Pattern Recognition Lab, Department of Computer Science, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany.
Magn Reson Imaging. 2011 Oct;29(8):1076-87. doi: 10.1016/j.mri.2011.02.034. Epub 2011 Jul 29.
Glaucoma is an optic neuropathy affecting the entire visual system. The understanding of the glaucoma mechanism and causes remains unresolved. Diffusion tensor imaging (DTI) has been used to analyze the optic nerve and optic radiation showing global fiber abnormalities associated with glaucoma. Nevertheless, the complex structure of the optic radiation and the limitations of DTI make the localization of the glaucoma effect a difficult task. The aim of this work is to establish a framework for the determination of the local changes of the optic radiation due to glaucoma using DTI. The proposed system utilizes a semiautomated algorithm to produce an efficient identification of the optic radiation. Segmented optic radiations are transformed to a unified space using shape-based nonrigid registration. Using the deformation fields that resulted from the registration, the maps of the diffusion tensor-derived parameters are transformed to the unified space. This allows for statistical voxel-wise analysis to produce significant abnormality maps. The proposed system is applied to a group of 13 glaucoma patients and a normal control group of 10 subjects. The groups are age matched to eliminate the age effect on the analysis. Diffusion-related parameters (axial, radial and mean diffusivities) and an anisotropy index (fractional anisotropy) are studied. The anisotropy analysis indicates that the majority of the significant voxels show decreased fractional anisotropy in the glaucoma patients compared with the control group. In addition, the significant regions are mainly distributed in the middle (in reference to anterior-posterior orientation) of the optic radiation. Glaucoma subjects have increased radial diffusivity and mean diffusivity significant voxels with a main concentration in the proximal part of the right optic radiation. The proposed analysis provides a framework to capture the significant local changes of the optic radiation due to glaucoma. The preliminary analysis suggests that the glaucomatous optic radiation may suffer from localized white matter degeneration. The framework facilitates further studies and understanding of the pathophysiology of glaucoma.
青光眼是一种影响整个视觉系统的视神经病变。青光眼的发病机制和病因尚不清楚。弥散张量成像（DTI）已被用于分析视神经和视辐射，显示与青光眼相关的整体纤维异常。然而，视辐射的复杂结构和 DTI 的局限性使得确定青光眼效应的定位成为一项艰巨的任务。本工作的目的是建立一个使用 DTI 确定青光眼引起的视辐射局部变化的框架。所提出的系统利用半自动算法对视辐射进行高效识别。分割的视辐射通过基于形状的非刚性配准转换到统一空间。使用配准产生的变形场，将扩散张量衍生参数的图谱转换到统一空间。这允许进行统计体素分析，以产生显著异常图谱。该系统应用于 13 名青光眼患者和 10 名正常对照组。对这些组进行年龄匹配，以消除年龄对分析的影响。研究了扩散相关参数（轴向、径向和平均扩散率）和各向异性指数（分数各向异性）。各向异性分析表明，与对照组相比，大多数显著体素的分数各向异性在青光眼患者中降低。此外，显著区域主要分布在视辐射的中部（相对于前后方向）。青光眼患者的右视辐射近端部分有更多的径向扩散率和平均扩散率显著体素。所提出的分析提供了一个框架来捕获青光眼引起的视辐射的显著局部变化。初步分析表明，青光眼视辐射可能遭受局部白质变性。该框架便于进一步研究和理解青光眼的病理生理学。
