It is shown that diffusion tensor MR imaging (DTI) can discretely delineate the microstructure of white matter and gray matter in embryonic and early postnatal mouse brains based on the existence and orientation of ordered structures. This order was found not only in white matter but also in the cortical plate and the periventricular zone, which are precursors of the cerebral cortex. This DTI-based information could be used to accomplish the automated spatial definition of the cortical plate and various axonal tracts. The DTI studies also revealed a characteristic evolution of diffusion anisotropy in the cortex of the developing brain. This ability to detect changes in the organization of the brain during development will greatly enhance morphological studies of transgenic and knockout models of cortical dysfunction. With the advent of murine models of disease and development generated by gene engineering, a new noninvasive technique is needed to characterize 3D morphological changes appearing over time in the brain. At present, the microscopic anatomical analyses of mammalian developmental studies are almost exclusively based on the histological examination. While this technique is most effective for examining microscopic changes in developing brains, it is not particularly suitable to characterize large-scale morphology, such as the anatomy of the entire brain. Although it is possible to reconstruct a macroscopic 3D-volume dataset using serial histological sections and stereology, this is an extremely labor-intensive process (1,2). To examine global anatomy in developing mouse brains, MRI technology is especially promising (3,4) because it can provide a 3D dataset without sectioning and is free of artifacts related to brain deformation or missing tissue due to imperfect sectioning. The data are intrinsically numerical and quantification for shape and volume analyses is more straightforward. Similar to various staining techniques for histological preparations, MRI also provides a family of contrast types based on the physical properties of water. For example, mouse embryonic imaging has been performed using proton density T 1 -and T 2 -weighted images (3-6). While these imaging methods can provide clear contrast for various tissue compartments in the entire body, it is not always optimal for the differentiation of compartments within the brain because of small differences in T 1 and T 2 relaxation parameters in young brains (7,8). Moreover, even in adult brains conventional MRI methods are not suitable to differentiate various white matter tracts within the brain white matter.In this report, we apply an MRI technology called diffusion tensor imaging (DTI) (9,10) to study mouse brain development from a period starting at embryonic day 15.5 in utero to adult. This technique uses water diffusion to probe tissue microstructure. For example, in regions where axon tracts form an ordered environment, water diffusion has directionality (anisotropy). Application of this technique to the adult brain has revealed that whi...

In patients with X-ALD, MR spectroscopic imaging can depict abnormalities in white matter that have a normal appearance on both conventional MR and DT images; this finding suggests that it may be the most sensitive technique for detecting early abnormalities of demyelination or axonal loss in patients with X-ALD.

No abstract