Multispectral analysis of magnetic resonance images

Magnetic resonance (MR) imaging systems produce spatial distribution estimates of proton density, relaxation time, and flow, in a two dimensional matrix form that is analogous to that of the image data obtained from multispectral imaging satellites. Advanced NASA satellite image processing offers sophisticated multispectral analysis of MR images. Spin echo and inversion recovery pulse sequence images were entered in a digital format compatible with satellite images and accurately registered pixel by pixel. Signatures of each tissue class were automatically determined using both supervised and unsupervised classification. Overall tissue classification was obtained in the form of a theme map. In MR images of the brain, for example, the classes included CSF, gray matter, white matter, subcutaneous fat, muscle, and bone. These methods provide an efficient means of identifying subtle relationships in a multi-image MR study.     

Independent representations for cursive and print style: Evidence from dysgraphia in Alzheimer's disease

In this paper we describe two mild Alzheimer's disease patients (AF and EZ) who show a double dissociation in written production of cursive and print styles. We analysed their performance on a number of different tasks. Both had no major difficulty in reading, direct copying, or spelling but displayed contrasting patterns of impairment in writing using different styles. AF was impaired when asked to write in cursive, whereas EZ was impaired when requested to write in print. The patients showed no general impairment in retrieving visual forms, but both failed a letter form judgement task, only for the affected style. Evidence from their overall performance adds support to opposing patterns of impairments in both patients. The double dissociation shown by AF's and EZ's performance strengthens previous arguments for independent representations of cursive and print style.