Investigation of interfractional range variation owing to anatomical changes with beam directions based on water equivalent thickness in proton therapy for pancreatic cancer.
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引用次数: 0
Abstract
To assess the interfractional anatomical range variations (ARVs) with beam directions and their impact on dose distribution in intensity modulated proton therapy, we analyzed water equivalent thickness (WET) from 10 patients with pancreatic cancer. The distributions of the interfractional WET difference ($\Delta{\mathrm{WET}}^{\theta }$) across 360° were visualized using polar histograms. Interfractional ARVs were evaluated using the mean absolute error and ΔWET pass rate, indicating the percentage of $\Delta \mathrm{WE}{\mathrm{T}}^{\theta }$ < thresholds. The impact on dose distribution in proton therapy was evaluated based on two treatment plans for 40 Gy(RBE)/5 fractions: 'Plan A', using two beam angles, in which the target was closest to the body surface among four perpendicular directions; and 'Plan B', using two beam angles with small ARVs. Analysis revealed individual variations in angular trends of interfractional ARVs. Three distinct trends were identified: Group 1 exhibited small ARVs around posterior directions; Group 2 exhibited small ARVs except ~60°; Group 3 demonstrated minimal ARVs only ~90°. In dose evaluation, while 150° and 210° were selected in Plan B for 9 out of 10 patients, for the remaining patient, 60° and 90° were chosen. Comparing dose volume histogram parameters for all patients, Plan B significantly reduced target coverage loss while maintaining organ-at-risk sparing comparable to Plan A. These results demonstrated that selecting beam angles with small interfractional ARVs for each patient enhances the robustness of dose distribution, reducing target coverage loss.
期刊介绍:
The Journal of Radiation Research (JRR) is an official journal of The Japanese Radiation Research Society (JRRS), and the Japanese Society for Radiation Oncology (JASTRO).
Since its launch in 1960 as the official journal of the JRRS, the journal has published scientific articles in radiation science in biology, chemistry, physics, epidemiology, and environmental sciences. JRR broadened its scope to include oncology in 2009, when JASTRO partnered with the JRRS to publish the journal.
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