锥形束CT在评价两种宫颈癌调强放疗中的应用

Application of cone beam CT in the evaluation of two intensity modulated radiotherapy for cervical cancer

摘要:

目的利用锥形束CT分析宫颈癌调强放疗两种治疗方法的临床应用价值。方法将56 例宫颈癌放疗患者按固定体位方式和治疗计划分为两组，常规组采用仰卧位体架和热塑体膜固定，执行静态调强计划治疗；观察组采用俯卧位体架和热塑体膜固定，执行容积调强计划治疗；治疗时每人每周第一次治疗前均扫描锥形束CT，利用骨性标记在线与计划CT 图像匹配，记录并分析两组患者左右方向（X）、头脚方向（Y）、前后方向（Z）摆位误差；利用剂量体积直方图分析两组患者小肠、膀胱、直肠和股骨头重要器官的受照剂量体积比。结果两 组患者共获取280幅锥形束CT图像，两组患者在Y、Z轴摆位误差比较差异有统计学意义（ TY=2.336， PY=0.021；TZ=3.278，PZ=0.0004），X轴比较，差异无统计学意义（t =0.573，P =0.290）；两组在X 轴旋转误差比较，差异有统计学意义（t =2.134，P =0.029），Y、Z轴比较，差异无统计学意义（P >0.05）；观察组在计划总跳字和治疗时间均优于常规组，差异有统计学意义（t =9.549 和17.324，均P=0.000）；观察组膀胱V50 优于常规组（P =0.031），在小肠、直肠、膀胱、左股骨头的平均剂量Dmean> 常规组（P <0.05），两组其余比较无差异。结论采用锥形束CT 技术对两种宫颈癌调强放疗的体位摆放进行指导，为提高放疗精度提供影像学上的依据，具有较好的临床应用价值。

Abstract:

Objective To analyze the clinical value in two intensity modulated radiotherapy ways for cervical cancer by cone beam CT. Methods A total of 56 cases of cervical cancers were divided into two groups by fixed position and treatment planning. The supine body frame and thermoplastic film were used and static intensity-modulated plan was carried out in conventional group; observation group used prone position body frame and thermoplastic film and volumetric modulated arc therapy plan. The cone beam CT was scanned before the first treatment per week for each person. Set-up errors were recorded and analyzed in X, Y and Z axis; the dose volume ratio of the vital organs including small intestine, bladder, rectum and femoral head were analyzed with dose-volume histogram. Results A total of 280 cone beam CT images were acquired for the two groups, and set-up error in X, Y, Z was (0.261± 0.160) / (0.246 ±0.155) cm, (0.297 ±0.167) /(0.232 ±0.181) cm and (0.267 ±0.154) / (0.190 ±0.172) cm, respectively between the groups. The set-up errors in Y and Z axis were statistically significant between the groups (T Y =2.336, PY= 0.021;T Z =3.278, PZ =0.004), but there was no significant difference in X axis (t = 0.573, P= 0.290). There was statistically significant for rotation error in X axis ( t= 2.134,P = 0.029), but were no significant differences in Y and Z axis ( P> 0.05). The total MU and treatment time of the observation group were better than those in the conventional group (t = 9.549 and 17.324, P= 0.000). The observation group is better than traditional group in bladder V50 ( P= 0.031). the Dmean of small intestine, rectum, bladder, and left femoral head in the observation group is lower than the conventional group (P < 0.01). Conclusions Application of cone beam CT technique in two intensity modulated radiation therapy for cervical cancer indicates a potential clinical value,which provides image basis for improving the accuracy of radiotherapy.