Experimentally Induced Cerebral Fat Embolism with Linoleic Acid: MR Imaging and Pathologic Correlation

PURPOSE: To investigate the correlation between the MRI findings of cerebral fat embolism induced by injecting linoleic acid into ten cats, and pathologic diagnosis. MATERIALS AND METHODS: Using a microcatheter, 30 microliter of linoleic acid was injected into the internal carotid artery of ten cats. MR T2-weighted (T2WI), diffusion-weighted (DWI), and Gd-enhanced T1-weighted images (Gd-enhanced T1WI) were obtained after 30 minutes and after 2 hours of embolization. We pathlogically examined endothelial cell damage, cellular change, perivascular abnormality and fat vacuoles, and then determined the correlation between MRI and the pathologic findings. RESULT: After 30 minutes of embolization, lesions of very high signal intensity were detected by T2WI in six cats, and of slightly high signal intensity in two; in the remaining two, signal intensity was normal. DWI showed lesions of very high intensity in nine animals and of slightly high intensity in one, while Gd-enhanced T1WI showed well-enhanced lesions in nine and a minimally enhanced lesion in one. After 2 hours of embolization, T2WI revealed lesions of very high signal intensity in nine cats, and of slightly high signal intensity in one, while DWI detected lesions of very high signal intensity in all cats. On Gd-enhanced T1WI, lesions in all cats were well enhanced. According to the findings of light microscopic examination, infarcted lesions mainly involved the gray matter, but also some white matter. In the lesions, neurophil matrix edema, neuronal degeneration, perivascular swelling, the widening of extracellular space, extravascular hemorrhage, and fat vacuoles were evident. CONCLUSION: During the initial two hours following injection, MR imaging of cerebral fat embolism induced by linoleic acid through the internal carotid artery in cats showed high signal intensity on T2WI and DWI, and clear enhancement on Gd-enhanced T1WI. In cases involving cellular edema, cerebrovascular injury and extracellular space widening, the pathologic evidence suggested the coexistence of cytotoxic and vasogenic edema.

Measurement of Regional Cerebral Blood Volume in Normal Rabbits on Perfusion-weighted MR Image

PURPOSE: To evaluate the usefulness of cerebral blood flow measurement applied to perfusion weighted image with short-scan time single shot gradient echo-planar technique in measuring cerebral blood volume(rCBV) of normal rabbits. MATERIALS AND METHODS: With 2.1-3.6 kg weighted rabbits, image is acquired when they are in supine position in children positioner. Perfusion weighted image is acquired to 44 seconds per 1 second successively. After 4 seconds later, Gd-DTPA 2ml are injected into int. jugular vein with 2 ml per second and normal saline is also injected after that. Same technique is applied 2 times per 30 minites in same rabbit. After Image is obtained in two part of cerebral cortex at vertex, convexity, in one of basal ganglia with choosing about 3-5mm2 areas. Curve of signal intensity changes in time sequence is drawn. After this images are transmitted by PC and software IDL, regional cerebral blood volume is measured with imaging processing program made by us. RESULTS: With 22 of 24 rabbits, satisfactory 1-2 signal intensity versus time curve is made. Cerebral blood capacity and contrast media stay time (ST) is measured in two cerebral cortex and basal ganglia refering in parietal cerebral cortex. Mean focal cerebral blood flow capacity ratio in cortex was 0.97+/-0.35 and in basal ganglia, 0.99+/-0.37, mean contrast media stay time in cortex was 9.83+/-1.63 sec and in basal ganglia, 9.42+/-1.14 sec, but there was no statistically significant difference between two areas (p=0.05). CONCLUSION: In cerebral cortex and basal ganglia, there is no difference in mean focal blood volume and mean contrast stay time. Therefore, PWI is useful in cerebral blood flow and early diagnosis, prognosis of cerebral ischemic disease. Hereafter, it is helpful in analysing cerebral blood flow changes with comparison difference in rCBV between normal tissue and ischemic tissue, and that with DWI finding in infarcted patient.