不同扫描与观察条件下三维适形放疗计划系统重建CT图像定义体积变化的研究

目的 测量不同扫描与观察条件下三维适形放疗计划系统重建CT图像定义体积的变化,为扫描与观察条件选择、靶区勾画及治疗计划制定提供参考依据.方法 用不同条件对自制模体进行CT扫描,所得数据输入治疗计划系统,在不同观察条件下进行三维重建,将重建大、中、小模拟瘤体CT图像体积分别与其实际体积进行比较.结果 不同扫描与观察条件下三维适形放疗计划系统重建CT图像定义体积不一样.扫描层厚为10.000 mm时,大、中、小模拟瘤体误差分别为-13.60%、-17.68%、-27.53%;扫描层厚为0.625 mm时,大、中、小模拟瘤体误差分别为-0.50%、-0.68%、-0.81%.扫描螺距值为0.562、0.938、1.375、1. 750时,误差分别为-1.06%、-1.09%、5.52%、4.75%.较极端条件的窗宽、窗位对重建CT图像定义体积影响很大,最大误差为80.06%.结论 本结果可用于指导扫描与观察条件选择、靶区勾画及治疗计划制定.

Impact of scanning and observing conditions on definitive volume of rebuilt CT images in three dimensional conformal radiotherapy planning system

Objective To measure changes of definitive volume of rebuild CT image in three dimensional conformal radiotherapy (3DCRT) treatment planning system (TPS) under different scanning and observing conditions, which may provide a reference in selecting proper condition of scanning and observing, delineating target volume, and delivering treatment plan. Methods A self-made phantom was scanned under different CT scanning conditions, datas were imported to TPS, CT images were rebuilt in three dimensions under different observing conditions, and then the volumes of large, middle and small simulated tumors on CT images were compared with their real volumes. Results The volume defined by rebuilt CT imags in 3DCRT TPS varied according to different scanning and observing conditions. When scanning axial thickness was set at 10. 000 mm, errors of large, middle and small simulated tumor were - 13.60%, - 17. 68% and - 27. 53%, respectively. When 0. 625 mm was set, errors changed to -0. 50%, -0. 68% and -0. 81% ,respectively. When scanning pitch was set at 0. 562, 0. 938, 1. 375 and 1. 750, the errors were - 1.06%, - 1.09%, 5.52% and 4.75%, respectively. Extreme observing condition, window width and window level markedly increased errors of definitive volume of rebuilt CT images with a maximum of 80. 06%. Conclusions This study may provide clues in selecting scanning and observing condition, delineating target volume, and delivering treatment plan.