Dean D, Kamath J, Duerk J L, Ganz E
Department of Neurological Surgery, Case Western Reserve University, Cleveland, OH 44106, USA.
IEEE Trans Med Imaging. 1998 Oct;17(5):810-6. doi: 10.1109/42.736049.
Spatial fidelity is a paramount issue in image guided neurosurgery. Until recently, three-dimensional computed tomography (3D CT) has been the primary modality because it provides fast volume capture with pixel level (1 mm) accuracy. While three-dimensional magnetic resonance (3D MR) images provide superior anatomic information, published image capture protocols are time consuming and result in scanner- and object-induced magnetic field inhomogeneities which raise inaccuracy above pixel size. Using available scanner calibration software, a volumetric algorithm to correct for object-based geometric distortion, and a Fast Low Angle SHot (FLASH) 3D MR-scan protocol, we were able to reduce mean CT to MR skin-adhesed fiducial marker registration error from 1.36 to 1.09 mm. After dropping the worst one or two of six fiducial markers, mean registration error dropped to 0.62 mm (subpixel accuracy). Three dimensional object-induced error maps present highest 3D MR spatial infidelity at the tissue interfaces (skin/air, scalp/skull) where frameless stereotactic fiducial markers are commonly applied. The algorithm produced similar results in two patient 3D MR-scans.
空间保真度是影像引导神经外科手术中的一个首要问题。直到最近，三维计算机断层扫描（3D CT）一直是主要的成像方式，因为它能够以像素级（1毫米）的精度快速获取容积数据。虽然三维磁共振（3D MR）图像能提供更出色的解剖信息，但已公布的图像采集方案耗时较长，并且会导致由扫描仪和物体引起的磁场不均匀性，从而使误差超过像素尺寸。通过使用现有的扫描仪校准软件、一种用于校正基于物体的几何畸变的容积算法以及一种快速低角度激发（FLASH）3D MR扫描方案，我们能够将CT与MR皮肤附着基准标记的平均配准误差从1.36毫米降至1.09毫米。在舍弃六个基准标记中最差的一两个之后，平均配准误差降至0.62毫米（亚像素精度）。三维物体引起的误差图显示，在通常应用无框架立体定向基准标记的组织界面（皮肤/空气、头皮/颅骨）处，3D MR的空间保真度最差。该算法在两名患者的3D MR扫描中产生了相似的结果。
