Osechinskiy Sergey, Kruggel Frithjof
Department of Biomedical Engineering, University of California, Irvine, CA 92697, USA.
Int J Biomed Imaging. 2012;2012:870196. doi: 10.1155/2012/870196. Epub 2012 Feb 1.
Reconstruction of the cerebral cortex from magnetic resonance (MR) images is an important step in quantitative analysis of the human brain structure, for example, in sulcal morphometry and in studies of cortical thickness. Existing cortical reconstruction approaches are typically optimized for standard resolution (~1 mm) data and are not directly applicable to higher resolution images. A new PDE-based method is presented for the automated cortical reconstruction that is computationally efficient and scales well with grid resolution, and thus is particularly suitable for high-resolution MR images with submillimeter voxel size. The method uses a mathematical model of a field in an inhomogeneous dielectric. This field mapping, similarly to a Laplacian mapping, has nice laminar properties in the cortical layer, and helps to identify the unresolved boundaries between cortical banks in narrow sulci. The pial cortical surface is reconstructed by advection along the field gradient as a geometric deformable model constrained by topology-preserving level set approach. The method's performance is illustrated on exvivo images with 0.25-0.35 mm isotropic voxels. The method is further evaluated by cross-comparison with results of the FreeSurfer software on standard resolution data sets from the OASIS database featuring pairs of repeated scans for 20 healthy young subjects.
从磁共振（MR）图像重建大脑皮层是人类脑结构定量分析中的重要一步，例如在脑沟形态测量和皮层厚度研究中。现有的皮层重建方法通常是针对标准分辨率（约1毫米）数据进行优化的，不适用于更高分辨率的图像。本文提出了一种基于偏微分方程（PDE）的新方法，用于自动皮层重建，该方法计算效率高，能随网格分辨率良好扩展，因此特别适用于体素大小为亚毫米级的高分辨率MR图像。该方法使用非均匀电介质中场的数学模型。这种场映射与拉普拉斯映射类似，在皮层层具有良好的分层特性，有助于识别狭窄脑沟中皮层岸之间未解析的边界。通过沿场梯度进行平流，将软膜皮层表面重建为受拓扑保持水平集方法约束的几何可变形模型。该方法在各向同性体素为0.25 - 0.35毫米的离体图像上展示了其性能。通过与FreeSurfer软件在来自OASIS数据库的标准分辨率数据集上的结果进行交叉比较，对20名健康年轻受试者的成对重复扫描数据，进一步评估了该方法。
