CHANGES OF RELAXATION-TIMES (T-1, T-2) AND APPARENT DIFFUSION-COEFFICIENT AFTER PERMANENT MIDDLE CEREBRAL-ARTERY OCCLUSION IN THE RAT - TEMPORAL EVOLUTION, REGIONAL EXTENT, AND COMPARISON WITH HISTOLOGY

The quantitative NMR parameters T-1, T-2, rho, and apparent diffusion coefficient (ADC) were determined during the 7 h after middle cerebral artery occlusion in rats. In the normal caudate-putamen (CP), 869 +/- 145 ms acid 72 +/- 2 ms for T-1 and for T-2, respectively, were found ; the corresponding values for cortex were 928 +/- 117 ms and 73 +/- 2 ms, The ADC showed significant dependence on gradient direction: diff usion along x resulted in 534 +/- 53 mu m(2)/s (CP) and 554 +/- 62 mu m(2)/s (cortex), and along y in 697 +/- 58 mu m(2)/s (CP) and 675 +/- 53 mu m(2)/s (cortex), In the ischemic territory, a continuous increas e over time of both relaxation times was observed in the CP, leading t o an increase of 29 +/- 20% (T-1) and 51 +/- 41% (T-2) above control l evel, ADC dropped to 63 +/- 15% of control in the CP and to 74 +/- 4% of control in the temporal cortex, No significant change was noted in proton density during the observation period, Strongest ADC reduction was in the center of the ischemic territory (less than or equal to 60% of control) surrounded by a region of lesser reduction (less than or equal to 80% of control), During the early part of the study, the area of reduced ADC was larger than that of elevated relaxation times, Tow ard the end of the experiment, the area of increased relaxation times approached that of decreased ADC at less than or equal to 80% of contr ol, Good agreement of histological presentation of infarct with the to tal area of decreased ADC (less than or equal to 80%) was demonstrated .