自供电纳米多孔气凝胶 X 射线传感器采用快速电子电流。

Department of Radiation Oncology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 02115, USA.

Department of Physics, University of Massachusetts Lowell, MA, 01854, USA.

Med Phys. 2019 Sep;46(9):4233-4240. doi: 10.1002/mp.13701. Epub 2019 Aug 1.

PURPOSE

We developed a new class of aerogel-based thin-film self-powered radiation sensors employing high-energy electron current (HEC) in periodic multilayer (high-Z | polyimide aerogel (PA) | low-Z) electrode microstructures.

MATERIALS

Low-Z (Al) and high-Z (Ta) electrodes were deposited on 50 μm-thick PA films to obtain sensors with Al-PA-Ta-PA-Al structures. Sensors were tested with x rays in the 40-120 kVp range and with 2.5 MV, 6 MV, and 6 MV-FFF linac beams (TrueBeam, Varian). Performance of PA-HEC sensors was compared to commercial A12 Farmer ionization chamber as well as to radiation transport simulations using CEPXS/ONEDANT with nanometer-to-micrometer spatial resolution. The computations included periodic and single-element structures N x (Al-PA-Ta-PA-Al) with variable layer thicknesses.

RESULTS

Signal from PA-HEC sensors was proportional to the simulated net leakage electron current (averaged over the PA thickness). Experimental response was linear with dose and independent of dose rate. Detector responses to different x-ray sources show higher signals for kVp photon energies, as expected, though a strong signal was obtained for MV energies as well. The signal scaled with total effective area inside the multielemental structures; for example, the yield of a multielement sensor made with 20 Ta layers compared to a single-element structure with 1 Ta layer of the same total thickness of Ta was 10 times greater for 6 MV beam and 23 times greater for 120 kVp. Beam attenuation per element in the detector was 0.5%, 1%, 3%, and 46%, respectively for 6 MV, 6 MV FFF, 2.5 MV, and 120 kVp.

CONCLUSION

We demonstrated the feasibility of aerogel-based multilayer HEC radiation detector and its application for flux/dose monitoring of kVp and radiotherapy MV beams with small beam attenuation.

目的

我们开发了一种新型基于气凝胶的薄膜自供电辐射传感器，采用高能电子电流（HEC）在周期性多层（高 Z | 聚酰亚胺气凝胶（PA）| 低 Z）电极微结构中。

材料

低 Z（Al）和高 Z（Ta）电极沉积在 50μm 厚的 PA 薄膜上，以获得具有 Al-PA-Ta-PA-Al 结构的传感器。使用 40-120 kVp 范围内的 X 射线和 2.5 MV、6 MV 和 6 MV-FFF 直线加速器束（TrueBeam，Varian）对传感器进行测试。将 PA-HEC 传感器的性能与商业 A12 农民电离室以及使用 CEPXS/ONEDANT 进行的辐射传输模拟进行了比较，模拟具有纳米到微米空间分辨率的周期性和单元素结构 N x（Al-PA-Ta-PA-Al），具有可变的层厚度。

结果

PA-HEC 传感器的信号与模拟的净泄漏电子电流成正比（在 PA 厚度上平均）。实验响应与剂量呈线性关系，与剂量率无关。不同 X 射线源的探测器响应显示出较高的光子能量 kVp 信号，这是预期的，尽管对于 MV 能量也获得了很强的信号。信号与多元素结构内的总有效面积成正比；例如，对于 6 MV 束，具有 20 个 Ta 层的多元素传感器的产额与相同 Ta 总厚度的单个 Ta 层的单元素结构相比增加了 10 倍，对于 120 kVp 则增加了 23 倍。探测器中每个元件的束衰减分别为 6 MV、6 MV FFF、2.5 MV 和 120 kVp 的 0.5%、1%、3%和 46%。