CT模拟机及模拟定位机在头颈部肿瘤IMRT位置验证中的应用

The application of CT simulator and simulator in IMRT position verification of head- and- neck cancers

目的:探讨GE Light Speed RT型CT模拟机及Nucletron SIMULIX HQ型模拟定位机在头颈部肿瘤IMRT靶区治疗中心位置校正方法及各自优势。方法:抽取60例采取头颈肩热塑网膜固定的头颈部肿瘤IMRT患者随机分成两组,利用DRR正侧位图像在模拟定位机下校正位置30例,利用中心层面的横断面图像在CT模拟机下复位30例。分别测量在X(左右)、Y(头脚)、Z(前后)三个方向上校位中心与治疗中心的位置差别,记录三个方向上的误差为Ex、Ey、Ez。结果:误差整理分为三个等级范围Ea≤±1mm,±1mm<Eb≤±2mm,Ec>±2mm。CT模拟机校正中心时X方向上各误差等级范围例数依次为8(26.7%)、18(60.0%)、4(13.3%);Y方向上为19(63.3%)、8(26.7%)、3(10.0%);Z方向上为9(30.0%)、14(46.7%)、7(23.3%)。模拟定位机校正中心时X方向为6(20.0%)、19(63.3%)、5(16.7%);Y方向上为9(30.0%)、18(60.0%)、3(10.0%);Z方向上为8(26.7%)、14(46.7%)、8(26.7%)。三个方向上CT模拟机校正中心的平均误差分别为1.39mm、0.53mm、1.48mm;模拟定位机分别为1.51mm、1.43mm、1.66mm。60例患者首次治疗时按照校正后的中心进行摆位,经加速器治疗前IGRT验证其三维方向上的误差均控制在±2mm以内。结论:对于采取头颈肩热塑网膜固定的头颈部肿瘤IMRT患者,无论是采取CT模拟机复位还是模拟定位机复位,其三维方向上整体最高只有40%的患者位移精度在1mm以内,所以为确保患者的治疗,IMRT计划出来后进行位置验证和修正是非常有必要的;三维方向上,CT模拟机和模拟定位机的复位平均精度都控制在2mm以内,所以两种设备都可以适用于IMRT计划的位置验证,有利于提高模拟机的使用率和工作效率;CT定位机复位方法在三维方向上平均精度高于模拟定位机的平均精度,主要是在Y方向上的差异明显。

Objective： To explore the method and advantages of the GE Light Speed RT CT and the Nucletron SIMULIX HQ simulator model in the treatment of head and neck cancer IMRT target region. Methods： Sixty patients fixed by head- neck- shoulder thermoplastic membrane with head and neck tumor IMRT were randomly divided into two groups,using the DRR FrontalSide image in 30 cases,and 30 cases were treated with the center of the tomograph image in the CT simulator. The position difference between the directions of X（ left- light）,Y（ head- feet）,Z（ front- back） three directions and the location of the treatment center were measured. The error was Ey,Ezand Exin three directions. Results： The errors are divided into three grades Ea≤ ±1mm,±1mm Eb≤ ±2mm,Ec ±2mm. CT simulation machine calibration center in the X direction of the error range of the number of cases in turn 8（ 26. 7%）,18（ 60. 0%）,4（ 13. 3%）; Y direction 19（ 63. 3%）,8（ 26. 7%）,3（ 10. 0%）; Z direction 9（ 30. 0%）,14（ 46. 7%）,7（ 23. 3%）.In Simulation calibration center X direction6（20. 0%）,19（ 63. 3%）,5（ 16. 7%）; Y direction 9（ 30. 0%）,18（ 60. 0%）,3（ 10. 0%）; Z direction 8（ 26. 7%）,14（ 46. 7%）,8（ 26. 7%）. The average error of the calibration center of the CT simulator in three directions were 1. 39 mm 0. 53 mm 1. 48 mm Simulation were 1. 51 mm,1. 43 mm,1. 66 mm. 60 patients were treated with the center for the first time,and the error of the IGRT was controlled by the2 mm test. Conclusion： IMRT patients with head and neck tumor fixed by head- neck- shoulder thermoplastic membrane,whether it is to take a CT simulation or a simulation of the positioning machine reset,the overall highest in the three- dimensional direction is only 40% of the displacement accuracy of the patients in 1mm,so to ensure that patients are treated,the IMRT plan to verify and modify the location of the location is very necessary. In the three- dimensional direction,the average precision of the CT simulator and simulation of the positioning machine is controlled within the 2mm. So the two devices can be applied to the location of the IMRT program verification,conducive to improving the use rate and working efficiency of the simulator. The average precision of the CT positioning method is higher than that of the average accuracy of the simulation. Mainly in the Y direction of the difference is obvious.