2D EPID dose calibration for pretreatment quality control of conformal and IMRT fields: A simple and fast convolution approach

Camilleri, J.; Mazurier, J.; Franck, D.; Dudouet, P.; Latorzeff, I.; Franceries, X.

doi:10.1016/j.ejmp.2015.10.094

Cited by 15 publications

(19 citation statements)

References 28 publications

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“…Some of Varian’s EPID is affected by the backscatter of the support arm, which must be removed before using EPID to measure the dose. Berry et al [ 21 ] and Camilleri et al [ 25 ] established a linear correction relationship for the backscatter of different square fields by comparing the values in the negative inline direction with those in the positive inline or crossline direction. Our study revealed that the dose response of different EPIDs was not the same.…”

Section: Discussionmentioning

confidence: 99%

“…In our model, the backscatter correction matrix was calculated as the ratio of the dose value measured by ICA to the EPID pixel value. The calculation method of this matrix is similar to that of Camilleri et al [ 25 ], so the common correction matrix can also correct the off-axis response of EPID. The response of the corrected EPID image is consistent with the measured value of ICA ( Figure 5 ).…”

Section: Discussionmentioning

confidence: 99%

“…The drawback of this method is that the MC approach requires detailed physical modeling of EPID, and the modeling process is complex. Moreover, to increase the calculation speed, convolution or deconvolution is generally applied in the frequency domain via fast Fourier transform [ 25 , 31 ]; in this situation, the kernel is required to have no spatial deformation; that is, each pixel of EPID applies the same backscatter kernel, which is not consistent with the actual situation. Second, a lead plate is placed under the EPID or above the support arm to create a shielding layer, and the influence of backscatter is calculated by comparing the off-support arm image [ 22 , 24 , 26 , 27 ].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the disassembly and installation of the support arm require a professional, and the process is time-consuming. Third, the linear correction functions corresponding to different fields are calculated by comparing the value in the inline positive direction with the negative direction or the crossline direction [ 21 , 25 ]. However, since different EPIDs have different responses, this linear correction relationship does not apply to all EPIDs.…”

Section: Introductionmentioning

confidence: 99%

“…This method required disassembly of the support arm, and the process was cumbersome. Camilleri et al [ 25 ] obtained the correction matrix as the ratio of the EPID image and the dose value in water scanned by the ionization chamber, but the process of measuring the dose using a water tank is time-consuming.…”

Section: Introductionmentioning

confidence: 99%

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Development of an Electronic Portal Imaging Device Dosimetry Method

et al. 2021

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Support arm backscatter and off-axis effects of an electronic portal imaging device (EPID) are challenging for radiotherapy quality assurance. Aiming at the issue, we proposed a simple yet effective method with correction matrices to rectify backscatter and off-axis responses for EPID images. First, we measured the square fields with ionization chamber array (ICA) and EPID simultaneously. Second, we calculated the dose-to-pixel value ratio and used it as the correction matrix of the corresponding field. Third, the correction value of the large field was replaced with that of the same point in the small field to generate a correction matrix suitable for different EPID images. Finally, we rectified the EPID image with the correction matrix, and then the processed EPID images were converted into the absolute dose. The calculated dose was compared with the measured dose via ICA. The gamma pass rates of 3%/3 mm and 2%/2 mm (5% threshold) were 99.6% ± 0.94% and 95.48% ± 1.03%, and the average gamma values were 0.28 ± 0.04 and 0.42 ± 0.05, respectively. Experimental results verified our method accurately corrected EPID images and converted pixel values into absolute dose values such that EPID was an efficient radiotherapy dosimetry tool.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Development of an Electronic Portal Imaging Device Dosimetry Method

et al. 2021

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Assessment of log‐based fingerprinting system of Mobius3D with Elekta linear accelerators

Noh

Kim

Shin

et al. 2021

J Applied Clin Med Phys

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Purpose:The purpose of this study was to investigate the matching error that occurs when the Mobius3D fingerprinting system is applied in conjunction with an Elekta linear accelerator (LINAC) and to offer an acceptable and alternative method for circumventing this problem. Material and methods: To avoid the multileaf collimator (MLC) conflicting error in the Mobius3D fingerprinting system, we developed an in-house program to move the MLC in the Digital Imaging and Communications in Medicine (DICOM) radiotherapy (RT)-Plan to pertinent positions, considering the relationship between log data and planned data. The re-delivered log files were calculated in the Mobius3D system, and the results were compared with those of corrected data (i.e., we analyzed a pair of re-collected log data and the previous DICOM RT-Plan data). The results were then evaluated by comparing several items, such as point dose errors, gamma index (GI) passing rates, and MLC root-mean-square (RMS) values. Results: For the point dose error, the maximum difference found was below 2.0%. In the case of GI analysis of all plans, the maximum difference in the passing rates was below 1.4%. The statistical results obtained using a paired Student's t-test showed that there were no significant differences within the uncertainty. In the case of the RMS test, the maximum difference found was approximately 0.08 mm. Conclusions: Our results showed that all the mismatched log files were sufficiently acceptable within the uncertainty. We conclude that the matching error obtained when applying Mobius3D to an Elekta LINAC may be addressed using a simple modification of the fingerprinting system, and we expect that our study findings will help vendors resolve this issue in the near future.

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Commissioning and clinical evaluation of a novel high‐resolution quality assurance digital detector array for SRS and SBRT

Zhou,

Liu,

Chen

et al. 2024

J Applied Clin Med Phys

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PurposeWe aimed to perform the commissioning and clinical evaluation of myQA SRS detector array for patient‐specific quality assurance (PSQA) of stereotactic radiosurgery (SRS)/ stereotactic body radiotherapy (SBRT) plans.MethodsTo perform the commissioning of myQA SRS, its dose linearity, dose‐rate dependence, angular dependence, and field‐size dependence were investigated. Ten SBRT plans were selected for clinical evaluation: 1) Common clinical deviations based on the original SBRT plan (Plan0), including multileaf collimator (MLC) positioning deviation and treatment positioning deviation were introduced. 2) Compared the performance of the myQA SRS and a high‐resolution EPID dosimetry system in PSQA measurement for the SBRT plans. Evaluation parameters include gamma passing rate (GPR) and distance‐to‐agreement (DTA) pass rate (DPR).ResultsThe dose linearity, angle dependence, and field‐size dependence of myQA SRS system exhibit excellent performance. The myQA SRS is highly sensitive in the detection of MLC deviations. The GPR of (3%/1 mm) decreases from 90.4% of the original plan to 72.7%/62.9% with an MLC outward/inward deviation of 3 mm. Additionally, when the setup error deviates by 1 mm in the X, Y, and Z directions with the GPR of (3%/1 mm) decreasing by an average of −20.9%, −25.7%, and −24.7%, respectively, and DPR (1 mm) decreasing by an average of −33.7%, −32.9%, and −29.8%. Additionally, the myQA SRS has a slightly higher GPR than EPID for PSQA, However, the difference is not statistically significant with the GPR of (3%/1 mm) of (average 90.4%% vs. 90.1%, p = 0.414).ConclusionDosimetry characteristics of the myQA SRS device meets the accuracy and sensitivity requirement of PSQA for SRS/SBRT treatment. The dose rate dependence should be adequately calibrated before its application and a more stringent GPR (3%/1 mm) evaluation criterion is suggested when it is used for SRS/SBRT QA.

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2D EPID dose calibration for pretreatment quality control of conformal and IMRT fields: A simple and fast convolution approach

Cited by 15 publications

References 28 publications

Development of an Electronic Portal Imaging Device Dosimetry Method

Development of an Electronic Portal Imaging Device Dosimetry Method

Assessment of log‐based fingerprinting system of Mobius3D with Elekta linear accelerators

Commissioning and clinical evaluation of a novel high‐resolution quality assurance digital detector array for SRS and SBRT

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