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Wang W, Deng Y, Huang Z. Experimental dosimetry of EDR2 films in scanning carbon-ion irradiation. J Appl Clin Med Phys 2022; 23:e13636. [PMID: 35594015 PMCID: PMC9278678 DOI: 10.1002/acm2.13636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 04/01/2022] [Accepted: 04/14/2022] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To investigate the dose-sensitometric response of extended dose range (EDR2) films to scanning carbon-ion beams and to evaluate the applications of the obtained response curves to carbon-ion dose distributions. METHODS EDR2 films were irradiated by mono-energetic scanning carbon-ion beams with different doses to obtain sensitometric curves at different integrated depth doses (DDDs). Six different DDDs were generated by using a proper buildup for each mono-energetic beam and were used to investigate the energy dependence. The sensitometric curves were obtained by fitting the net optical density (netOD) to dose at different DDDs. The dose difference between the value converted from the netOD and that calculated in the treatment planning system (TPS) was investigated to evaluate the application scope of the sensitometric curve. RESULTS Digitizing the EDR2 film with a resolution of 0.36 (72 dpi) provided a good signal-to-noise ratio, and the sensitometric curve was linear at all DDDs of clinically relevant incident kinetic energies in the netOD range of 0.02-1.70 for carbon-ion film dosimetry. The factors used to convert the netOD to absorbed dose were expressed as a linear function of DDDs, with which the depth dose difference between converted and TPS was less than 3% in the proximal area for incident kinetic energies lower than 307.5 MeV/u. CONCLUSION The EDR2 film is a feasible tool for scanning carbon-ion beam profile measurements by directly evaluating the netOD distribution with proper digitizing resolution and netOD range. By applying the conversion factors, the EDR2 film can also be employed to perform the percentage depth dose consistency checking and linear energy transfer comparison of carbon-ion lower than 307.5 MeV/u.
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Affiliation(s)
- Weiwei Wang
- Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Shanghai, China.,Shanghai Key Laboratory of Radiation Oncology(20dz2261000), Shanghai, China.,Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy, Shanghai, China
| | - Yu Deng
- Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Shanghai, China.,Shanghai Key Laboratory of Radiation Oncology(20dz2261000), Shanghai, China.,Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy, Shanghai, China
| | - Zhijie Huang
- Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Shanghai, China.,Shanghai Key Laboratory of Radiation Oncology(20dz2261000), Shanghai, China.,Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy, Shanghai, China
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The effect of SSD, Field size, Energy and Detector type for Relative Output Factor measurement in small photon beams as compared with Monte Carlo simulation. POLISH JOURNAL OF MEDICAL PHYSICS AND ENGINEERING 2019. [DOI: 10.2478/pjmpe-2019-0014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
Introduction: Small fields photon dosimetry is associated with many problems. Using the right detector for measurement plays a fundamental role. This study investigated the measurement of relative output for small photon fields with different detectors. It was investigated for three-photon beam energies at SSDs of 90, 95, 100 and 110 cm. As a benchmark, the Monte Carlo simulation was done to calculate the relative output of these small photon beams for the dose in water.
Materials and Methods: 6, 10 and 15 MV beams were delivered from a Synergy LINAC equipped with an Agility 160 multileaf collimator (MLC). A CC01 ion chamber, EFD-3G diode, PTW60019 microdiamond, EBT2 radiochromic film, and EDR2 radiographic film were used to measure the relative output of the linac. Measurements were taken in water for the CC01 ion chamber, EFD-3G diode, and the PTW60019. Films were measured in water equivalent RW3 phantom slabs. Measurements were made for 1 × 1, 2 × 2, 3 × 3, 4 × 4, 5 × 5 and a reference field of 10 × 10 cm2. Field sizes were defined at 100cm SSD. Relative output factors were also compared with Monte Carlo (MC) simulation of the LINAC and a water phantom model. The influence of voxel size was also investigated for relative output measurement. Results and Discussion: The relative output factor (ROF) increased with energy for all fields large enough to have lateral electronic equilibrium (LEE). This relation broke down as the field sizes decreased due to the onset of lateral electronic disequilibrium (LED). The high-density detector, PTW60019 gave the highest ROF for the different energies, with the less dense CC01 giving the lowest ROFs.
Conclusion: These are results compared to MC simulation, higher density detectors give higher ROF values. Relative to water, the ROF measured with the air-chamber remained virtually unchanged. The ROFs, as measured in this study showed little variation due to increased SSDs. The effect of voxel size for the Monte Carlo calculations in water does not lead to significant ROF variation over the small fields studied.
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Markovic M, Narayanasamy G, Stathakis S, Mavroidis P, Jurkovic IA, Saenz D, Papanikolaou N. Clinical Evaluation of a Two-dimensional Liquid-Filled Ion chamber Detector Array for Verification of High Modulation Small Fields in Radiotherapy. J Med Phys 2019; 44:91-98. [PMID: 31359926 PMCID: PMC6580813 DOI: 10.4103/jmp.jmp_4_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
INTRODUCTION Clinical evaluation of a two-dimensional (2D) liquid-filled ion chamber detector array used in the verification of highly modulated small beams of stereotactic body radiation therapy (SBRT) has been conducted. MATERIALS AND METHODS Measurements with the Octavius 1000 SRS (PTW, Freiburg, Germany) detector with 977 liquid-filled ion chambers were compared against EDR2 film and PTW Octavius Seven29. The performance of detector array has been evaluated on ten SBRT patient plans. Dose profiles of individual and composite fields' calculated using Pinnacle3 treatment planning system were compared against measurements with Octavius 1000 SRS detector array, EDR2 film, and Octavius Seven29 detector. Gamma index and profile comparison were used in the evaluation and assessment of the detector's performance. RESULTS The Gamma index measurements show agreement between Pinnacle3 computations and Octavius 1000 SRS array, PTW Octavius Seven29, and EDR2 film for >90% of the points using 2%, 2 mm tolerance criteria. Profiles obtained with the Octavius 1000 SRS were in agreement with the EDR2 film profiles, demonstrating the detector's superior sampling rate. CONCLUSIONS The Octavius 1000 SRS is a dosimetrically accurate device to perform quality assurance checks in SBRT treatments. The broad range of measurements performed in this study quantified the dosimetric accuracy of Octavius 1000 SRS detector in the clinical setup of the small fields in radiotherapy.
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Affiliation(s)
- Miljenko Markovic
- Department of Radiation Oncology, University of Texas Health San Antonio, San Antonio, TX, USA,Address for correspondence: Dr. Miljenko Markovic, Department of Radiation Oncology, University of Texas Health San Antonio, 7979 Wurzbach Rd, San Antonio, TX 78229, USA. E-mail:
| | - Ganesh Narayanasamy
- Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Sotirios Stathakis
- Department of Radiation Oncology, University of Texas Health San Antonio, San Antonio, TX, USA
| | - Panayiotis Mavroidis
- Department of Radiation Oncology, University of North Carolina, Chapel Hill, NC, USA
| | - Ines-Ana Jurkovic
- Department of Radiation Oncology, University of Texas Health San Antonio, San Antonio, TX, USA
| | - Daniel Saenz
- Department of Radiation Oncology, University of Texas Health San Antonio, San Antonio, TX, USA
| | - Niko Papanikolaou
- Department of Radiation Oncology, University of Texas Health San Antonio, San Antonio, TX, USA
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Yang B, Wong WKR, Geng H, Lam WW, Ho YW, Kwok WM, Cheung KY, Yu SK. Filmless methods for quality assurance of Tomotherapy using ArcCHECK. Med Phys 2017; 44:7-16. [PMID: 28044341 DOI: 10.1002/mp.12009] [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: 05/30/2016] [Revised: 10/15/2016] [Accepted: 11/08/2016] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Tomotherapy delivers an intensity-modulated radiation therapy (IMRT) treatment by the synchronization of gantry rotation, multileaf collimator (MLC), and couch movement. This dynamic nature makes the quality assurance (QA) important and challenging. The purpose of this study is to develop some methodologies using an ArcCHECK for accurate QA measurements of the gantry angle and speed, MLC synchronization and leaf open time, couch translation per gantry rotation, couch speed and uniformity, and constancy of longitudinal beam profile for a Tomotherapy unit. METHODS Four test plans recommended by AAPM Task Group 148 (TG148) and the manufacturer were chosen for this study. Helical and static star shot tests are used for checking the leaves opened at the expected gantry angles. Another helical test is to verify the couch traveled the expected distance per gantry rotation. The final test is for checking the couch speed constancy with a static gantry. ArcCHECK can record the detector signal every 50 ms as a movie file, and has a virtual inclinometer for gantry angle measurement. These features made the measurement of gantry angle and speed, MLC synchronization and leaf open time, and longitudinal beam profile possible. A shaping parameter was defined for facilitating the location of the beam center during the plan delivery, which was thereafter used to calculate the couch translation per gantry rotation and couch speed. The full width at half maximum (FWHM) was calculated for each measured longitudinal beam profile and then used to evaluate the couch speed uniformity. Furthermore, a mean longitudinal profile was obtained for constancy check of field width. The machine trajectory log data were also collected for comparison. Inhouse programs were developed in MATLAB to process both the ArcCHECK and machine log data. RESULTS The deviation of our measurement results from the log data for gantry angle was calculated to be less than 0.4°. The percentage differences between measured and planned leaf open time were found to be within 0.5% in all the tests. Our results showed mean values of MLC synchronization of 0.982, 0.983, and 0.995 at static gantry angle 0°, 45°, and 135°, respectively. The mean value of measured couch translation and couch speed by ArcCHECK had less than 0.1% deviation from the planned values. The variation in the value of FWHM suggested the couch speed uniformity was better than 1%. The mean of measured longitudinal profiles was suitable for constancy check of field width. CONCLUSION Precise and efficient methods for measuring the gantry angle and speed, leaf open time, couch translation per gantry rotation, couch speed and uniformity, and constancy of longitudinal beam profile of Tomotherapy using ArcCHECK have been developed and proven to be accurate compared with machine log data. Estimation of the Tomotherapy binary MLC leaf open time is proven to be precise enough to verify the leaf open time as small as 277.8 ms. Our method also makes the observation and quantification of the synchronization of leaves possible.
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Affiliation(s)
- B Yang
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - W K R Wong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - H Geng
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - W W Lam
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - Y W Ho
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - W M Kwok
- Biomedical Engineering Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - K Y Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - S K Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
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Yohannes I, Prasetio H, Kallis K, Bert C. Dosimetric accuracy of the cone-beam CT-based treatment planning of the Vero system: a phantom study. J Appl Clin Med Phys 2016; 17:106-113. [PMID: 27455496 PMCID: PMC5690058 DOI: 10.1120/jacmp.v17i4.6194] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 02/25/2016] [Accepted: 02/23/2016] [Indexed: 11/23/2022] Open
Abstract
We report an investigation on the accuracy of dose calculation based on the cone‐beam computed tomography (CBCT) images of the nonbowtie filter kV imaging system of the Vero linear accelerator. Different sets of materials and tube voltages were employed to generate the Hounsfield unit lookup tables (HLUTs) for both CBCT and fan‐beam CT (FBCT) systems. The HLUTs were then implemented for the dose calculation in a treatment planning system (TPS). Dosimetric evaluation was carried out on an in‐house‐developed cube phantom that consists of water‐equivalent slabs and inhomogeneity inserts. Two independent dosimeters positioned in the cube phantom were used in this study for point‐dose and two‐dimensional (2D) dose distribution measurements. The differences of HLUTs from various materials and tube voltages in both CT systems resulted in differences in dose calculation accuracy. We found that the higher the tube voltage used to obtain CT images, the better the point‐dose calculation and the gamma passing rate of the 2D dose distribution agree to the values determined in the TPS. Moreover, the insert materials that are not tissue‐equivalent led to higher dose‐calculation inaccuracy. There were negligible differences in dosimetric evaluation between the CBCT‐ and FBCT‐based treatment planning if the HLUTs were generated using the tissue‐equivalent materials. In this study, the CBCT images of the Vero system from a complex inhomogeneity phantom can be applied for the TPS dose calculation if the system is calibrated using tissue‐equivalent materials scanned at high tube voltage (i.e., 120 kV). PACS number(s): 87.55.de, 87.56.Fc, 87.57.qp
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Yohannes I, Prasetio H, Bert C. Noncoplanar verification: a feasibility study using Philips' Pinnacle3 treatment planning system. J Appl Clin Med Phys 2015; 16:84–90. [PMID: 26699558 PMCID: PMC5691022 DOI: 10.1120/jacmp.v16i6.5492] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 08/17/2015] [Accepted: 07/07/2015] [Indexed: 01/09/2023] Open
Abstract
Noncoplanar fields are normally used to improve the dose conformity of the target while sparing organs at risk. One of the methods to verify the dose distribution from the noncoplanar fields is by comparing their planar dose distributions from the treatment planning system (TPS) and the measured ones; for example, using film or electronic portal imaging devices (EPID). The planar dose distributions of the measurement tools, that are normally perpendicular to the central axis of the beam, can be calculated by creating special structures to mimic them in the TPS. With TPS commercially available today, however, it is not easy to create these special structures, especially in the noncoplanar configuration. For this work, we have written in‐house scripts in the Pinnacle3 TPS that can create the structures and define them as virtual planes. These virtual planes can be generated for any arbitrary gantry and couch angles, as well as source to planar distance, so that the planar dose maps at these planes can be computed. Two independent quality assurance (QA) tools were used to validate the planar dose distributions computed using the scripts for three open fields and one IMRT field at several different couch angles. The absolute planar dose patterns measured by the QA tools for all fields at all couch angles were found to be in good agreement, more than 95% (gamma criteria 3% delta dose and 3 mm distance to agreement), with the calculated ones by TPS. The results of this feasibility study can be valuable either for pretreatment dose verification or for in vivo dosimetry that directly implements the planar dose distributions from the TPS, particularly for the noncoplanar fields. PACS numbers: 87.55.de, 87.55.Qr, 87.56.Fc
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Bazalova-Carter M, Schlosser J, Chen J, Hristov D. Monte Carlo modeling of ultrasound probes for image guided radiotherapy. Med Phys 2015; 42:5745-56. [PMID: 26429248 PMCID: PMC4567581 DOI: 10.1118/1.4929978] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 08/05/2015] [Accepted: 08/21/2015] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To build Monte Carlo (MC) models of two ultrasound (US) probes and to quantify the effect of beam attenuation due to the US probes for radiation therapy delivered under real-time US image guidance. METHODS MC models of two Philips US probes, an X6-1 matrix-array transducer and a C5-2 curved-array transducer, were built based on their megavoltage (MV) CT images acquired in a Tomotherapy machine with a 3.5 MV beam in the EGSnrc, BEAMnrc, and DOSXYZnrc codes. Mass densities in the probes were assigned based on an electron density calibration phantom consisting of cylinders with mass densities between 0.2 and 8.0 g/cm(3). Beam attenuation due to the US probes in horizontal (for both probes) and vertical (for the X6-1 probe) orientation was measured in a solid water phantom for 6 and 15 MV (15 × 15) cm(2) beams with a 2D ionization chamber array and radiographic films at 5 cm depth. The MC models of the US probes were validated by comparison of the measured dose distributions and dose distributions predicted by MC. Attenuation of depth dose in the (15 × 15) cm(2) beams and small circular beams due to the presence of the probes was assessed by means of MC simulations. RESULTS The 3.5 MV CT number to mass density calibration curve was found to be linear with R(2) > 0.99. The maximum mass densities in the X6-1 and C5-2 probes were found to be 4.8 and 5.2 g/cm(3), respectively. Dose profile differences between MC simulations and measurements of less than 3% for US probes in horizontal orientation were found, with the exception of the penumbra region. The largest 6% dose difference was observed in dose profiles of the X6-1 probe placed in vertical orientation, which was attributed to inadequate modeling of the probe cable. Gamma analysis of the simulated and measured doses showed that over 96% of measurement points passed the 3%/3 mm criteria for both probes placed in horizontal orientation and for the X6-1 probe in vertical orientation. The X6-1 probe in vertical orientation caused the highest attenuation of the 6 and 15 MV beams, which at 10 cm depth accounted for 33% and 43% decrease compared to the respective (15 × 15) cm(2) open fields. The C5-2 probe in horizontal orientation, on the other hand, caused a dose increase of 10% and 53% for the 6 and 15 MV beams, respectively, in the buildup region at 0.5 cm depth. For the X6-1 probe in vertical orientation, the dose at 5 cm depth for the 3-cm diameter 6 MV and 5-cm diameter 15 MV beams was attenuated compared to the corresponding open fields to a greater degree by 65% and 43%, respectively. CONCLUSIONS MC models of two US probes used for real-time image guidance during radiotherapy have been built. Due to the high beam attenuation of the US probes, the authors generally recommend avoiding delivery of treatment beams that intersect the probe. However, the presented MC models can be effectively integrated into US-guided radiotherapy treatment planning in cases for which beam avoidance is not practical due to anatomy geometry.
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Affiliation(s)
- Magdalena Bazalova-Carter
- Department of Radiation Oncology, Stanford University, Stanford, California 94305 and Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada
| | | | - Josephine Chen
- Department of Radiation Oncology, UCSF, San Francisco, California 94143
| | - Dimitre Hristov
- Department of Radiation Oncology, Stanford University, Stanford, California 94305
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Reynolds TA, Higgins P. Surface dose measurements with commonly used detectors: a consistent thickness correction method. J Appl Clin Med Phys 2015; 16:358–366. [PMID: 26699319 PMCID: PMC5690169 DOI: 10.1120/jacmp.v16i5.5572] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 05/06/2015] [Accepted: 04/29/2015] [Indexed: 11/23/2022] Open
Abstract
The purpose of this study was to review application of a consistent correction method for the solid state detectors, such as thermoluminescent dosimeters (chips (cTLD) and powder (pTLD)), optically stimulated detectors (both closed (OSL) and open (eOSL)), and radiochromic (EBT2) and radiographic (EDR2) films. In addition, to compare measured surface dose using an extrapolation ionization chamber (PTW 30-360) with other parallel plate chambers RMI-449 (Attix), Capintec PS-033, PTW 30-329 (Markus) and Memorial. Measurements of surface dose for 6MV photons with parallel plate chambers were used to establish a baseline. cTLD, OSLs, EDR2, and EBT2 measurements were corrected using a method which involved irradiation of three dosimeter stacks, followed by linear extrapolation of individual dosimeter measurements to zero thickness. We determined the magnitude of correction for each detector and compared our results against an alternative correction method based on effective thickness. All uncorrected surface dose measurements exhibited overresponse, compared with the extrapolation chamber data, except for the Attix chamber. The closest match was obtained with the Attix chamber (-0.1%), followed by pTLD (0.5%), Capintec (4.5%), Memorial (7.3%), Markus (10%), cTLD (11.8%), eOSL (12.8%), EBT2 (14%), EDR2 (14.8%), and OSL (26%). Application of published ionization chamber corrections brought all the parallel plate results to within 1% of the extrapolation chamber. The extrapolation method corrected all solid-state detector results to within 2% of baseline, except the OSLs. Extrapolation of dose using a simple three-detector stack has been demonstrated to provide thickness corrections for cTLD, eOSLs, EBT2, and EDR2 which can then be used for surface dose measurements. Standard OSLs are not recommended for surface dose measurement. The effective thickness method suffers from the subjectivity inherent in the inclusion of measured percentage depth-dose curves and is not recommended for these types of measurements.
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Affiliation(s)
- Tatsiana A. Reynolds
- Department of Radiation OncologyUniversity of Minnesota Med School‐Twin CitiesMinneapolisMNUSA
| | - Patrick Higgins
- Department of Radiation OncologyUniversity of Minnesota Med School‐Twin CitiesMinneapolisMNUSA
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Hatanaka S, Miyabe Y, Tohyama N, Kumazaki Y, Kurooka M, Okamoto H, Tachibana H, Kito S, Wakita A, Ohotomo Y, Ikagawa H, Ishikura S, Nozaki M, Kagami Y, Hiraoka M, Nishio T. Dose calculation accuracies in whole breast radiotherapy treatment planning: a multi-institutional study. Radiol Phys Technol 2015; 8:200-8. [PMID: 25646770 DOI: 10.1007/s12194-015-0308-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 01/22/2015] [Accepted: 01/22/2015] [Indexed: 11/30/2022]
Abstract
Our objective in this study was to evaluate the variation in the doses delivered among institutions due to dose calculation inaccuracies in whole breast radiotherapy. We have developed practical procedures for quality assurance (QA) of radiation treatment planning systems. These QA procedures are designed to be performed easily at any institution and to permit comparisons of results across institutions. The dose calculation accuracy was evaluated across seven institutions using various irradiation conditions. In some conditions, there was a >3 % difference between the calculated dose and the measured dose. The dose calculation accuracy differs among institutions because it is dependent on both the dose calculation algorithm and beam modeling. The QA procedures in this study are useful for verifying the accuracy of the dose calculation algorithm and of the beam model before clinical use for whole breast radiotherapy.
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Affiliation(s)
- Shogo Hatanaka
- Department of Radiation Oncology, Saitama Medical University Saitama Medical Center, 1981, Kamoda, Kawagoe City, Saitama, 350-8550, Japan,
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Huang JY, Pulliam KB, McKenzie EM, Followill DS, Kry SF. Effects of spatial resolution and noise on gamma analysis for IMRT QA. J Appl Clin Med Phys 2014; 15:4690. [PMID: 25207399 PMCID: PMC4283459 DOI: 10.1120/jacmp.v15i4.4690] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 04/15/2014] [Accepted: 03/24/2014] [Indexed: 11/23/2022] Open
Abstract
We investigated the sensitivity of the gamma index to two factors: the spatial resolution and the noise level in the measured dose distribution. We also examined how the choice of reference distribution and analysis software affect the sensitivity of gamma analysis to these two factors for quality assurance (QA) of intensity-modulated radiation therapy (IMRT) treatment plans. For ten clinical IMRT plans, the dose delivered to a transverse dose plane was measured with EDR2 radiographic film. To evaluate the effects of spatial resolution, each irradiated film was digitized using three different resolutions (71, 142, and 285 dpi). To evaluate the effects of image noise, 1% and 2% local Gaussian noise was added to the film images. Gamma analysis was performed using 2%/2 mm and 3%/3 mm acceptance criteria and two commercial software packages, OmniPro I'mRT and DoseLab Pro. Dose comparisons were performed with the treatment planning system (TPS)-calculated dose as the reference, and then repeated with the film as the reference to evaluate how the choice of reference distribution affects the results of dose comparisons. When the TPS-calculated dose was designated as the reference distribution, the percentage of pixels with passing gamma values increased with both increasing resolution and noise. For 3%/3 mm acceptance criteria, increasing the film image resolution by a factor of two and by a factor of four caused a median increase of 0.9% and 2.6%, respectively, in the percentage of pixels passing. Increasing the noise level in the film image resulted in a median increase in percentage of pixels passing of 5.5% for 1% added local Gaussian noise and 5.8% for 2% added noise. In contrast, when the film was designated as the reference distribution, the percentage of pixels passing decreased with increased film noise, while increased resolution had no significant effect on passing rates. Furthermore, the sensitivity of gamma analysis to noise and resolution differed between OmniPro I'mRT and DoseLab Pro, with DoseLab Pro being less sensitive to the effects of noise and resolution. Noise and high scanning resolution can artificially increase the percentage of pixels with passing gamma values in IMRT QA. Thus, these factors, if not properly taken into account, can potentially affect the results of IMRT QA by causing a plan that should be classified as failing to be falsely classified as passing. In designing IMRT QA protocols, it is important to be aware that gamma analysis is sensitive to these parameters.
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Takahashi Y, Hui SK. Fast, simple, and informative patient-specific dose verification method for intensity modulated total marrow irradiation with helical tomotherapy. Radiat Oncol 2014; 9:34. [PMID: 24461048 PMCID: PMC3922911 DOI: 10.1186/1748-717x-9-34] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 01/23/2014] [Indexed: 11/20/2022] Open
Abstract
Background Patient-specific dose verification for treatment planning in helical tomotherapy is routinely performed using a homogeneous virtual water cylindrical phantom of 30 cm diameter and 18 cm length (Cheese phantom). Because of this small length, treatment with total marrow irradiation (TMI) requires multiple deliveries of the dose verification procedures to cover a wide range of the target volumes, which significantly prolongs the dose verification process. We propose a fast, simple, and informative patient-specific dose verification method which reduce dose verification time for TMI with helical tomotherapy. Methods We constructed a two-step solid water slab phantom (length 110 cm, height 8 cm, and two-step width of 30 cm and 15 cm), termed the Whole Body Phantom (WB phantom). Three ionization chambers and three EDR-2 films can be inserted to cover extended field TMI treatment delivery. Three TMI treatment plans were conducted with a TomoTherapy HiArt Planning Station and verified using the WB phantom with ion chambers and films. Three regions simulating the head and neck, thorax, and pelvis were covered in a single treatment delivery. The results were compared to those with the cheese phantom supplied by Accuray, Inc. following three treatment deliveries to cover the body from head to pelvis. Results Use of the WB phantom provided point doses or dose distributions from head and neck to femur in a single treatment delivery of TMI. Patient-specific dose verification with the WB phantom was 62% faster than with the cheese phantom. The average pass rate in gamma analysis with the criteria of a 3-mm distance-to-agreement and 3% dose differences was 94% ± 2% for the three TMI treatment plans. The differences in pass rates between the WB and cheese phantoms at the upper thorax to abdomen regions were within 2%. The calculated dose agreed with the measured dose within 3% for all points in all five cases in both the WB and cheese phantoms. Conclusions Our dose verification method with the WB phantom provides simple and rapid quality assurance without limiting dose verification information in total marrow irradiation with helical tomotherapy.
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Affiliation(s)
| | - Susanta K Hui
- Masonic Cancer Center, University of Minnesota, 424 Harvard Street SE, Minneapolis 55455, MN, USA.
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Shukla AK, Oinam AS, Kumar S, Sandhu IS, Sharma SC. A calibration method for patient specific IMRT QA using a single therapy verification film. Rep Pract Oncol Radiother 2014; 18:235-40. [PMID: 24416558 DOI: 10.1016/j.rpor.2013.04.033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Revised: 03/01/2013] [Accepted: 04/15/2013] [Indexed: 10/26/2022] Open
Abstract
AIM The aim of the present study is to develop and verify the single film calibration procedure used in intensity-modulated radiation therapy (IMRT) quality assurance. BACKGROUND Radiographic films have been regularly used in routine commissioning of treatment modalities and verification of treatment planning system (TPS). The radiation dosimetery based on radiographic films has ability to give absolute two-dimension dose distribution and prefer for the IMRT quality assurance. However, the single therapy verification film gives a quick and significant reliable method for IMRT verification. MATERIALS AND METHODS A single extended dose rate (EDR 2) film was used to generate the sensitometric curve of film optical density and radiation dose. EDR 2 film was exposed with nine 6 cm × 6 cm fields of 6 MV photon beam obtained from a medical linear accelerator at 5-cm depth in solid water phantom. The nine regions of single film were exposed with radiation doses raging from 10 to 362 cGy. The actual dose measurements inside the field regions were performed using 0.6 cm(3) ionization chamber. The exposed film was processed after irradiation using a VIDAR film scanner and the value of optical density was noted for each region. Ten IMRT plans of head and neck carcinoma were used for verification using a dynamic IMRT technique, and evaluated using the gamma index method with TPS calculated dose distribution. RESULTS Sensitometric curve has been generated using a single film exposed at nine field region to check quantitative dose verifications of IMRT treatments. The radiation scattered factor was observed to decrease exponentially with the increase in the distance from the centre of each field region. The IMRT plans based on calibration curve were verified using the gamma index method and found to be within acceptable criteria. CONCLUSION The single film method proved to be superior to the traditional calibration method and produce fast daily film calibration for highly accurate IMRT verification.
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Affiliation(s)
- Arvind Kumar Shukla
- Department of Radiotherapy, Post Graduate Institute of Medical Education and Research, 160 012, India
| | - Arun S Oinam
- Department of Radiotherapy, Post Graduate Institute of Medical Education and Research, 160 012, India
| | - Sanjeev Kumar
- Department of Applied Sciences, Chitkara University, Rajpura 140 401, India
| | - I S Sandhu
- Department of Applied Sciences, Chitkara University, Rajpura 140 401, India
| | - S C Sharma
- Department of Radiotherapy, Post Graduate Institute of Medical Education and Research, 160 012, India
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Mohammad A, Nedaie HA, YarAhmadi M, Banaee N, Naderi M, Tizmaghz Z. Dosimetric Evaluation of Heterogeneities in Small Circular Fields of 6 MV Photon Beams with EBT2 and EDR2 Films: Comparison with Monte Carlo Calculation. ACTA ACUST UNITED AC 2014. [DOI: 10.4236/jmp.2014.516162] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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14
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Uehara R, Tachibana H, Ito Y, Yoshino S, Matsubayashi F, Sato T. [A practical procedure to improve the accuracy of radiochromic film dosimetry: a integration with a correction method of uniformity correction and a red/blue correction method]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2013; 69:617-31. [PMID: 23782774 DOI: 10.6009/jjrt.2013_jsrt_69.6.617] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
It has been reported that the light scattering could worsen the accuracy of dose distribution measurement using a radiochromic film. The purpose of this study was to investigate the accuracy of two different films, EDR2 and EBT2, as film dosimetry tools. The effectiveness of a correction method for the non-uniformity caused from EBT2 film and the light scattering was also evaluated. In addition the efficacy of this correction method integrated with the red/blue correction method was assessed. EDR2 and EBT2 films were read using a flatbed charge-coupled device scanner (EPSON 10000G). Dose differences on the axis perpendicular to the scanner lamp movement axis were within 1% with EDR2, but exceeded 3% (Maximum: +8%) with EBT2. The non-uniformity correction method, after a single film exposure, was applied to the readout of the films. A corrected dose distribution data was subsequently created. The correction method showed more than 10%-better pass ratios in dose difference evaluation than when the correction method was not applied. The red/blue correction method resulted in 5%-improvement compared with the standard procedure that employed red color only. The correction method with EBT2 proved to be able to rapidly correct non-uniformity, and has potential for routine clinical IMRT dose verification if the accuracy of EBT2 is required to be similar to that of EDR2. The use of red/blue correction method may improve the accuracy, but we recommend we should use the red/blue correction method carefully and understand the characteristics of EBT2 for red color only and the red/blue correction method.
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Affiliation(s)
- Ryuzo Uehara
- Department of Radiation Oncology, The Cancer Institute Hospital of JFCR
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15
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Tachibana H, Takahashi R. Quantitative analysis of geometric information from an end-to-end examination of IMRT and VMAT using the optimal selection method. Med Phys 2013; 40:061709. [PMID: 23718588 DOI: 10.1118/1.4805103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Gamma index, distance-to-agreement, and dose difference (DD) are commonly used to evaluate planar dose distributions. In this evaluation, the agreement between calculated and measured dose distributions can be susceptible to steep dose gradients along another axis perpendicular to the evaluation plane. Visual registration of the measured dose distribution may be performed to achieve better agreement, although doing so might lose geometric information related to beam targeting in an end-to-end test of intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). The optimal selection (OS) method was developed to take into consideration a dose distribution in three-dimensions, and also to quantitatively analyze geometric information along with better agreement. METHODS The OS method was composed of two steps. These steps were based on two algorithms, the gamma index and DD, to (1) find the best-matched plane, which is parallel to the planar measured dose distribution and is reconstructed by a volumetric dose distribution calculated by a treatment planning system; and (2) to get shifts and rotation along with better agreement between the calculated and measured dose distribution, compared with the planar dose distribution from the test. The OS method computes shifts and rotation against a user-defined coregistered location for the measured dose distribution. Thirteen prostate IMRT plans (two planes per plan for a total of 26 planes) were analyzed retrospectively to compare the pass ratios of DD and gamma index evaluations with and without the OS method. The computed shifts and rotations were evaluated. RESULTS Compared with the method without OS, the average pass ratios of DD and gamma index with the OS method increased by 8.2% and 5.7%, respectively, in the dose region from 30% to 100%. A particular result from one of the planes showed an increase of 43.5% and 32.5% in the pass ratios of DD and gamma, respectively, with the OS method in the same dose region. The shifts in the x-, y-, z-axes and rotation, which were computed using the OS method, were 0.5 ± 0.6, 0.3 ± 0.5, 1.0 ± 1.1 mm, and 0.3 ± 0.3°, respectively. In terms of the comparatively large difference between the z-shift and the x- and y-shifts, an additional geometric test was performed. A systematic error of 0.7 mm in the z-axis was found at the location of the film placed in the phantom that we used. CONCLUSIONS The OS method improved the quality of the end-to-end test of IMRT and VMAT plans by providing additional information regarding shifts and rotation, which were calculated and found to be in better agreement.
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Affiliation(s)
- Hidenobu Tachibana
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, 5801 Forest Park Road, Dallas, Texas 75390-9183, USA.
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16
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Srivastava SP, Das IJ. Effect of processor temperature on film dosimetry. Med Dosim 2012; 37:138-9. [DOI: 10.1016/j.meddos.2011.06.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 09/07/2010] [Accepted: 06/10/2011] [Indexed: 10/17/2022]
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Nakamura M, Kishimoto S, Iwamura K, Shiinoki T, Nakamura A, Matsuo Y, Shibuya K, Hiraoka M. Dosimetric investigation of breath-hold intensity-modulated radiotherapy for pancreatic cancer. Med Phys 2012; 39:48-54. [PMID: 22225274 DOI: 10.1118/1.3668314] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
PURPOSE To experimentally investigate the effects of variations in respiratory motion during breath-holding (BH) at end-exhalation (EE) on intensity-modulated radiotherapy (BH-IMRT) dose distribution using a motor-driven base, films, and an ionization chamber. METHODS Measurements were performed on a linear accelerator, which has a 120-leaf independently moving multileaf collimator with 5-mm leaf width at the isocenter for the 20-cm central field. Polystyrene phantoms with dimensions of 40 × 40 × 10 cm were set on a motor-driven base. All gantry angles of seven IMRT plans (a total of 35 fields) were changed to zero, and doses were then delivered to a film placed at a depth of 4 cm and an ionization chamber at a depth of 5 cm in the phantom with a dose rate of 600 MU/min under the following conditions: pulsation from the abdominal aorta and baseline drift with speeds of 0.2 mm/s (BD(0.2mm/s)) and 0.4 mm/s (BD(0.4mm/s)). As a reference for comparison, doses were also delivered to the chamber and film under stationary conditions. RESULTS In chamber measurements, means ± standard deviations of the dose deviations between stationary and moving conditions were -0.52% ± 1.03% (range: -3.41-1.05%), -0.07% ± 1.21% (range: -1.88-4.31%), and 0.03% ± 1.70% (range: -2.70-6.41%) for pulsation, BD(0.2mm/s), and BD(0.4mm/s), respectively. The γ passing rate ranged from 99.5% to 100.0%, even with the criterion of 2%/1 mm for pulsation pattern. In the case of BD(0.4mm/s), the γ passing rate for four of 35 fields (11.4%) did not reach 90% with a criterion of 3%/3 mm. The differences in γ passing rate between BD(0.2mm/s) and BD(0.4mm/s) were statistically significant for each criterion. Taking γ passing rates of > 90% as acceptable with a criterion of 3%/3 mm, large differences were observed in the γ passing rate between the baseline drift of ≤5 mm and that of >5 mm (minimum γ passing rate: 92.0% vs 82.7%; p < 0.01). CONCLUSIONS This study suggested that the baseline drift of >5 mm should be avoided in the BH-IMRT.
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Affiliation(s)
- Mitsuhiro Nakamura
- Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto 606-8507, Japan.
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Boggula R, Jahnke L, Wertz H, Lohr F, Wenz F. Patient-Specific 3D Pretreatment and Potential 3D Online Dose Verification of Monte Carlo–Calculated IMRT Prostate Treatment Plans. Int J Radiat Oncol Biol Phys 2011; 81:1168-75. [DOI: 10.1016/j.ijrobp.2010.09.010] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Revised: 08/13/2010] [Accepted: 09/20/2010] [Indexed: 11/16/2022]
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19
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Wertz H, Jahnke L, Schneider F, Polednik M, Fleckenstein J, Lohr F, Wenz F. A novel lateral disequilibrium inclusive (LDI) pencil-beam based dose calculation algorithm: Evaluation in inhomogeneous phantoms and comparison with Monte Carlo calculations. Med Phys 2011; 38:1627-34. [DOI: 10.1118/1.3557952] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Novotny J, Bhatnagar JP, Quader MA, Bednarz G, Lunsford LD, Huq MS. Measurement of relative output factors for the 8 and 4 mm collimators of Leksell Gamma Knife Perfexion by film dosimetry. Med Phys 2009; 36:1768-74. [PMID: 19544795 DOI: 10.1118/1.3113904] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Three types of films, Kodak EDR2, Gafchromic EBT, and Gafchromic MD-V2-55, were used to measure relative output factors of 4 and 8 mm collimators of the Leksell Gamma Knife Perfexion. The optical density to dose calibration curve for each of the film types was obtained by exposing the films to a range of known doses. Ten data points were acquired for each of the calibration curves in the dose ranges from 0 to 4 Gy, 0 to 8 Gy, and 0 to 80 Gy for Kodak EDR2, Gafchromic EBT, and Gafchromic MD-V2-55 films, respectively. For the measurement of relative output factors, five films of each film type were exposed to a known dose. All films were scanned using EPSON EXPRESSION 10000 XL scanner with 200 dpi resolution in 16 bit gray scale for EDR2 film and 48 bit color scale for Gafchromic films. The scanned images were imported in the red channel for both Gafchromic films. The background corrections from an unexposed film were applied to all films. The output factors obtained from film measurements were in a close agreement both with the Monte Carlo calculated values of 0.924 and 0.805 for 8 and 4 mm collimators, respectively. These values are provided by the vendor and used as default values in the vendor's treatment planning system. The largest differences were noted for the Kodak EDR 2 films (-2.1% and -4.5% for 8 and 4 mm collimators, respectively). The best agreement observed was for EBT Gafchromic film (-0.8% and +0.6% differences for 8 and 4 mm collimators, respectively). Based on the present values, no changes in the default relative output factor values were made in the treatment planning system.
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Affiliation(s)
- Josef Novotny
- Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213, USA.
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Frelin AM, Fontbonne JM, Ban G, Colin J, Labalme M, Batalla A, Vela A, Boher P, Braud M, Leroux T. The DosiMap, a new 2D scintillating dosimeter for IMRT quality assurance: characterization of two Cerenkov discrimination methods. Med Phys 2008; 35:1651-62. [PMID: 18561640 DOI: 10.1118/1.2897966] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
New radiation therapy techniques such as IMRT present significant efficiency due to their highly conformal dose distributions. A consequence of the complexity of their dose distributions (high gradients, small irradiation fields, low dose distribution, ...) is the requirement for better precision quality assurance than in classical radiotherapy in order to compare the conformation of the delivered dose with the planned dose distribution and to guarantee the quality of the treatment. Currently this control is mostly performed by matrices of ionization chambers, diode detectors, dosimetric films, portal imaging, or dosimetric gels. Another approach is scintillation dosimetry, which has been developed in the last 15 years mainly through scintillating fiber devices. Despite having many advantages over other methods it is still at an experimental level for routine dosimetry because the Cerenkov radiation produced under irradiation represents an important stem effect. A new 2D water equivalent scintillating dosimeter, the DosiMap, and two different Cerenkov discrimination methods were developed with the collaboration of the Laboratoire de Physique Corpusculaire of Caen, the Comprehensive Cancer Center François Baclesse, and the ELDIM Co., in the frame of the MAESTRO European project. The DosiMap consists of a plastic scintillating sheet placed inside a transparent polystyrene phantom. The light distribution produced under irradiation is recorded by a CCD camera. Our first Cerenkov discrimination technique is subtractive. It uses a chessboard pattern placed in front of the scintillator, which provides a background signal containing only Cerenkov light. Our second discrimination technique is colorimetric. It performs a spectral analysis of the light signal, which allows the unfolding of the Cerenkov radiation and the scintillation. Tests were carried out with our DosiMap prototype and the performances of the two discrimination methods were assessed. The comparison of the dose measurements performed with the DosiMap and with dosimetric films for three different irradiation configurations showed discrepancies smaller than 3.5% for a 2 mm spatial resolution. Two innovative discrimination solutions were demonstrated to separate the scintillation from the Cerenkov radiation. It was also shown that the DosiMap, which is water equivalent, fast, and user friendly, is a very promising tool for radiotherapy quality assurance.
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Affiliation(s)
- A M Frelin
- Laboratoire de Physique Corpusculaire, 6 Bd du Maréchal Juin, F14050 Caen, France.
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Dosimetry for a microbeam array generated by synchrotron radiation at SPring-8. Eur J Radiol 2008; 68:S114-7. [PMID: 18602783 DOI: 10.1016/j.ejrad.2008.04.052] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2008] [Accepted: 04/28/2008] [Indexed: 11/22/2022]
Abstract
A microbeam array was formed with a multi-slit collimator (MSC) for research on radiation therapy (MRT). Kodak EDR2 film was used to measure the dose distribution of the microbeam array. The calibration curve of optical density of the film with respect to a dose was established using a standard Farmer chamber and (60)Co gamma-ray source. The peak dose of 3.6 Gy/s at the maximum was derived from the film dosimetry using the calibration curve. The uncertainty was estimated to be 5% which was mainly attributed to the uncertainty of the calibration. It was found that the ionization chamber used for monitoring the dose during the MRT experiments gave lower dose by about 30% than the dose derived from the film dosimetry.
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Sarkar V, Lin L, Shi C, Papanikolaou N. Quality assurance of the multileaf collimator with helical tomotherapy: Design and implementation. Med Phys 2007; 34:2949-56. [PMID: 17822003 DOI: 10.1118/1.2748105] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Quality assurance (QA) of the multileaf collimator (MLC) is a critical step for the delivery of intensity modulated radiation therapy treatment plan. While QA procedures for motor-driven MLC have been published extensively, those for binary MLCs such as the one used for helical tomotherapy have not been presented in the literature, as this is still a fairly new technology. In this study, seven test patterns for the MLC QA of a helical tomotherapy unit have been designed and implemented. The seven test patterns check the MLC alignment, MLC leakage, MLC timing and MLC leaf position error in detail. Those patterns can be easily implemented in any center with a helical tomotherapy unit as part of the routine QA. The QA procedures can be performed using existing QA resources such as solid water phantom and EDR2 film. A software toolkit called "Tomo MLC QA" has been developed to assist in generating the QA procedures and analyzing the results. Our results showed that the helical tomotherapy MLC is very robust, exhibiting interleaf leakage of 0.53% +/-0.09%. Several issues with the MLC have been found and discussed. The QA results also illustrate the utilization and usefulness of the proposed QA procedures.
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Affiliation(s)
- Vikren Sarkar
- University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229, USA
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Kinhikar RA, Upreti R, Sharma S, Tambe CM, Deshpande DD. Intensity modulated radiotherapy dosimetry with ion chambers, TLD, MOSFET and EDR2 film. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2007; 30:25-32. [PMID: 17508598 DOI: 10.1007/bf03178406] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Purpose of this study was to report in a together our experience of using ion chambers, TLD, MOSFET and EDR2 film for dosimetric verification of IMRT plans delivered with dynamic multileaf collimator (DMLC). Two ion chambers (0.6 and 0.13 CC) were used. All measurements were performed with a 6MV photon beam on a Varian Clinac 6EX LINAC equipped with a Millennium MLC. All measurements were additionally carried out with (LiF:Mg,TI) TLD chips. Five MOSFET detectors were also irradiated. EDR2 films were used to measure coronal planar dose for 10 patients. Measurements were carried out simultaneously for cumulative fields at central axis and at off-axis at isocenter plane (+/- 1, and +/- 2 cm). The mean percentage variation between measured cumulative central axis dose with 0.6 cc ion chamber and calculated dose with TPS was -1.4% (SD 3.2). The mean percentage variation between measured cumulative absolute central axis dose with 0.13 cc ion chamber and calculated dose with TPS was -0.6% (SD 1.9). The mean percentage variation between measured central axis dose with TLD and calculated dose with TPS was -1.8% (SD 2.9). A variation of less than 5% was found between measured off-axis doses with TLD and calculated dose with TPS. For all the cases, MOSFET agreed within +/- 5%. A good agreement was found between measured and calculated isodoses. Both ion chambers (0.6 CC and 0.13 CC) were found in good agreement with calculated dose with TPS.
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Affiliation(s)
- R A Kinhikar
- Department of Medical Physics, Tata Memorial Hospital, Dr. Ernest Borges Marg, Parel, Mumbai, India.
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