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T1 weighted image
1. MRI made with pulse spin echo or inversion recovery sequence with short TR and TE to show contrast between tissues with different T1 values; an image with greater signal intensity from fat-containing tissues.
http://www.medilexicon.com/medicaldictionary.php?t=43573

axonal - definition of axonal by the Free Online Dictionary ...
www.thefreedictionary.com/axonal
ax·on ( k s n ) also ax·one (-s n ). n. The usually long process of a nerve fiber that generally conducts impulses away from the body of the nerve cell. ...


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Note added at 1 hr (2011-10-29 20:33:39 GMT)
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A T1-weighted magnetic resonance imaging (MRI) scan shows “black holes,” which are areas of permanent axonal damage. These are called hypointense lesions, meaning that they display as dark areas on the MRI image. T1-weighted lesions can also be areas of edema (swelling), which are not permanent and disappear on subsequent scans.
http://ms.about.com/od/glossary/g/T1_lesion.htm