Lange Thomas, Eulenstein Sebastian, Hünerbein Michael, Schlag Peter-Michael
Department of Surgery and Surgical Oncology, Charité--Universitary Medicine, Berlin, Germany.
Comput Aided Surg. 2003;8(5):228-40. doi: 10.3109/10929080309146058.
Computer assisted planning of liver surgery based on preoperative computed tomography (CT) or magnetic resonance imaging (MRI) data can be an important aid to operability decisions and visualization of individual patients' 3D anatomy. A navigation system based on intraoperative 3D ultrasound may help the surgeon to precisely localize vessels, vascular territories or tumors. The preoperative planning must be transferred to the intraoperative ultrasound data and thus to the patient on the operating table. Due to deformations of the liver between planning and surgery, a fast non-rigid registration method is needed.
A feature-based non-rigid registration approach based on the centerlines of the portal veins has been developed. The combination of an iterative closest point (ICP) approach and Multilevel B-Spline transformations offers a fast registration method. The vessels are segmented and their centerlines extracted from preoperative CT/MRI and intraoperative 3D Powerdoppler ultrasound data. Anatomical corresponding points on the centerlines of both modalities are determined in each iteration of the ICP algorithm. The search for corresponding points is restricted to a given search radius and the direction of the vessels is incorporated.
The algorithm has been evaluated on two transcutaneous and one intraoperative clinical ultrasound data set from three different patients. Only a very few vessel segments were not assigned correctly compared to manual assignments. Using non-rigid transformations improved the root mean square target registration error of the vessels by approximately 3-5 mm.
The proposed registration method is fast enough for clinical application in liver surgery. Initial accuracy results are promising and must be further evaluated, particularly in the operating room.
基于术前计算机断层扫描（CT）或磁共振成像（MRI）数据进行肝脏手术的计算机辅助规划，对于手术可行性决策以及个体患者三维解剖结构的可视化而言，可能是一项重要的辅助手段。基于术中三维超声的导航系统或许有助于外科医生精确地定位血管、血管区域或肿瘤。术前规划必须转换为术中超声数据，进而应用于手术台上的患者。鉴于肝脏在规划与手术期间会发生变形，因此需要一种快速的非刚性配准方法。
已开发出一种基于门静脉中心线的特征非刚性配准方法。迭代最近点（ICP）方法与多级B样条变换相结合，提供了一种快速配准方法。从术前CT/MRI以及术中三维能量多普勒超声数据中分割出血管并提取其中心线。在ICP算法的每次迭代中，确定两种模态中心线的解剖学对应点。对应点的搜索限定在给定的搜索半径内，并纳入血管方向。
该算法已在来自三名不同患者的两个经皮和一个术中临床超声数据集上进行了评估。与手动标注相比，但只有极少数血管段未被正确标注。使用非刚性变换使血管的均方根目标配准误差降低了约3 - 5毫米。
所提出的配准方法对于肝脏手术的临床应用而言足够快速。初步的准确性结果很有前景，必须进一步评估，尤其是在手术室环境中。
