Hans P, Grant A J, Laitt R D, Ramsden R T, Kassner A, Jackson A
Department of Diagnostic Radiology, Stopford Medical School, Manchester, UK.
AJNR Am J Neuroradiol. 1999 Aug;20(7):1197-206.
Cochlear implantation requires introduction of a stimulating electrode array into the scala vestibuli or scala tympani. Although these structures can be separately identified on many high-resolution scans, it is often difficult to ascertain whether these channels are patent throughout their length. The aim of this study was to determine whether an optimized combination of an imaging protocol and a visualization technique allows routine 3D rendering of the scala vestibuli and scala tympani.
A submillimeter T2 fast spin-echo imaging sequence was designed to optimize the performance of 3D visualization methods. The spatial resolution was determined experimentally using primary images and 3D surface and volume renderings from eight healthy subjects. These data were used to develop the imaging sequence and to compare the quality and signal-to-noise dependency of four data visualization algorithms: maximum intensity projection, ray casting with transparent voxels, ray casting with opaque voxels, and isosurface rendering. The ability of these methods to produce 3D renderings of the scala tympani and scala vestibuli was also examined. The imaging technique was used in five patients with sensorineural deafness.
Visualization techniques produced optimal results in combination with an isotropic volume imaging sequence. Clinicians preferred the isosurface-rendered images to other 3D visualizations. Both isosurface and ray casting displayed the scala vestibuli and scala tympani throughout their length. Abnormalities were shown in three patients, and in one of these, a focal occlusion of the scala tympani was confirmed at surgery.
Three-dimensional images of the scala vestibuli and scala tympani can be routinely produced. The combination of an MR sequence optimized for use with isosurface rendering or ray-casting algorithms can produce 3D images with greater spatial resolution and anatomic detail than has been possible previously.
人工耳蜗植入需要将刺激电极阵列插入前庭阶或鼓阶。尽管在许多高分辨率扫描中可以分别识别这些结构，但通常很难确定这些通道在其全长范围内是否通畅。本研究的目的是确定成像方案和可视化技术的优化组合是否能实现前庭阶和鼓阶的常规三维重建。
设计了一种亚毫米级的T2快速自旋回波成像序列，以优化三维可视化方法的性能。使用来自8名健康受试者的原始图像以及三维表面和容积重建图像，通过实验确定空间分辨率。这些数据用于开发成像序列，并比较四种数据可视化算法的质量和信噪比依赖性：最大强度投影、透明体素光线投射、不透明体素光线投射和等值面渲染。还检查了这些方法生成鼓阶和前庭阶三维重建图像的能力。该成像技术应用于5名感音神经性耳聋患者。
可视化技术与各向同性容积成像序列相结合产生了最佳效果。临床医生更喜欢等值面渲染图像而非其他三维可视化图像。等值面和光线投射均显示了前庭阶和鼓阶的全长。3名患者显示出异常，其中1例在手术中证实为鼓阶局灶性闭塞。
可以常规生成前庭阶和鼓阶的三维图像。与等值面渲染或光线投射算法配合使用而优化的磁共振序列组合，能够生成具有比以前更高空间分辨率和解剖细节的三维图像。
