胰腺癌调强放疗的摆位和图像引导参数

Image-guided intensity modulate radiotherapy in treatment of patients with pancreatic cancer

目的分析胰腺癌调强放疗(intensity modulate radiation therapy,IMRT)的治疗摆位和图像引导位移参数及其影响因素,为提高治疗精确度提供重要信息。方法 2011年1月-2014年12月解放军总医院43例接受大分割螺旋断层放疗的胰腺癌患者采用体膜固定,分时口服造影剂及CT模拟定位,勾画胰腺肿瘤靶区。胰腺癌患者接受治疗前根据体表标志摆位兆伏级计算机断层(Megavoltage CT,MVCT)扫描,获取患者左右(x)、头脚(y)、前后(z)和横断面旋转(Roll)方向的位移参数,校正位移误差并图像配准后行调强放疗。分析图像引导相关参数及影响参数的因素。结果 43例共接受923次MVCT扫描,在x、y、z方向线性位移的系统误差±随机误差分别为(0.02±0.68)mm、(-0.34±2.41)mm、(0.52±1.03)mm;Roll方向旋转误差为(0.08±0.26)°,在x、y、z方向外扩5.38 mm、14.19 mm、4.65 mm。既往化疗、年龄对z方向位移的影响,性别对Roll方向位移的影响均有统计学差异(P<0.05)。引导频率(每天及每周图像引导)存在统计学差异(P<0.05)的比例在x、y、z、Roll方向上分别为25.6%、9.3%、25.6%、14.0%,x、y、z、Roll图像引导方向上至少1个存在明显差异的患者占51.2%。治疗时间上(每周之间)图像引导存在统计学差异(P<0.05)的比率在x、y、z、Roll方向上分别为23.08%、17.95%、10.26%、10.26%,x、y、z、Roll图像引导方向上至少1个存在明显差异的患者占51.3%。结论图像引导和治疗靶区外放可以有效减小摆位误差,提高胰腺癌放疗的精确度。每天1次图像引导,为胰腺癌调强放疗提供了必要的质量保证。

Objective To analyze the set-up and displacement parameters of intensity modulated radiation therapy（IMRT） and its related factors for pancreatic cancer, so as to provide guidance for treatment precision. Methods Forty-three consecutive patients with pancreatic cancer treated with hypofractionated radiotherapy using tomotherapy in Chinese PLA General Hospital from January 2011 to December 2014 were enrolled in this study. The Megavoltage CT（MVCT） images before each treatment were registered with kilovoltage CT（KVCT） images with CT simulation. The setup errors of the left/right（x）, superior/inferior（y）, anterior/posterior（z） and transverse profile rotation（Roll） were recorded, and its related impact factors were analyzed. Results All patients had undergone 923 MCT scans. The average setup errors in the x, y, z and roll directions were（0.02±0.68） mm,（-0.34±2.41） mm,（0.52±1.03） mm,（0.08±0.26）°, respectively. The corresponding enlargement margins in the direction of x, y, and z were 5.38 mm, 14.19 mm, and 4.65 mm, respectively. The setup errors of z direction were significantly associated with chemotherapy and age（P〈0.05）, and the setup errors of roll direction were significantly associated with gender（P〈0.05）. There were significant differences of image guide radiation therapy（IGRT） between once daily and once weekly in the directions of x, y, z and roll（P〈0.05）. The corresponding patients accounted for 25.6%, 9.3%, 25.6% and 14.0%, respectively. There were also significant differences between weekly intervals in the directions of x, y, z and roll（P〈0.05）. The corresponding patients accounted for 23.08%, 17.95%, 10.26% and 10.26%, respectively. The patients with at least once significant difference in directions of x, y, z and roll were 51.2% in once daily IGRT and 51.3% in once weekly IGRT. Conclusion The application of IGRT and enlargement margins can reduce setup errors and improve the precision of radiotherapy in maximum extent. It is necessary for patients to undergo IGRT once daily, which will provide quality assurance of precise radiation for pancreatic cancer.