Santhosh Kannath, Thomas Bejoy, Radhakrishnan Vishnupuri V, Saini Jitender, Kesavadas Chandrasekharan, Gupta Arun Kumar, Kapilamoorthy Tirur Raman, Nair Suresh N
Department of Imaging Sciences and Interventional Radiology, Sree Chitra Tirunal Institute for Medical Science and Technology, Trivandrum, Kerala, India.
J Magn Reson Imaging. 2009 Apr;29(4):967-70. doi: 10.1002/jmri.21686.
To explore the utility of diffusion tensor imaging (DTI) and diffusion tensor metrics (DTM) in characterizing the structural pathology of epidermoid cysts. DTI gives information about the tissue structure; a high fractional anisotropy (FA) indicates a highly structured orientation of the tissue, fibers, or white matter tracts. Based on the tensor rank, a set of three metrics has been described that can be used to measure the directional dependence of diffusion: linear anisotropy (CL), planar anisotropy (CP), and spherical anisotropy (CS). DTM takes into account the shape of diffusion anisotropy and hence may provide better insight into the orientation of structures than FA.
DTI was performed in three patients with epidermoid cysts. FA, directionally-averaged mean diffusivity (Dav), exponential apparent diffusion coefficient (eADC), and DTM, such as CL, CP, and CS, were measured from the tumor core as well as from the normal-appearing white matter. Histopathological correlation was obtained.
Epidermoid cysts showed high FA with Dav values similar to that of normal white matter. eADC maps did not show any restriction of diffusion. FA values were high, but not as high as that for the white matter. CP values were higher and CL values were lower than those obtained for the white matter in various regions.
High CP values suggest preferential diffusion of water molecules along a two-dimensional geometry, which could be attributed to the well-structured orientation of keratin filaments and flakes within the tumor as demonstrated by histopathology. Advanced imaging modalities like DTI with DTM can provide information regarding the microstructural anatomy of the epidermoid cysts.
探讨扩散张量成像（DTI）和扩散张量指标（DTM）在表皮样囊肿结构病理学特征描述中的应用。DTI可提供有关组织结构的信息；高分数各向异性（FA）表明组织、纤维或白质束具有高度结构化的方向。基于张量秩，已描述了一组三个指标，可用于测量扩散的方向依赖性：线性各向异性（CL）、平面各向异性（CP）和球形各向异性（CS）。DTM考虑了扩散各向异性的形状，因此可能比FA能更好地洞察结构的方向。
对三名表皮样囊肿患者进行DTI检查。从肿瘤核心以及外观正常的白质中测量FA、方向平均扩散率（Dav）、指数表观扩散系数（eADC）和DTM，如CL、CP和CS。获得了组织病理学相关性。
表皮样囊肿显示出高FA，Dav值与正常白质相似。eADC图未显示任何扩散受限。FA值较高，但不如白质高。在各个区域，CP值高于白质，CL值低于白质。
高CP值表明水分子沿二维几何结构优先扩散，这可能归因于肿瘤内角蛋白丝和薄片的结构良好的方向，这在组织病理学中得到了证实。像DTI结合DTM这样的先进成像模式可以提供有关表皮样囊肿微观结构解剖学的信息。
