不同部位体表轮廓对Catalyst HD体表光学系统引导放疗摆位的影响

Effects of body contours on the setup errors of the Catalyst HD optical surface imaging systemguided radiotherapy

目的探究人体不同部位的体表轮廓对Catalyst HD体表光学系统引导放疗摆位的影响。方法采用3D打印技术打印出底角5°~45°(步长为5°)的圆模型和椭圆模型,模拟患者不同部位的体表轮廓。使用Catalyst HD进行监测,调节其增益及积分时间。手动移动治疗床(-5~5 mm,步长为2 mm),记录所有模型的横纵比,及其在横向和纵向放置下腹背(AP)、头脚(SI)、左右(LR)3个方向的床值误差及Catalyst HD监测的摆位误差。将Catalyst HD增益、积分时间与不同体表轮廓的模型进行关联性分析,比较两种不同放置方式下的摆位误差,分析Catalyst HD监测值与床值的相关性。结果Catalyst HD监测时所需增益和积分时间对数呈显著线性负相关,斜率为-0.001,截距与模型横纵比存在一定函数关系。相同增益下积分时间随模型底边角度的增大而减小。模型在不同放置条件下Catalyst HD监测精度存在差异(Z=-8.59~-0.02,P<0.05),横向放置时LR和AP方向监测精度更高。Catalyst HD监测值与真实床值的相关性,在LR和SI方向随模型底边角度增加而增大,≥25°时呈强相关;AP方向均相关性显著(R>0.9)。结论Catalyst HD系统获取最佳表面影像时,增益、积分时间和患者体表轮廓存在关联。Catalyst HD监测在AP方向精度高,当体表轮廓横纵比≤2或底边角度≥25°时在所有方向均存在较高的准确性。

Objective To explore the influence of the contours of different parts of the human body on the setup errors of Catalyst HD optical surface imaging(OSI)system-guided radiotherapy.Methods Using the 3D printing technology,arc-and oval arc-shaped phantoms with base angles of 5°-45°(step length:5°)were designed to simulate the contours of different body parts of patients.A Catalyst HD system was employed for monitoring,during which the gains and integration time of the system were adjusted.The treatment couches were manually moved(range:-5 mm to 5 mm,with a step length of 2 mm).The ratios of transverse to longitudinal dimensions of all phantoms were recorded.The recorded items also included couch value errors in the anterior-posterior(AP),inferior-superior(SI),and left-right(LR)directions for transversely and longitudinally placed phantoms,as well as the setup errors monitored using the Catalyst HD system.Then,this study presented an analysis of the correlation between phantoms for different body contours and the gains and integration time of the Catalyst HD system.The purpose was to compare the setup errors under the two different placement conditions of phantoms and to analyze the correlation between the monitored values of the Catalyst HD system and couch values.Results There was a significant linear negative correlation between the gain and the logarithm of integration time required for monitoring using the Catalyst HD system,with a slope of-0.001.There was a certain functional relationship between the intercept and the ratio of the transverse to longitudinal dimensions of the phantoms.Under the same gain,the integration time decreased with an increase in the base angles of phantoms.The Catalyst HD system showed different monitoring accuracy under different placement conditions of the phantoms(Z=-8.59 to-0.02,P<0.05),with the monitoring accuracy in the LR and AP directions higher in the transverse position.The correlation between the monitored values of the Catalyst HD system and the actual couch values increased in the LR and SI directions with an increase in the base angle of the phantoms,showing a strong correlation in the case of base angles of≥25°.Furthermore,the correlation was always significant in the AP direction(R>0.9).Conclusions When the best surface images are obtained using the Catalyst HD system,the gains and integration time of the system are correlated with body surface contours.The Catalyst HD system shows high monitoring accuracy in the AP direction.This system shows high accuracy in all directions when the ratios of transverse to longitudinal dimensions are≤2 or the base angles≥25°.