放疗期间运用CBCT调整治疗中心

目的应用锥形束CT（CBCT）评价分析放疗过程中因患者体型变化、肿瘤大小改变等因素导致的摆位误差,并修正治疗等中心。方法80例胸腹部肿瘤患者行调强放射治疗,治疗进行到一半的时候,运用CBCT的图像与靶区勾画轮廓线进行重新匹配,并以新的中心作为后半期放疗的中心。分析两次CBCT的治疗中心点的位置变化,并进行统计学分析。结果分析结果表明,56例患者治疗中心点位移等于或少于5mm,无需调整治疗中心。24例患者中心点位移大于5mm,需调整治疗中心。按调整后的治疗中心完成后期治疗。需调整比例占总病例的30％。结论利用CBCT对放疗摆位的误差测量准确有效。放疗时间跨度长,患者体型、肿瘤在治疗期间变化大,所以在治疗的中期进行合理的调整非常必要。

Adjustment of the treatment center displacement errors during radiotherapy on CBCT

Objective To evaluate setup errors result in some inevitable factors during radiotherapy such as somatotypes obviously changed, changes in tumor size using cone beam CT（CBCT）, and modify the treatment isocenter. Methods Eighty patients with thorax and abdomen malignant received radiotherapy by Varian Trilogy linear accelerator. CBCT images were collected for each patient on the time of half course of treatment, and were dimensionally rematched with planned CT images in planning system, then analyzed treatment center displacement between the first and the medium radiotherapy.The results were obtained by SPSS. Results For 56 patients, the treatment center displacement was equal to or less than 5mm, no need to adjust the isocenter. However, the treatment center displacement was more than 5mm for 24 patients, 30% of the total cases, need to adjust the errors. The left treatment was enfored according to the new isocenter. Conclusion It is accurate to reduce the setup errors with CBCT. Somatotypes and tumor size changed obviously in the long time radiotherapy course, so that the adjustment during medium treatment was necessary and reasonable.