Marqués de Valdecilla University Hospital, Department of Radiation Oncology and Radiophysics, Santander, Spain.
Servicio de Radiofísica y Protección Radiológica, Hospital Universitario Dr. Negrín, Gran Canaria, Spain.
Med Phys. 2020 Jun;47(5):2242-2253. doi: 10.1002/mp.14080. Epub 2020 Mar 18.
The objective of this study was to characterize the Best Medical Canada microMOSFET detectors for their application in in vivo dosimetry for high-dose-rate brachytherapy (HDRBT) with Ir. We also developed a mathematical model to correct dependencies under the measurement conditions of these detectors.
We analyzed the linearity, reproducibility, and interdetector variability and studied the microMOSFET response dependence on temperature, source-detector distance, and angular orientation of the receptor with respect to the source. The correction model was applied to 19 measurements corresponding to five simulated treatments in a custom phantom specifically designed for this purpose.
The detectors (high bias applied in all measurements) showed excellent linearity up to 160 Gy. The response dependence on source-detector distance varied by (8.65 ± 0.06)% (k = 1) for distances between 1 and 7 cm, and the variation with temperature was (2.24 ± 0.05)% (k = 1) between 294 and 310 K. The response difference due to angular dependence can reach (10.3 ± 1.3)% (k = 1). For the set of measurements analyzed, regarding angular dependences, the mean difference between administered and measured doses was -4.17% (standard deviation of 3.4%); after application of the proposed correction model, the mean difference was -0.1% (standard deviation of 2.2%). For the treatments analyzed, the average difference between calculations and measures was 4.7% when only the calibration coefficient was used, but it is reduced to 0.9% when the correction model is applied.
Important response dependencies of microMOSFET detectors used for in vivo dosimetry in HDRBT treatments, especially the angular dependence, can be adequately characterized by a correction model that increases the accuracy of this system in clinical applications.
本研究旨在对 Best Medical Canada 微 MOSFET 探测器进行特性描述，以将其应用于 Ir 高剂量率近距离治疗（HDRBT）的体内剂量测量。我们还开发了一个数学模型，以校正这些探测器在测量条件下的依赖性。
我们分析了线性度、可重复性和探测器间的变异性，并研究了微 MOSFET 响应对温度、源-探测器距离以及受体相对于源的角度方位的依赖性。该校正模型应用于 19 次测量，这些测量对应于专门为此目的设计的定制体模中的 5 种模拟治疗。
探测器（所有测量中均施加高偏压）在高达 160Gy 时表现出优异的线性度。源-探测器距离的响应依赖性在 1 至 7cm 之间变化了（8.65±0.06）%（k=1），而温度变化为（2.24±0.05）%（k=1）在 294 至 310K 之间。由于角度依赖性引起的响应差异可达（10.3±1.3）%（k=1）。对于分析的测量集，关于角度依赖性，给予剂量和测量剂量之间的平均差异为-4.17%（标准偏差为 3.4%）；应用所提出的校正模型后，平均差异为-0.1%（标准偏差为 2.2%）。对于分析的治疗，仅使用校准系数时，计算值与测量值之间的平均差异为 4.7%，但应用校正模型后，该差异降低至 0.9%。
用于 HDRBT 治疗中的体内剂量测量的微 MOSFET 探测器存在重要的响应依赖性，特别是角度依赖性，可以通过校正模型来充分描述，这可以提高该系统在临床应用中的准确性。
