MR imaging of experimentally induced intracranial hemorrhage in rabbits during the first 6 hours

Purpose: To evaluate the MR appearance of intracranial, especially intrapar enchymal, hemorrhage during the first 6 hours after bleeding with various p ulse sequences in an animal model. Material and Methods: Intracerebral hematomas and subarachnoid hemorrhage w ere created by injecting autologous blood in 9 rabbits. MR studies were per formed using a 1.5 T scanner with pixel size and slice thickness comparable to those used in clinical practice before blood injection, immediately aft er injection, and at regular intervals during 6 hours. The images were comp ared with the hematoma sizes on formalin-fixed brain slices. Results: In every animal, susceptibility-weighted gradient-echo (GRE) pulse sequences depicted the intraparenchymal hematomas and blood escape in the ventricles or subarachnoid space best as areas of sharply defined, strong h ypointensity. The findings remained essentially unchanged during follow-up. The sizes corresponded well to the post-mortem findings. Gradient- and spi n-echo (GRA-SE) imaging revealed some hypointensities, but these were small er and less well defined. Spin-echo (SE) sequences (proton density-, T1- an d T2-weighted) as well as a fluid-attenuated inversion recovery turbo spin- echo sequence (fast FLAIR) depicted the hemorrhage sites as mostly isointen se to brain. Conclusion: Susceptibility-weighted GRE imaging at 1.5 T is highly sensitiv e to both hyperacute hemorrhage in the brain parenchyma and to subarachnoid and intraventricular hemorrhage.