Stroke onset time estimation from multispectral quantitative magnetic resonance imaging in a rat model of focal permanent cerebral ischaemia

摘要

Background: Quantitative T2 (qT2) relaxation Magnetic Resonance Imaging (MRI) allows estimation of stroke onset time. Aims: We aimed to examine the accuracy of quantitative T1 (qT1) and qT2 relaxation times alone and in combination to provide estimates of stroke onset time in a rat model of permanent focal cerebral ischaemia and map the spatial distribution of elevated qT1 and qT2 to assess tissue status.Methods: Permanent middle cerebral artery occlusion (MCAo) was induced in Wistar rats. Animals were scanned at 9.4T for qT1, qT2 and Trace of Diffusion Tensor (Dav) up to 4 hours post MCAo. Time courses of differentials of qT1 and qT2 in ischaemic and non-ischaemic contralateral brain tissue (ΔT1, ΔT2) and volumes of tissue with elevated T1 and T2 relaxation times (f_(1 ), f_(2 )) were determined. TTC staining was used to highlight permanent ischaemic damage.Results: ΔT1, ΔT2,f_(1 ), f_(2 ) and the volume of tissue with both elevated qT1 and qT2 (VOverlap) increased with time post MCAo allowing stroke onset time to be estimated. VOverlap provided the most accurate estimate with an uncertainty of ±25 minutes. At all times-points regions with elevated relaxation times were smaller than areas with Dav defined ischaemia.Conclusions: Stroke onset time can be determined by qT1 and qT2 relaxation times and tissue volumes. Combining qT1 and qT2 provides the most accurate estimate and potentially identifies irreversibly damaged brain tissue.