USA
| | - Hilde Bosmans
- University of Leuven, Herestraat 49, Leuven, B-3000, Belgium
| | | | - Christoffer Granberg
- Department of Radiation Sciences, Radiation Physics, Umeå University, SE-901 85, Umeå, Sweden
| | - Max Hellstrom
- Department of Radiation Sciences, Radiation Physics, Umeå University, SE-901 85, Umeå, Sweden
| | - Kalpana Kanal
- University of Washington Medical Center, 1959 NE Pacific Street, Seattle, WA, 98195, USA
| | - Ed McDonagh
- Joint Department of Physics, The Royal Marsden NHS Foundation Trust, Fulham Road, London, SW3 6JJ, UK
| | - Robert Paden
- Mayo Clinic, 5777 East Mayo Blvd, Phoenix, AZ, 85054, USA
| | | | - Yasaman Khodadadegan
- Progressive Insurance, Customer Relation Management, 6300 Wilson Mills Rd., Mayfield Village, OH, 44143, USA
| | - Alberto Torresin
- Niguarda Ca'Granda Hospital, Via Leon Battista Alberti 5, Milano, 20149, Italy
| | - Annalisa Trianni
- Udine University Hospital, Piazzale S. Maria Della Misericordia, n. 15, 33100, Udine, Italy
| | - David Zamora
- University of Washington Medical Center, 6852 31st Ave NE, Seattle, WA, 98115-7245, USA
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Layman RR, Hardy AJ, Kim HJ, Chou EN, Bostani M, Cagnon C, Cody D, McNitt‐Gray M. A comparison of breast and lung doses from chest CT scans using organ-based tube current modulation (OBTCM) vs. Automatic tube current modulation (ATCM). J Appl Clin Med Phys 2021; 22:97-109. [PMID: 33939253 PMCID: PMC8130227 DOI: 10.1002/acm2.13198] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 01/12/2021] [Accepted: 01/20/2021] [Indexed: 12/11/2022] Open
Abstract
PURPOSE The purpose of this work was to estimate and compare breast and lung doses of chest CT scans using organ-based tube current modulation (OBTCM) to those from conventional, attenuation-based automatic tube current modulation (ATCM) across a range of patient sizes. METHODS Thirty-four patients (17 females, 17 males) who underwent clinically indicated CT chest/abdomen/pelvis (CAP) examinations employing OBTCM were collected from two multi-detector row CT scanners. Patient size metric was assessed as water equivalent diameter (Dw ) taken at the center of the scan volume. Breast and lung tissues were segmented from patient image data to create voxelized models for use in a Monte Carlo transport code. The OBTCM schemes for the chest portion were extracted from the raw projection data. ATCM schemes were estimated using a recently developed method. Breast and lung doses for each TCM scenario were estimated for each patient model. CTDIvol -normalized breast (nDbreast ) and lung (nDlung ) doses were subsequently calculated. The differences between OBTCM and ATCM normalized organ dose estimates were tested using linear regression models that included CT scanner and Dw as covariates. RESULTS Mean dose reduction from OBTCM in nDbreast was significant after adjusting for the scanner models and patient size (P = 0.047). When pooled with females and male patient, mean dose reduction from OBTCM in nDlung was observed to be trending after adjusting for the scanner model and patient size (P = 0.085). CONCLUSIONS One specific manufacturer's OBTCM was analyzed. OBTCM was observed to significantly decrease normalized breast relative to a modeled version of that same manufacturer's ATCM scheme. However, significant dose savings were not observed in lung dose over all. Results from this study support the use of OBTCM chest protocols for females only.
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Affiliation(s)
- Rick R. Layman
- Department of Imaging PhysicsThe University of Texas MD Anderson Cancer CenterHoustonTXUSA
| | - Anthony J. Hardy
- Materials Engineering Division/Non‐destructive Evaluation GroupLivermore National LaboratoryLivermoreCA94550USA
| | - Hyun J. Kim
- Department of Radiological SciencesDavid Geffen School of MedicineUniversity of California, Los AngelesLos AngelesCAUSA
| | - Ei Ne Chou
- Fielding School of Public HealthUniversity of California Los AngelesLos AngelesCAUSA
| | - Maryam Bostani
- Department of Radiological SciencesDavid Geffen School of MedicineUniversity of California, Los AngelesLos AngelesCAUSA
- Physics and Biology in Medicine Graduate ProgramDavid Geffen School of MedicineUniversity of California Los AngelesLos AngelesCA90024USA
| | - Chris Cagnon
- Department of Radiological SciencesDavid Geffen School of MedicineUniversity of California, Los AngelesLos AngelesCAUSA
- Physics and Biology in Medicine Graduate ProgramDavid Geffen School of MedicineUniversity of California Los AngelesLos AngelesCA90024USA
| | - Dianna Cody
- Department of Imaging PhysicsThe University of Texas MD Anderson Cancer CenterHoustonTXUSA
| | - Michael McNitt‐Gray
- Department of Radiological SciencesDavid Geffen School of MedicineUniversity of California, Los AngelesLos AngelesCAUSA
- Physics and Biology in Medicine Graduate ProgramDavid Geffen School of MedicineUniversity of California Los AngelesLos AngelesCA90024USA
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Haba T, Yasui K, Saito Y, Kobayashi M, Koyama S. A new cone-beam computed tomography dosimetry method providing optimal measurement positions: A Monte Carlo study. Phys Med 2021; 81:130-140. [PMID: 33453505 DOI: 10.1016/j.ejmp.2020.12.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 12/01/2020] [Accepted: 12/05/2020] [Indexed: 11/18/2022] Open
Abstract
PURPOSE The conventional weighted computed tomography dose index (CTDIw) may not be suitable for cone-beam computed tomography (CBCT) dosimetry because a cross-sectional dose distribution is angularly inhomogeneous owing to partial angle irradiations. This study was conducted to develop a new dose metric (f(0)CBw) for CBCT dosimetry to determine a more accurate average dose in the central cross-sectional plane of a cylindrical phantom using Monte Carlo simulations. METHODS First, cross-sectional dose distributions of cylindrical polymethyl methacrylate phantoms over a wide range of phantom diameters (8-40 cm) were calculated for various CBCT scan protocols. Then, by obtaining linear least-squares fits of the full datasets of the cross-sectional dose distributions, the optimal radial positions, which represented measurement positions for the average phantom dose, were determined. Finally, the f(0)CBw method was developed by averaging point doses at the optimal radial positions of the phantoms. To demonstrate its validity, the relative differences between the average doses and each dose index value were estimated for the devised f(0)CBw, conventional CTDIw, and Haba's CTDIw methods, respectively. RESULTS The relative differences between the average doses and each dose index value were within 4.1%, 16.7%, and 11.9% for the devised, conventional CTDIw, and Haba's CTDIw methods, respectively. CONCLUSIONS The devised f(0)CBw value was calculated by averaging four "point doses" at 90° intervals and the optimal radial positions of the cylindrical phantom. The devised method can estimate the average dose more accurately than the previously developed CTDIw methods for CBCT dosimetry.
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Affiliation(s)
- Tomonobu Haba
- Faculty of Radiological Technology, School of Medical Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan.
| | - Keisuke Yasui
- Faculty of Radiological Technology, School of Medical Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
| | - Yasunori Saito
- Department of Radiology, Fujita Health University Hospital, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
| | - Masanao Kobayashi
- Faculty of Radiological Technology, School of Medical Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
| | - Shuji Koyama
- Brain & Mind Research Center, Nagoya University, 1-1-20 Daiko-Minami, Higashi-ku, Nagoya, Aichi, Japan
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Kawamoto K, Fukushima Y, Matsuda A, Nakata M. EVALUATION OF ORGAN DOSE BASED ON PATIENT DATA IN EAST ASIAN DESCENT PEDIATRIC HEAD CT EXAMINATIONS. RADIATION PROTECTION DOSIMETRY 2020; 192:335-340. [PMID: 33326990 DOI: 10.1093/rpd/ncaa200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 10/20/2020] [Accepted: 11/11/2020] [Indexed: 06/12/2023]
Abstract
The purpose of this study was to investigate other indices estimating absorbed dose for eye lens and brain, using clinical images of East Asian pediatric patients. We simulated head computed tomography (CT ) examinations in 104 pediatric patients. Effective diameter (deff) and water equivalent diameter (dw) were measured on clinical images. Various size metrics and age were compared with absorbed dose normalised by CTDIvol (nD). The nD was estimated for eye and brain. The nD tended to decrease with advancing age. R2 between age and nD were 0.38 and 0.31 for eye and brain, respectively. Increasing head diameters decreased each nD. R2 between deff and dw, and nD were 0.20-0.24 and 0.51-0.53 for eye and brain, respectively. Head sizes allowed us to estimate absorbed dose in brain CT on East Asian pediatric patients. Scanning parameters for pediatric head CT may need to be based on individual patient information.
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Affiliation(s)
- Keishin Kawamoto
- Division of Clinical Radiology Service, Kyoto University Hospital, 54 Kawaharacho, Shogoin, Sakyo-ku Kyoto 606-8507, Japan
| | - Yasuhiro Fukushima
- Division of Clinical Radiology Service, Kyoto University Hospital, 54 Kawaharacho, Shogoin, Sakyo-ku Kyoto 606-8507, Japan
| | - Akira Matsuda
- Division of Clinical Radiology Service, Kyoto University Hospital, 54 Kawaharacho, Shogoin, Sakyo-ku Kyoto 606-8507, Japan
| | - Manabu Nakata
- Division of Clinical Radiology Service, Kyoto University Hospital, 54 Kawaharacho, Shogoin, Sakyo-ku Kyoto 606-8507, Japan
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Hardy AJ, Bostani M, Angel E, Cagnon C, Sechopoulos I, McNitt-Gray MF. Reference dataset for benchmarking fetal doses derived from Monte Carlo simulations of CT exams. Med Phys 2020; 48:523-532. [PMID: 33128259 DOI: 10.1002/mp.14573] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 07/26/2020] [Accepted: 10/06/2020] [Indexed: 11/09/2022] Open
Abstract
PURPOSE Task Group Report 195 of the American Association of Physicists in Medicine contains reference datasets for the direct comparison of results among different Monte Carlo (MC) simulation tools for various aspects of imaging research that employs ionizing radiation. While useful for comparing and validating MC codes, that effort did not provide the information needed to compare absolute dose estimates from CT exams. Therefore, the purpose of this work is to extend those efforts by providing a reference dataset for benchmarking fetal dose derived from MC simulations of clinical CT exams. ACQUISITION AND VALIDATION METHODS The reference dataset contains the four necessary elements for validating MC engines for CT dosimetry: (a) physical characteristics of the CT scanner, (b) patient information, (c) exam specifications, and (d) fetal dose results from previously validated and published MC simulations methods in tabular form. Scanner characteristics include non-proprietary descriptions of equivalent source cumulative distribution function (CDF) spectra and bowtie filtration profiles, as well as scanner geometry information. Additionally, for the MCNPX MC engine, normalization factors are provided to convert raw simulation results to absolute dose in mGy. The patient information is based on a set of publicly available fetal dose models and includes de-identified image data; voxelized MC input files with fetus, uterus, and gestational sac identified; and patient size metrics in the form of water equivalent diameter (Dw ) z-axis distributions from a simulated topogram (Dw,topo ) and from the image data (Dw,image ). Exam characteristics include CT scan start and stop angles and table and patient locations, helical pitch, nominal collimation and measured beam width, and gantry rotation time for each simulation. For simulations involving estimating doses from exams using tube current modulation (TCM), a realistic TCM scheme is presented that is estimated based upon a validated method. (d) Absolute and CTDIvol -normalized fetal dose results for both TCM and FTC simulations are given for each patient model under each scan scenario. DATA FORMAT AND USAGE NOTES Equivalent source CDFs and bowtie filtration profiles are available in text files. Image data are available in DICOM format. Voxelized models are represented by a header followed by a list of integers in a text file representing a three-dimensional model of the patient. Size distribution metrics are also given in text files. Results of absolute and normalized fetal dose with associated MC error estimates are presented in tabular form in an Excel spreadsheet. All data are stored on Zenodo and are publicly accessible using the following link: https://zenodo.org/record/3959512. POTENTIAL APPLICATIONS Similar to the work of AAPM Report 195, this work provides a set of reference data for benchmarking fetal dose estimates from clinical CT exams. This provides researchers with an opportunity to compare MC simulation results to a set of published reference data as part of their efforts to validate absolute and normalized fetal dose estimates. This could also be used as a basis for comparison to other non-MC approaches, such as deterministic approaches, or to commercial packages that provide estimates of fetal doses from clinical CT exams.
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Affiliation(s)
- Anthony J Hardy
- Livermore National Laboratory, Materials Engineering Division/Non-destructive Evaluation Group, Livermore, CA, 94550, USA
| | - Maryam Bostani
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Livermore, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, CA, 90024, USA
| | - Erin Angel
- Canon Medical Systems USA, Inc, Tustin, CA, 92780, USA
| | - Chris Cagnon
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Livermore, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, CA, 90024, USA
| | - Ioannis Sechopoulos
- Department of Medical Imaging, Radboud University Medical Center, Geert Grooteplein 10, Nijmegen, 6525 GA, The Netherlands.,Dutch Expert Center for Screening (LRCB), Wijchenseweg 101, Nijmegen, 6538 SW, The Netherlands
| | - Michael F McNitt-Gray
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Livermore, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, CA, 90024, USA
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10
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Fujii K, Nomura K, Muramatsu Y, Goto T, Obara S, Ota H, Tsukagoshi S. Correlation analysis of organ doses determined by Monte Carlo simulation with dose metrics for patients undergoing chest-abdomen-pelvis CT examinations. Phys Med 2020; 77:1-9. [DOI: 10.1016/j.ejmp.2020.07.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 07/04/2020] [Accepted: 07/12/2020] [Indexed: 01/09/2023] Open
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11
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Fehrmann ML, Schegerer A, Werncke T, Schlattl H. COMPARISON OF EXPERIMENTAL AND NUMERICAL METHODS OF PATIENT DOSE ESTIMATIONS IN CT USING ANTHROPOMORPHIC MODELS. RADIATION PROTECTION DOSIMETRY 2020; 190:71-83. [PMID: 32744624 DOI: 10.1093/raddos/ncaa070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 02/20/2020] [Accepted: 04/05/2020] [Indexed: 06/11/2023]
Abstract
The common methods for patient dose estimations in computed tomography (CT) are thermoluminescence dosemeter (TLD) measurements or the usage of software packages based on Monte Carlo simulations like CT-Expo or the newer CTVoxDos, which uses the ICRP Reference Adult Male (ICRP 110). Organ (OD) and effective doses of a CT protocol of the upper abdomen are compared. Compared to CTVoxDos, ODs inferred by TLD measurement using an anthropomorphic phantom differ by $\mathbf{(19\pm 16)\,\%}$ inside the primary radiation field, $\mathbf{(14\pm 2)\,\%}$ for partially primary irradiated organs and $\mathbf{(34\pm 38)\,\%}$ in the scattered radiation field. ODs estimated by CT-Expo show a mean deviation of $\mathbf{(16\pm 9)\,\%}$ (primary irradiated) and $\mathbf{(28\pm 31)\,\%}$ (scatter irradiated) from ODs estimated by CTVoxDos.
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Affiliation(s)
- M L Fehrmann
- Institute of Radiation Medicine, Helmholtz Zentrum München-German Research Center for Environmental Health, 85764 Neuherberg, Germany
- Lehrstuhl für Experimentelle Physik IV, Technische Universität Dortmund, 44227 Dortmund, Germany
| | - A Schegerer
- Medizinischer und beruflicher Strahlenschutz, Bundesamt für Strahlenschutz, 85764 Neuherberg, Germany
- Hirslanden AG, 8152 Glattpark, Switzerland
| | - T Werncke
- Institut für Diagnostische und Interventionelle Radiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany
| | - H Schlattl
- Institute of Radiation Medicine, Helmholtz Zentrum München-German Research Center for Environmental Health, 85764 Neuherberg, Germany
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12
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Lopez-Rendon X, Stratis A, Zhang G, Coudyzer W, Develter W, Bogaerts R, Bosmans H, Zanca F. Peak skin and eye lens radiation dose from brain perfusion CT: CTDI vol and Monte Carlo based estimations. Eur J Radiol 2020; 126:108950. [PMID: 32199141 DOI: 10.1016/j.ejrad.2020.108950] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 03/04/2020] [Accepted: 03/07/2020] [Indexed: 11/16/2022]
Abstract
PURPOSE To quantify the eye lens, peak skin and brain doses associated with head CT perfusion exam by means of thermoluminescent dosimeters (TLDs) measurements in a cadaver and compare them to Monte Carlo (MC) dose estimations as well as to the CTDIvol. METHOD 18 TLDs were inserted in the brain, skin, and eye lenses of a female cadaver head, who underwent a CT brain perfusion scan using a Siemens Definition Flash. The table-toggling protocol used 80 kVp, 200 mAs, 32 × 1.2 mm collimation and 30 sequences. From the CT images, a voxel model was created. Doses were calculated with a MC framework (EGSnrc) and compared to TLD measurements. TLD measurements were also compared to the displayed CTDIvol. RESULTS The average measured doses were: 185 mGy for the eyes lenses, 107 mGy for the skin, 172 mGy for the brain and 273 mGy for the peak skin. The reported CTDIvol of 259 mGy overestimated the averaged organ doses but not the peak skin dose. MC estimated organ doses were 147 mGy for the eyes (average), 104 mGy for the skin and 178 mGy for the brain (-20 %, -3% and 4% difference respect to the TLDs measurements, respectively). CONCLUSIONS CTDIvol remains a conservative metric for average brain, skin and eyes lenses doses. For accurate eye lens and skin dose estimates MC simulations can be used. CTDIvol should be used with caution as it was of the same order of magnitude as the peak skin dose for this protocol and this particular CT scanner.
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Affiliation(s)
- X Lopez-Rendon
- Department of Imaging and Pathology, Division of Medical Physics & Quality Assessment, KU Leuven, Herestraat 49 box 7003, 3000, Leuven, Belgium.
| | - A Stratis
- Department of Imaging and Pathology, Division of Medical Physics & Quality Assessment, KU Leuven, Herestraat 49 box 7003, 3000, Leuven, Belgium
| | - G Zhang
- Department of Radiology, University Hospitals Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - W Coudyzer
- Department of Radiology, University Hospitals Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - W Develter
- Department of Imaging and Pathology, Division of Medical Physics & Quality Assessment, KU Leuven, Herestraat 49 box 7003, 3000, Leuven, Belgium
| | - R Bogaerts
- Laboratory of Experimental Radiotherapy, Department of Oncology, Biomedical Sciences Group, University of Leuven, Leuven, Belgium
| | - H Bosmans
- Department of Imaging and Pathology, Division of Medical Physics & Quality Assessment, KU Leuven, Herestraat 49 box 7003, 3000, Leuven, Belgium; Department of Radiology, University Hospitals Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - F Zanca
- Department of Imaging and Pathology, Division of Medical Physics & Quality Assessment, KU Leuven, Herestraat 49 box 7003, 3000, Leuven, Belgium
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13
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Yamauchi-Kawaura C, Fujii K, Yamauchi M, Yamamoto S, Kozuka M, Ohzawa N, Suga N, Ito N. SHAPE ESTIMATION OF BOWTIE FILTERS BASED ON THE LUMINESCENCE FROM POLYETHYLENE TEREPHTHALATE RESIN BY X-RAY IRRADIATION. RADIATION PROTECTION DOSIMETRY 2019; 185:432-439. [PMID: 30916354 DOI: 10.1093/rpd/ncz031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 01/27/2019] [Accepted: 02/28/2019] [Indexed: 06/09/2023]
Abstract
In this study, we devised a novel method estimating the bowtie filter shapes by imaging luminescence from a polyethylene terephthalate (PET) resin with X-ray irradiation in a computed tomography (CT) scanner. The luminescence distribution of the PET resin corresponding to the thickness of bowtie filter was imaged using a charge-coupled device camera. On the assumption that the material of bowtie filter is aluminium (Al), the shape of bowtie filters was estimated from the correlation between Al attenuation curves and the angular-dependent luminance attenuation profiles according to the thickness of bowtie filters. Dose simulations based on the estimated bowtie filter shapes were performed using head and body PMMA phantoms with 16 and 32 cm in diameter. The simulated values of head and body weighted CT dose index (CTDIw) based on bowtie filter shape by the luminescence imaging method agreed within ~9% with the measured values by a dosemeter.
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Affiliation(s)
- C Yamauchi-Kawaura
- Department of Radiological Sciences, Graduate School of Medicine, Nagoya University, 1-1-20 Daikominami, Higashi-ku, Nagoya 461-8673, Japan
| | - K Fujii
- Department of Radiological Sciences, Graduate School of Medicine, Nagoya University, 1-1-20 Daikominami, Higashi-ku, Nagoya 461-8673, Japan
| | - M Yamauchi
- Division of Radiology, Aichi Medical University Hospital, Nagakute, Aichi 480-1195, Japan
| | - S Yamamoto
- Department of Radiological Sciences, Graduate School of Medicine, Nagoya University, 1-1-20 Daikominami, Higashi-ku, Nagoya 461-8673, Japan
| | - M Kozuka
- Department of Radiological Technology, School of Health Sciences, Nagoya University, 1-1-20 Daikominami, Higashi-ku, Nagoya 461-8673, Japan
| | - N Ohzawa
- Department of Radiological Technology, School of Health Sciences, Nagoya University, 1-1-20 Daikominami, Higashi-ku, Nagoya 461-8673, Japan
| | - N Suga
- Department of Radiological Technology, School of Health Sciences, Nagoya University, 1-1-20 Daikominami, Higashi-ku, Nagoya 461-8673, Japan
| | - N Ito
- Department of Radiological Technology, School of Health Sciences, Nagoya University, 1-1-20 Daikominami, Higashi-ku, Nagoya 461-8673, Japan
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14
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Haba T, Kobayashi M, Koyama S. Size-specific dose estimates for various weighting factors of CTDI equation. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2019; 43:10.1007/s13246-019-00830-w. [PMID: 31811559 DOI: 10.1007/s13246-019-00830-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Accepted: 12/02/2019] [Indexed: 11/30/2022]
Abstract
Size-specific dose estimate (SSDE) was proposed by the American Association of Physicists in Medicine (AAPM) Task Group 204 to consider the effect of patient size in the x-ray CT dose estimation. Size correction factors to calculate SSDE were derived based on the conventional weighted CT dose index (CTDIw) equation. This study aims to investigate the influence of Bakalyar's and the authors' own CTDIw equations on the size correction factors described by the AAPM Task Group 204, using Monte Carlo simulations. The simulations were performed by modeling four types of x-ray CT scanner designs, to compute the dose values in water for cylindrical phantoms with 8-40 cm diameters. CTDI100 method and the AAPM Task Group 111's proposed method were employed as the CT dosimetry models. Size correction factors were obtained for the computed dose values of various phantom diameters for the conventional, Bakalyar's, and the authors' weighting factors. Maximum difference between the size correction factors for the Bakalyar's weighting factor and those of the AAPM Task Group 204 was 27% for a phantom diameter of 11.2 cm. On the other hand, the size correction factors calculated for the authors' weighting factor were in good agreement with those from the AAPM Task Group 204 report with a maximum difference of 17%. The results indicate that the SSDE values obtained with the authors' weighting factor can be evaluated by using the size correction factors reported by the AAPM Task Group 204, which is currently accepted as a standard.
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Affiliation(s)
- Tomonobu Haba
- Faculty of Radiological TechnologySchool of Medical Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, Japan.
| | - Masanao Kobayashi
- Faculty of Radiological TechnologySchool of Medical Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, Japan
| | - Shuji Koyama
- Brain & Mind Research Center, Nagoya University, 1-1-20 Daiko-Minami, Higashi-ku, Nagoya, Aichi, Japan
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15
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Marshall EL, Rajderkar D, Brown JL, Stepusin EJ, Borrego D, Duncan J, Sammet CL, Munneke JR, Kwan ML, Miglioretti DL, Smith-Bindman R, Bolch WE. A Scalable Database of Organ Doses for Common Diagnostic Fluoroscopy Procedures of Children: Procedures of Historical Practice for Use in Radiation Epidemiology Studies. Radiat Res 2019; 192:649-661. [PMID: 31609677 DOI: 10.1667/rr15445.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Assessment of health effects from low-dose radiation exposures in patients undergoing diagnostic imaging is an active area of research. High-quality dosimetry information pertaining to these medical exposures is generally not readily available to clinicians or epidemiologists studying radiation-related health risks. The purpose of this study was to provide methods for organ dose estimation in pediatric patients undergoing four common diagnostic fluoroscopy procedures: the upper gastrointestinal (UGI) series, the lower gastrointestinal (LGI) series, the voiding cystourethrogram (VCUG) and the modified barium swallow (MBS). Abstracted X-ray film data and physician interviews were combined to generate procedure outlines detailing X-ray beam projections, imaged anatomy, length of X-ray exposure, and presence and amount of contrast within imaged anatomy. Monte Carlo radiation transport simulations were completed for each of the four diagnostic fluoroscopy procedures across the 162-member (87 males and 75 females) University of Florida/National Cancer Institute pediatric phantom library, which covers variations in both subject height and weight. Absorbed doses to 28 organs, including the active marrow and bone endosteum, were assigned for all 162 phantoms by procedure. Additionally, we provide dose coefficients (DCs) in a series of supplementary tables. The DCs give organ doses normalized to procedure-specific dose metrics, including: air kerma-area product (µGy/mGy · cm2), air kerma at the reference point (µGy/µGy), number of spot films (SF) (µGy/number of SFs) and total fluoroscopy time (µGy/s). Organs accumulating the highest absorbed doses per procedure were as follows: kidneys between 0.9-25.4 mGy, 1.1-16.6 mGy and 1.1-9.7 mGy for the UGI, LGI and VCUG procedures, respectively, and salivary glands between 0.2-3.7 mGy for the MBS procedure. Average values of detriment-weighted dose, a phantom-specific surrogate for the effective dose based on ICRP Publication 103 tissue-weighting factors, were 0.98 mSv, 1.16 mSv, 0.83 mSv and 0.15 mSv for the UGI, LGI, VCUG and MBS procedures, respectively. Scalable database of organ dose coefficients by patient sex, height and weight, and by procedure exposure time, reference point air kerma, kerma-area product or number of spot films, allows clinicians and researchers to compute organ absorbed doses based on their institution-specific and patient-specific dose metrics. In addition to informing on patient dosimetry, this work has the potential to facilitate exposure assessments in epidemiological studies designed to investigate radiation-related risks.
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Affiliation(s)
| | | | - Justin L Brown
- Department of Medical Physics Program, College of Medicine, University of Florida, Gainesville, Florida
| | | | - David Borrego
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - James Duncan
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri
| | | | - Julie R Munneke
- Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois
| | - Marilyn L Kwan
- Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois
| | - Diana L Miglioretti
- Division of Research, Kaiser Permanente Northern California, Oakland, California
- Department of Public Health Sciences, University of California Davis School of Medicine, Sacramento, California
| | - Rebecca Smith-Bindman
- Department of Public Health Sciences, University of California Davis School of Medicine, Sacramento, California
| | - Wesley E Bolch
- J. Crayton Pruitt Family Department of Biomedical Engineering
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16
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Kostou T, Papadimitroulas P, Papaconstadopoulos P, Devic S, Seuntjens J, Kagadis GC. Size-specific dose estimations for pediatric chest, abdomen/pelvis and head CT scans with the use of GATE. Phys Med 2019; 65:181-190. [PMID: 31494372 DOI: 10.1016/j.ejmp.2019.08.020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 07/24/2019] [Accepted: 08/29/2019] [Indexed: 01/17/2023] Open
Abstract
PURPOSE The purpose of this study is to create an organ dose database for pediatric individuals undergoing chest, abdomen/pelvis, and head computed tomography (CT) examinations, and to report the differences in absorbed organ doses, when anatomical differences exist for pediatric patients. METHODS The GATE Monte Carlo (MC) toolkit was used to model the GE BrightSpeed Elite CT model. The simulated scanner model was validated with the standard Computed Tomography Dose Index (CTDI) head phantom. Twelve computational models (2.1-14 years old) were used. First, contributions to effective dose and absorbed doses per CTDIvol and per 100 mAs were estimated for all organs. Then, doses per CTDIvol were correlated with patient model weight for the organs inside the scan range for chest and abdomen/pelvis protocols. Finally, effective doses per dose-length product (DLP) were estimated and compared with the conventional conversion k-factors. RESULTS The system was validated against experimental CTDIw measurements. The doses per CTDIvol and per 100 mAs for selected organs were estimated. The magnitude of the dependency between the dose and the anatomical characteristics was calculated with the coefficient of determination at 0.5-0.7 for the internal scan organs for chest and abdomen/pelvis protocols. Finally, effective doses per DLP were compared with already published data, showing discrepancies between 13 and 29% and were correlated strongly with the total weight (R2 > 0.8) for the chest and abdomen protocols. CONCLUSIONS Big differences in absorbed doses are reported even for patients of similar age or same gender, when anatomical differences exist on internal organs of the body.
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Affiliation(s)
- Theodora Kostou
- University of Patras, Department of Medical Physics, Patras, Greece
| | | | | | - Slobodan Devic
- McGill University, Department of Medical Physics, Montreal, Canada
| | - Jan Seuntjens
- McGill University, Department of Medical Physics, Montreal, Canada
| | - George C Kagadis
- University of Patras, Department of Medical Physics, Patras, Greece.
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17
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Marshall EL, Rajderkar D, Brown JL, Stepusin EJ, Borrego D, Bolch WE. A scalable database of organ doses for common diagnostic fluoroscopy examinations of children: procedures of current practice at the University of Florida. Phys Med Biol 2019; 64:135023. [PMID: 31013486 DOI: 10.1088/1361-6560/ab1bad] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Of all the medical imaging modalities that utilize ionizing radiation, fluoroscopy proves to be the most difficult to assess values of patient organ dose owing to the dynamic and patient-specific nature of the irradiation geometry and its associated x-ray beam characteristics. With the introduction of the radiation dose structured report (RDSR) in the mid-2000s, however, computational tools have been developed to extract patient and procedure-specific data for each irradiation event of the study, and when coupled to a computational phantom of the patient, values of skin and internal organ dose may be assessed. Unfortunately, many legacy and even current diagnostic fluoroscopy units do not have RDSR reporting capabilities, thus limiting these dosimetry reporting advances. Nevertheless, knowledge of patient organ doses for patient care, as well as for radiation epidemiology studies, remains a research and regulatory priority. In this study, we created procedural outlines which document all radiation exposure information required for organ dose assessment, akin to a reference RDSR, for six common diagnostic fluoroscopy procedures performed at the University of Florida (UF) Shands Pediatric Hospital. These procedures include the voiding cystourethrogram, the gastrostomy-tube placement, the lower gastrointestinal study, the rehabilitation swallow, the upper gastrointestinal study, and the upper gastrointestinal study with follow through. These procedural outlines were used to develop an extensive database of organ doses for the 162-member UF/NCI (National Cancer Institute) library of pediatric hybrid phantoms, with each member varying combinations of sex, height, and weight. The organ dose assessment accounts for the varying x-ray fields, fluoroscopy time, relative concentration of x-ray contrast in the organs, and changes in the fluoroscope output due to patient size. Furthermore, we are also reporting organ doses normalized to total fluoroscopy time, reference point air kerma, and kerma-area product, effectively providing procedure dose coefficients. The extensive organ dose library produced in this study may be used prospectively for patient organ dose reporting or retrospectively in epidemiological studies of radiation-associated health risks.
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Affiliation(s)
- Emily L Marshall
- J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, United States of America. Present address: Diagnostic Physics Residency Program, Department of Radiology, University of Chicago, Chicago, IL, United States of America
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18
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Stratis A, Zhang G, Jacobs R, Bogaerts R, Bosmans H. The growing concern of radiation dose in paediatric dental and maxillofacial CBCT: an easy guide for daily practice. Eur Radiol 2019; 29:7009-7018. [DOI: 10.1007/s00330-019-06287-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2018] [Revised: 04/21/2019] [Accepted: 05/24/2019] [Indexed: 11/24/2022]
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19
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Increasing organ dose accuracy through voxel phantom organ matching with individual patient anatomy. Radiat Phys Chem Oxf Engl 1993 2019. [DOI: 10.1016/j.radphyschem.2019.02.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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20
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Hardy AJ, Angel E, Bostani M, Cagnon C, McNitt-Gray M. Estimating fetal dose from tube current-modulated (TCM) and fixed tube current (FTC) abdominal/pelvis CT examinations. Med Phys 2019; 46:2729-2743. [PMID: 30893477 DOI: 10.1002/mp.13499] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 03/12/2019] [Accepted: 03/13/2019] [Indexed: 11/05/2022] Open
Abstract
PURPOSE The purpose of this work was to estimate scanner-independent CTDIvol -to-fetal-dose coefficients for tube current-modulated (TCM) and fixed tube current (FTC) computed tomography (CT) examinations of pregnant patients of various gestational ages undergoing abdominal/pelvic CT examinations. METHODS For 24 pregnant patients of gestational age from <5 to 36 weeks who underwent clinically indicated CT examinations, voxelized models of maternal and fetal (or embryo) anatomy were created from abdominal/pelvic image data. Absolute fetal dose (Dfetus ) was estimated using Monte Carlo (MC) simulations of helical scans covering the abdomen and pelvis for TCM and FTC scans. Estimated TCM schemes were generated for each patient model using a validated method that accounts for patient attenuation and scanner output limits for one scanner model and were incorporated into MC simulations. FTC scans were also simulated for each patient model with multidetector row CT scanners from four manufacturers. Normalized fetal dose estimates, nDfetus , was obtained by dividing Dfetus from the MC simulations by CTDIvol . Patient size was described using water equivalent diameter (Dw ) measured at the three-dimensional geometric centroid of the fetus. Fetal depth (DEf ) was measured from the anterior skin surface to the anterior part of the fetus. nDfetus and Dw were correlated using an exponential model to develop equations for fetal dose conversion coefficients for TCM and FTC abdominal/pelvic CT examinations. Additionally, bivariate linear regression was performed to analyze the correlation of nDfetus with Dw and fetal depth (DEf ). For one scanner model, nDfetus from TCM was compared to FTC and the size-specific dose estimate (SSDE) conversion coefficients (f-factors) from American Association of Physicists in Medicine (AAPM) Report 204. nDfetus from FTC simulations was averaged across all scanners for each patient ( n D fetus ¯ ) . n D fetus ¯ was then compared with SSDE f-factors and correlated with Dw using an exponential model and with Dw and DEf using a bivariate linear model. RESULTS For TCM, the coefficient of determination (R2 ) of nDfetus and Dw was observed to be 0.73 using an exponential model. Using the bivariate linear model with Dw and DEf , an R2 of 0.78 was observed. For the TCM technology modeled, TCM yielded nDfetus values that were on average 6% and 17% higher relative to FTC and SSDE f-factors, respectively. For FTC, the R2 of n D fetus ¯ with respect to Dw was observed to be 0.64 using an exponential model. Using the bivariate linear model, an R2 of 0.75 was observed for n D fetus ¯ with respect to Dw and DEf . A mean difference of 0.4% was observed between n D fetus ¯ and SSDE f-factors. CONCLUSION Good correlations were observed for nDfetus from TCM and FTC scans using either an exponential model with Dw or a bivariate linear model with both Dw and DEf . These results indicate that fetal dose from abdomen/pelvis CT examinations of pregnant patients of various gestational ages may be reasonably estimated with models that include (a) scanner-reported CTDIvol and (b) Dw as a patient size metric, in addition to (c) DEf if available. These results also suggest that SSDE f-factors may provide a reasonable (within ±25%) estimate of nDfetus for TCM and FTC abdomen/pelvis CT exams.
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Affiliation(s)
- Anthony J Hardy
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - Erin Angel
- Canon Medical Systems USA, Inc., Tustin, CA, 92780, USA
| | - Maryam Bostani
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - Chris Cagnon
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - Michael McNitt-Gray
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
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21
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Rosendahl S, Büermann L, Borowski M, Kortesniemi M, Sundell VM, Kosunen A, Siiskonen T. CT beam dosimetric characterization procedure for personalized dosimetry. Phys Med Biol 2019; 64:075009. [PMID: 30856614 DOI: 10.1088/1361-6560/ab0e97] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Personalized dosimetry in computed tomography (CT) can be realized by a full Monte Carlo (MC) simulation of the scan procedure. Essential input data needed for the simulation are appropriate CT x-ray source models and a model of the patient's body which is based on the CT image. The purpose of this work is to develop comprehensive procedures for the determination of CT x-ray source models and their verification by comparison of calculated and measured dose distributions in physical phantoms. Mobile equipment together with customized software was developed and used for non-invasive determination of equivalent source models of CT scanners under clinical conditions. Standard and physical anthropomorphic CT dose phantoms equipped with real-time CT dose probes at five representative positions were scanned. The accumulated dose was measured during the scan at the five positions. ImpactMC, an MC-based CT dose software program, was used to simulate the scan. The necessary inputs were obtained from the scan parameters, from the equivalent source models and from the material-segmented CT images of the phantoms. 3D dose distributions in the phantoms were simulated and the dose values calculated at the five positions inside the phantom were compared to measured dose values. Initial results were obtained by means of a General Electric Optima CT 660 and a Toshiba (Canon) Aquilion ONE. In general, the measured and calculated dose values were within relative uncertainties that had been estimated to be less than 10%. The procedures developed were found to be viable and rapid. The procedures are applicable to any scanner type under clinical conditions without making use of the service mode with stationary x-ray tube position. Results show that the procedures are well suited for determining and verifying the equivalent source models needed for personalized CT dosimetry based on post-scan MC calculations.
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Affiliation(s)
- S Rosendahl
- Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany
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22
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Somasundaram E, Artz NS, Brady SL. Development and validation of an open source Monte Carlo dosimetry model for wide-beam CT scanners using Fluka. J Appl Clin Med Phys 2019; 20:132-147. [PMID: 30851155 PMCID: PMC6448170 DOI: 10.1002/acm2.12559] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 01/14/2019] [Accepted: 02/13/2019] [Indexed: 12/30/2022] Open
Abstract
PURPOSE Development and validation of an open source Fluka-based Monte Carlo source model for diagnostic patient dose calculations. METHODS A framework to simulate a computed tomography (CT) scanner using Fluka Monte Carlo particle transport code was developed. The General Electric (GE) Revolution scanner with the large body filter and 120 kV tube potential was characterized using measurements. The model was validated on benchmark CT test problems and on dose measurements in computed tomography dose index (CTDI) and anthropomorphic phantoms. Axial and helical operation modes with provision for tube current modulation (TCM) were implemented. The particle simulations in Fluka were accelerated by executing them on a high-performance computing cluster. RESULTS The simulation results agreed to better than an average of 4% of the reference simulation results from the AAPM Report 195 test scenarios, namely: better than 2% for both test problems in case 4 using the PMMA phantom, and better than 5% of the reference result for 14 of 17 organs in case 5, and within 10% for the three remaining organs. The Fluka simulation results agreed to better than 2% of the air kerma measured in-air at isocenter of the GE Revolution scanner. The simulated air kerma in the center of the CTDI phantom overestimated the measurement by 7.5% and a correction factor was introduced to account for this. The simulated mean absorbed doses for a chest scan of the pediatric anthropomorphic phantom was completed in ~9 min and agreed to within the 95% CI for bone, soft tissue, and lung measurements made using MOSFET detectors for fixed current axial and helical scans as well as helical scan with TCM. CONCLUSION A Fluka-based Monte Carlo simulation model of axial and helical acquisition techniques using a wide-beam collimation CT scanner demonstrated good agreement between measured and simulated results for both fixed current and TCM in complex and simple geometries. Code and dataset will be made available at https://github.com/chezhia/FLUKA_CT.
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Affiliation(s)
- Elanchezhian Somasundaram
- Department of Diagnostic Imaging, St Jude Children's Research Hospital, Memphis, TN, USA.,Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Nathan S Artz
- Department of Diagnostic Imaging, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Samuel L Brady
- Department of Diagnostic Imaging, St Jude Children's Research Hospital, Memphis, TN, USA.,Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Department of Radiology, University of Cincinnati, Cincinnati, OH, USA
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23
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Scarboro SB, Cody D, Stingo FC, Alvarez P, Followill D, Court L, Zhang D, McNitt‐Gray M, Kry SF. Calibration strategies for use of the nanoDot OSLD in CT applications. J Appl Clin Med Phys 2019; 20:331-339. [PMID: 30426664 PMCID: PMC6333198 DOI: 10.1002/acm2.12491] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 09/26/2018] [Accepted: 10/06/2018] [Indexed: 11/06/2022] Open
Abstract
Aluminum oxide based optically stimulated luminescent dosimeters (OSLD) have been recognized as a useful dosimeter for measuring CT dose, particularly for patient dose measurements. Despite the increasing use of this dosimeter, appropriate dosimeter calibration techniques have not been established in the literature; while the manufacturer offers a calibration procedure, it is known to have relatively large uncertainties. The purpose of this work was to evaluate two clinical approaches for calibrating these dosimeters for CT applications, and to determine the uncertainty associated with measurements using these techniques. Three unique calibration procedures were used to calculate dose for a range of CT conditions using a commercially available OSLD and reader. The three calibration procedures included calibration (a) using the vendor-provided method, (b) relative to a 120 kVp CT spectrum in air, and (c) relative to a megavoltage beam (implemented with 60 Co). The dose measured using each of these approaches was compared to dose measured using a calibrated farmer-type ion chamber. Finally, the uncertainty in the dose measured using each approach was determined. For the CT and megavoltage calibration methods, the dose measured using the OSLD nanoDot was within 5% of the dose measured using an ion chamber for a wide range of different CT scan parameters (80-140 kVp, and with measurements at a range of positions). When calibrated using the vendor-recommended protocol, the OSLD measured doses were on average 15.5% lower than ion chamber doses. Two clinical calibration techniques have been evaluated and are presented in this work as alternatives to the vendor-provided calibration approach. These techniques provide high precision for OSLD-based measurements in a CT environment.
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Affiliation(s)
- Sarah B. Scarboro
- The University of Texas MD Anderson Cancer CenterHoustonTXUSA
- Graduate School of Biomedical SciencesThe University of Texas Health Science Center HoustonHoustonTXUSA
| | - Dianna Cody
- The University of Texas MD Anderson Cancer CenterHoustonTXUSA
- Graduate School of Biomedical SciencesThe University of Texas Health Science Center HoustonHoustonTXUSA
| | - Francesco C. Stingo
- The University of Texas MD Anderson Cancer CenterHoustonTXUSA
- Graduate School of Biomedical SciencesThe University of Texas Health Science Center HoustonHoustonTXUSA
| | - Paola Alvarez
- The University of Texas MD Anderson Cancer CenterHoustonTXUSA
| | - David Followill
- The University of Texas MD Anderson Cancer CenterHoustonTXUSA
- Graduate School of Biomedical SciencesThe University of Texas Health Science Center HoustonHoustonTXUSA
| | - Laurence Court
- The University of Texas MD Anderson Cancer CenterHoustonTXUSA
- Graduate School of Biomedical SciencesThe University of Texas Health Science Center HoustonHoustonTXUSA
| | - Di Zhang
- Biomedical Physics Graduate ProgramDavid Geffen School of Medicine at UCLALos AngelesCAUSA
- Present address:
Toshiba American Medical SystemsTustinCAUSA
| | - Michael McNitt‐Gray
- The Department of Radiological SciencesDavid Geffen School of Medicine at UCLALos AngelesCAUSA
| | - Stephen F. Kry
- The University of Texas MD Anderson Cancer CenterHoustonTXUSA
- Graduate School of Biomedical SciencesThe University of Texas Health Science Center HoustonHoustonTXUSA
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24
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Hardy AJ, Bostani M, Hernandez AM, Zankl M, McCollough C, Cagnon C, Boone JM, McNitt-Gray M. Estimating a size-specific dose for helical head CT examinations using Monte Carlo simulation methods. Med Phys 2018; 46:902-912. [PMID: 30565704 DOI: 10.1002/mp.13301] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 10/22/2018] [Accepted: 10/23/2018] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Size-specific dose estimates (SSDE) conversion factors have been determined by AAPM Report 204 to adjust CTDIvol to account for patient size but were limited to body CT examinations. The purpose of this work was to determine conversion factors that could be used for an SSDE for helical, head CT examinations for patients of different sizes. METHODS Validated Monte Carlo (MC) simulation methods were used to estimate dose to the center of the scan volume from a routine, helical head examination for a group of patient models representing a range of ages and sizes. Ten GSF/ICRP voxelized phantom models and five pediatric voxelized patient models created from CT image data were used in this study. CT scans were simulated using a Siemens multidetector row CT equivalent source model. Scan parameters were taken from the AAPM Routine Head protocols for a fixed tube current (FTC), helical protocol, and scan lengths were adapted to the anatomy of each patient model. MC simulations were performed using mesh tallies to produce voxelized dose distributions for the entire scan volume of each model. Three tally regions were investigated: (1) a small 0.6 cc volume at the center of the scan volume, (2) 0.8-1.0 cm axial slab at the center of the scan volume, and (3) the entire scan volume. Mean dose to brain parenchyma for all three regions was calculated. Mean bone dose and a mass-weighted average dose, consisting of brain parenchyma and bone, were also calculated for the slab in the central plane and the entire scan volume. All dose measures were then normalized by CTDIvol for the 16 cm phantom (CTDIvol,16 ). Conversion factors were determined by calculating the relationship between normalized doses and water equivalent diameter (Dw ). RESULTS CTDIvol,16 -normalized mean brain parenchyma dose values within the 0.6 cc volume, 0.8-1.0 cm central axial slab, and the entire scan volume, when parameterized by Dw , had an exponential relationship with a coefficient of determination (R2 ) of 0.86, 0.84, and 0.88, respectively. There was no statistically significant difference between the conversion factors resulting from these three different tally regions. Exponential relationships between CTDIvol,16 -normalized mean bone doses had R2 values of 0.83 and 0.87 for the central slab and for the entire scan volume, respectively. CTDIvol,16 -normalized mass-weighted average doses had R2 values of 0.39 and 0.51 for the central slab and for the entire scan volume, respectively. CONCLUSIONS Conversion factors that describe the exponential relationship between CTDIvol,16 -normalized mean brain dose and a size metric (Dw ) for helical head CT examinations have been reported for two different interpretations of the center of the scan volume. These dose descriptors have been extended to describe the dose to bone in the center of the scan volume as well as a mass-weighted average dose to brain and bone. These may be used, when combined with other efforts, to develop an SSDE dose coefficients for routine, helical head CT examinations.
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Affiliation(s)
- Anthony J Hardy
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - Maryam Bostani
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - Andrew M Hernandez
- Departments of Radiology and Biomedical Engineering, Biomedical Engineering Graduate Group, University of California Davis, Sacramento, CA, 95817, USA
| | - Maria Zankl
- Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Institute of Radiation Protection, Ingolstaedter Landstrasse 1, Neuherberg, 85764, Germany
| | | | - Chris Cagnon
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - John M Boone
- Departments of Radiology and Biomedical Engineering, Biomedical Engineering Graduate Group, University of California Davis, Sacramento, CA, 95817, USA
| | - Michael McNitt-Gray
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
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25
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Fujii K, Nomura K, Muramatsu Y, Obara S, Goto T, Akahane K, Ota H, Tsukagoshi S, Kusumoto M. VALIDATION OF MONTE CARLO DOSE CALCULATION FOR PAEDIATRIC CT EXAMINATIONS USING TUBE CURRENT MODULATION BASED ON IN-PHANTOM DOSIMETRY. RADIATION PROTECTION DOSIMETRY 2018; 182:508-517. [PMID: 30032259 DOI: 10.1093/rpd/ncy109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 06/20/2018] [Indexed: 06/08/2023]
Abstract
The aim of this study is to estimate tube current modulation (TCM) profiles in paediatric computed tomography (CT) examinations with a TCM scheme (Volume-EC) and evaluate the estimation accuracy of TCM profiles. Another aim is to validate organ doses calculated using Monte Carlo-based CT dosimetry software and estimated TCM profiles by comparing them with those measured using 5-year-old and 10-year-old anthropomorphic phantoms and radio-photoluminescence glass dosemeters. Dose calculations were performed by inputting detailed descriptions of a CT scanner, scan parameters and CT images of the phantoms into the software. Organ doses were evaluated from the calculated dose distribution images. Average relative differences (RDs) between the estimated and actual TCM profiles ranged from -3.6 to 5.6%. RDs between the calculated and measured organ doses ranged from -4.2 to 13.0% and -18.1 to 4.9% for 5-year-old and 10-year-old phantoms, respectively. These results validate dose calculations for paediatric CT scans using TCM.
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Affiliation(s)
- K Fujii
- Department of Radiological Sciences, Nagoya University Graduate School of Medicine, 1-1-20, Daikominami, Higashi-ku, Nagoya, Japan
- Department of Radiological Technology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, Japan
- Department of Radiation Measurement and Dose Assessment, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, Japan
| | - K Nomura
- Department of Radiological Technology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, Japan
| | - Y Muramatsu
- Department of Radiological Technology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, Japan
| | - S Obara
- Department of Radiation Measurement and Dose Assessment, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, Japan
| | - T Goto
- Canon Medical Systems Corporation, 1385 Shimoishigami, Otawara, Tochigi, Japan
| | - K Akahane
- Department of Radiation Measurement and Dose Assessment, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, Japan
| | - H Ota
- Department of Radiological Technology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, Japan
| | - S Tsukagoshi
- Canon Medical Systems Corporation, 1385 Shimoishigami, Otawara, Tochigi, Japan
| | - M Kusumoto
- Department of Diagnostic Radiology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, Japan
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26
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Al‐Senan R. A method to estimate transmission profiles of bow‐tie filters using rotating tube measurements. Med Phys 2018; 45:4964-4976. [DOI: 10.1002/mp.13203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 09/03/2018] [Accepted: 09/09/2018] [Indexed: 01/20/2023] Open
Affiliation(s)
- Rani Al‐Senan
- Department of Radiology Columbia University Medical Center 177 Ft Washington Ave. New York NY 10032 USA
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27
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Hardy AJ, Bostani M, McMillan K, Zankl M, McCollough C, Cagnon C, McNitt-Gray M. Estimating lung, breast, and effective dose from low-dose lung cancer screening CT exams with tube current modulation across a range of patient sizes. Med Phys 2018; 45:4667-4682. [PMID: 30118143 DOI: 10.1002/mp.13131] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 06/26/2018] [Accepted: 07/12/2018] [Indexed: 12/12/2022] Open
Abstract
PURPOSE The purpose of this study was to estimate the radiation dose to the lung and breast as well as the effective dose from tube current modulated (TCM) lung cancer screening (LCS) scans across a range of patient sizes. METHODS Monte Carlo (MC) methods were used to calculate lung, breast, and effective doses from a low-dose LCS protocol for a 64-slice CT that used TCM. Scanning parameters were from the protocols published by AAPM's Alliance for Quality CT. To determine lung, breast, and effective doses from lung cancer screening, eight GSF/ICRP voxelized phantom models with all radiosensitive organs identified were used to estimate lung, breast, and effective doses. Additionally, to extend the limited size range provided by the GSF/ICRP phantom models, 30 voxelized patient models of thoracic anatomy were generated from LCS patient data. For these patient models, lung and breast were semi-automatically segmented. TCM schemes for each of the GSF/ICRP phantom models were generated using a validated method wherein tissue attenuation and scanner limitations were used to determine the TCM output as a function of table position and source angle. TCM schemes for voxelized patient models were extracted from the raw projection data. The water equivalent diameter, Dw, was used as the patient size descriptor. Dw was estimated for the GSF/ICRP models. For the thoracic patient models, Dw was extracted from the DICOM header of the CT localizer radiograph. MC simulations were performed using the TCM scheme for each model. Absolute organ doses were tallied and effective doses were calculated using ICRP 103 tissue weighting factors for the GSF/ICRP models. Metrics of scanner radiation output were determined based on each model's TCM scheme, including CTDIvol , dose length product (DLP), and CTDIvol, Low Att , a previously described regional metric of scanner output covering most of the lungs and breast. All lung and breast doses values were normalized by scan-specific CTDIvol and CTDIvol, Low Att . Effective doses were normalized by scan-specific CTDIvol and DLP. Absolute and normalized doses were reported as a function of Dw. RESULTS Lung doses normalized by CTDIvol, Low Att were modeled as an exponential relationship with respect to Dw with coefficients of determination (R2 ) of 0.80. Breast dose normalized by CTDIvol, Low Att was modeled with an exponential relationship to Dw with an R2 of 0.23. For all eight GSF/ICRP phantom models, the effective dose using TCM protocols was below 1.6 mSv. Effective doses showed some size dependence but when normalized by DLP demonstrated a constant behavior. CONCLUSION Lung, breast, and effective doses from LCS CT exams with TCM were estimated with respect to patient size. Normalized lung dose can be reasonably estimated with a measure of a patient size such as Dw and regional metric of CTDIvol covering the thorax such as CTDIvol, Low Att , while normalized breast dose can also be estimated with a regional metric of CTDIvol but with a larger degree of variability than observed for lung. Effective dose normalized by DLP can be estimated with a constant multiplier.
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Affiliation(s)
- Anthony J Hardy
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - Maryam Bostani
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - Kyle McMillan
- Formerly with Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Maria Zankl
- Helmholtz Zentrum München, German Research Center for Environmental Health (GmBH) Institute of Radiation Protection, Ingolstaedter Landstrasse 1, Neuherberg, 85764, Germany
| | | | - Chris Cagnon
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - Michael McNitt-Gray
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
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28
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Dedulle A, Fitousi N, Zhang G, Jacobs J, Bosmans H. Two-step validation of a Monte Carlo dosimetry framework for general radiology. Phys Med 2018; 53:72-79. [PMID: 30241757 DOI: 10.1016/j.ejmp.2018.08.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 07/27/2018] [Accepted: 08/06/2018] [Indexed: 10/28/2022] Open
Abstract
The Monte Carlo technique is considered gold standard when it comes to patient-specific dosimetry. Any newly developed Monte Carlo simulation framework, however, has to be carefully calibrated and validated prior to its use. For many researchers this is a tedious work. We propose a two-step validation procedure for our newly built Monte Carlo framework and provide all input data to make it feasible for future related application by the wider community. The validation was at first performed by benchmarking against simulation data available in literature. The American Association of Physicists in Medicine (AAPM) report of task group 195 (case 2) was considered most appropriate for our application. Secondly, the framework was calibrated and validated against experimental measurements for trunk X-ray imaging protocols using a water phantom. The dose results obtained from all simulations and measurements were compared. Our Monte Carlo framework proved to agree with literature data, by showing a maximal difference below 4% to the AAPM report. The mean difference with the water phantom measurements was around 7%. The statistical uncertainty for clinical applications of the dosimetry model is expected to be within 10%. This makes it reliable for clinical dose calculations in general radiology. Input data and the described procedure allow for the validation of other Monte Carlo frameworks.
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Affiliation(s)
- An Dedulle
- Qaelum NV, Gaston Geenslaan 9, 3001 Leuven, Belgium; University of Leuven, Department of Imaging and Pathology, Division of Medical Physics and Quality Assessment, Herestraat 49, 3000 Leuven, Belgium.
| | - Niki Fitousi
- Qaelum NV, Gaston Geenslaan 9, 3001 Leuven, Belgium.
| | - Guozhi Zhang
- Department of Radiology, University Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium.
| | - Jurgen Jacobs
- Qaelum NV, Gaston Geenslaan 9, 3001 Leuven, Belgium.
| | - Hilde Bosmans
- University of Leuven, Department of Imaging and Pathology, Division of Medical Physics and Quality Assessment, Herestraat 49, 3000 Leuven, Belgium; Department of Radiology, University Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium.
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29
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Tsujiguchi T, Obara H, Ono S, Saito Y, Kashiwakura I. Consideration of the usefulness of a size-specific dose estimate in pediatric CT examination. JOURNAL OF RADIATION RESEARCH 2018; 59:430-435. [PMID: 29659978 PMCID: PMC6054202 DOI: 10.1093/jrr/rry022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 11/23/2017] [Indexed: 06/08/2023]
Abstract
Computed tomography (CT) has recently been utilized in various medical settings, and technological advances have resulted in its widespread use. However, medical radiation exposure associated with CT scans accounts for the largest share of examinations using radiation; thus, it is important to understand the organ dose and effective dose in detail. The CT dose index and dose-length product are used to evaluate the organ dose. However, evaluations using these indicators fail to consider the age and body type of patients. In this study, we evaluated the effective dose based on the CT examination data of 753 patients examined at our hospital using the size-specific dose estimate (SSDE) method, which can calculate the exposure dose with consideration of the physique of a patient. The results showed a large correlation between the SSDE conversion factor and physique, with a larger exposure dose in patients with a small physique when a single scan is considered. Especially for children, the SSDE conversion factor was found to be 2 or more. In addition, the patient exposed to the largest dose in this study was a 10-year-old, who received 40.4 mSv (five series/examination). In the future, for estimating exposure using the SSDE method and in cohort studies, the diagnostic reference level of SSDE should be determined and a low-exposure imaging protocol should be developed to predict the risk of CT exposure and to maintain the quality of diagnosis with better radiation protection of patients.
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Affiliation(s)
- Takakiyo Tsujiguchi
- Department of Radiation Sciences, Hirosaki University Graduate School of Health Sciences, 66-1 Hon-cho, Hirosaki, Aomori, Japan
| | - Hideki Obara
- Department of Radiology, Division of Medical Technology, Hirosaki University School of Medicine Hospital, 53 Hon-cho Hirosaki, Aomori, Japan
| | - Shuichi Ono
- Department of Radiology and Radiation Oncology, Hirosaki University Graduate School of Medicine, 5 Zaifu-cho Hirosaki, Aomori, Japan
| | - Yoko Saito
- Department of Radiation Sciences, Hirosaki University Graduate School of Health Sciences, 66-1 Hon-cho, Hirosaki, Aomori, Japan
| | - Ikuo Kashiwakura
- Department of Radiation Sciences, Hirosaki University Graduate School of Health Sciences, 66-1 Hon-cho, Hirosaki, Aomori, Japan
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30
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Marshall EL, Borrego D, Fudge JC, Rajderkar D, Bolch WE. Organ doses in pediatric patients undergoing cardiac-centered fluoroscopically guided interventions: Comparison of three methods for computational phantom alignment. Med Phys 2018; 45:10.1002/mp.13044. [PMID: 29896882 PMCID: PMC6292782 DOI: 10.1002/mp.13044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 05/15/2018] [Accepted: 06/07/2018] [Indexed: 01/16/2023] Open
Abstract
PURPOSE To assess various computational phantom alignment techniques within Monte Carlo radiation transport models of pediatric fluoroscopically guided cardiac interventional studies. METHODS Logfiles, including all procedure radiation and machine data, were extracted from a Toshiba infinix-I unit in the University of Florida Pediatric Catheterization Laboratory for a cohort of 10 patients. Two different alignment methods were then tested against a ground truth standard based upon identification of a unique anatomic reference point within images co-registered to specific irradiation events within each procedure. The first alignment method required measurement of the distance from the edge of the exam table to the top of the patient's head (table alignment method). The second alignment method fixed the anatomic reference point to be the geometric center of the heart muscle, as all 10 studies were cardiac in nature. Monte Carlo radiation transport simulations were performed for each patient and intervention using morphometry-matched hybrid computational phantoms for the reference and two tested alignment methods. For each combination, absorbed doses were computed for 28 organs and root mean square organ doses were assessed and compared across the alignment methods. RESULTS The percent error in root mean square organ dose ranged from -57% to +41% for the table alignment method, and from -27% to +22% for the heart geometric centroid alignment method. Absorbed doses to specific organs, such as the heart and lungs, demonstrated higher accuracy in the heart geometric centroid alignment method, with average percent errors of 10% and 1.4%, respectively, compared to average percent errors of -32% and 24%, respectively, using the table alignment method. CONCLUSIONS Of the two phantom alignment methods investigated in this study, the use of an anatomical reference point - in this case the geometric centroid of the heart - provided a reliable method for radiation transport simulations of organ dose in pediatric interventional cardiac studies. This alignment method provides the added benefit of requiring no physician input, making retrospective calculations possible. Moving forward, additional anatomical reference methods can be tested to assess the reliability of anatomical reference points beyond cardiac centered procedures.
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Affiliation(s)
- Emily L Marshall
- J. Crayton Pruitt Family, Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA
| | - David Borrego
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - James C Fudge
- Div. of Pediatric Cardiology, UF Health Congenital Heart Center, University of Florida, Gainesville, FL, USA
| | - Dhanashree Rajderkar
- Department of Radiology, Chief of Pediatric Radiology, University of Florida, Gainesville, FL, USA
| | - Wesley E Bolch
- J. Crayton Pruitt Family, Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA
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31
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Borrego D, Marshall EL, Tran T, Siragusa DA, Bolch WE. Physical validation of UF-RIPSA: A rapid in-clinic peak skin dose mapping algorithm for fluoroscopically guided interventions. J Appl Clin Med Phys 2018; 19:343-350. [PMID: 29577612 PMCID: PMC5978976 DOI: 10.1002/acm2.12312] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 07/21/2017] [Accepted: 02/13/2018] [Indexed: 12/03/2022] Open
Abstract
Purpose The purpose of this study was to experimentally validate UF‐RIPSA, a rapid in‐clinic peak skin dose mapping algorithm developed at the University of Florida using optically stimulated luminescent dosimeters (OSLDs) and tissue‐equivalent phantoms. Methods The OSLDs used in this study were InLightTM Nanodot dosimeters by Landauer, Inc. The OSLDs were exposed to nine different beam qualities while either free‐in‐air or on the surface of a tissue equivalent phantom. The irradiation of the OSLDs was then modeled using Monte Carlo techniques to derive correction factors between free‐in‐air exposures and more complex irradiation geometries. A grid of OSLDs on the surface of a tissue equivalent phantom was irradiated with two fluoroscopic x ray fields generated by the Siemens Artis zee bi‐plane fluoroscopic unit. The location of each OSLD within the grid was noted and its dose reading compared with UF‐RIPSA results. Results With the use of Monte Carlo correction factors, the OSLD's response under complex irradiation geometries can be predicted from its free‐in‐air response. The predicted values had a percent error of −8.7% to +3.2% with a predicted value that was on average 5% below the measured value. Agreement within 9% was observed between the values of the OSLDs and RIPSA when irradiated directly on the phantom and within 14% when the beam first traverses the tabletop and pad. Conclusions The UF‐RIPSA only computes dose values to areas of irradiated skin determined to be directly within the x ray field since the algorithm is based upon ray tracing of the reported reference air kerma value, with subsequent corrections for air‐to‐tissue dose conversion, x ray backscatter, and table/pad attenuation. The UF‐RIPSA algorithm thus does not include the dose contribution of scatter radiation from adjacent fields. Despite this limitation, UF‐RIPSA is shown to be fairly robust when computing skin dose to patients undergoing fluoroscopically guided interventions.
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Affiliation(s)
- David Borrego
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA
| | - Emily L Marshall
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA
| | - Trung Tran
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA
| | - Daniel A Siragusa
- Radiology, Division of Vascular Interventional Radiology, University of Florida, Jacksonville, FL, USA
| | - Wesley E Bolch
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA
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32
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Borrego D, Lowe EM, Kitahara CM, Lee C. Assessment of PCXMC for patients with different body size in chest and abdominal x ray examinations: a Monte Carlo simulation study. Phys Med Biol 2018; 63:065015. [PMID: 29465419 DOI: 10.1088/1361-6560/aab13e] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A PC Program for x ray Monte Carlo (PCXMC) has been used to calculate organ doses in patient dosimetry and for the exposure assessment in epidemiological studies of radiogenic health related risks. This study compared the dosimetry from using the built-in stylized phantoms in the PCXMC to that of a newer hybrid phantom library with improved anatomical realism. We simulated chest and abdominal x ray projections for 146 unique body size computational phantoms, 77 males and 69 females, with different combinations of height (125-180 cm) and weight (20-140 kg) using the built-in stylized phantoms in the PCXMC version 2.0.1.4 and the hybrid phantom library using the Monte Carlo N-particle eXtended transport code 2.7 (MCNPX). Unfortunately, it was not possible to incorporate the hybrid phantom library into the PCXMC. We compared 14 organ doses, including dose to the active bone marrow, to evaluate differences between the built-in stylized phantoms in the PCXMC and the hybrid phantoms (Cristy and Eckerman 1987 Technical Report ORNL/TM-8381/V1, Oak Ridge National Laboratory, Eckerman and Ryman 1993 Technical Report 12 Oak Ridge, TN, Geyer et al 2014 Phys. Med. Biol. 59 5225-42). On average, organ doses calculated using the built-in stylized phantoms in the PCXMC were greater when compared to the hybrid phantoms. This is most prominent in AP abdominal exams by an average factor of 2.4-, 2.8-, and 2.8-fold for the 10-year-old, 15-year-old, and adult phantoms, respectively. For chest exams, organ doses are greater by an average factor of 1.1-, 1.4-, and 1.2-fold for the 10-year-old, 15-year-old, and adult phantoms, respectively. The PCXMX, due to its ease of use, is often selected to support dosimetry in epidemiological studies; however, it uses simplified models of the human anatomy that fail to account for variations in body morphometry for increasing weight. For epidemiological studies that use PCXMC dosimetry, associations between radiation-related disease risks and organ doses may be underestimated, and to a greater degree in pediatric, especially obese pediatric, compared to adult patients.
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Affiliation(s)
- David Borrego
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, 9609 Medical Center Drive, Bethesda, MD 20892-9778, United States of America
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Marshall EL, Borrego D, Tran T, Fudge JC, Bolch WE. Evaluation of the UF/NCI hybrid computational phantoms for use in organ dosimetry of pediatric patients undergoing fluoroscopically guided cardiac procedures. Phys Med Biol 2018; 63:055006. [PMID: 29405126 DOI: 10.1088/1361-6560/aaad1d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Epidemiologic data demonstrate that pediatric patients face a higher relative risk of radiation induced cancers than their adult counterparts at equivalent exposures. Infants and children with congenital heart defects are a critical patient population exposed to ionizing radiation during life-saving procedures. These patients will likely incur numerous procedures throughout their lifespan, each time increasing their cumulative radiation absorbed dose. As continued improvements in long-term prognosis of congenital heart defect patients is achieved, a better understanding of organ radiation dose following treatment becomes increasingly vital. Dosimetry of these patients can be accomplished using Monte Carlo radiation transport simulations, coupled with modern anatomical patient models. The aim of this study was to evaluate the performance of the University of Florida/National Cancer Institute (UF/NCI) pediatric hybrid computational phantom library for organ dose assessment of patients that have undergone fluoroscopically guided cardiac catheterizations. In this study, two types of simulations were modeled. A dose assessment was performed on 29 patient-specific voxel phantoms (taken as representing the patient's true anatomy), height/weight-matched hybrid library phantoms, and age-matched reference phantoms. Two exposure studies were conducted for each phantom type. First, a parametric study was constructed by the attending pediatric interventional cardiologist at the University of Florida to model the range of parameters seen clinically. Second, four clinical cardiac procedures were simulated based upon internal logfiles captured by a Toshiba Infinix-i Cardiac Bi-Plane fluoroscopic unit. Performance of the phantom library was quantified by computing both the percent difference in individual organ doses, as well as the organ dose root mean square values for overall phantom assessment between the matched phantoms (UF/NCI library or reference) and the patient-specific phantoms. The UF/NCI hybrid phantoms performed at percent differences of between 15% and 30% for the parametric set of irradiation events. Among internal logfile reconstructed procedures, the UF/NCI hybrid phantoms performed with RMS organ dose values between 7% and 29%. Percent improvement in organ dosimetry via the use of hybrid library phantoms over the reference phantoms ranged from 6.6% to 93%. The use of a hybrid phantom library, Monte Carlo radiation transport methods, and clinical information on irradiation events provide a means for tracking organ dose in these radiosensitive patients undergoing fluoroscopically guided cardiac procedures.
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Affiliation(s)
- Emily L Marshall
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, United States of America. Present address: Diagnostic Physics Residency Program, Department of Radiology, University of Chicago, Chicago, IL 60637, United States of America
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Hassan AI, Skalej M, Schlattl H, Hoeschen C. Determination and verification of the x-ray spectrum of a CT scanner. J Med Imaging (Bellingham) 2018; 5:013506. [PMID: 29430476 DOI: 10.1117/1.jmi.5.1.013506] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 01/10/2018] [Indexed: 11/14/2022] Open
Abstract
The accuracy of Monte Carlo (MC) simulations in estimating the computed tomography radiation dose is highly dependent on the proprietary x-ray source information. To address this, this study develops a method to precisely estimate the x-ray spectrum and bowtie (BT) filter thickness of the x-ray source based on physical measurements and calculations. The static x-ray source of the CT localizer radiograph was assessed to measure the total filtration at the isocenter for the x-ray spectrum characterization and the BT profile (air-kerma values as a function of fan angle). With these values, the utilized BT filter in the localizer radiograph was assessed by integrating the measured air kerma in a full 360-deg cycle. The consistency observed between the integrated BT filter profiles and the directly measured profiles pointed to the similarity in the utilized BT filter in terms of thickness and material between the static and rotating x-ray geometries. Subsequently, the measured air kerma was used to calculate the BT filter thickness and was verified using MC simulations by comparing the calculated and measured air-kerma values, where a very good agreement was observed. This would allow a more accurate computed tomography simulation and facilitate the estimation of the dose delivered to the patients.
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Affiliation(s)
- Ahmad Ibrahim Hassan
- Otto von Guericke Universität Magdeburg, Universitätsklinikum Magdeburg A.ö.R., Institut für Neuroradiologie, Magdeburg, Deutschland, Germany.,Otto von Guericke Universität, Institut für Medizintechnik, Fakultät für Elektrotechnik und Informationstechnik Universitätsplatz, Magdeburg, Deutschland, Germany
| | - Martin Skalej
- Otto von Guericke Universität Magdeburg, Universitätsklinikum Magdeburg A.ö.R., Institut für Neuroradiologie, Magdeburg, Deutschland, Germany
| | - Helmut Schlattl
- Institute of Radiation Protection, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Deutschland, Germany
| | - Christoph Hoeschen
- Otto von Guericke Universität, Institut für Medizintechnik, Fakultät für Elektrotechnik und Informationstechnik Universitätsplatz, Magdeburg, Deutschland, Germany
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Haba T, Koyama S, Kinomura Y, Ida Y, Kobayashi M. New weighting factor of weighted CTDI equation for PMMA phantom diameter from 8 to 40 cm: A Monte Carlo study. Med Phys 2017; 44:6603-6609. [PMID: 28960375 DOI: 10.1002/mp.12601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 09/17/2017] [Accepted: 09/18/2017] [Indexed: 11/09/2022] Open
Abstract
PURPOSE The weighted computed tomography dose index (CTDIw ) uses measured CTDI values at the center and periphery of a cylindrical phantom. The CTDIw value is calculated using conventional, Bakalyar's, and Choi's weighting factors. However, these weighting factors were produced from only 16- and 32-cm-diameter cylindrical phantoms. This study aims to devise new weighting factors to provide more accurate average dose in the central cross-sectional plane of cylindrical phantoms over a wide range of object diameters, by using Monte Carlo simulations. METHODS Simulations were performed by modeling a Toshiba Aquilion ONE CT scanner, in order to compute the cross-sectional dose profiles of polymethyl methacrylate (PMMA) cylindrical phantoms of each diameter (8-40 cm at 4-cm steps), for various tube voltages and longitudinal beam widths. Two phantom models were simulated, corresponding to the CTDI100 method and the method recommended by American Association of Physicists in Medicine (AAPM) task group 111. The dose-computation PMMA cylinders of 1 mm diameter were located between the phantom surfaces and the centers at intervals of 1 mm, from which cross-sectional dose profiles were calculated. By using linear least-squares fits to the obtained cross-sectional dose profiles data, we determined new weighting factors to estimate more accurate average doses in the PMMA cylindrical phantoms by using the CTDIw equation: CTDIw = Wcenter ・ CTDIcenter + Wperiphery ・ CTDIperiphery . In order to demonstrate the validity of the devised new weighting factors, the percentage difference between average dose and CTDIw value was evaluated for the weighting factors (conventional, Bakalyar's, Choi's, and devised new weighting factors) in each calculated cross-sectional dose profile. RESULTS With the use of linear least-squares techniques, new weighting factors (Wcenter = 3/8 and Wperiphery = 5/8 where Wcenter and Wperiphery are weighting factors for CTDIcenter and CTDIperiphery ) were determined. The maximum percentage differences between average dose and CTDIw value were 16, -12, -8, and -6% for the conventional, Bakalyar's, Choi's, and devised new weighting factors, respectively. CONCLUSIONS We devised new weighting factors (Wcenter = 3/8 and Wperiphery = 5/8) to provide more accurate average dose estimation in PMMA cylindrical phantoms over a wide range of diameter. The CTDIw equation with devised new weighting factors could estimate average dose in PMMA cylindrical phantoms with a maximum difference of -6%. The results of this study can estimate the average dose in PMMA cylindrical phantoms more accurately than the conventional weighting factors (Wcenter = 1/3 and Wperiphery = 2/3).
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Affiliation(s)
- Tomonobu Haba
- Department of Radiology, Fujita Health University Hospital, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, 470-1192, Japan
| | - Shuji Koyama
- Brain and Mind Research Center, Nagoya University, 1-1-20 Daiko-Minami, Higashi-ku, Nagoya, Aichi, 461-8673, Japan
| | - Yutaka Kinomura
- Department of Radiology, Fujita Health University Hospital, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, 470-1192, Japan
| | - Yoshihiro Ida
- Department of Radiology, Fujita Health University Hospital, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, 470-1192, Japan
| | - Masanao Kobayashi
- Faculty of Radiological Technology, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, 470-1192, Japan
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Stepusin EJ, Long DJ, Ficarrotta KR, Hintenlang DE, Bolch WE. Physical validation of a Monte Carlo-based, phantom-derived approach to computed tomography organ dosimetry under tube current modulation. Med Phys 2017; 44:5423-5432. [PMID: 28688151 DOI: 10.1002/mp.12461] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 06/26/2017] [Accepted: 06/30/2017] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To physically validate the accuracy of a Monte Carlo-based, phantom-derived methodology for computed tomography (CT) dosimetry that utilizes organ doses from precomputed axial scans and that accounts for tube current modulation (TCM). METHODS The output of a Toshiba Aquilion ONE CT scanner was modeled, based on physical measurement, in the Monte Carlo radiation transport code MCNPX (v2.70). CT examinations were taken of two anthropomorphic phantoms representing pediatric and adult patients (15-yr-old female and adult male) at various energies, in which physical organ dose measurements were made using optically stimulated luminescence dosimeters (OSLDs). These exams (chest-abdomen-pelvis) were modeled using organ dose data obtained from the computationally equivalent phantom of each anthropomorphic phantom. TCM was accounted for by weighting all organ dose contributions by both the relative attenuation of the phantom and the image-derived mA value (from the DICOM header) at the same z-extent (cranial-caudal direction) of the axial dose data. RESULTS The root mean squares of percent difference in organ dose when comparing the physical organ dose measurements to the computational estimates were 21.2, 12.1, and 15.1% for the uniform (no attenuation weighting), weighted (computationally derived), and image-based methodologies, respectively. CONCLUSIONS Overall, these data suggest that the Monte Carlo-based dosimetry presented in this work is viable for CT dosimetry. Additionally, for CT exams with TCM, local attenuation weighting of organ dose contributions from precomputed axial dosimetry libraries increases organ dose accuracy.
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Affiliation(s)
- Elliott J Stepusin
- J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, 32611-6131, USA
| | - Daniel J Long
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY, 10065, USA
| | - Kayla R Ficarrotta
- J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, 32611-6131, USA
| | - David E Hintenlang
- J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, 32611-6131, USA
| | - Wesley E Bolch
- J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, 32611-6131, USA
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Stepusin EJ, Long DJ, Marshall EL, Bolch WE. Assessment of different patient-to-phantom matching criteria applied in Monte Carlo-based computed tomography dosimetry. Med Phys 2017; 44:5498-5508. [PMID: 28777466 DOI: 10.1002/mp.12502] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 06/14/2017] [Accepted: 07/25/2017] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To quantify differences in computationally estimated computed tomography (CT) organ doses for patient-specific voxel phantoms to estimated organ doses in matched computational phantoms using different matching criteria. MATERIALS AND METHODS Fifty-two patient-specific computational voxel phantoms were created through CT image segmentation. In addition, each patient-specific phantom was matched to six computational phantoms of the same gender based, respectively, on age and gender (reference phantoms), height and weight, effective diameter (both central slice and exam range average), and water equivalent diameter (both central slice and exam range average). Each patient-specific phantom and matched computational phantom were then used to simulate six different torso examinations using a previously validated Monte Carlo CT dosimetry methodology that accounts for tube current modulation. Organ doses for each patient-specific phantom were then compared with the organ dose estimates of each of the matched phantoms. RESULTS Relative to the corresponding patient-specific phantoms, the root mean square of the difference in organ dose was 39.1%, 20.3%, 22.7%, 21.6%, 20.5%, and 17.6%, for reference, height and weight, effective diameter (central slice and scan average), and water equivalent diameter (central slice and scan average), respectively. The average magnitude of difference in organ dose was 24%, 14%, 16.9%, 16.2%, 14%, and 11.9%, respectively. CONCLUSION Overall, these data suggest that matching a patient to a computational phantom in a library is superior to matching to a reference phantom. Water equivalent diameter is the superior matching metric, but it is less feasible to implement in a clinical and retrospective setting. For these reasons, height-and-weight matching is an acceptable and reliable method for matching a patient to a member of a computational phantom library with regard to CT dosimetry.
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Affiliation(s)
- Elliott J Stepusin
- J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, 32611-6131, USA
| | - Daniel J Long
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY, 10065, USA
| | - Emily L Marshall
- J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, 32611-6131, USA
| | - Wesley E Bolch
- J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, 32611-6131, USA
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Two examples of indication specific radiation dose calculations in dental CBCT and Multidetector CT scanners. Phys Med 2017; 41:71-77. [DOI: 10.1016/j.ejmp.2017.03.027] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 02/24/2017] [Accepted: 03/29/2017] [Indexed: 11/22/2022] Open
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Borrego D, Siragusa DA, Balter S, Bolch WE. A hybrid phantom system for patient skin and organ dosimetry in fluoroscopically guided interventions. Med Phys 2017. [PMID: 28636805 DOI: 10.1002/mp.12419] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The purpose of this study was to investigate calibrations for improved estimates of skin dose and to develop software for computing absorbed organ doses for fluoroscopically guided interventions (FGIs) with the use of radiation dose structured reports (RDSR) and the UF/NCI family of hybrid computational phantoms. METHODS AND MATERIALS Institutional review board approval was obtained for this retrospective study in which ten RDSRs were selected for their high cumulative reference air kerma values. Skin doses were computed using the University of Florida's rapid in-clinic peak skin dose algorithm (or UF-RIPSA). Kerma-area product (KAP) meter calibrations and attenuation of the tabletop with pad were incorporated into the UF-RIPSA. To compute absorbed organ doses the RDSRs were coupled with software to develop Monte Carlo input decks for each irradiation event. The effects of spectrum matching were explored by modeling (a) a polychromatic x-ray energy beam made to match measured first half-value layers of aluminum, (b) an unmatched spectrum, (c) and a mono-energetic beam equivalent to the effective x-ray energy. The authors also considered the practicality of computing organ doses for each irradiation event within a RDSR. RESULTS The KAP meter is highly dependent on the quality of the x-ray spectra. Monte Carlo based attenuation coefficients for configurations in which the beam is transmitted through the tabletop with pad reduced the amount by which the software overestimated skin doses. For absorbed organ dose computations, the average ratios of computed organ doses for a non-fitted to fitted spectrum and effective energy to fitted spectrum were 0.45 and 0.03, respectively. Monte Carlo simulations on average took 38 min per patient. All in-field organ tallies converged with a relative error of less than 1% and out-of-field organs tallies within 10% relative error. CONCLUSIONS This work details changes to the UF-RIPSA software that include an expanded library of computational phantoms, attenuation coefficients for tabletop with pad, and calibration curves for the KAP meter. For the computation of absorbed organ dose, it is possible to model each irradiation event separately on a patient-dependent model that best morphometrically matches the patient, thus providing a full report of internal organ doses for FGI patients.
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Affiliation(s)
- David Borrego
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, 32611-6131, USA
| | - Daniel A Siragusa
- Radiology, Division of Vascular Interventional Radiology, University of Florida, Jacksonville, FL, 32209, USA
| | - Stephen Balter
- Departments of Radiology and Medicine, Columbia University Medical Center, New York, NY, 10032, USA
| | - Wesley E Bolch
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, 32611-6131, USA
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McMillan K, Bostani M, Cagnon CH, Yu L, Leng S, McCollough CH, McNitt-Gray MF. Estimating patient dose from CT exams that use automatic exposure control: Development and validation of methods to accurately estimate tube current values. Med Phys 2017; 44:4262-4275. [PMID: 28477342 DOI: 10.1002/mp.12314] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 04/04/2017] [Accepted: 04/09/2017] [Indexed: 02/05/2023] Open
Abstract
PURPOSE The vast majority of body CT exams are performed with automatic exposure control (AEC), which adapts the mean tube current to the patient size and modulates the tube current either angularly, longitudinally or both. However, most radiation dose estimation tools are based on fixed tube current scans. Accurate estimates of patient dose from AEC scans require knowledge of the tube current values, which is usually unavailable. The purpose of this work was to develop and validate methods to accurately estimate the tube current values prescribed by one manufacturer's AEC system to enable accurate estimates of patient dose. METHODS Methods were developed that took into account available patient attenuation information, user selected image quality reference parameters and x-ray system limits to estimate tube current values for patient scans. Methods consistent with AAPM Report 220 were developed that used patient attenuation data that were: (a) supplied by the manufacturer in the CT localizer radiograph and (b) based on a simulated CT localizer radiograph derived from image data. For comparison, actual tube current values were extracted from the projection data of each patient. Validation of each approach was based on data collected from 40 pediatric and adult patients who received clinically indicated chest (n = 20) and abdomen/pelvis (n = 20) scans on a 64 slice multidetector row CT (Sensation 64, Siemens Healthcare, Forchheim, Germany). For each patient dataset, the following were collected with Institutional Review Board (IRB) approval: (a) projection data containing actual tube current values at each projection view, (b) CT localizer radiograph (topogram) and (c) reconstructed image data. Tube current values were estimated based on the actual topogram (actual-topo) as well as the simulated topogram based on image data (sim-topo). Each of these was compared to the actual tube current values from the patient scan. In addition, to assess the accuracy of each method in estimating patient organ doses, Monte Carlo simulations were performed by creating voxelized models of each patient, identifying key organs and incorporating tube current values into the simulations to estimate dose to the lungs and breasts (females only) for chest scans and the liver, kidney, and spleen for abdomen/pelvis scans. Organ doses from simulations using the actual tube current values were compared to those using each of the estimated tube current values (actual-topo and sim-topo). RESULTS When compared to the actual tube current values, the average error for tube current values estimated from the actual topogram (actual-topo) and simulated topogram (sim-topo) was 3.9% and 5.8% respectively. For Monte Carlo simulations of chest CT exams using the actual tube current values and estimated tube current values (based on the actual-topo and sim-topo methods), the average differences for lung and breast doses ranged from 3.4% to 6.6%. For abdomen/pelvis exams, the average differences for liver, kidney, and spleen doses ranged from 4.2% to 5.3%. CONCLUSIONS Strong agreement between organ doses estimated using actual and estimated tube current values provides validation of both methods for estimating tube current values based on data provided in the topogram or simulated from image data.
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Affiliation(s)
- Kyle McMillan
- Biomedical Physics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Maryam Bostani
- Biomedical Physics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - Christopher H Cagnon
- Biomedical Physics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
| | - Lifeng Yu
- Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Shuai Leng
- Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
| | | | - Michael F McNitt-Gray
- Biomedical Physics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.,Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA
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Carver DE, Kost SD, Fraser ND, Segars WP, Pickens DR, Price RR, Stabin MG. Realistic phantoms to characterize dosimetry in pediatric CT. Pediatr Radiol 2017; 47:691-700. [PMID: 28283725 PMCID: PMC5420344 DOI: 10.1007/s00247-017-3805-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 12/07/2016] [Accepted: 02/10/2017] [Indexed: 10/24/2022]
Abstract
BACKGROUND The estimation of organ doses and effective doses for children receiving CT examinations is of high interest. Newer, more realistic anthropomorphic body models can provide information on individual organ doses and improved estimates of effective dose. MATERIALS AND METHODS Previously developed body models representing 50th-percentile individuals at reference ages (newborn, 1, 5, 10 and 15 years) were modified to represent 10th, 25th, 75th and 90th height percentiles for both genders and an expanded range of ages (3, 8 and 13 years). We calculated doses for 80 pediatric reference phantoms from simulated chest-abdomen-pelvis exams on a model of a Philips Brilliance 64 CT scanner. Individual organ and effective doses were normalized to dose-length product (DLP) and fit as a function of body diameter. RESULTS We calculated organ and effective doses for 80 reference phantoms and plotted them against body diameter. The data were well fit with an exponential function. We found DLP-normalized organ dose to correlate strongly with body diameter (R2>0.95 for most organs). Similarly, we found a very strong correlation with body diameter for DLP-normalized effective dose (R2>0.99). Our results were compared to other studies and we found average agreement of approximately 10%. CONCLUSION We provide organ and effective doses for a total of 80 reference phantoms representing normal-stature children ranging in age and body size. This information will be valuable in replacing the types of vendor-reported doses available. These data will also permit the recording and tracking of individual patient doses. Moreover, this comprehensive dose database will facilitate patient matching and the ability to predict patient-individualized dose prior to examination.
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Affiliation(s)
- Diana E Carver
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, TN, 37232, USA.
| | - Susan D Kost
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, TN, 37232, USA
| | - Nicholas D Fraser
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, TN, 37232, USA
| | - W Paul Segars
- Carl E. Ravin Advanced Imaging Laboratories, Duke University, Hock Plaza Suite 302, 2424 Erwin Road, Durham, NC, 27705, USA
| | - David R Pickens
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, TN, 37232, USA
| | - Ronald R Price
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, TN, 37232, USA
| | - Michael G Stabin
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, TN, 37232, USA
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Bostani M, McMillan K, Lu P, Kim GHJ, Cody D, Arbique G, Greenberg SB, DeMarco JJ, Cagnon CH, McNitt-Gray MF. Estimating organ doses from tube current modulated CT examinations using a generalized linear model. Med Phys 2017; 44:1500-1513. [PMID: 28112399 DOI: 10.1002/mp.12119] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 12/19/2016] [Accepted: 01/15/2017] [Indexed: 12/16/2022] Open
Abstract
PURPOSE Currently, available Computed Tomography dose metrics are mostly based on fixed tube current Monte Carlo (MC) simulations and/or physical measurements such as the size specific dose estimate (SSDE). In addition to not being able to account for Tube Current Modulation (TCM), these dose metrics do not represent actual patient dose. The purpose of this study was to generate and evaluate a dose estimation model based on the Generalized Linear Model (GLM), which extends the ability to estimate organ dose from tube current modulated examinations by incorporating regional descriptors of patient size, scanner output, and other scan-specific variables as needed. METHODS The collection of a total of 332 patient CT scans at four different institutions was approved by each institution's IRB and used to generate and test organ dose estimation models. The patient population consisted of pediatric and adult patients and included thoracic and abdomen/pelvis scans. The scans were performed on three different CT scanner systems. Manual segmentation of organs, depending on the examined anatomy, was performed on each patient's image series. In addition to the collected images, detailed TCM data were collected for all patients scanned on Siemens CT scanners, while for all GE and Toshiba patients, data representing z-axis-only TCM, extracted from the DICOM header of the images, were used for TCM simulations. A validated MC dosimetry package was used to perform detailed simulation of CT examinations on all 332 patient models to estimate dose to each segmented organ (lungs, breasts, liver, spleen, and kidneys), denoted as reference organ dose values. Approximately 60% of the data were used to train a dose estimation model, while the remaining 40% was used to evaluate performance. Two different methodologies were explored using GLM to generate a dose estimation model: (a) using the conventional exponential relationship between normalized organ dose and size with regional water equivalent diameter (WED) and regional CTDIvol as variables and (b) using the same exponential relationship with the addition of categorical variables such as scanner model and organ to provide a more complete estimate of factors that may affect organ dose. Finally, estimates from generated models were compared to those obtained from SSDE and ImPACT. RESULTS The Generalized Linear Model yielded organ dose estimates that were significantly closer to the MC reference organ dose values than were organ doses estimated via SSDE or ImPACT. Moreover, the GLM estimates were better than those of SSDE or ImPACT irrespective of whether or not categorical variables were used in the model. While the improvement associated with a categorical variable was substantial in estimating breast dose, the improvement was minor for other organs. CONCLUSIONS The GLM approach extends the current CT dose estimation methods by allowing the use of additional variables to more accurately estimate organ dose from TCM scans. Thus, this approach may be able to overcome the limitations of current CT dose metrics to provide more accurate estimates of patient dose, in particular, dose to organs with considerable variability across the population.
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Affiliation(s)
- Maryam Bostani
- Departments of Biomedical Physics and Radiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, 90024, USA
| | - Kyle McMillan
- Department of Radiology, Mayo Clinic, CT Clinical Innovation Center, Rochester, MN, 55905, USA
| | - Peiyun Lu
- Departments of Biomedical Physics and Radiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, 90024, USA
| | - Grace Hyun J Kim
- Departments of Biomedical Physics and Radiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, 90024, USA
| | - Dianna Cody
- Department of Imaging Physics, University of Texas, MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Gary Arbique
- UT Southwestern Medical Center, Dallas, TX, 75390, USA
| | - S Bruce Greenberg
- Department of Radiology, Arkansas Children's Hospital, Little Rock, AR, 72202, USA
| | - John J DeMarco
- Department of Radiation Oncology, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA
| | - Chris H Cagnon
- Departments of Biomedical Physics and Radiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, 90024, USA
| | - Michael F McNitt-Gray
- Departments of Biomedical Physics and Radiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, 90024, USA
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Fujii K, Nomura K, Muramatsu Y, Obara S, Akahane K, Kusumoto M. Organ Dose Evaluations Based on Monte Carlo Simulation for CT Examinations Using Tube Current Modulation. RADIATION PROTECTION DOSIMETRY 2017; 174:387-394. [PMID: 27342451 DOI: 10.1093/rpd/ncw144] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 05/25/2016] [Indexed: 06/06/2023]
Abstract
The aims of this study were to estimate tube current values for each X-ray projection angle used in adult chest computed tomography (CT) and abdomen-pelvis CT examinations with tube current modulation (TCM) and to validate organ doses determined using Monte Carlo (MC) simulations through comparisons with the doses measured using in-phantom dosimetry. For dose simulations, dose distribution images were obtained by inputting the geometry of a CT scanner, scan parameters including estimated TCM curves and CT images of an adult anthropomorphic phantom into MC simulation software. Organ doses were then determined from the dose distribution images. For dose measurements, organ doses were evaluated using radio-photoluminescence glass dosemeters located at various organ positions within the phantom. Relative differences between the simulated and measured organ doses were -2.5 to 11.0% and -1.5 to 10.5% for organs in chest and abdomen-pelvis CT scan ranges, respectively. Thus, the simulated and measured doses agreed well.
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Affiliation(s)
- K Fujii
- Department of Radiological Sciences, Nagoya University Graduate School of Medicine, 1-1-20, Daikominami, Higashi-ku, Nagoya, Japan
- Department of Radiology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, Japan
| | - K Nomura
- Department of Radiology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, Japan
| | - Y Muramatsu
- Department of Radiology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, Japan
| | - S Obara
- Department of Radiation Measurement and Dose Assessment, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, Japan
| | - K Akahane
- Department of Radiation Measurement and Dose Assessment, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, Japan
| | - M Kusumoto
- Department of Radiology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, Japan
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44
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Gao Y, Quinn B, Mahmood U, Long D, Erdi Y, St. Germain J, Pandit-Taskar N, Xu XG, Bolch WE, Dauer LT. A comparison of pediatric and adult CT organ dose estimation methods. BMC Med Imaging 2017; 17:28. [PMID: 28446130 PMCID: PMC5406971 DOI: 10.1186/s12880-017-0199-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 04/11/2017] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Computed Tomography (CT) contributes up to 50% of the medical exposure to the United States population. Children are considered to be at higher risk of developing radiation-induced tumors due to the young age of exposure and increased tissue radiosensitivity. Organ dose estimation is essential for pediatric and adult patient cancer risk assessment. The objective of this study is to validate the VirtualDose software in comparison to currently available software and methods for pediatric and adult CT organ dose estimation. METHODS Five age groups of pediatric patients and adult patients were simulated by three organ dose estimators. Head, chest, abdomen-pelvis, and chest-abdomen-pelvis CT scans were simulated, and doses to organs both inside and outside the scan range were compared. For adults, VirtualDose was compared against ImPACT and CT-Expo. For pediatric patients, VirtualDose was compared to CT-Expo and compared to size-based methods from literature. Pediatric to adult effective dose ratios were also calculated with VirtualDose, and were compared with the ranges of effective dose ratios provided in ImPACT. RESULTS In-field organs see less than 60% difference in dose between dose estimators. For organs outside scan range or distributed organs, a five times' difference can occur. VirtualDose agrees with the size-based methods within 20% difference for the organs investigated. Between VirtualDose and ImPACT, the pediatric to adult ratios for effective dose are compared, and less than 21% difference is observed for chest scan while more than 40% difference is observed for head-neck scan and abdomen-pelvis scan. For pediatric patients, 2 cm scan range change can lead to a five times dose difference in partially scanned organs. CONCLUSIONS VirtualDose is validated against CT-Expo and ImPACT with relatively small discrepancies in dose for organs inside scan range, while large discrepancies in dose are observed for organs outside scan range. Patient-specific organ dose estimation is possible using the size-based methods, and VirtualDose agrees with size-based method for the organs investigated. Careful range selection for CT protocols is necessary for organ dose optimization for pediatric and adult patients.
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Affiliation(s)
- Yiming Gao
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, Box 84, New York, NY 10065 USA
| | - Brian Quinn
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, Box 84, New York, NY 10065 USA
| | - Usman Mahmood
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, Box 84, New York, NY 10065 USA
| | - Daniel Long
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, Box 84, New York, NY 10065 USA
| | - Yusuf Erdi
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, Box 84, New York, NY 10065 USA
| | - Jean St. Germain
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, Box 84, New York, NY 10065 USA
| | - Neeta Pandit-Taskar
- Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065 USA
| | - X. George Xu
- Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 USA
| | - Wesley E. Bolch
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611 USA
| | - Lawrence T. Dauer
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, Box 84, New York, NY 10065 USA
- Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065 USA
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45
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Muryn JS, Morgan AG, Liptak CL, Dong FF, Segars WP, Primak AN, Li X. Analysis of uncertainties in Monte Carlo simulated organ and effective dose in chest CT: scanner- and scan-related factors. Phys Med Biol 2017; 62:3175-3203. [DOI: 10.1088/1361-6560/aa60d7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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46
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Yang K, Li X, George Xu X, Liu B. Direct and fast measurement of CT beam filter profiles with simultaneous geometrical calibration. Med Phys 2017; 44:57-70. [PMID: 28102951 DOI: 10.1002/mp.12024] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 11/03/2016] [Accepted: 11/12/2016] [Indexed: 01/28/2023] Open
Abstract
PURPOSE To accurately measure the beam filter profiles from a variety of CT scanner models and to provide reference data for Monte Carlo simulations of CT scanners. METHODS This study proposed a new method to measure CT beam filter profiles using a linear-array x-ray detector (X-Scan 0.8f3-512; Detection Technology Inc., Espoo, Finland) under gantry rotation mode. A robust geometrical calibration approach was developed to determine key geometrical parameters by considering the x-ray focal spot location relative to the linear-array detector and the gantry's angular increment at each acquisition point. CT beam intensity profiles were synthesized from continuously measured data during a 10° gantry rotation range with calibrated detector response and system geometry information. Relative transmission profiles of nineteen sets of beam filters were then derived for nine different CT scanner models from three different manufacturers. Equivalent aluminum thickness profiles of these beam filters were determined by analytical calculation using the Spektr Matlab software package to match the measured transmission profiles. Three experiments were performed to validate the accuracy of the geometrical calibration, detector response modeling, and the derived equivalent aluminum thickness profiles. RESULTS The beam intensity profiles measured from gantry rotation mode showed very good agreement with those measured with gantry stationary mode, with a maximal difference of 3%. The equivalent aluminum thickness determined by this proposed method agreed well with what was measured by an ion chamber, with a mean difference of 0.4%. The determined HVL profiles matched well with data from a previous study (max difference of 4.7%). CONCLUSIONS An accurate and robust method to directly measure profiles from a broad list of beam filters and CT scanner models was developed, implemented, and validated. Useful reference data was provided for future research on CT system modeling.
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Affiliation(s)
- Kai Yang
- Division of Diagnostic Imaging Physics, Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA
| | - Xinhua Li
- Division of Diagnostic Imaging Physics, Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA
| | - X George Xu
- Nuclear Engineering Program, Rensselaer Polytechnic Institute, Troy, New York, 12180, USA
| | - Bob Liu
- Division of Diagnostic Imaging Physics, Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA
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Ming X, Feng Y, Liu R, Yang C, Zhou L, Zhai H, Deng J. A measurement-based generalized source model for Monte Carlo dose simulations of CT scans. Phys Med Biol 2017; 62:1759-1776. [PMID: 28079526 DOI: 10.1088/1361-6560/aa5911] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The goal of this study is to develop a generalized source model for accurate Monte Carlo dose simulations of CT scans based solely on the measurement data without a priori knowledge of scanner specifications. The proposed generalized source model consists of an extended circular source located at x-ray target level with its energy spectrum, source distribution and fluence distribution derived from a set of measurement data conveniently available in the clinic. Specifically, the central axis percent depth dose (PDD) curves measured in water and the cone output factors measured in air were used to derive the energy spectrum and the source distribution respectively with a Levenberg-Marquardt algorithm. The in-air film measurement of fan-beam dose profiles at fixed gantry was back-projected to generate the fluence distribution of the source model. A benchmarked Monte Carlo user code was used to simulate the dose distributions in water with the developed source model as beam input. The feasibility and accuracy of the proposed source model was tested on a GE LightSpeed and a Philips Brilliance Big Bore multi-detector CT (MDCT) scanners available in our clinic. In general, the Monte Carlo simulations of the PDDs in water and dose profiles along lateral and longitudinal directions agreed with the measurements within 4%/1 mm for both CT scanners. The absolute dose comparison using two CTDI phantoms (16 cm and 32 cm in diameters) indicated a better than 5% agreement between the Monte Carlo-simulated and the ion chamber-measured doses at a variety of locations for the two scanners. Overall, this study demonstrated that a generalized source model can be constructed based only on a set of measurement data and used for accurate Monte Carlo dose simulations of patients' CT scans, which would facilitate patient-specific CT organ dose estimation and cancer risk management in the diagnostic and therapeutic radiology.
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Affiliation(s)
- Xin Ming
- Department of Biomedical Engineering, Tianjin University, Tianjin, People's Republic of China
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48
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Ohno T, Araki F, Onizuka R, Hatemura M, Shimonobou T, Sakamoto T, Okumura S, Ideguchi D, Honda K, Kawata K. Comparison of dosimetric properties among four commercial multi-detector computed tomography scanners. Phys Med 2017; 35:50-58. [DOI: 10.1016/j.ejmp.2017.02.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 02/09/2017] [Accepted: 02/11/2017] [Indexed: 10/20/2022] Open
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As Low Dose as Sufficient Quality: Optimization of Cone-beam Computed Tomographic Scanning Protocol for Tooth Autotransplantation Planning and Follow-up in Children. J Endod 2017; 43:210-217. [DOI: 10.1016/j.joen.2016.10.022] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 10/11/2016] [Accepted: 10/16/2016] [Indexed: 12/11/2022]
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50
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Stepusin EJ, Maynard MR, O'Reilly SE, Redzovic S, Bolch WE, Hintenlang DE, Borak TB. Organ Doses to Airline Passengers Screened by X-Ray Backscatter Imaging Systems. Radiat Res 2017; 187:229-240. [PMID: 28118113 DOI: 10.1667/rr4516.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Advanced imaging technologies (AIT) are being developed for passenger airline transportation. They are designed to provide enhanced security benefits by identifying objects on passengers that would not be detected by methodologies now used for routine surveillance. X-ray backscatter imaging is one AIT system being considered. Since this technology is based on scanning passengers with ionizing radiation, concern has been raised relating to the health risks associated with these exposures. Recommendations for standards of radiation safety have been proposed by the American National Standards Institute published in ANSI/HPS N43.17-2009. A Monte Carlo based methodology for estimating organ doses received from an X-ray backscatter AIT system is presented. Radiological properties of a reference scanner including beam intensity, geometry and energy spectra were modeled based on previous studies and physical measurements. These parameters were incorporated into a Monte Carlo source subroutine and validated with comparison of simulated versus measured data. One extension of this study was to calculate organ and effective dose on a wide range of potential passengers. Computational phantoms with realistic morphologies were used including adults of 5th, 25th, 50th, 75th and 95th percentile weight, children of 5th, 50th and 95th percentile weight, and the developing fetus of 15, 25, and 38 weeks after conception. Additional sensitivity studies were performed to evaluate effects of passenger positioning within the scanner, energy spectrum and beam geometry, as well as failure mode analyses. Results for routine operations yielded a maximum effective dose to the adult and pediatric passengers of 15 and 25 nSv per screen, respectively. The developing fetus received a maximum organ dose and whole body dose of 16 nGy and 8.5 nGy per screen, respectively. The sensitivity analyses indicated that variations in positioning, energy spectra, and beam geometry yielded a range of effective doses per screen that were an order of magnitude below the ANSI recommendation.
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Affiliation(s)
- Elliott J Stepusin
- a J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611-6131 and
| | - Matthew R Maynard
- a J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611-6131 and
| | - Shannon E O'Reilly
- a J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611-6131 and
| | - Sadije Redzovic
- a J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611-6131 and
| | - Wesley E Bolch
- a J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611-6131 and
| | - David E Hintenlang
- a J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611-6131 and
| | - Thomas B Borak
- b Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, Colorado 80523-1601
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