宫颈癌调强放疗和三维适形放疗剂量对比研究

Dosimetric Analysis and Comparison for Cervical Cancer Patients Recei ving 3D-CRT and IMRT

目的:研究宫颈癌调强放疗(IMRT)和三维适形放疗(3D-CRT)时靶区及其周围正常组织受照剂量的差异。材料方法:用拓能公司生产的WiMRT三维适形调强放疗计划系统分别进行6～9个照射角度的3D-CRT和IMRT计划设计,肿瘤量45Gy,计算出正常组织和靶区的剂量—体积直方图以及所需照射的总跳数。用Siemens生产的Primart电子直线加速器(X射线能量6MV,MLC叶片29对)实施放疗计划,测量出10cm×10cm射野外漏射线和散射线剂量率,估算放疗时正常组织所受辐射剂量随距离的变化关系。结果:照射野数和照射角度一致,IMRT时膀胱、直肠、阴道所受平均剂量分别只有3D-CRT时的19.5%(29.3/150.3)、64.5%(538.0/833.0)和61.0%(1553.6/2546.3),靶区平均受照剂量略高于3D-CRT。IMRT病人正常组织所受散射线和漏射线剂量约为3D-CRT病人的1.5倍。结论:宫颈癌IMRT剂量分布优于3D-CRT。

Objective: To estimate the dosimetric differences for patients with cer vical carcinoma who receive three-dimensional conformal radiotherapy (3D-CRT) an d intensity modulated radiation therapy (IMRT) respectively. Methods: The 3D-CRT and IMRT plans with 6 to 9 beam fields respectively for cervical cancer patient s were created by a commercial WiMRT 3D TPS. The DVH for bladder, rectum, vagina and GTV and the total number of monitor units (MU) of each plan were calculated by the WiMRT 3D-TPS, and the treatment was delivered with 6 MV photons using a 'step-and-shoot' technique on a Siemens Primart linac with 29-leaf MLC. The X-ra y leakage and scattered dose (LSD) at the dmax (maximum dose depth) in the water was measured by dosimeter and ion chamber. The irradiation dose to normal tiss ues at a certain distance outside the treatment fields was calculated by using t he LSD and the total MU of each plan. Result: The average dose of bladder, rectu m and vagina of IMRT patients are respectably only 19.5%, 64.5% and 61.0% that o f 3D-CRT patients with the same number of fields and gantry angles, but the dose to GTV of IMRT patients is higher than that of 3D-CRT patients. The LSD for nor mal tissues of patients receiving IMRT is about 1.5 times that of 3D-CRT patient s. Conclusion: IMRT has more advantages than 3D-CRT for patients with cervical c arcinoma.