VOLUMETRIC METHOD FOR EVALUATING MAGNETIZATION-TRANSFER RATIO OF TISSUE CATEGORIES - APPLICATION TO AREAS OF WHITE-MATTER SIGNAL HYPERINTENSITY IN THE ELDERLY

An objective technique for analyzing magnetization transfer ratio of s egmented tissues was used to evaluate differences between normal-appea ring white matter and areas of white matter signal hyperintensity on T 2-weighted magnetic resonance images in 23 healthy elderly subjects (m ean age, 75 years). Segmented brain images (cerebrospinal fluid, gray matter, white matter, areas of white matter signal hyperintensity) com puted from T1- and T2-weighted images were combined with magnetization -transfer-ratio images to produce magnetization-transfer-ratio histogr ams for each tissue. There was a significant 8.1% reduction in mean ma gnetization transfer ratio for areas of white matter signal hyperinten sity compared with normal-appearing white matter (P < .001). The magne tization transfer ratio for all tissue categories was significantly ne gatively correlated with age (all, P <.05). This method of measuring m agnetization transfer ratio was objective, independent of regional var iations, and as reproducible as the segmentation procedure.