北京生物医学工程

膀胱癌放疗中两种图像引导方法校准精度比较

Comparing the calibration accuracy of two image guided methods in bladder cancer radiotherapy

作者：闫洁诚田龙胡逸民

单位：河北北方学院附属第一医院放疗科（河北张家口 075000）中国医学科学院北京协和医科大学肿瘤医院肿瘤研究所放疗科（北京 100021）

关键词：膀胱癌；锥形束CT；内植标记物；校准

分类号：R318； R812

出版年·卷·期（页码）：2021·40·3（303-308）

摘要：

目的比较在膀胱癌放疗中,基于锥形束CT的正交拍照和扫描两种图像引导方法校准精度，从中选择最合适膀胱癌放疗的图像引导方法。方法依据纳排标准，筛选符合条件的15例膀胱癌患者，每周周一、周四使用锥形束CT对其进行放疗前正交拍照和扫描，分别采用自研算法和X线容积成像系统自带算法计算两种方法中由3枚内植标记物构成的空间三角形质心坐标，之后分别同计划CT重建获取的空间三角形质心坐标比较，计算左右、腹背和头脚方向上校准位移绝对值和平均值，最后采用配对样本t检验比较校准精度。结果正交拍照法中，所有患者空间三角形质心在左右，腹背和头脚方向上校准位移分别为0.994±0.773 mm，1.788±1.121 mm和2.443±1.357 mm；扫描法为0.812±0.215 mm，1.299±0.680 mm和1.871±1.092 mm。三个方向上正交拍照法校准位移均较大于扫描法，差异无统计学意义（P＞0.05）。结论锥形束CT正交拍照法校准精度略低于扫描法，但是在临床实践中，正交拍照法成像剂量低，操作时间短，对患者额外影响小，故选择作为最合适膀胱癌放疗的图像引导方法。

Objective To compare the calibration accuracy of two image guided methods-orthogonal photography and scan based on cone beam CT in bladder cancer radiotherapy, so as to select the best image guidance method for bladder cancer radiotherapy. Methods Fifteen eligible patients with bladder cancer were screened according to the inclusion-exclusion criteria for test. Cone beam CT was used to take orthogonal photography and scan for the patients before radiotherapy twice a week on Monday and Thursday.?A self-developed algorithm and the built-in algorithm in X-ray volumetric imaging system were used to calculate the center coordinates of spatial triangle built with three implanted markers in two methods respectively. After that, absolute value and average value of calibration displacement on left-right, anterior-posterior and superior-inferior direction were calculated by comparing with the center coordinates of spatial triangle obtained in planned CT reconstruction respectively. Finally, paired sample t test was used to compare the calibration accuracy. Results The calibration displacement of the center of spatial triangle on left-right, anterior-posterior and superior-inferior direction for all the patients was 0.994±0.773 mm, 1.788±1.121 mm and 2.443±1.357 mm respectively in orthogonal photography method and 0.812±0.215 mm, 1.299±0.680mm and 1.871±1.092 mm respectively in scanning method. The calibration displacement of orthogonal photography method was larger than that of scanning method on three directions, and the differences were not statistically significant (P＞0.05). Conclusions The calibration accuracy of cone beam CT orthogonal photography method is slightly lower than that of scanning method. However, in clinical practice, the imaging dose of orthogonal photography method is low, working time is short and the additional effect on patients is small. Therefore, orthogonal photography method can be selected as the best image guidance method for bladder cancer radiotherapy.

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