Acute Cerebral Infarction in a Rabbit Model: Perfusion and Diffusion MR Imaging

PURPOSE: The present study was undertaken to evaluate the usefulness of cerebral diffusion (DWI) and perfusion MR imaging (PWI) in rabbit models with hyperacute cerebral ischemic infarction. MATERIALS AND METHODS: Experimental cerebral infarction were induced by direct injection of mixture of Histoacryl glue, lipiodol, and tungsten powder into the internal cerebral artery of 6 New-Zealand white rabbits, and they underwent conventional T1 and T2 weighted MR imaging, DWI, and PWI within 1 hour after the occlusion of internal cerebral artery. The PWI scan for each rabbit was obtained at the level of lateral ventricle and 1cm cranial to the basal ganglia. By postprocessing using special imaging software, perfusion images including cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) maps were obtained. The detection of infarcted lesion were evaluated on both perfusion maps and DWI. MTT difference time were measured in the perfusion defect lesion and symmetric contralateral normal cerebral hemisphere. RESULTS: In all rabbits, there was no abnormal signal intensity on T2WI. But on DWI, abnormal high signal intensity, suggesting cerebral infarction, were detected in all rabbits. PWI (rCBV, CBF, and MTT map) also showed perfusion defect in all rabbits. In four rabbits, the calculated square of perfusion defect in MTT map is larger than that of CBF map and in two rabbits, the calculated size of perfusion defect in MTT map and CBF map is same. Any rabbits do not show larger perfusion defect on CBF map than MTT map. In comparison between CBF map and DWI, 3 rabbits show larger square of lesion on CBF map than on DWI. The others shows same square of lesion on both technique. The size of lesion shown in 6 MTT map were larger than DWI. In three cases, the size of lesion shown in CBF map is equal to DWI. But these were smaller than MTT map. The calculated square of lesion in CBF map, equal to that of DWI and smaller than MTT map was three. And in one case, the calculated square of perfusion defect in MTT map was largest, and that of DWI was smallest. CONCLUSION: DWI and PWI may be useful in diagnosing hyperacute cerebral ischemic infarction and in evaluating the cerebral hemodynamics in the rabbits.

The Usefulness of Perfusion MR Imaging in Patients with Brain Tumors

PURPOSE: To determine the usefulness of perfusion weighted MR imaging in the assessment of relative cerebral blood volume(rCBV) in brain tumors. MATERIALS AND METHODS: Twenty-three patients with primary or metastatic brain tumors [nine gliomas (6 high grade and 3 low), six metastatic tumors, five meningiomas (4 benign and 1 atypical), two neurilemmomas and one hemangioblastoma] underwent perfusion-weighted and conventional MR imaging. A total of 240 perfusion MR images were obtained from four axial slices after rapid injection of contrast media using a gradient echo planar imaging pulse sequence, and this was followed by postprocessing of these images to give CBV maps. In order to calculate the rCBV of tumor to normal white matter, ROIs were defined on the CBV map of a tumor and its contralateral normal white matter. RESULTS: The rCBV ratio of tumors to contralateral normal side was as follows: high-grade glioma, 0.40-5.64(mean +/-SD = 2.91 0.95); low grade astrocytoma, 0.77 -1.66 (mean +/-SD = 1.15 +/-0.28); benign menin-gioma,2.06 -4.90 (mean +/-SD = 3.59 +/-0.84); atypical meningioma, 0.46 -1.18 (mean +/-SD = 0.72 +/-0.25); neurilemmoma, 1.45 -3.85 (mean +/-SD = 2.56 +/-0.92); and hemangioblastoma, 6.16 -8.35 (mean +/-SD = 7.02 +/-1.12). High grade gliomas were more hypervascular than low grade astrocytomas, and showed a variable range of relative cerebral blood volume. In metaststic cancer, CBV maps showed a relatively high and variable blood volume. Benign meningiomas exhibited high relative cerebral blood volume, while in the atypical meningioma with cystic degeneration, this volume was low. In neurilemmomas, a variable range of relative cerebral blood volume, was noted, while in the mural nodule of the hemangioblastoma, this volume was the highest. CONCLUSION: Perfusion-weighted MRI indicated the rCBV of various brain tumor lesions, and this suggests that the modality can provide a very useful means of assessing brain tumor vascularity.