Centre for Cancer Research and Cell Biology, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7AE, UK.
Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast City Hospital, Belfast, BT9 7AB, UK.
Radiat Oncol. 2017 Dec 28;12(1):204. doi: 10.1186/s13014-017-0936-3.
Preclinical radiation biology has become increasingly sophisticated due to the implementation of advanced small animal image guided radiation platforms into laboratory investigation. These small animal radiotherapy devices enable state-of-the-art image guided therapy (IGRT) research to be performed by combining high-resolution cone beam computed tomography (CBCT) imaging with an isocentric irradiation system. Such platforms are capable of replicating modern clinical systems similar to those that integrate a linear accelerator with on-board CBCT image guidance.
In this study, we present a dosimetric evaluation of the small animal radiotherapy research platform (SARRP, Xstrahl Inc.) focusing on small field dosimetry. Physical dosimetry was assessed using ion chamber for calibration and radiochromic film, investigating the impact of beam focus size on the dose rate output as well as beam characteristics (beam shape and penumbra). Two film analysis tools) have been used to assess the dose output using the 0.5 mm diameter aperture.
Good agreement (between 1.7-3%) was found between the measured physical doses and the data provided by Xstrahl for all apertures used. Furthermore, all small field dosimetry data are in good agreement for both film reading methods and with our Monte Carlo simulations for both focal spot sizes. Furthermore, the small focal spot has been shown to produce a more homogenous beam with more stable penumbra over time.
FilmQA Pro is a suitable tool for small field dosimetry, with a sufficiently small sampling area (0.1 mm) to ensure an accurate measurement. The electron beam focus should be chosen with care as this can potentially impact on beam stability and reproducibility.
由于先进的小动物图像引导辐射平台在实验室研究中的应用，临床前放射生物学已经变得越来越复杂。这些小动物放射治疗设备能够通过将高分辨率锥形束计算机断层扫描（CBCT）成像与等中心照射系统相结合，实现最先进的图像引导治疗（IGRT）研究。这些平台能够复制类似于将线性加速器与机载 CBCT 图像引导集成的现代临床系统。
在这项研究中，我们对小动物放射治疗研究平台（SARRP，Xstrahl Inc.）进行了剂量评估，重点是小视野剂量学。使用电离室进行校准和光致变色胶片进行物理剂量评估，研究了光束焦点大小对剂量率输出以及光束特性（光束形状和半影）的影响。使用两种胶片分析工具评估了使用 0.5 毫米直径孔径的剂量输出。
对于使用的所有孔径，测量的物理剂量与 Xstrahl 提供的数据之间存在良好的一致性（1.7-3%之间）。此外，两种胶片读取方法以及针对两种焦点大小的我们的蒙特卡罗模拟都与所有小视野剂量数据吻合良好。此外，小焦点能够产生更均匀的光束，半影随时间更加稳定。
FilmQA Pro 是小视野剂量学的合适工具，具有足够小的采样面积（0.1 毫米），可以确保准确测量。应谨慎选择电子束焦点，因为这可能会影响光束稳定性和可重复性。
