Changes of relaxation times (T1, T2) and apparent diffusion coefficient after permanent middle cerebral artery occlusion in the rat: temporal evolution, regional extent, and comparison with histology

Abstract

The quantitative NMR parameters T1, T2, 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 and 72 +/- 2 ms for T1 and for T2, respectively, were found; the corresponding values for cortex were 928 +/- 117 ms and 73 +/- 2 ms. The ADC showed significant dependence on gradient direction: diffusion along x resulted in 534 +/- 53 microns 2/s (CP) and 554 +/- 62 microns 2/s (cortex), and along y in 697 +/- 58 microns 2/s (CP) and 675 +/- 53 microns 2/s (cortex). In the ischemic territory, a continuous increase over time of both relaxation times was observed in the CP, leading to an increase of 29 +/- 20% (T1) and 51 +/- 41% (T2) above control level. 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 (< or = 60% of control) surrounded by a region of lesser reduction (< or = 80% of control). During the early part of the study, the area of reduced ADC was larger than that of elevated relaxation times. Toward the end of the experiment, the area of increased relaxation times approached that of decreased ADC at < or = 80% of control. Good agreement of histological presentation of infarct with the total area of decreased ADC (< or = 80%) was demonstrated.

Temporal profile of T2-Weighted MRI Distinguishes between Pannecrosis and Selective Neuronal Death after Transient Focal Cerebral Ischemia in the Rat

“…Absolute T 1 and T 2 Times in the Lesions T 1 and T 2 relaxation times derived from quantitative parameter maps on the unaffected, contralateral side corresponded to previously published values for normal tissue during the whole observation period (Table 1) (Hoehn-Berlage et al, 1995;van Dorsten et al, 2002). Both groups showed higher absolute T 1 and T 2 times within the lesioned area on parameter maps 1 day after MCAO (Figure 1).…”

Noninvasive Quantification of Brain Edema and the Space-Occupying Effect in Rat Stroke Models Using Magnetic Resonance Imaging

“…This finding is in contradiction to previous statements that edema volume may be negligible at early time points with respect to LV calculation. 5,15 …”

Stroke onset time estimation from multispectral quantitative magnetic resonance imaging in a rat model of focal permanent cerebral ischemia

“…qT 1 increases gradually over time from stroke onset within regions of decreased diffusion (16,9). Pathophysiological mechanisms thought to underlie this qT 1 increase are similar to qT 2 , including altered water dynamics and content in ischaemic tissue (14,19) qT 1 is additionally sensitive to changes in cerebral blood flow and volume (16,20), temperature (21), pH (22) and tissue oxygen tension (16 Five male Wistar rats (300 -400 g, Animal Resource Facility, University of Eastern Finland, Kuopio, Finland) underwent permanent middle cerebral artery occlusion (MCAo) (24).…”