A collapsed-cone based transit EPID dosimetry method

Ortega, J. Martínez; Monedero, M. Pinto; González, Nuria; Tolani, Naresh; Castro, Pablo; Álvarez, Miguel Castanedo; Martín, Luis Núñez; Montero, Rocío Sánchez

doi:10.1016/j.ejmp.2018.01.006

Cited by 4 publications

(1 citation statement)

References 22 publications

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“…Due to its large imaging area, fast acquisition speed, high resolution, good linear response, long-term measurement stability, and being mounted on the linac, EPID has been extensively used in IMRT and VMAT quality assurance [ 2 , 3 , 4 , 5 , 6 , 7 ], including pretreatment and in-vivo dose verification. Pretreatment dose verification usually involves the following two approaches: first, the fluence generated by the treatment planning system (TPS) is convolved with the kernel to predict the EPID image; then, the predicted image is compared with the measured EPID image for verification [ 8 , 9 , 10 ]. This method is widely used in clinics, but may not reflect the errors introduced in the TPS calculation process.…”

Section: Introductionmentioning

confidence: 99%

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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