National Cancer Center Hospital East, Kashiwa, Chiba, Japan.
J Appl Clin Med Phys. 2012 Mar 8;13(2):3699. doi: 10.1120/jacmp.v13i2.3699.
When in vivo proton dosimetry is performed with a metal-oxide semiconductor field-effect transistor (MOSFET) detector, the response of the detector depends strongly on the linear energy transfer. The present study reports a practical method to correct the MOSFET response for linear energy transfer dependence by using a simplified Monte Carlo dose calculation method (SMC). A depth-output curve for a mono-energetic proton beam in polyethylene was measured with the MOSFET detector. This curve was used to calculate MOSFET output distributions with the SMC (SMC(MOSFET)). The SMC(MOSFET) output value at an arbitrary point was compared with the value obtained by the conventional SMC(PPIC), which calculates proton dose distributions by using the depth-dose curve determined by a parallel-plate ionization chamber (PPIC). The ratio of the two values was used to calculate the correction factor of the MOSFET response at an arbitrary point. The dose obtained by the MOSFET detector was determined from the product of the correction factor and the MOSFET raw dose. When in vivo proton dosimetry was performed with the MOSFET detector in an anthropomorphic phantom, the corrected MOSFET doses agreed with the SMC(PPIC) results within the measurement error. To our knowledge, this is the first report of successful in vivo proton dosimetry with a MOSFET detector.
当使用金属氧化物半导体场效应晶体管 (MOSFET) 探测器进行体内质子剂量测定时，探测器的响应强烈依赖于线性能量传递。本研究报告了一种实用的方法，通过使用简化的蒙特卡罗剂量计算方法 (SMC) 来校正 MOSFET 响应对线性能量传递的依赖性。使用 MOSFET 探测器测量了聚乙烯中单能质子束的深度-输出曲线。该曲线用于通过 SMC（SMC（MOSFET））计算 MOSFET 输出分布。在任意点处的 SMC（MOSFET）输出值与通过使用平行板电离室 (PPIC) 确定的深度剂量曲线计算质子剂量分布的常规 SMC（PPIC）获得的值进行比较。使用这两个值的比值来计算任意点处 MOSFET 响应的校正因子。MOSFET 探测器获得的剂量是通过校正因子和 MOSFET 原始剂量的乘积确定的。当在人体模型体模中使用 MOSFET 探测器进行体内质子剂量测定时，校正后的 MOSFET 剂量与 SMC（PPIC）结果在测量误差范围内一致。据我们所知，这是首次成功使用 MOSFET 探测器进行体内质子剂量测定的报告。
