1Department of Neurosurgery, University of Marburg; and.
2Marburg Center for Mind, Brain and Behavior (MCMBB), Marburg, Germany.
Neurosurg Focus. 2019 Dec 1;47(6):E11. doi: 10.3171/2019.8.FOCUS19621.
Low registration errors are an important prerequisite for reliable navigation, independent of its use in cranial or spinal surgery. Regardless of whether navigation is used for trajectory alignment in biopsy or implant procedures, or for sophisticated augmented reality applications, all depend on a correct registration of patient space and image space. In contrast to fiducial, landmark, or surface matching-based registration, the application of intraoperative imaging allows user-independent automatic patient registration, which is less error prone. The authors' aim in this paper was to give an overview of their experience using intraoperative CT (iCT) scanning for automatic registration with a focus on registration accuracy and radiation exposure.
A total of 645 patients underwent iCT scanning with a 32-slice movable CT scanner in combination with navigation for trajectory alignment in biopsy and implantation procedures (n = 222) and for augmented reality (n = 437) in cranial and spine procedures (347 craniotomies and 42 transsphenoidal, 56 frameless stereotactic, 59 frame-based stereotactic, and 141 spinal procedures). The target registration error was measured using skin fiducials that were not part of the registration procedure. The effective dose was calculated by multiplying the dose length product with conversion factors.
Among all 1281 iCT scans obtained, 1172 were used for automatic patient registration (645 initial registration scans and 527 repeat iCT scans). The overall mean target registration error was 0.86 ± 0.38 mm (± SD) (craniotomy, 0.88 ± 0.39 mm; transsphenoidal, 0.92 ± 0.39 mm; frameless, 0.74 ± 0.39 mm; frame-based, 0.84 ± 0.34 mm; and spinal, 0.80 ± 0.28 mm). Compared with standard diagnostic scans, a distinct reduction of the effective dose could be achieved using low-dose protocols for the initial registration scan with mean effective doses of 0.06 ± 0.04 mSv for cranial, 0.50 ± 0.09 mSv for cervical, 4.12 ± 2.13 mSv for thoracic, and 3.37 ± 0.93 mSv for lumbar scans without impeding registration accuracy.
Reliable automatic patient registration can be achieved using iCT scanning. Low-dose protocols ensured a low radiation exposure for the patient. Low-dose scanning had no negative effect on navigation accuracy.
低配准误差是可靠导航的重要前提，无论其在颅脑或脊柱手术中的应用如何。无论导航是否用于活检或植入程序中的轨迹对准，还是用于复杂的增强现实应用，都依赖于患者空间和图像空间的正确配准。与基于基准标记、地标或表面匹配的配准方法相比，术中成像的应用允许用户独立的自动患者配准，其误差较小。作者的目的是概述他们使用术中 CT（iCT）扫描进行自动配准的经验，重点介绍配准精度和辐射暴露。
共有 645 例患者使用 32 层移动 CT 扫描仪进行 iCT 扫描，结合导航进行活检和植入程序（n=222）以及颅脊柱手术中的增强现实（n=437）（347 例开颅术和 42 例经蝶窦入路、56 例无框架立体定向、59 例框架立体定向和 141 例脊柱手术）。使用不属于配准过程一部分的皮肤基准标记来测量靶标注册误差。通过将剂量长度乘积乘以转换因子来计算有效剂量。
在获得的 1281 次 iCT 扫描中，1172 次用于自动患者注册（645 次初始注册扫描和 527 次重复 iCT 扫描）。总体平均靶标注册误差为 0.86±0.38mm（±SD）（开颅术为 0.88±0.39mm；经蝶窦入路为 0.92±0.39mm；无框架立体定向术为 0.74±0.39mm；框架立体定向术为 0.84±0.34mm；脊柱手术为 0.80±0.28mm）。与标准诊断扫描相比，初始注册扫描使用低剂量方案可显著降低有效剂量，颅部的平均有效剂量为 0.06±0.04mSv，颈部为 0.50±0.09mSv，胸部为 4.12±2.13mSv，腰部为 3.37±0.93mSv，而不会影响注册准确性。
使用 iCT 扫描可以实现可靠的自动患者注册。低剂量方案确保了患者的低辐射暴露。低剂量扫描对导航精度没有负面影响。
