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为了探讨MVCT在线图像引导技术分析前列腺癌螺旋断层放疗过程中分次间误差及分次内误差,并计算CTV-PTV的外扩边界,对10例早期前列腺癌患者行螺旋断层调强放疗。靶区为前列腺及精囊,剂量76 Gy/34次。所有患者每次治疗前及治疗后均行MVCT扫描,10例患者共行MVCT扫描680次。分次间误差在左右方向最小,≤5 mm的占95%;头脚方向最大,≥8 mm的占38.8%;前后方向≤5 mm的占81.8%。分次内误差绝大部分≤3 mm,左右、头脚及前后方向分别占99.1%、90.6%及95.6%。仅根据皮肤标记摆位,不实施图像引导所需的CTV-PTV外扩边界在左右、头脚及前后方向分别为5.3、14.2和8.5 mm;如每次治疗前均行在线图像引导校正,则外扩边界分别缩小至1.8、2.1和2.4 mm。初步研究结果提示,每日放疗前图像引导可纠正分次间误差,显著缩小CTV-PTV外扩边界;但由于分次内误差及其他不确定因素的存在,此外扩边界仍不宜过小,建议3~5 mm。
To investigate the sub-level error and intra-sub-level error in MVCT guided tomography with CT-guided image analysis, the CTV-PTV expansion boundary was calculated and 10 cases of early-stage prostate cancer received IMRT. Target area for the prostate and seminal vesicles, dose 76 Gy / 34 times. All patients underwent MVCT scans before and after each treatment, and 10 patients underwent MVCT scans 680 times. The error between sub-orders was the smallest in left-right direction, 95% of ≤5 mm, the largest in head-foot direction, 38.8% of ≥8 mm, and 81.8% in front-back direction ≤5 mm. Most of the error within the sub-level ≤ 3 mm, left and right, head and fore and aft directions accounted for 99.1%, 90.6% and 95.6% respectively. CTV-PTV flared boundary required for imaging guidance was 5.3, 14.2, and 8.5 mm on the left, right, head, and anteroposterior directions, respectively, only based on skin markers. For online image guided correction before each treatment, Expanded boundaries were reduced to 1.8, 2.1 and 2.4 mm. Preliminary results suggest that daily pre-radiotherapy image guidance can correct the sub-order error, significantly reduce the CTV-PTV flared boundary; but due to sub-level error and other uncertainties exist, in addition to expanding the boundary is still not too small, it is recommended 3 ~ 5 mm.