Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
Med Phys. 2013 Jun;40(6):062101. doi: 10.1118/1.4803510.
The goal of this study was to prove the feasibility of using a single-fiber multipoint plastic scintillation detector (mPSD) as an in vivo verification tool during (192)Ir high-dose-rate brachytherapy treatments.
A three-point detector was built and inserted inside a catheter-positioning template placed in a water phantom. A hyperspectral approach was implemented to discriminate the different optical signals composing the light output at the exit of the single collection optical fiber. The mPSD was tested with different source-to-detector positions, ranging from 1 to 5 cm radially and over 10.5 cm along the longitudinal axis of the detector, and with various integration times. Several strategies for improving the accuracy of the detector were investigated. The device's accuracy in detecting source position was also tested.
Good agreement with the expected doses was obtained for all of the scintillating elements, with average relative differences from the expected values of 3.4 ± 2.1%, 3.0 ± 0.7%, and 4.5 ± 1.0% for scintillating elements from the distal to the proximal. A dose threshold of 3 cGy improved the general accuracy of the detector. An integration time of 3 s offered a good trade-off between precision and temporal resolution. Finally, the mPSD measured the radioactive source positioning uncertainty to be no more than 0.32 ± 0.06 mm. The accuracy and precision of the detector were improved by a dose-weighted function combining the three measurement points and known details about the geometry of the detector construction.
The use of a mPSD for high-dose-rate brachytherapy dosimetry is feasible. This detector shows great promise for development of in vivo applications for real-time verification of treatment delivery.
本研究旨在证明使用单纤维多点塑料闪烁探测器（mPSD）作为（192）Ir 高剂量率近距离放射治疗过程中的体内验证工具的可行性。
构建了一个三点探测器，并将其插入放置在水模体中的导管定位模板内。实施了高光谱方法来区分在单收集光纤出口处组成光输出的不同光学信号。用不同的源-探测器位置测试了 mPSD，范围从 1 到 5cm 径向和超过 10.5cm 沿探测器的纵轴，并使用不同的积分时间。研究了几种提高探测器精度的策略。还测试了该设备检测源位置的准确性。
对于所有闪烁元件，都获得了与预期剂量非常吻合的结果，从远端到近端的闪烁元件的平均相对差异分别为 3.4±2.1%、3.0±0.7%和 4.5±1.0%。3cGy 的剂量阈值提高了探测器的总体精度。3s 的积分时间在精度和时间分辨率之间提供了良好的折衷。最后，mPSD 测量放射性源定位不确定性不超过 0.32±0.06mm。通过结合三个测量点和探测器结构的几何形状的已知细节的剂量加权函数，提高了探测器的准确性和精度。
使用 mPSD 进行高剂量率近距离放射治疗剂量测定是可行的。该探测器为实时验证治疗输送的体内应用的发展提供了很大的前景。
