방사선치료의 실물 볼루스와 RTPS 기반 가상 볼루스의 선량분포 비교 분석

초록

This study aimed to quantitatively compare the dose calculation results between a virtual bolus applied in a radiotherapy treatment planning system (RTPS) and a physical bolus acquired through CT imaging, in order to evaluate the clinical applicability and accuracy of the virtual bolus. 15 cm-thick physical bolus was scanned using CT, and the dose distribution was calculated using RTPS (CorePLAN) under 6 MV and 10 MV photon beam conditions. The virtual bolus was applied on top of the physical bolus in 5 mm increments ranging from 0 mm to 40 mm in thickness. Doses were calculated along the central axis of the beam at 5 mm intervals to a depth of 150 mm. For direct comparison, a 10 cm-thick virtual bolus was added atop the CT image containing the physical bolus, and the depth dose distribution was calculated at 1 mm intervals. Depth dose curves were generated and compared, and statistical analysis was performed using ANOVA and Bland–Altman analysis. In the 6 MV condition, no statistically significant differences in dose were observed across different virtual bolus thicknesses. For 10 MV, statistical significance was found, but post-hoc analysis did not reveal significant group differences. Bland–Altman analysis showed minimal systematic bias between the physical and virtual bolus doses, with most data points falling within the limits of agreement, indicating clinically acceptable consistency. However, noticeable dose discrepancies were observed between the two bolus types in the surface and build-up regions. The virtual bolus implemented in RTPS can be considered a reliable alternative to the physical bolus for general depth dose calculations, contributing to improved treatment planning flexibility and patient convenience. However, in treatment scenarios where precise surface or build-up region dosing is critical, CT-based planning including the physical bolus may be more appropriate.

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