Article
MR angiography for diagnosis of cerebral vasospasm in an experimental subarachnoid hemorrhage model in rats – establishment of reference values
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Published: | June 9, 2017 |
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Objective: Imaging plays an important role in the experimental research on subarachnoid hemorrhage (SAH). 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. Magnetic resonance angiography (MRA) would be a convenient noninvasive alternative for this issue. The definition of reference values is essential for a reliable interpretation of the MRA data. The aim of this study was to establish reference values for the diagnosis of VSP in the double-hemorrhage SAH model in rats.
Methods: SAH was induced in 25 Sprague Dawley male rats using the double-hemorrhage model. Five rats were operated as sham with injection of saline solution instead of blood. MRA (time of flight=TOF) was performed in all rats on day 1 (baseline), on day 2 and on day 5. Measurements of the vessel diameter were performed in all large basal cerebral arteries (basilar artery = BA, internal carotid artery = ICA, middle cerebral artery = MCA and anterior cerebral artery = ACA) by a blinded neuroradiologist. The baseline data were used to establish reference values for every vessel. The datasets of day 2 and day 5 were analyzed for the presence of VSP. The severity of VSP was defined as followed: vessel narrowing of <25% mild, 25-75% moderate and >75% severe VSP.
Results: A total of 90 MRA datasets of 30 rats were analyzed. The following reference values of the mean vessel diameter were established: BA 0.6mm, ICA 0.7mm, MCA 0.6mm and ACA 0.6mm. No VSP was found in the sham-group. In the SAH-group VSP was detected in 32% (8/25) on day 2 and in 55% (14/25) on day 5. On day 2 mild/moderate VSP was observed in 80% (6/8) rats and severe in two rats. On day 5 mild/moderate VSP was found in 50% (7/14) and severe VSP in 50% (7/14).
Conclusion: MRA allows a good visualization of the cerebral vasculature. With the implementation of the established reference values in this study, MRA provides reproducible results concerning the detection of VSP and its differentiation in three severity grades.