Article
MR-angiography allows to differentiate severity grades of cerebral vasospasm in an experimental double blood injection subarachnoid hemorrhage model in rats
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Published: | June 2, 2015 |
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Objective: Magnetic resonance imaging (MRI) has been used for the detection of cerebral infarction in experimental subarachnoid hemorrhage and stroke studies in rats. For the detection of cerebral vasospasm (VSP) conventional angiography is generally used, which is an invasive and elaborate technique with a possible subsequent increase in morbidity and mortality. In this study we have evaluated the validity of MR-angiography in detecting cerebral VSP in rats using the double blood injection model. Second, the possibility to differentiate severity grades of VSP was analysed.
Method: Subarachnoid hemorrhage was induced using the double blood injection model in 10 male Sprague Dawley rats. In two cases, saline solution was injected instead of blood (sham group). Prior to that the left common carotid artery was ligated in order to increase the incidence and severity of VSP. The blood injection was performed with autologous arterial blood on two consecutive days. MRI was performed on day 2 after the second blood injection and on day 5. The following parameters were applied: T1-weighted, T2-weighted, T2*-weighted and time of flight (TOF) sequence. The analysis of the MRA datasets for the detection of VSP and/or infarction was performed by a blinded neuroradiologist.The severity of VSP was defined as followed: vessel narrowing of <25% mild, 25-75% moderate and >75% severe VSP.
Results: We have performed a total of 17 MRI scans in 10 rats. In seven rats, MRI was performed on day 2 and day 5, respectively. In three rats, MRI was restricted to day 2, because the rats died earlier. In all cases, we were able to achieve a good visualization of the circle of Willis. On day 2 mild VSP was found in 5 cases (5/10; 50%) and moderate VSP in 2 cases. On day 5 mild VSP was found in 2 cases (2/7; 29%) and severe VSP in 3 cases (3/7; 43%), respectively.
Conclusions: According to the results of our study, MRA is a reliable, noninvasive diagnostic tool, which allows a good visualization of the cerebral vasculature and provides reproducible results concerning the detection of cerebral VSP and the differentiation in mild/moderate/severe without the application of contrast media. Future studies are needed to directly compare the results of MRA with conventional angiography.