应用机载千伏级CBCT研究鼻咽癌IMRT的摆位误差及其对受照剂量的影响

发布时间：2018-03-25 12:28

  本文选题：摆位误差　切入点：体重指数　出处：《苏州大学》2010年硕士论文

【摘要】： 目的:应用机载千伏级CBCT监测鼻咽癌调强放疗患者疗程中摆位误差的变化和影响因素,分析摆位误差对物理剂量的影响,以达到减少和/或消除摆位误差对放疗的影响。 方法:本实验选取病理学确诊的鼻咽癌早期患者15例,行调强放疗。患者每周按治疗计划标志点摆位,利用机载KV-CBCT扫描获取摆位误差,将摆位误差代入治疗计划,模拟出未使用IGRT时,实际摆位位置中剂量分布情况。计算在相同治疗阶段所有患者三维线性方向和水平面旋转方向摆位误差平均值、标准差及95%可信区间(CI);分析随疗程进行摆位误差的变化情况;探讨体重指数和体重变化对摆位误差的影响;研究不同方向的摆位误差对危及器官剂量影响;分析三维移动矢量和旋转误差对靶区剂量影响,并探讨本科室鼻咽癌患者靶区外放边界范围。 结果:患者在腹背、头脚、左右三个坐标轴和水平面旋转方向的摆位误差均值分别为-0.1833cm、-0.0322cm、0.0967cm和-0.8333°,95%的可信区间分别为[-0.2117cm,-0.1549cm],[-0.0768cm,0.0124cm],[0.0563cm,0.1371cm]和[-1.0987°,-0.5687°]。随疗程进行,摆位中心点向腹侧偏移。BMI≥25患者在左右方向及水平面旋转方向首次摆位误差绝对值较BMI25患者明显增大;BMI≥25患者在左右方向及水平面旋转方向的系统误差较BMI25患者明显;患者体重下降会引起摆位中心点往腹侧偏移和水平面逆时针旋转。摆位中心点向背侧偏移0.2cm,脑干D1和脊髓D1cc增高率均值分别为6.58%和4.70%,摆位中心点向头侧偏移0.2cm,视交叉D1增高率均值为8.94%,摆位中心点向左侧偏移0.2cm,同侧腮腺D50增高率均值为4.95%。CTV2 D95、GTVnd D98与三维移动矢量和旋转误差有相关性(P0.05,|r|0.4);CTV1 D95和GTVnx D98与旋转误差无明显相关性(P0.05);而GTVnx D98与三维移动矢量无明显相关性(P=0.077,|r|=0.187)。BMI≥25患者各个方向的MPTV值较BMI25患者明显增大。 结论:在鼻咽癌调强放疗中:1、BMI≥25患者有必要进行自适应放疗;2放疗疗程中体重减少超过7.10%时,需要及时调整放疗计划;3、摆位中心点偏移应尽量控制在0.2cm以内;4、GTVnd和CTV2剂量较GTVnx、CTV1剂量对线性误差和旋转误差敏感;5、BMI≥25患者可通过机载千伏级CBCT在线或离线纠正摆位误差,缩小CTV至PTV外放边界而获益。
[Abstract]:Objective: to monitor the changes and influencing factors of positioning error in the course of intensity modulated radiotherapy for nasopharyngeal carcinoma (NPC) by airborne kilovolt CBCT, and to analyze the effect of pendulum error on physical dose in order to reduce and / or eliminate the effect of pendulum error on radiotherapy. Methods: fifteen patients with early stage nasopharyngeal carcinoma diagnosed by pathology were selected and received intensity modulated radiotherapy. The patients were placed weekly according to the treatment plan. The positioning error was obtained by airborne KV-CBCT scan, and the positioning error was substituted into the treatment plan. The dose distribution in the actual pendulum position was simulated when IGRT was not used. The mean value of three dimensional linear direction and horizontal rotation direction pendulum error were calculated for all patients in the same treatment stage. The standard deviation and 95% confidence interval (CI) were analyzed, the effects of body mass index (BMI) and body mass change on the pendulum error were discussed, and the effects of different directions on organ dose were studied. The effects of 3D moving vector and rotation error on target dose were analyzed, and the boundary range of target area extravasation in nasopharyngeal carcinoma patients was discussed. Results: the mean values of pendulum error in the rotation direction of the three axes and horizontal plane were -0.1833 cm ~ (-1) -0.0322 cm ~ (-1) and -0.8333 掳~ 95% confidence interval [-0.2117 cm ~ (-1) -0.1549 cm], [-0.0768 cm ~ 0.0124 cm], [0.056 3 cm ~ 0.1371 cm] and [-1.0987 掳-0.5687 掳], respectively. The absolute value of the first pendulum error in the left and right direction and horizontal rotation direction in the patients with center point deviation to the ventral side. BMI 鈮，

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