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Jansen JT, Shrimpton PC, Edyvean S. CT scanner-specific organ dose coefficients generated by Monte Carlo calculation for the ICRP adult male and female reference computational phantoms. Phys Med Biol 2022; 67. [PMID: 36317285 DOI: 10.1088/1361-6560/ac9e3d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 10/27/2022] [Indexed: 11/17/2022]
Abstract
Objective.Provide analyses of new organ dose coefficients (hereafter also referred to as normalized doses) for CT that have been developed to update the widely-utilized collection of data published 30 years ago in NRPB-SR250.Approach.In order to reflect changes in technology, and also ICRP recommendations concerning use of the computational phantoms adult male (AM) and adult female (AF), 102 series of new Monte Carlo simulations have been performed covering the range of operating conditions for 12 contemporary models of CT scanner from 4 manufacturers. Normalized doses (relative to free air on axis) have been determined for 39 organs, and for every 8 mm or 4.84 mm slab of AM and AF, respectively.Main results.Analyses of results confirm the significant influence (by up to a few tens of percent), on values of normalized organ (or contributions to effective dose (E103,phan)), for whole body exposure arising from selection of tube voltage and beam shaping filter. Use of partial (when available) rather than a Full fan beam reduced both organ and effective dose by up to 7%. Normalized doses to AF were larger than corresponding figures for AM by up to 30% for organs and by 10% forE103,phan. Additional simulations for whole body exposure have also demonstrated that: practical simplifications in the main modelling (point source, single slice thickness, neglect of patient couch and immobility of phantom arms) have sufficiently small (<5%) effect onE103,phan; mis-centring of the phantom away from the axis of rotation by 5 mm (in any direction) leads to changes in normalized organ dose andE103,phanby up to 20% and 6%, respectively; and angular tube current modulation can result in reductions by up to 35% and <15% in normalized organ dose andE103,phan, respectively, for 100% cosine variation.Significance.These analyses help advance understanding of the influence of operational scanner settings on organ dose coefficients for contemporary CT, in support of improved patient protection. The results will allow the future development of a new dose estimation tool.
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Affiliation(s)
- Jan Tm Jansen
- Radiation, Chemical and Environmental Hazards, United Kingdom Health Security Agency, Chilton, Didcot, Oxfordshire, OX11 0RQ, United Kingdom
| | - Paul C Shrimpton
- Radiation, Chemical and Environmental Hazards, United Kingdom Health Security Agency, Chilton, Didcot, Oxfordshire, OX11 0RQ, United Kingdom.,Retired, United Kingdom
| | - Sue Edyvean
- Radiation, Chemical and Environmental Hazards, United Kingdom Health Security Agency, Chilton, Didcot, Oxfordshire, OX11 0RQ, United Kingdom
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Abdulkadir MK, Shuaib IL, Achuthan A, Nasirudin RA, Samsudin AHZ, Osman ND. ESTIMATION OF PEDIATRIC DOSE DESCRIPTORS ADAPTED TO INDIVIDUAL SPECIFIC SIZE FROM CT EXAMINATIONS. RADIATION PROTECTION DOSIMETRY 2022; 198:1292-1302. [PMID: 35896148 DOI: 10.1093/rpd/ncac163] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 06/15/2022] [Accepted: 07/01/2022] [Indexed: 06/15/2023]
Abstract
Clinical challenges in pediatrics dose estimation by the displayed computed tomography (CT) dose indices may lead to inaccuracy, and thus size-specific dose estimate (SSDE) is introduced for better-personalized dose estimation. This study aims to estimate pediatric dose adapted to specific size. This retrospective study involved pediatric population aged 0-12 y. SSDE was derived from scanner reported volume CT dose index (CTDIvol), based on individual effective diameter (Deff) with corresponding size correction factors. The correlations of Deff with other associated factors such as age, exposure setting, CTDIvol and SSDE were also studied. The average Deff of Malaysian pediatric was smaller than reference phantom size (confidence interval, CI = 0.28, mean = 14.79) and (CI = 0.51, mean = 16.33) for head and abdomen, respectively. These have led to underestimation of pediatric dose as SSDE was higher than displayed CTDIvol. The percentage differences were statistically significant (p < .001) ranged from 0 to 17% and 37 to 60% for head and abdominal CT, respectively. In conclusion, the clinical implementation of SSDE in pediatric CT imaging is highly relevant to reduce radiation risk.
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Affiliation(s)
- Muhammad Kabir Abdulkadir
- Advanced Medical and Dental Institute, Universiti Sains Malaysia, Kepala Batas, 13200 Penang, Malaysia
- Department of Medical Radiography, Faculty of Basic Clinical Sciences, University of Ilorin, 240213 Ilorin, Nigeria
| | - Ibrahim Lutfi Shuaib
- Advanced Medical and Dental Institute, Universiti Sains Malaysia, Kepala Batas, 13200 Penang, Malaysia
| | - Anusha Achuthan
- Advanced Medical and Dental Institute, Universiti Sains Malaysia, Kepala Batas, 13200 Penang, Malaysia
- School of Computer Science, Universiti Sains Malaysia, Minden, 11800 Penang, Malaysia
| | - Radin A Nasirudin
- Advanced Medical and Dental Institute, Universiti Sains Malaysia, Kepala Batas, 13200 Penang, Malaysia
| | - Ahmad Hadif Zaidin Samsudin
- Department of Radiology, School of Medical Sciences, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
| | - Noor Diyana Osman
- Advanced Medical and Dental Institute, Universiti Sains Malaysia, Kepala Batas, 13200 Penang, Malaysia
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He J, Dong G, Deng Y, He J, Xiu Z, Feng F. Comparison of Application Value of Different Radiation Dose Evaluation Methods in Evaluating Radiation Dose of Adult Thoracic and Abdominal CT Scan. Front Surg 2022; 9:860968. [PMID: 35402481 PMCID: PMC8990916 DOI: 10.3389/fsurg.2022.860968] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 02/22/2022] [Indexed: 11/13/2022] Open
Abstract
Objective To explore the differences among volumetric CT dose index (CTDIvol), body-specific dose assessment (SSDEED) based on effective diameter (ED), and SSDEWED based on water equivalent diameter (WED) in evaluating the radiation dose of adult thoracic and abdominal CT scanning. Methods From January 2021 to October 2021, enhanced chest CT scans of 100 patients and enhanced abdomen CT scans of another 100 patients were collected. According to the body mass index (BMI), they can be divided into groups A and D (BMI < 20 kg/m2), groups B and E (20 kg/m2 ≤ BMI ≤ 24.9 kg/m2), and groups C and F (BMI > 24.9 kg/m2). The CTDIvol, anteroposterior diameter (AP), and the left and rght diameter (LAT) of all the patients were recorded, and the ED, water equivalent diameter (WED), the conversion factor (f size,ED), (f size, WED), SSDEED, and SSDEWED were calculated. The differences were compared between the different groups. Results The AP, LAT, ED, and WED of groups B, E, C, and F were higher than those of groups A and D, and those of groups C and F were higher than those of groups B and E (P < 0.05). The f size,ED and f size, WED of groups B, E, C, and F are lower than those of groups A and D, and those of groups C and F are lower than those of groups B and E (P < 0.05). CTDIvol, SSDEED, and SSDEWED in groups B, E, C, and F are higher than those in groups A and D, and those in groups C and F are higher than those in groups B and E (p < 0.05). In the same group, patients with chest- and abdomen-enhanced have higher SSDEWED and SSDEED than CTDIvol, patients with chest-enhanced CT scans have higher SSDEWED than SSDEED, and patients with abdomen-enhanced CT scans have higher SSDEED than SSDEWED (P < 0.05). Conclusion CTDIvol and ED-based SSDEED underestimated the radiation dose of the subject exposed, where the patient was actually exposed to a greater dose. However, SSDEWED based on WED considers better the difference in patient size and attenuation characteristics, and can more accurately evaluate the radiation dose received by patients of different sizes during the chest and abdomen CT scan.
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Affiliation(s)
- Jimin He
- Department of Radiology, The First People's Hospital of Longquanyi District, Chengdu, China
| | - Guanwei Dong
- Department of Radiology, The First People's Hospital of Longquanyi District, Chengdu, China
| | - Yi Deng
- Department of Rehabilitation, The First People's Hospital of Longquanyi District, Chengdu, China
| | - Jun He
- Department of Radiology, The First People's Hospital of Longquanyi District, Chengdu, China
| | - ZhiGang Xiu
- Department of Radiology, The First People's Hospital of Longquanyi District, Chengdu, China
| | - Fanzi Feng
- Department of Radiology, The First People's Hospital of Longquanyi District, Chengdu, China
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Estimating Specific Patient Organ Dose for Chest CT Examinations with Monte Carlo Method. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11198961] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Purpose: The purpose of this study was to preliminarily estimate patient-specific organ doses in chest CT examinations for Chinese adults, and to investigate the effect of patient size on organ doses. Methods: By considering the body-size and body-build effects on the organ doses and taking the mid-chest water equivalent diameter (WED) as a body-size indicator, the chest scan images of 18 Chinese adults were acquired on a multi-detector CT to generate the regional voxel models. For each patient, the lungs, heart, and breasts (glandular breast tissues for both breasts) were segmented, and other organs were semi-automated segmented based on their HU values. The CT scanner and patient models simulated by MCNPX 2.4.0 software (Los Alamos National LaboratoryLos Alamos, USA) were used to calculate lung, breast, and heart doses. CTDIvol values were used to normalize simulated organ doses, and the exponential estimation model between the normalized organ dose and WED was investigated. Results: Among the 18 patients in this study, the simulated doses of lung, heart, and breast were 18.15 ± 2.69 mGy, 18.68 ± 2.87 mGy, and 16.11 ± 3.08 mGy, respectively. Larger patients received higher organ doses than smaller ones due to the higher tube current used. The ratios of lung, heart, and breast doses to the CTDIvol were 1.48 ± 0.22, 1.54 ± 0.20, and 1.41 ± 0.13, respectively. The normalized organ doses of all the three organs decreased with the increase in WED, and the normalized doses decreased more obviously in the lung and the heart than that in the breasts. Conclusions: The output of CT scanner under ATCM is positively related to the attenuation of patients, larger-size patients receive higher organ doses. The organ dose normalized by CTDIvol was negatively correlated with patient size. The organ doses could be estimated by using the indicated CTDIvol combined with the estimated WED.
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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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Yang Y, Zhuo W, Chen B, Lu S, Zhou P, Ren W, Liu H. A new phantom developed to test the ATCM performance of chest CT scanners. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2021; 41:349-359. [PMID: 33862608 DOI: 10.1088/1361-6498/abf900] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 04/16/2021] [Indexed: 06/12/2023]
Abstract
In this study, a new ATCM phantom was developed to test the performance of the automatic tube current modulation (ATCM) of computed tomography (CT) scanners.. Based on the Chinese reference man and Monte Carlo simulations of x-ray attenuation, a more realistic ATCM phantom made of polymethyl methacrylate was developed. The phantom has a length of 20 cm, and it can be used to measure the dose profile along the central axis using 19 real-time MOSFET detectors. The image noise can be calculated slice by slice in the phantom's center. Test experiments showed that the phantom could initiate tube current modulation under different modulation levels of CT scans, and the actual effects of ATCM could be evaluated with the aid of the dose profile measurements. Using the measured dose profiles and image noise, the preferred dose can easily be identified from a choice of different modulation levels. The new phantom developed in this study can be used to test the ATCM performance of CT scanners, and is useful for further studies of the optimization of CT scan protocols with ATCM.
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Affiliation(s)
- Yang Yang
- Institute of Radiation Medicine, Fudan University, Shanghai 200032,People's Republic of China
| | - Weihai Zhuo
- Institute of Radiation Medicine, Fudan University, Shanghai 200032,People's Republic of China
| | - Bo Chen
- Institute of Radiation Medicine, Fudan University, Shanghai 200032,People's Republic of China
| | - Shunqi Lu
- Institute of Radiation Medicine, Fudan University, Shanghai 200032,People's Republic of China
| | - Pei Zhou
- Shanghai United Imaging Healthcare, Shanghai 201807, People's Republic of China
| | - Wenliang Ren
- Shanghai United Imaging Healthcare, Shanghai 201807, People's Republic of China
| | - Haikuan Liu
- Institute of Radiation Medicine, Fudan University, Shanghai 200032,People's Republic of China
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7
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Radiation dose monitoring in computed tomography: Status, options and limitations. Phys Med 2020; 79:1-15. [DOI: 10.1016/j.ejmp.2020.08.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 07/21/2020] [Accepted: 08/19/2020] [Indexed: 02/02/2023] Open
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Gharbi S, Labidi S, Mars M. AUTOMATIC BRAIN DOSE ESTIMATION IN COMPUTED TOMOGRAPHY USING PATIENT DICOM IMAGES. RADIATION PROTECTION DOSIMETRY 2020; 188:536-542. [PMID: 32043150 DOI: 10.1093/rpd/ncaa006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 12/03/2019] [Accepted: 01/13/2020] [Indexed: 06/10/2023]
Abstract
This study aims to develop an Automatic Brain Dose Estimation (ABDE) methodology for head computed tomography examinations. The ABDE is to be applied first to an anthropomorphic Alderson phantom to obtain a Correction factor (Cf) between the ABDE and the direct absorbed brain dose using dosemeters positioned within the anthropomorphic phantom. Then, in order to estimate the correct brain dose for patient, the Cf was multiplied by the mean ABDE values for each patient. Results were compared to those registered with a mathematical simulation phantom using CT-Expo V 2.4 software. Results showed no significant difference between the correct ABDE values and the CT-Expo values with a mean percent difference of 2.54 ± 0.01%. In conclusion, ABDE yields a correct estimation of brain dose, taking into account the size and attenuation of the irradiated region. Thus, it is clinically recommended for accurate patient brain dose assessment.
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Affiliation(s)
- Souha Gharbi
- Université Tunis EL Manar, Institut Supérieur des Technologies Médicales de Tunis, Laboratoire de recherche de Biophysique et de Technologies Médicales, 9, Avenue du Docteur Z. Essafi, Tunis 1006, Tunisia
| | - Salam Labidi
- Université Tunis EL Manar, Institut Supérieur des Technologies Médicales de Tunis, Laboratoire de recherche de Biophysique et de Technologies Médicales, 9, Avenue du Docteur Z. Essafi, Tunis 1006, Tunisia
| | - Mokhtar Mars
- Université Tunis EL Manar, Institut Supérieur des Technologies Médicales de Tunis, Laboratoire de recherche de Biophysique et de Technologies Médicales, 9, Avenue du Docteur Z. Essafi, Tunis 1006, Tunisia
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Zhang D, Liu X, Duan X, Bankier AA, Rong J, Palmer MR. Estimating patient water equivalent diameter from CT localizer images - A longitudinal and multi-institutional study of the stability of calibration parameters. Med Phys 2020; 47:2139-2149. [PMID: 32086943 DOI: 10.1002/mp.14102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 02/07/2020] [Accepted: 02/12/2020] [Indexed: 11/06/2022] Open
Abstract
PURPOSE Water equivalent diameter (WED) is a robust patient-size descriptor. Localizer-based WED estimation is less sensitive to truncation errors resulting from limited field of view, and produces WED estimates at different locations within one localizer radiograph, prior to the initiation of axial scans. This method is considered difficult to implement by the clinical community due to the necessary calibration between localizer pixel values (LPV) and attenuation, and the unknown stability of calibration results across scanners and over time. We investigated the stability of calibration results across 25 computed tomography (CT) scanners from three medical centers, and their stability over 3 ∼ 29 months for 14 of those scanners. METHODS Localizer and axial images of ACR and body computed tomography dose index phantoms were acquired, using routine clinical techniques (120 kV and lateral localizers) on each of the 25 CT scanners: 8 GE scanners (CT750HD, VCT, and Revolution), 8 Siemens scanners (Definition AS, Force, Flash, and Edge), 5 Canon scanners (Aquilion-One, Aquilion-Prime80, and Aquilion-64), and 4 Philips scanners (iCT 256, iQon, and Ingenuity). By associating axial images with the corresponding localizer lines, the relationship between the scaled water equivalent area (WEA) and averaged LPV were established through regression analysis. RESULTS Linear relationships between the scaled WEA and the averaged LPV were observed in all 25 CT scanners ( R 2 > 0.999 ). Calibration parameters were similar for CT scanners from the same vendor: the coefficients of variation (COV) were ≤ 1% in all four vendor groups for the calibration slope, and < 7% for the intercept. By analyzing the deviation of WED resulted from errors in the calibration slope or intercept alone, we derived the tolerance ranges for the slope or intercept for a given WED error level. The variation of slope and intercept from different CT scanners of the same vendor introduced <±2.5% error in the estimated WED for subjects of 20 and 30-cm WED. The calibration parameters remained stable over time, with the maximum deviations all within the boundary values that introduce ±2.5% error in the estimated WED for subjects of 20 and 30-cm WED. CONCLUSIONS The stability in calibration results among CT scanners of the same vendor and over time demonstrated the feasibility of implementing WED estimation for routine clinical use.
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Affiliation(s)
- Da Zhang
- Department of Radiology, Beth Israel Deaconess Medical Center, Boston, MA, 02215, USA.,Harvard Medical School, Boston, MA, 02215, USA
| | - Xinming Liu
- Department of Imaging Physics, MD Anderson Cancer Center, Houston, TX, 77230, USA
| | - Xinhui Duan
- Department of Radiology, UT Southwest Medical Center, Dallas, TX, 75390, USA
| | - Alexander A Bankier
- Department of Radiology, University of Massachusetts Medical School, Worcester, MA, 01655, USA
| | - John Rong
- Department of Imaging Physics, MD Anderson Cancer Center, Houston, TX, 77230, USA
| | - Matthew R Palmer
- Department of Radiology, Beth Israel Deaconess Medical Center, Boston, MA, 02215, USA.,Harvard Medical School, Boston, MA, 02215, USA
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10
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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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11
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Li X, Yang K, Liu B. Radiation dose dependence on subject size in abdominal computed tomography: Water phantom and patient model comparison. Med Phys 2018; 45:2309-2317. [PMID: 29582439 DOI: 10.1002/mp.12888] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 03/14/2018] [Accepted: 03/15/2018] [Indexed: 11/06/2022] Open
Abstract
PURPOSE Development of patient organ dose evaluation method in computed tomography (CT) needs to model the correlation between organ dose and patient size, under various conditions of scan length, tube current lineshape, and organ location. To facilitate this task, this work was to perform a comprehensive study of the relationship between the dose to water phantom and its diameter under various settings of phantom axis, scan length, and the location across or beyond the scanned range. METHODS A dose calculation algorithm and the published data by Li et al. [Med. Phys. 39, 5347-5352 (2012); 40, 031903 (2013); 43, 5878-5888 (2016)] were used to calculate longitudinal dose distribution DL (z) in 10- to 50-cm diameter water phantoms undergoing constant tube current scans. The relationship between dose and phantom diameter was examined on three phantom axes (center, cross-sectional average, periphery), at seven scan lengths from 15 to 70 cm, and at eight longitudinal locations within or beyond each scan range. The water phantom results were compared to those of patient models of eight previous studies. RESULTS For the water phantoms matching the abdominal perimeters (36.3-124.5 cm) of the GSF family of voxelized phantoms, the median and range of DL (z)(water) across scan range were consistent with those of the organ doses from the GSF phantom abdominal scans of a previous study. In 41 water phantoms (diameters 10-50 cm), DL (z)(water) at locations inside scan range decreased with increasing phantom diameters. Exponential regression analysis of the above trend yielded regression parameters approximately consistent with those of phantom or patient models of eight previous studies. However, the usual exponential function might not be optimal for modeling the dose dependence on subject size. Inside scan range, the log(dose) vs diameter curve was non-linear on a semilogarithmic graph. Outside of scan range, dose might increase with larger subject sizes, contradicting to the exponential attenuation law. In the CT examinations of a patient population, direct modeling of organ dose dependence on patient size would be more challenging due to varying scan lengths and changing organ distances to the scan range centers. CONCLUSION An efficient approach to take into account the abdominal organ dose dependences on other factors is to calculate DL (z)(water) with the water equivalent diameter, scan length, and tube current lineshape from the patient examinations, and to evaluate the organ dose to DL (z)(water) ratio, where z is at the organ's longitudinal location. The ratio may be used for abdominal organ dose evaluation in the patient examinations. How to make use of DL (z)(water) for organ dose evaluation in other body regions may be explored in the future.
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Affiliation(s)
- Xinhua Li
- Division of Diagnostic Imaging Physics, Department of Radiology, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Kai Yang
- Division of Diagnostic Imaging Physics, Department of Radiology, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Bob Liu
- Division of Diagnostic Imaging Physics, Department of Radiology, Massachusetts General Hospital, Boston, MA, 02114, USA
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Bostani M, McMillan K, Lu P, Kim GHJ, Cody D, Arbique G, Bruce Greenberg S, DeMarco JJ, Cagnon CH, McNitt-Gray MF. Erratum: "Estimating organ doses from tube current modulated CT examinations using a generalized linear model" [Med. Phys. Vol 44 (4), 1500-1513 (2017)]. Med Phys 2017; 44:3883. [PMID: 28685929 DOI: 10.1002/mp.12324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 12/19/2016] [Accepted: 01/15/2017] [Indexed: 11/07/2022] Open
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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