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目的比较基于三维CT(3DCT)和锥形束CT(CBCT)图像定义的胸中下段食管癌内在大体肿瘤靶区即内靶区的体积(IGTV)及匹配度。方法 15例胸中下段食管癌患者,首先完成胸部3DCT扫描,基于3DCT制定放疗计划,在3DCT上勾画得到GTV3D,依据山东省肿瘤医院通过四维CT(4DCT)图像测得的胸中下段食管癌靶区运动范围95%可信区间上限外扩得到IGTV,胸中下段食管癌GTV头脚、前后、左右方向分别外扩6.0、3.0、3.0 mm得到IGTV3D,放疗治疗前5次拍摄CBCT,并基于骨性标志配准校正,在CBCT图像上勾画得到IGTVCBCT。比较IGTV3D与IGTVCBCT靶区间体积及匹配度。结果 IGTV3D大于IGTVCBCT(t=2.531,P=0.018),IGTV3D与IGTVCBCT总匹配指数为(0.604±0.0430),亚组胸中段食管癌IGTV3D与IGTVCBCT匹配指数为(0.611±0.0371),胸下段食管癌IGTV3D与IGTVCBCT匹配指数为(0.562±0.0168),胸中段与胸下段食管癌IGTV3D与IGTVCBCT匹配指数比较,差异具有统计学意义(t=2.478,P=0.028)。结论在胸中下段食管癌的放疗中IGTV3DCT明显大于IGTVCBCT,两靶区的匹配指数为(0.604±0.0430),IGTV3DCT不能有效的包含IGTVCBCT,即使3DCT与CBCT配准校正后,也有可能导致较严重的脱靶,放疗期间利用CBCT图像不能提供可靠有效的在线校正。
OBJECTIVE: To compare the volume (IGTV) and the matching degree of internal target region, which is defined as the gross tumor target area, based on three-dimensional CT (3DCT) and cone beam CT (CBCT) images. Methods Fifteen patients with lower thoracic esophageal cancer underwent thoracoscopic 3DCT scan. Radiotherapy was planned based on 3DCT. GTV3D was delineated on 3DCT. According to the 4DCT images of Shandong Tumor Hospital, The upper limit of 95% confidence interval was extended to IGTV. The upper and lower esophageal cancer GTV head and thoracic esophageal cancer were expanded by 6.0, 3.0 and 3.0 mm respectively, and IGTV3D was obtained. The CBCT was taken 5 times before radiotherapy. Quasi-correction, outlined in CBCT images get IGTVCBCT. The volume and matching between IGTV3D and IGTVCBCT target were compared. Results IGTV3D was greater than IGTVCBCT (t = 2.531, P = 0.018). The matched index of IGTV3D and IGTVCBCT was (0.604 ± 0.0430). The matching index of IGTV3D and IGTVCBCT was (0.611 ± 0.0371) in the middle and lower thoracic esophagus. The matching index with IGTVCBCT was (0.562 ± 0.0168). The matching index between IGTV3D and IGTVCBCT in the middle and lower thoracic esophagus was statistically significant (t = 2.478, P = 0.028). Conclusion IGTV3DCT is significantly larger than IGTVCBCT in the treatment of lower thoracic esophageal cancer. The match index of the two target areas is (0.604 ± 0.0430). IGTV3DCT can not effectively contain IGTVCBCT. Even after registration of 3DCT and CBCT, it is possible to cause more serious off-target , The use of CBCT images during radiotherapy does not provide reliable and effective online correction.