Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.
Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, NSW, 2500, Australia.
Med Phys. 2017 May;44(5):1965-1968. doi: 10.1002/mp.12209. Epub 2017 Apr 17.
A high resolution, water equivalent, optical and passive x-ray dosimeter has been constructed using plastic scintillator and optical fiber. This dosimeter has a peak edge-on spatial resolution of 100 μm in one dimension, with a 10 μm resolution dosimeter under investigation. The dosimeter design has a potential application in synchrotron x-ray microbeam radiation therapy where a high resolution is vital for accurate dose measurements and quality assurance.
BC-400 plastic scintillator, of thickness 100 μm, was optically coupled to an optical fiber with core diameter 1 mm. The end was coated in optical paint to improve sensitivity. An identical fiber was made without the scintillator to measure the background Cherenkov radiation induced in the fiber, to allow background signal subtraction. The light captured by the fibers was measured by PMTs. The probe system was exposed to a 6 MV, 10 × 10 cm LINAC x-ray field and the beam profile was measured at 100 cm, as well as the depth dose profile.
The measured profiles matched well with ionisation chamber data. Important beam parameters such as penumbra width and percent depth dose at various depths matched the ionisation chamber data, within uncertainty.
This work demonstrates that high resolutions can be achieved with a scintillation and optical fiber system. The probe is water-equivalent, passive, energy independent, radiation hard and inexpensive, making it ideal for further improvements for use with microbeam radiation therapy.
我们使用塑料闪烁体和光纤构建了一种高分辨率、水等效、光学和无源 X 射线剂量计。该剂量计在一维方向上具有 100μm 的峰边空间分辨率，在研究中具有 10μm 的分辨率剂量计。该剂量计设计在同步加速器 X 射线微束放射治疗中有潜在的应用，其中高分辨率对于准确的剂量测量和质量保证至关重要。
将厚度为 100μm 的 BC-400 塑料闪烁体与直径为 1mm 的光纤光学耦合。末端涂有光学涂料以提高灵敏度。制作了一根没有闪烁体的相同光纤，以测量光纤中诱导的背景切伦科夫辐射，以允许背景信号扣除。光纤捕获的光由 PMT 测量。将探头系统暴露于 6 MV、10×10cm LINAC X 射线场，并在 100cm 处测量束轮廓以及深度剂量轮廓。
测量的轮廓与电离室数据吻合良好。重要的束参数，如半影宽度和不同深度处的百分深度剂量，在不确定度范围内与电离室数据匹配。
这项工作表明，使用闪烁体和光纤系统可以实现高分辨率。探头是水等效的、无源的、能量无关的、辐射硬化的且廉价的，使其成为微束放射治疗进一步改进的理想选择。
