宫颈癌图像引导调强放射治疗减少摆位误差的分析

目的 探讨锥形束CT(CBCT)扫描在宫颈癌病人调强放疗摆位中的意义.方法 选取宫颈癌调强放射治疗病人20例,利用俯卧体架和热塑体膜进行体位固定,初次治疗前对病人行锥形束CT扫描,治疗过程当中每周行1次CBCT扫描,获取病人左右、头脚、腹背3个方向上的误差数值,对这些数值进行分析并在线校正.结果 20例病人总共进行了120次CBCT扫描验证,校正前病人在左右X方向,头脚Y方向,腹背Z方向上的摆位误差分别为(0.295±0.074)、(0.373±0.090)、(0.302±0.078) cm;校正后三个方向的误差分别为(0.014±0.012)、(0.034±0.022)、(0.020±0.017) cm;每例病人治疗过程中摆位的误差逐渐降低,体位重复率高,20例病人的放疗按计划顺利完成,肿瘤1年局部控制率100%,不良反应明显减少.结论 CBCT扫描有利于对摆位误差的原因进行分析并采取有效措施减少误差,以保证实施准确的处方剂量,减少辐射损伤周围的正常组织器官,为临床放射治疗提供质量保证.

Setup error analysis for cervical cancer in image guided intensitymodulated radiotherapy

Objective To investigate the importance of cone-beam computed tomography (CBCT) scan in setup of intensity-modulated radiation therapy (IMRT) for cervical cancer.Methods 20 patients with cervical cancer were enrolled into the study and were immbolized with abdomen board and thermoplastic.All the patients were scanned by kilo voltage cone-beam computed tomography before radiotherapy every week.The setup errors isocenter positions on the axes of X,Y and Z were record and the data and correct placement error were analyzed online.Results 20 patients (120 cases) were verified about the position by CBCT.Before correction,the setup error of 3 directions (X,Y,Z axis) is (0.295±0.074),(0.373±0.090) and (0.302±0.078),respectively;After the correction,the setup error is (0.014±0.012),(0.034±0.022),(0.020±0.017) cm,respectively.All patients were successfully treated and the setup error decreased gradually.One year local tumor control rate was 100% and the adverse reaction decreased significantly.Conclusion CBCT scan is useful to analyze the causes of errors,taking effective measures to reduce the setup errors can make the does distribution of target and normal tissues around the organs more accurate,which provide quality assurance for clinical radiotherapy.