前列腺癌图像引导放疗中kV级CBCT扫描的剂量学研究

Dosimetric Study on kV-CBCT Scanning Based on Image Guided Radiotherapy for Prostate Cancer

目的评估前列腺癌图像引导放疗中,kV-CBCT扫描对直肠、膀胱及股骨头产生的额外图像剂量。方法采用蒙特卡罗方法建立kV-CBCT物理模型,结合患者的CT图像,模拟扫描条件,计算感兴趣区域的剂量。结果 44次CBCT扫描,直肠受到的平均剂量为77.8 cGy,膀胱为79.6 cGy,股骨头为159 cGy。结论图像引导放疗将对危及器官产生不可忽略的图像剂量,在计划设计中,需谨慎评估原计划是否依然满足处方要求。

Objective To evaluate the additional image dose （rectum, bladder and femoral head） of kV-CBCT scanning based on image guided radiotherapy for prostate cancer. Methods The Monte Carlo method was used to establish kV-CBCT physical model combined with patient CT images, simulate the scanning condition and calculate the dose in region of interest. Results In 44 times of CBCT scanning, the average dose of rectum was 77.8 cGy, bladder was 79.6 cGy and femoral head was 159 cGy. Conclusions Image guided radiotherapy can make an non-ignorable image dose for organs at risk. In plan designing, the original treatment planning need to be carefully evaluated in order to still satisfy the dose constraints.