论文部分内容阅读
目的:应用三种探测器测量外置微型多叶准直器的射野相对输出因子(Relative Output Factor,ROF),并与蒙特卡罗(Monte Carlo,MC)方法的计算结果进行比较,对结果予以分析评估。方法:在6 MV、15 MV X线条件下,采用cc01、cc13、SFD三种探测器在IBA第二代蓝水箱中测量医科达APEX外置微型多叶准直器0.49 cm×0.49 cm~11.3 cm×11.3 cm照射野的ROF值;采用商业化的蒙特卡罗XVMC(X-Ray Voxel Monte Carlo,XVMC)源程序计算上述几何条件下的ROF,并与测量值进行比较。结果:对于cc01探测器,0.49 cm×0.49 cm照射野条件下,ROF测量值与MC计算值相对偏差较大,射线能量6 MV时为21.11%,射线能量15 MV时为11.34%。对于cc13探测器,照射野面积为0.49 cm×0.49cm、0.98 cm×0.98 cm时,测量值与MC计算值偏差很大,射线能量6 MV时分别达到53.17%和15.03%,射线能量15 MV时分别达到49.66%和15.85%。对于SFD探测器,由于其内径仅为0.6 mm,各个射野面积条件下测量结果基本不受空腔尺寸的影响,各个射野面积条件下其测量值与MC计算值吻合均较好。结论:测量外置微型多叶准直器小照射野ROF值时,由于缺侧向电子平衡和边缘剂量梯度多大,需要谨慎选择探测器。本研究证实,不同的探测器对ROF值的准确性存在较大的影响。选择灵敏区体积极小的半导体探测器并注意测量的几何条件,可以准确地测量小照射野的ROF值。
OBJECTIVE: To measure the relative output factor (ROF) of external micro-multi-leaf collimator with three detectors, and to compare with Monte Carlo (MC) method. The results Be analyzed and evaluated. Methods: The CMX APEX external micro-leaf collimator 0.49 cm × 0.49 cm ~ 11.3 was measured in the IBA second-generation blue water tank under the condition of 6 MV and 15 MV X-ray with cc01, cc13 and SFD detectors cm × 11.3 cm. The ROF under the above geometrical conditions was calculated using a commercially available X-Ray Voxel Monte Carlo (XVMC) source program and compared with the measured values. Results: For the cc01 detector, the ROF and MC calculated at 0.49 cm × 0.49 cm irradiation field showed large relative deviation. The energy of the beam was 21.11% at 6 MV and 11.34% at 15 MV. For the cc13 detector, the measured field has a large deviation from the MC calculated at 0.49 cm × 0.49 cm and 0.98 cm × 0.98 cm, with 53.17% and 15.03% of the energy at 6 MV and 15 MV at 15 MV Reaching 49.66% and 15.85% respectively. For the SFD detector, its diameter is only 0.6 mm, and its measurement results are basically unaffected by the size of the cavity under each field area. The measured values of the SFD detectors are in good agreement with the calculated values of MC under each field area. CONCLUSIONS: When measuring the ROF values of external micro-leaflet collimators, the detector should be chosen with caution due to the lack of lateral electron balance and the marginal dose gradient. This study confirms that different detectors have a greater impact on the accuracy of ROF values. Choosing a semiconductor detector of very small size in the sensitive area and paying attention to the geometrical conditions of the measurement can accurately measure the ROF of the small radiation field.