目的:表面引导放射治疗(SGRT,AlignRT)用于分析肺癌患者立体定向放疗(SBRT)期间的运动,并探索计划目标体积(PTV)的边缘。
方法:在每次治疗之前,根据灰度锥束计算机断层扫描配准结果评估AlignRT的残余误差。使用AlignRT日志文件分析大于2mm且持续时间大于2s的错误频率和最长持续时间与年龄和治疗持续时间的最大错误之间的相关性。治疗结束时的位移值,平均位移值,95%的概率密度位移间隔被定义为帧内误差,采用VanHerk公式或Z评分分析计算PTV1、PTV2、PTV3。用PTV3代替基于经验的边缘后,比较了器官剂量测定的差异。
结果:分数间残差为Vrt0,0.06±0.18cm;Lng0,-0.03±0.19厘米;Lat0,0.02±0.15cm;Pitch0,0.23±0.7°;Roll0,0.1±0.69°;Rtn0,-0.02±0.79°。频率,最长持续时间和垂直方向上的最大误差与治疗持续时间相关(r分别为0.404、0.353、0.283,p<0.05)。在纵向上,频率与年龄和治疗时间相关(r=0.376,0.283,p<0.05),最大误差与年龄相关(r=0.4,P<0.05)。垂直,纵向,PTV1,PTV2,PTV3的侧缘为2mm,4mm,2毫米;2毫米,2mm,2mm,3mm,5mm,3mm,分别。更换原始PTV后,平均肺剂量(MLD),2-cm3胸壁剂量(CD),肺V20减少0.2Gy,2.1Gy,0.5%,分别为(p<0.05)。
结论:AlignRT可用于分数间设置和监测帧内运动。使用95%概率密度间隔的上限和下限作为帧内误差更为合理。
OBJECTIVE: Surface-guided radiation therapy (SGRT, AlignRT) was used to analyze motion during stereotactic body radiotherapy (SBRT) in lung cancer patients and to explore the margin of the planning target volume (PTV).
METHODS: The residual errors of the AlignRT were evaluated based on grayscale cone-beam computed tomography registration results before each treatment. AlignRT log file was used to analyze the correlation between the frequency and longest duration of errors larger than 2 mm and lasting longer than 2 s and maximum error with age and treatment duration. The displacement value at the end of treatment, the average displacement value, and the 95% probability density displacement interval were defined as intrafraction errors, and PTV1, PTV2, PTV3 were calculated by Van Herk formula or Z score analysis. Organ dosimetric differences were compared after the experience-based margin was replaced with PTV3.
RESULTS: The interfraction residual errors were Vrt0 , 0.06 ± 0.18 cm; Lng0 , -0.03 ± 0.19 cm; Lat0 , 0.02 ± 0.15 cm; Pitch0 , 0.23 ± 0.7°; Roll0 , 0.1 ± 0.69°; Rtn0 , -0.02 ± 0.79°. The frequency, longest duration and maximum error in vertical direction were correlated with treatment duration (r = 0.404, 0.353, 0.283, p < 0.05, respectively). In the longitudinal direction, the frequency was correlated with age and treatment duration (r = 0.376, 0.283, p < 0.05, respectively), maximum error was correlated with age (r = 0.4, P < 0.05). Vertical, longitudinal, lateral margins of PTV1, PTV2, PTV3 were 2 mm, 4 mm, 2 mm; 2 mm, 2 mm, 2 mm, 3 mm, 5 mm, 3 mm, respectively. After replacing the original PTV, mean lung dose (MLD), 2-cm3 chest wall dose (CD), lung V20 decreased by 0.2 Gy, 2.1 Gy, 0.5%, respectively (p < 0.05).
CONCLUSIONS: AlignRT can be used for interfraction setup and monitoring intrafraction motion. It is more reasonable to use upper and lower limits of the 95% probability density interval as an intrafraction error.