Development of a one-stop beam verification system using electronic portal imaging devices for routine quality assurance

Lim, Sangwook; Young, Sun; Jeung, Tae Sig; Yi, B; Lee, Sang Hoon; Lee, Suk; Cho, Sam Ju; Choi, Jin‐Ho

doi:10.1016/j.meddos.2011.11.003

Cited by 6 publications

(3 citation statements)

References 11 publications

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“…Because of the flood field correction, the EPID‐based profile QA present in the literature 6 , 7 , 8 , 9 has generally been a constancy check relative to a baseline that was set once the system had been calibrated using an alternate device. The EPID cannot currently be used for evaluation of the absolute beam profile as this is removed by flood field calibration, and thus the user must apply different and less‐efficient QA methods.…”

Section: Introductionmentioning

confidence: 99%

Determination of the electronic portal imaging device pixel‐sensitivity‐map for quality assurance applications. Part 1: Comparison of methods

Barnes

Sun

Oborn

et al. 2022

J Applied Clin Med Phys

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Calibration of a radiotherapy electronic portal imaging device (EPID) using the pixel-sensitivity-map (PSM) in place of the flood field correction improves the utility of the EPID for quality assurance applications.Multiple methods are available for determining the PSM and this study provides an evaluation to inform on which is superior. Methods: Three different empirical methods ("Calvary Mater Newcastle"[CMN], "Varian,"and "WashU") and a Monte Carlo-based method of PSM determination were investigated on a single Varian TrueBeam STx linear accelerator (linac) with an aS1200 EPID panel. PSM measurements were performed for each empirical method three successive times using the 6 MV beam. The resulting PSM from each method was compared to the Monte Carlo method as a reference using 2D percentage deviation maps and histograms plus crossplane profiles. The repeatability of generated PSMs was also assessed via 2D standard deviation (SD) maps and histograms. Additionally, the Beam-Response generated by removal of the PSM from a raw EPID image for each method was visually contrasted. Finally, the practicality of each method was assessed qualitatively and via the measured time required to acquire and export the required images. Results:The median pixel-by-pixel percentage deviation between each of the empirical PSM methods and the Monte Carlo PSM was -0.36%, 0.24%, and 0.74% for the CMN, Varian, and WashU methods, respectively. Ninety-five percent of pixels were found to be repeatable to within -0.21%, 0.08%, 0.19%, and 0.35% (1 SD) for the CMN, Monte Carlo, Varian, and WashU methods, respectively. The WashU method was found to be quickest for data acquisition and export and the CMN the slowest. Conclusion: For the first time four methods of generating the EPID PSM have been compared in detail and strengths and weaknesses of each method have been identified. All methods are considered likely to be clinically acceptable and with similar practical requirements.

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Section: Introductionmentioning

confidence: 99%

Determination of the electronic portal imaging device pixel‐sensitivity‐map for quality assurance applications. Part 1: Comparison of methods

Barnes

Sun

Oborn

et al. 2022

J Applied Clin Med Phys

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show abstract

“…The amorphous silicon electronic portal imaging device (EPID) has been used as a detector for linac QA measurements 2, 3, 4, 5, 6, 7, 8, 9, 10. EPID is well suited to a number of linac QA tests as it provides a high spatial and temporal resolution two‐dimensional digital measurement from a device that requires minimal setup time and is integrated into the linac.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the TrueBeam machine performance check (MPC) beam constancy checks for flattened and flattening filter‐free (FFF) photon beams

Barnes

Greer

2016

J Applied Clin Med Phys

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Machine Performance Check (MPC) is an automated and integrated image‐based tool for verification of beam and geometric performance of the TrueBeam linac. The aims of the study were to evaluate the MPC beam performance tests against current daily quality assurance (QA) methods, to compare MPC performance against more accurate monthly QA tests and to test the sensitivity of MPC to changes in beam performance. The MPC beam constancy checks test the beam output, uniformity, and beam center against the user defined baseline. MPC was run daily over a period of 5 months (n = 115) in parallel with the Daily QA3 device. Additionally, IC Profiler, in‐house EPID tests, and ion chamber measurements were performed biweekly and results presented in a form directly comparable to MPC. The sensitivity of MPC was investigated using controlled adjustments of output, beam angle, and beam position steering. Over the period, MPC output agreed with ion chamber to within 0.6%. For an output adjustment of 1.2%, MPC was found to agree with ion chamber to within 0.17%. MPC beam center was found to agree with the in‐house EPID method within 0.1 mm. A focal spot position adjustment of 0.4 mm (at isocenter) was measured with MPC beam center to within 0.01 mm. An average systematic offset of 0.5% was measured in the MPC uniformity and agreement of MPC uniformity with symmetry measurements was found to be within 0.9% for all beams. MPC uniformity detected a change in beam symmetry of 1.5% to within 0.3% and 0.9% of IC Profiler for flattened and FFF beams, respectively.

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“…Daily QA, having the highest frequency, are used to evaluate radiotherapy machines prior to using them in daily practice of treating patients. Multiple systems are utilized to perform daily QA in clinical radiotherapy [8][9][10][11][12][13][14][15][16][17]. Daily morning QA are generally done with conventional phantom that, besides being time consuming, only measures beam quality via Tissue Phantom Ratio (TPR 20,10 ), for available photon beams.…”

Section: Introductionmentioning

confidence: 99%

Monitoring Linear Accelerator Output Constancy and Overall Performance Using the PTW Quickcheckwebline

et al. 2022

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Daily morning quality assurance (QA) for all available beams using conventional phantom measures only output and beam quality. PTW QUICKCHECKwebline (PTW QCw) is a compact movable light-weight dosimetry equipment used for daily QA, capable of measuring flatness, symmetry, beam quality and output constancy of a given beam in a single exposure. The purpose of this study was to analyze and monitor the output constancy of a medical linear accelerator using PTW QCw and assess the overall performance of the PTW QCw. The output parameters of 4, 6 and 15 MV photon beams and 4, 6, 8, 10, 12 and 15 MeV electron beams of the Elekta Synergy linear accelerator in Kathmandu Cancer Center were analyzed. It was found in the study that all the parameters were well within the recommended tolerance limit of ±3%. Some known modifications in the settings of the linear accelerator gantry, couch, and collimator were introduced separately during the exposures, and the percentage variations from the baseline values were noted to check the sensitivity of the PTW QCw using 6 MV photon beam. The PTW QCw was able to detect the deviations introduced to the external irradiation conditions for both photon and electron beams under daily testing conditions. The results from this study suggest that daily dosimetric consistency measurements using the PTW QCw helps to monitor the overall performance of the linear accelerator.

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Development of a one-stop beam verification system using electronic portal imaging devices for routine quality assurance

Cited by 6 publications

References 11 publications

Determination of the electronic portal imaging device pixel‐sensitivity‐map for quality assurance applications. Part 1: Comparison of methods

Determination of the electronic portal imaging device pixel‐sensitivity‐map for quality assurance applications. Part 1: Comparison of methods

Evaluation of the TrueBeam machine performance check (MPC) beam constancy checks for flattened and flattening filter‐free (FFF) photon beams

Monitoring Linear Accelerator Output Constancy and Overall Performance Using the PTW Quickcheckwebline

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