Raj Sathiya, Saminathan Sathiyan, Prakasam Kiruthika
Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India.
J Med Phys. 2025 Jan-Mar;50(1):155-159. doi: 10.4103/jmp.jmp_156_24. Epub 2025 Mar 7.
The purpose of this study was to investigate the tolerance limits (TL) and action limits (AL) in gamma passing rate for craniospinal irradiation volumetric modulated arc therapy (VMAT) treatment plans.
Twenty-eight patients were planned using the VMAT technique; plans were delivered on an Elekta Versa HD. The delivered fluence was recorded by PTW 2D array, and the gamma passing rate (%GP) was analyzed using PTW VeriSoft. The universal TL and AL from TG 218 were applied to analyze the %GP for each plan. As per AAPM TG 218, a statistical process control of %GP was performed to set the TL and AL.
The average %GP for the brain, upper spine, and lower spine was 98.4%, 98.8%, and 98.4%, respectively. The TL and AL for the brain, upper spine, and lower spine were TL: 95.1%, 95.1% and 94.8%, and AL: 89.7%, 89.3%, and 86.7%, respectively. The analysis of variance test showed that the value in %GP among the brain, upper spine, and lower spine was >0.1679. The %GP rate between the sites was not statistically significant.
AAPM TG 218 guidelines are more suitable for establishing TL and AL for craniospinal irradiation (CSI) VMAT plans. This study suggests that a single value of TL and AL for CSI plans, rather than site-specific values, could be suitable for monitoring CSI patient-specific quality assurance trends and the same can be utilized.
本研究旨在探讨颅脊髓照射容积调强弧形治疗（VMAT）计划中伽马通过率的耐受限度（TL）和行动限度（AL）。
采用VMAT技术为28例患者制定计划；计划在Elekta Versa HD设备上实施。通过PTW二维阵列记录输出的注量，并使用PTW VeriSoft分析伽马通过率（%GP）。应用来自TG 218的通用TL和AL来分析每个计划的%GP。根据AAPM TG 218，对%GP进行统计过程控制以设定TL和AL。
脑、上脊柱和下脊柱的平均%GP分别为98.4%、98.8%和98.4%。脑、上脊柱和下脊柱的TL分别为95.1%、95.1%和94.8%，AL分别为89.7%、89.3%和86.7%。方差分析表明，脑、上脊柱和下脊柱之间%GP的 值>0.1679。各部位之间的%GP率无统计学差异。
AAPM TG 218指南更适合为颅脊髓照射（CSI）VMAT计划建立TL和AL。本研究表明，CSI计划采用单一的TL和AL值，而非特定部位的值，可能适用于监测CSI患者特定的质量保证趋势，并且可以采用相同的值。
