Scanning Parameter Optimization of Silicon Detector for Flattening Filter-Free Model Photon
Beam Basic Data Measurement
YUE Haizhen, WANG Meijiao, LIU Zhuolun, YAO Kaining, GONG Jian, WANG Ruoxi, DU Yi, ZHANG Yibao, WU Hao
Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Radiotherapy, Peking
University Cancer Hospital & Institute, Beijing 100142, China
Abstract：Objective To optimize the scanning parameters of silicone detector used for radiotherapy Flattening filter-free (FFF)
model photon beam basic data measurement, such as the percentage depth dose (PDD) and off-axis ratio (OAR). Methods We
obtained measurements of basic beam data from a 6 FFF photo radiotherapy linac using the PTW-60016 diode-p detector. The
measurements were performed with various scanning parameter sets and were compared with Monte Carlo simulation as reference.
The differences in were quantitatively analyzed with respect to the dependence on sampling steps and times. Results The standard
deviation in the PDD quality index of each small field (1 cm×1 cm, 2 cm×2 cm, 3 cm×3 cm, 4 cm×4 cm) was within 0.005.
The increase of sampling time had little influence on the measurement accuracy of PDD and OAR. The decrease of sampling
step size was conducive to improving the measurement accuracy of OAR penumbra area and PDD built-up area, but it was
meaningless to improve the measurement accuracy of PDD at large depth. In the meantime, we found that while penumbra
measurements were insensitive to sampling time, the penumbra width broadened with increased sampling step. Conclusion
PDD quality index was not sensitive to sampling time and step. The OAR penumbra was not sensitive to sampling
time. However, penumbra width was positively correlated with sampling step. As a trade-off between measurement
accuracy and efficiency, two scanning parameter sets with (0.5 s, 1.0 mm) and (0.5 s, 0.5 mm) was recommended as
optimized protocols using PTW-60016 silicon detector for FFF photo beam basic data measurement.
岳海振，王美娇，刘卓伦，姚凯宁，弓健，王若曦，杜乙，张艺宝，吴昊. 使用硅半导体探测器采集FFF小野光子束基础数据的扫描参数优选研究[J]. 中国医疗设备, 2019, 34(7): 60-64.
YUE Haizhen, WANG Meijiao, LIU Zhuolun, YAO Kaining, GONG Jian, WANG Ruoxi, DU Yi, ZHANG Yibao, WU Hao. Scanning Parameter Optimization of Silicon Detector for Flattening Filter-Free Model Photon
Beam Basic Data Measurement. China Medical Devices, 2019, 34(7): 60-64.
