基于锥形束CT直肠癌调强放疗固定方式的临床效果分析

The analysis of clinical effect of different fixed methods for intensity modulated radiation therapy of rectal cancer with cone beam computed tomography

目的:利用锥形束CT(CBCT)分析直肠癌调强放疗两种固定方法的临床效果。方法:将48例直肠癌放疗患者按固定方式分为两组,常规组采用仰卧体架加热塑体膜固定,观察组采用俯卧体架加热塑体膜固定。每人每周第一次治疗前利用机载影像系统进行CBCT图像扫描,利用骨性结构将CT图像和定位时的数字影像重建图像进行匹配,获取并分析两组患者X(左右方向)、Y(头脚方向)、Z(前后方向)的摆位误差;由观察组摆位误差计算临床靶区(CTV)到计划靶区(PTV)外放范围MPTV大小;分析两组患者小肠、膀胱受照剂量体积比。结果:常规组与观察组患者共获取240幅CBCT图像,在X、Y、Z三个方向的摆位误差分别为(2.65±1.56)mm/(2.45±1.50)mm、(2.99±1.76)mm/(2.33±1.82)mm、(2.78±1.45)mm/(2.10±1.73)mm,两组患者在Y、Z方向摆位误差比较差异有统计学意义(P<0.05),X方向比较,差异无统计学意义(P>0.05);观察组CTV到PTV外扩范围MPTV在X、Y、Z方向依次为4.28 mm、5.14 mm、4.82 mm;观察组小肠、膀胱的平均受照剂量Dmean小于常规组,差异有统计学意义(P<0.05)。结论:直肠癌调强治疗时采用俯卧体架加热塑体膜能更好地保持体位,同时减少小肠、膀胱的受照剂量,临床应用优势明显。

Objective To analyze the clinical effect of two fixed methods in intensity modulated radiation therapy for rectal cancer by cone beam computed tomography.Method 48 cases of rectal cancers was divided into two groups by ways of fixed position.The conventional group was fixed with the supine body frame and thermoplastic film.Observation group was fixed with the prone body frame and thermoplastic film.Every person scaned cone beam computed tomography by OBI before the first treatment per week,and cone beam computed tomography images online matched with the digital reconstructed radiograph of CT localization by bony structure,to record and analyze the set-up errors in X、Y and Z axis;To calculate the range of MPTV by set-up errors of the observation group;Analyze the dose volume ratio of small intestine and bladder.Results The conventional group and the observation group patients acquired 240 CBCT images,the set-up errors in X、Y and Z axis were(2.65±1.56)mm/(2.45±1.50)mm,(2.99±1.76)mm/(2.33±1.82)mm,(2.78±1.45)mm/(2.10±1.73)mm,respectively,the set-up error comparison of two groups of patients in Y and Z axis was statistically significant(P<0.05),but the set-up error comparison of the X axis was no significant difference(P>0.05);The MPTV range of the observation group in X、Y and Z axis were 4.28 mm、5.14 mm and 4.82 mm.Observation group was lower than conventional group in the Dmean of small intestine and bladder,the difference was statistically significant(P<0.05).Conclusion Using prone body frame and thermoplastic film can better keep position in intensity modulated radiation therapy for rectal cancer,and reduce the exposure dose of small intestine and bladder,it has obvious clinical advantages.