评估在高能临床质子束中使用合成单晶金刚石探测器的剂量学特性。

Evaluation of the dosimetric properties of a synthetic single crystal diamond detector in high energy clinical proton beams.

机构信息

Department of Radiation Medicine, Loma Linda University Medical Center, 11234 Anderson Street, Loma Linda, California 92354.

出版信息

Med Phys. 2013 Dec;40(12):121702. doi: 10.1118/1.4828777.

DOI:10.1118/1.4828777

PMID:24320488

Abstract

PURPOSE

To investigate the dosimetric properties of a synthetic single crystal diamond Schottky diode for accurate relative dose measurements in large and small field high-energy clinical proton beams.

METHODS

The dosimetric properties of a synthetic single crystal diamond detector were assessed by comparison with a reference Markus parallel plate ionization chamber, an Exradin A16 microionization chamber, and Exradin T1a ion chamber. The diamond detector was operated at zero bias voltage at all times. Comparative dose distribution measurements were performed by means of Fractional depth dose curves and lateral beam profiles in clinical proton beams of energies 155 and 250 MeV for a 14 cm square cerrobend aperture and 126 MeV for 3, 2, and 1 cm diameter circular brass collimators. ICRU Report No. 78 recommended beam parameters were used to compare fractional depth dose curves and beam profiles obtained using the diamond detector and the reference ionization chamber. Warm-up∕stability of the detector response and linearity with dose were evaluated in a 250 MeV proton beam and dose rate dependence was evaluated in a 126 MeV proton beam. Stem effect and the azimuthal angle dependence of the diode response were also evaluated.

RESULTS

A maximum deviation in diamond detector signal from the average reading of less than 0.5% was found during the warm-up irradiation procedure. The detector response showed a good linear behavior as a function of dose with observed deviations below 0.5% over a dose range from 50 to 500 cGy. The detector response was dose rate independent, with deviations below 0.5% in the investigated dose rates ranging from 85 to 300 cGy∕min. Stem effect and azimuthal angle dependence of the diode signal were within 0.5%. Fractional depth dose curves and lateral beam profiles obtained with the diamond detector were in good agreement with those measured using reference dosimeters.

CONCLUSIONS

The observed dosimetric properties of the synthetic single crystal diamond detector indicate that its behavior is proton energy independent and dose rate independent in the investigated energy and dose rate range and it is suitable for accurate relative dosimetric measurements in large as well as in small field high energy clinical proton beams.

摘要

目的

研究合成单晶金刚石肖特基二极管的剂量学特性，以便在大、小束场高能临床质子束中进行精确的相对剂量测量。

方法

通过与参考 Markus 平行板电离室、Exradin A16 微电离室和 Exradin T1a 离子室进行比较，评估合成单晶金刚石探测器的剂量学特性。金刚石探测器在任何时候都工作在零偏置电压下。通过 155 和 250 MeV 能量的临床质子束的部分深度剂量曲线和横向束轮廓，以及 3、2 和 1 cm 直径的圆形黄铜准直器的 126 MeV 能量，进行比较剂量分布测量。使用 ICRU 报告 No.78 推荐的束参数，比较使用金刚石探测器和参考电离室获得的部分深度剂量曲线和束轮廓。在 250 MeV 质子束中评估探测器响应的预热/稳定性和剂量线性度，在 126 MeV 质子束中评估剂量率依赖性。还评估了二极管响应的茎效应和方位角依赖性。

结果

在预热照射过程中，发现金刚石探测器信号的最大偏差小于平均读数的 0.5%。探测器响应表现出良好的剂量线性行为，在 50 至 500 cGy 的剂量范围内，观察到的偏差小于 0.5%。探测器响应与剂量率无关，在所研究的剂量率范围内，偏差小于 0.5%，剂量率范围为 85 至 300 cGy/min。茎效应和二极管信号的方位角依赖性在 0.5%以内。使用金刚石探测器获得的部分深度剂量曲线和横向束轮廓与使用参考剂量计测量的结果非常吻合。