Temporal MRI assessment of intracerebral hemorrhage in rats

Background and Purpose - MRI was used to evaluate the effects of experimental intracerebral hemorrhage (ICH) on brain tissue injury and recovery. Methods - Primary ICH was induced in rats (n = 6) by direct infusion of autologous blood into the striatum. The evolution of ICH damage was assessed by MRI estimates of T(2) and T(1sat) relaxation times, cerebral blood flow, vascular permeability, and susceptibility-weighted imaging before surgery ( baseline) and at 2 hours and 1, 7, and 14 days post-ICH. Behavioral testing was done before and at 1, 7, and 14 days post-ICH. Animals were euthanized for histology at 14 days. Results - The MRI appearance of the hemorrhage and surrounding regions changed in a consistent manner over time. Two primary regions of interest were identified based on T2 values. These included a core, corresponding to the bulk of the hemorrhage, and an adjacent rim; both varied with time. The core was associated with significantly lower cerebral blood flow values at all post-ICH time points, whereas cerebral blood flow varied in the rim. Increases in vascular permeability were noted at 1, 7, and 14 days. Changes in T1sat were similar to those of T2. MRI and histological estimates of tissue loss were well correlated and showed approximately 9% hemispheric tissue loss. Conclusions - Although the cerebral blood flow changes observed with this ICH model may not exactly mimic the clinical situation, our results suggest that the evolution of ICH injury can be accurately characterized with MRI. These methods may be useful to evaluate therapeutic interventions after experimental ICH and eventually in humans.