鼻咽癌调强放射治疗中心点Y轴精度的临床分析

发布时间：2018-03-24 14:08

本文选题：鼻咽癌　切入点：放射治疗　出处：《中国医学计算机成像杂志》2017年03期

【摘要】：目的:探讨鼻咽癌调强放射治疗中心点Y轴精度的情况。方法:2016年1月至5月病理明确诊断鼻咽低分化鳞癌患者50例进入本研究。年龄43~58岁,平均年龄55岁,男女比例为3:1;使用飞利浦CT模拟机进行常规CT螺旋扫描,扫描层厚为5mm;使用Pinnacle放射治疗计划系统制订放射治疗计划,并确保进行研究的50例患者的放射治疗计划所生成的中心是采用原始的中心点即标记点(放疗中心点),重建生成数字重建放射图像(DRR);治疗前使用瓦里安Acuity模拟机(DR)进行验证。模拟机透视记录治疗中心点与CT扫描重建出的DRR图像的中心点确定放射治疗中心点Y轴精度误差发生情况(上移或下移),并分析误差发生的原因。结果:模拟机透视的放疗中心点与DRR图像的中心点相配准后,记录Y轴方向上移或下移的情况。50例患者中,有23例的患者需要上下移动5mm(仅为一个层面),其中12例患者需要上移,11例患者需要下移;27例患者不需移动。模拟机下Y轴中心点精度误差表现为离散均衡,未发现离散至一侧倾向趋势。误差主要发生原因为由于摆位Mark点的几何体积尺寸(1.5mm)和CT扫描层厚(5mm)和CT的扫描方式(螺旋扫描)的原因导致CT扫描中心点(Mark点)出现在临近的上下两层CT扫描层面,使得DRR图像的中心点与模拟机下摆位中心点发生偏差,导致表观上Y轴精度发生误差。结论:CT螺旋扫描会导致Mark点在相邻层面同时出现,导致治疗中心点在Y轴出现误差,治疗前仍需要模拟机验证。
[Abstract]:Objective: to investigate the accuracy of Y-axis at the focal point of intensity modulated radiotherapy for nasopharyngeal carcinoma (NPC). Methods: from January to May 2016, 50 patients with poorly differentiated squamous cell carcinoma of nasopharynx were enrolled in this study. The ratio of men and women was 3: 1; conventional CT helical scanning was performed using Philips CT simulator with a slice thickness of 5 mm; and radiotherapy was planned using the Pinnacle radiotherapy planning system. And make sure that the center generated by the radiotherapy program of 50 patients in the study is to use the original central point, that is, the marker point (the central point of radiotherapy), to reconstruct the digital reconstruction radiographic image, and to use the Varian Acuity simulator before treatment. The analogue machine recorded the treatment center point and the center point of the DRR image reconstructed by CT scan to determine the occurrence of Y axis accuracy error (upward or downward shift) of the center point of radiation therapy, and to analyze the reason of the error. Results: after the radiotherapeutic center point of the simulator fluoroscopy was matched with the center point of the DRR image, Recorded upward or downward movement of Y-axis. 50 patients, There were 23 patients who needed to move up and down 5mm (just one layer, 12 patients needed to move up and down, 11 patients needed to move down, 27 patients didn't need to move.) the accuracy error of the Y-axis center point under the simulator was discrete equalization. No tendency of dispersion to one side was found. The main causes of the errors were due to the geometric volume size of the pendulum Mark point (1.5mm) and the CT scanning slice thickness (5mm) and the CT scanning mode (helical scan). On the next two slice CT scans, This makes the center point of DRR image deviate from the center point of the lower pendulum of the simulator, which results in the error of apparent Y axis accuracy. Conclusion the Mark points appear simultaneously on the adjacent plane and the treatment center point appears error on the Y axis in the spiral scan of the CT. Analogue verification is still required before treatment.
【作者单位】：复旦大学附属肿瘤医院放疗科;复旦大学上海医学院肿瘤学系;
【分类号】：R730.55;R739.63

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