Department of Oral and Maxillofacial Surgery, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
Biomed Eng Online. 2012 Sep 4;11:65. doi: 10.1186/1475-925X-11-65.
To improve the accuracy of catheter navigation, it is important to develop a method to predict shifts of carotid artery (CA) bifurcations caused by intraoperative deformation. An important factor affecting the accuracy of electromagnetic maxillofacial catheter navigation systems is CA deformations. We aimed to assess CA deformation in different head and neck positions.
Using two sets of computed tomography angiography (CTA) images of six patients, displacements of the skull (maxillofacial segments), C1-C4 cervical vertebrae, mandible (mandibular segment), and CA along with its branches were analyzed. Segmented rigid bones around CA were considered the main causes of CA deformation. After superimposition of maxillofacial segments, C1-C4 and mandible segments were superimposed separately for displacement measurements. Five bifurcation points (vA-vE) were assessed after extracting the CA centerline. A new standardized coordinate system, regardless of patient-specific scanning positions, was employed. It was created using the principal axes of inertia of the maxillofacial bone segments of patients. Position and orientation parameters were transferred to this coordinate system. CA deformation in different head and neck positions was assessed.
Absolute shifts in the center of gravity in the bone models for different segments were C1, 1.02 ± 0.9; C2, 2.18 ± 1.81; C3, 4.25 ± 3.85; C4, 5.90 ± 5.14; and mandible, 1.75 ± 2.76 mm. Shifts of CA bifurcations were vA, 5.52 ± 4.12; vB, 4.02 ± 3.27; vC, 4.39 ± 2.42; vD, 4.48 ± 1.88; and vE, 2.47 ± 1.32. Displacements, position changes, and orientation changes of C1-C4 segments as well as the displacements of all CA bifurcation points were similar in individual patients.
CA deformation was objectively proven as an important factor contributing to errors in maxillofacial navigation. Our study results suggest that small movements of the bones around CA can result in small CA deformations. Although patients' faces were not fixed properly during CT scanning, C1-C4 and vA-vE displacements were similar in individual patients. We proposed a novel method for accumulation of the displacement data, and this study indicated the importance of surrounding bone displacements in predicting CA bifurcation.
为了提高导管导航的准确性，开发一种预测术中颈动脉（CA）分叉移位的方法非常重要。电磁颌面导管导航系统准确性的一个重要影响因素是 CA 变形。我们旨在评估不同头颈部位置的 CA 变形。
使用六名患者的两组计算机断层血管造影（CTA）图像，分析颅骨（颌面段）、C1-C4 颈椎、下颌骨（下颌段）和 CA 及其分支的位移。考虑到 CA 变形的主要原因是 CA 周围分段的刚性骨骼。在颌面段叠加后，分别对 C1-C4 和下颌骨段进行叠加以进行位移测量。在提取 CA 中心线后评估了五个分叉点（vA-vE）。使用患者颌面骨段的惯性主轴创建了一个新的标准化坐标系，无论患者特定的扫描位置如何。它创建了使用患者颌面骨段的惯性主轴。位置和方向参数被转移到这个坐标系统中。评估了不同头颈部位置的 CA 变形。
不同节段骨模型的重心的绝对位移为 C1，1.02±0.9；C2，2.18±1.81；C3，4.25±3.85；C4，5.90±5.14；和下颌骨，1.75±2.76mm。CA 分叉的移位为 vA，5.52±4.12；vB，4.02±3.27；vC，4.39±2.42；vD，4.48±1.88；和 vE，2.47±1.32。个体患者的 C1-C4 节段的位移、位置变化和方向变化以及所有 CA 分叉点的位移相似。
客观证明 CA 变形是颌面导航误差的重要因素。我们的研究结果表明，CA 周围骨骼的小运动可导致 CA 变形小。尽管在 CT 扫描期间患者的面部未被正确固定，但个体患者的 C1-C4 和 vA-vE 位移相似。我们提出了一种新的累积位移数据的方法，本研究表明周围骨骼位移在预测 CA 分叉中的重要性。
