北京生物医学工程

C形臂X光机的原位投影增强系统

A projection-augmented system for in situ projection for mobile C-arms

作者：邢树伟丁辉王广志

单位：清华大学医学院生物医学工程系（北京 100084）

关键词：移动C型臂X光机; 投影增强; 原位投影; 光路重合; 校正

分类号：R318.6

出版年·卷·期（页码）：2019·38·6（551-559）

摘要：

目的移动C型臂X光机是微创骨科手术中必不可少的成像设备。针对当前微创骨科手术需要反复透视和操作直观性差的问题，本文提出一个针对移动C型臂X光机的原位投影增强系统。方法首先设计了一种双重反射的投影增强模块；然后基于上述模块，提出一种基于动态追踪的系统标定方法，以实现投影光路与X射线光路重合；接下来利用图像的单应性变换关系，分别对投影模块与X射线成像模型间的几何模型偏差和系统残留偏差进行校正，进而优化系统投影精度；最后构建原型系统，测试了系统性能并设计腰椎体膜和猪腿胫骨实验进行验证。结果在精度验证模体距影像探测器不同高度下，系统投影误差为；固定验证模体，在移动C型臂X光机不同摆放角度下，系统投影误差为。腰椎体膜和猪腿胫骨模体实验表明，可直接在患者体表观察到患者骨骼等结构的投影信息。结论本文提出的移动C型臂X光机投影增强系统，能够原位投射患者透视影像，直观地辅助医生术中操作，减少了术中反复透视获取手术工具和患者内部结构位置关系的次数，显示出系统未来临床应用的可行性。

Objective The mobile C-arm is an essential imaging device in minimally invasive orthopedic surgery. To reduce radiation exposure from frequently capturing X-ray images and improve unintuitive operations, we proposed a projection-augmented system for in situ projection for mobile C-arms. Methods First, we design a double projection projection-augmented module. Second, we propose a calibration method based on dynamic tracking to realize the alignment of X-ray and projection light. Third, the geometric model deviation and system residual deviation between the projection module and the X-ray imaging model are corrected by using the homography to improve projection accuracy. Finally, a prototype of the system was constructed, and performance tests and experiments of spine phantom and swine tibia were performed. Results The system overlay error is at different heights from image intensifier to experiment phantom, and is at different rotation angles of mobile C-arms. The experiments of spine phantom and swine tibia show that we can intuitively observe the projection information such as bone structure on the patients’ body surface. Conclusions The proposed projection-augmented system can project X-ray images onto patients in situ, and surgeons can perform intuitive operations and reduce X-ray radiation exposure. Furthermore, we verify the feasibility of our system by phantom experiments.

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