Performance optimization of a tri‐hybrid method for estimation of patient scatter into the EPID
Autor: | Boyd McCurdy, Timothy Van Beek, Idris A. Elbakri, Harry Ingleby, Kaiming Guo, Eric Van Uytven |
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Rok vydání: | 2021 |
Předmět: |
Accuracy and precision
Photon Physics::Medical Physics Monte Carlo method Fluence 030218 nuclear medicine & medical imaging 03 medical and health sciences 0302 clinical medicine Range (statistics) Radiation Oncology Physics Humans Scattering Radiation EPID dosimetry Radiology Nuclear Medicine and imaging hybrid scatter method Monte Carlo Instrumentation Physics Photons Radiation in vivo dose verification Phantoms Imaging Sampling (statistics) Kernel method patient scatter 030220 oncology & carcinogenesis portal dosimetry Monte Carlo Method Algorithm Algorithms Energy (signal processing) |
Zdroj: | Journal of Applied Clinical Medical Physics |
ISSN: | 1526-9914 |
Popis: | On‐treatment EPID images are contaminated with patient‐generated scattered photons. If this component can be accurately estimated, its effect can be removed, and therefore a corresponding in vivo patient dose estimate will be more accurate. Our group previously developed a "tri‐hybrid" (TH) algorithm to provide fast but accurate estimates of patient‐generated photon scatter. The algorithm uses an analytical method to solve for singly‐scattered photon fluence, a modified Monte Carlo hybrid method to solve for multiply‐scattered photon fluence, and a pencil beam scatter kernel method to solve for electron interaction generated scattered photon fluence. However, for efficient clinical implementation, spatial and energy sampling must be optimized for speed while maintaining overall accuracy. In this work, the most significant sampling issues were examined, including spatial sampling settings for the patient voxel size, the number of Monte Carlo histories used in the modified hybrid MC method, scatter order sampling for the hybrid method, and also a range of energy spectrum sampling (i.e., energy bin sizes). The total predicted patient‐scattered photon fluence entering the EPID was compared with full MC simulation (EGSnrc) for validation. Three phantoms were tested with 6 and 18 MV beam energies, field sizes of 4 × 4, 10 × 10, and 20 × 20 cm2, and source‐to‐imager distance of 140 cm to develop a set of optimal sampling settings. With the recommended sampling, accuracy and precision of the total‐scattered energy fluence of the TH patient scatter prediction method are within 0.9% and 1.2%, respectively, for all test cases compared with full MC simulation results. For the mean energy spectrum across the imaging plane, comparison of TH with full MC simulation showed 95% overlap. This study has optimized sampling settings so that they have minimal impact on patient scatter prediction accuracy while maintaining maximum execution speed, a critical step for future clinical implementation. |
Databáze: | OpenAIRE |
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