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目的初步分析和总结鼻咽癌逆向调强放疗(IMRT)中肿瘤及腮腺的体积与位移随放疗时间变化的规律。方法选取10例鼻咽癌患者,放疗前用千伏级锥形束CT(kV-CBCT)扫描采集每次治疗前CBCT图像,并将采集的图像导回计划系统,由同一人用图像分析软件TomCon 3.0在CBCT图像上逐层勾画靶区和两侧腮腺;位移则以寰椎(即第一颈椎)为参考,用Pinnacle 8.0分别算出寰椎及两侧腮腺的质量中心(COM),观察腮腺相对于寰椎的位移变化。分析肿瘤及腮腺的体积与位移随放疗时间变化的规律。结果肿瘤区(GTV)缩小较为明显,体积退缩中位值为9.85 cm3(5.10~21.40 cm3),退缩速度中位值为0.20 cm3/d(0.10~0.46 cm3/d),GTV位移变化主要呈现出由前向后的不规则退缩趋势;左侧腮腺体积缩小中位值为5.70 cm3(3.20~12.00 cm3),缩小速度中位值为0.13 cm3/d(0.07~0.27 cm3/d);右侧腮腺体积缩小中位值为8.05 cm3(3.00~13.40 cm3),缩小速度中位值为0.18 cm3/d(0.06~0.29 cm3/d);左侧腮腺COM向寰椎COM靠近的距离中位值为3.45 mm(0.70~7.60mm),靠近速度中位值为0.07 mm/d(0.01~0.11 mm/d),右侧腮腺COM向寰椎COM靠近的距离中位值为2.60mm(1.50~4.40 mm),靠近速度中位值为0.05 mm/d(0.03~0.12 mm/d)。结论本研究中鼻咽癌患者肿瘤在3~4周放疗结束后已存在比较明显的退缩,提示可在放疗3~4周后重扫CT或作第2次放疗计划,以减少危及器官的受照剂量。
Objective To analyze and summarize the regularity of the volume and the displacement of tumor and parotid gland in the treatment of nasopharyngeal carcinoma (IMRT) with radiotherapy time. Methods Ten patients with nasopharyngeal carcinoma were selected. CBCT images before each treatment were collected by kV-CBCT before radiotherapy. The collected images were returned to the planning system and analyzed by the same human image analysis software TomCon 3.0 sketched the target area and bilateral parotid glands on the CBCT images one by one. The displacement was based on the atlas vertebrae (ie, the first cervical vertebra). Pinnacle 8.0 was used to calculate the mass center (COM) of the atlas and parotid glands respectively. Relative to the displacement of the atlas. Analysis of tumor and parotid gland volume and displacement with the law of radiation changes. The results showed that the size of GTV decreased significantly, the median value of volumetric withdrawal was 9.85 cm3 (5.10-21.10 cm3), and the median of withdrawal velocity was 0.20 cm3 / d (0.10-0.46 cm3 / d) The median parotid gland size was 5.70 cm3 (3.20-12.00 cm3) and the median reduction rate was 0.13 cm3 / d (0.07-0.27 cm3 / d). The right parotid gland The median value of volume reduction was 8.05 cm3 (3.00 ~ 13.40 cm3), and the median reduction rate was 0.18 cm3 / d (0.06-0.29 cm3 / d). The median distance from the left parotid COM to the atlas COM was 3.45 (0.70 ~ 7.60mm). The median velocity near the parotid gland was 0.07mm / d (0.01 ~ 0.11mm / d). The median distance from the right parotid COM to the atlas COM was 2.60mm (1.50 ~ 4.40mm) , And the median speed close to 0.05 mm / d (0.03-0.12 mm / d). CONCLUSIONS: Nasopharyngeal carcinoma patients had obvious tumor regression after 3 to 4 weeks of radiotherapy, suggesting that CT scan or radiotherapy may be performed 3 to 4 weeks after radiotherapy to reduce the risk of organ damage According to the dose.