Clark Megan, Xiao Zhiyan, Sloop Austin, Zhang Yongbin, Lee Eunsin, Vasyltsiv Roman, Gladstone David, Zhang Rongxiao, Bruza Petr, Mascia Anthony E
Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire.
Cancer and Blood Diseases Institute, Cincinnati Children's Hospital; Department of Radiation Oncology, College of Medicine, University of Cincinnati, Cincinnati, Ohio.
Int J Radiat Oncol Biol Phys. 2025 May 1;122(1):194-198. doi: 10.1016/j.ijrobp.2024.12.005. Epub 2024 Dec 16.
To retrospectively validate the dose and dose rates delivered in FAST-01 clinical trial fields via submillimeter spatial and <0.25 ms temporal resolution scintillation imaging.
An ultrafast intensified CMOS camera (4.5-12 kHz sampling rate) imaged the light response of a scintillator sheet at the treatment isocenter and irradiated by pencil beam scanning proton fields, including FAST-01 clinical fields. Dose and dose rate linearity studies were performed, followed by camera calibration via gafchromic (external beam therapy 3) film. An EDGE diode detector was placed directly under the scintillator at the surface and at a 5 cm depth for comparison with the imaging data and log files. Frame-by-frame analysis of image stacks yielded dose and dose rate maps for each delivery at the surface. Using the percent depth dose curves and 3-dimensional spot profiles, the surface images were projected to a 5 cm depth for comparison with a secondary diode and log file recordings.
Camera response was linear with dose (R = 0.9998) and beam current (R = 0.9883) from 2 to 12 Gy and 20 to 210 nA, respectively. Gamma analysis of the cumulative dose maps at 3%/2 mm indicated a mean passing rate of 100% compared with film. Total irradiation time agreed with the log file recordings with an average deviation of 0.20 ± 0.07 ms. At the surface, the average imaged dose rate across the 7 fields was 114 ± 1 Gy/s, agreeing with the diode within 1% ± 1%. The dose at a 5 cm depth from the projected images (mean, 8.4 Gy) agreed with the reported dose (log files) within 0.13 ± 0.03 Gy (2% ± 1%). The average dose rate from projected images at a 5 cm depth was 62 ± 1 Gy/s, which agreed with the reported and diode values within 2% ± 3%.
This study provides the first independent validation of dose and dose rate for clinical proton FAST-01 fields at unprecedented spatiotemporal resolution. Owing to the nontrivial dose rate distributions in pencil beam scanning fields, such direct 2-dimensional dose rate mapping will be important in future pretreatment plan quality assurance.
通过亚毫米空间分辨率和<0.25毫秒时间分辨率的闪烁成像，回顾性验证FAST - 01临床试验野中所给予的剂量和剂量率。
一台超快增强型互补金属氧化物半导体相机（采样率为4.5 - 12千赫兹）对位于治疗等中心的闪烁体片的光响应进行成像，该闪烁体片由笔形束扫描质子野照射，包括FAST - 01临床试验野。进行了剂量和剂量率线性研究，随后通过辐射变色（外照射治疗3型）胶片对相机进行校准。在表面和5厘米深度处，将EDGE二极管探测器直接置于闪烁体下方，以与成像数据和日志文件进行比较。对图像堆栈进行逐帧分析，得出每次照射在表面的剂量和剂量率图。利用百分深度剂量曲线和三维光斑轮廓，将表面图像投影至5厘米深度，以与二级二极管和日志文件记录进行比较。
相机响应在2至12戈瑞和20至210纳安范围内分别与剂量（R = 0.9998）和束流（R = 0.9883）呈线性关系。对3%/2毫米处的累积剂量图进行伽马分析表明，与胶片相比，平均通过率为100%。总照射时间与日志文件记录相符，平均偏差为0.20±0.07毫秒。在表面，7个野的平均成像剂量率为114±1戈瑞/秒，与二极管测量值的偏差在1%±1%以内。投影图像在5厘米深度处的剂量（平均值为8.4戈瑞）与报告剂量（日志文件）的偏差在±0.13±0.03戈瑞（2%±1%）以内。投影图像在5厘米深度处的平均剂量率为62±1戈瑞/秒，与报告值和二极管测量值的偏差在2%±3%以内。
本研究以前所未有的时空分辨率首次对临床质子FAST - 01野的剂量和剂量率进行了独立验证。由于笔形束扫描野中剂量率分布复杂，这种直接的二维剂量率映射在未来的治疗前计划质量保证中将具有重要意义。
