肿瘤快速旋转调强放疗摆位误差的测量与分析

目的:采用直线加速器机载的千伏级锥形束CT扫描技术对不同部位肿瘤患者的摆位误差进行探讨。方法:应用瓦里安RapidArc直线加速器治疗肿瘤患者180例,其中头颈部患者53例,胸部患者58例,盆腔患者69例。所有患者在首次放疗前行KV-CBCT扫描,以后每周扫描1次。将CBCT扫描图像和计划CT图像及其靶中心匹配,分析靶中心在x、y、z方向上的误差值及其误差分布情况,探讨我科CTV–PTV外放边界大小。结果:系统误差(均数)±随机误差(标准差)在平移误差Lateral左右(x)方向、Vertical背腹(y)方向、Longitudinal头脚(z)方向分别为头颈部x(0.55±0.79)mm,y(0.81±1.00)mm,z(1.21±1.12)mm;胸部x(1.13±1.26)mm,y(1.03±1.09)mm,z(2.12±2.15)mm;盆腔x(0.94±1.16)mm,y(0.87±1.08)mm,z(2.02±1.78)mm;绕y轴方向旋转(Rtn)误差分别为头颈部(0.39±0.48)°,胸部(0.47±0.54)°,盆腔(0.44±0.51)°。结论:CBCT可以减少分次治疗间的摆位误差,保证放疗摆位精度。

Measurement and Analysis of Setup Errors in RapidArc Radiotherapy for Tumors

Objective： To investigate the set-up errors in the treatment of different regions by using kilovoltage cone-beam com- puted tomography scanning technique of linear accelerator airborne. Methods： 180 patients were treated with the Varian Rapi- dArc linear accelerator,including 53 head and neck tumors,58 thoracic tumors and 69 Pelvic tumors.All the patients were scanned by kilovoltage cone-beam computed tomography before the first radiotherapy and afterward once a week.The acquired CBCT images were co-registered with planning CT and setup errors of iso-center positions on the axes of x,y and z were ob- tained for statistical analyses.Corresponding CTV to PTV margins were also calculated. Results： The systemic± random errors on lateral （x）, vertieal（y）and longitudinal （z）directions were（0.55±0.79） ram, （0.81 ±1.00）mm, （ 1.21 ± 1.12）mm for the head and neck tumors; （1.13±1.26）mm, （1.03±1.09）mm, （2.12±2.15）mm for the thoracic tumors; （0.94±1.16）mm, （0.87±1.08） mm, （2.02±1.78）mm for the Pelvic tumors ,respectively. The systemic＋ random errors on the rotational deviations were （0.39±0.48）° for the head and neck tumors; （0.47±0.54）° for the thoracic tumors; （0.44±0.51）° for the Pelvic tumors,respectively. Conclusions： Using CBCT can decrease positioning errors and ensure high radiotherapy precision.