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

Abstract

. (2016). Stroke onset time estimation from multispectral quantitative magnetic resonance imaging in a rat model of focal permanent cerebral ischaemia.

Determining Stroke Onset Time Using Quantitative MRI: High Accuracy, Sensitivity and Specificity Obtained from Magnetic Resonance Relaxation Times

“…qMRI data from our previous studies [ 5 , 7 ] were used. Although qT 1 and qT 2 are dependent on magnetic field strength, combining data from 4.7 T and 9.4 T, was not considered problematic as the net magnitude of qT 1 and qT 2 change due to ischaemia is independent of field strength during the initial hours of stroke [ 7 ].…”

“…During MRI, breathing rate and rectal temperature were monitored and core temperature maintained at 37°C with a water heating pad. After MRI, rats were sacrificed [ 5 , 7 ].…”

“…Hemispheric differences in the apparent diffusion coefficient (ADC) [ 4 ], signal intensities of T 2 -weighted (T 2 -w) images (with and without FLAIR) [ 4 , 5 , 6 ] and quantitative T 1 (qT 1 ) [ 7 ] and T 2 (qT 2 ) relaxation times [ 5 , 7 ] correlate with time from stroke onset. This relationship is attributed to changes in tissue-water dynamics due to cytotoxic and/or vasogenic oedema [ 1 ] and enabled onset time to be determined with varying levels of accuracy [ 3 , 4 , 5 , 6 , 7 , 8 ]. In rat focal ischaemia, the spatial distribution and volume of abnormal qT 1 or qT 2 tissue is initially smaller than total ischaemia volume (delineated by decreased ADC) but increases with ischaemia duration [ 5 , 7 ].…”

“…This relationship is attributed to changes in tissue-water dynamics due to cytotoxic and/or vasogenic oedema [ 1 ] and enabled onset time to be determined with varying levels of accuracy [ 3 , 4 , 5 , 6 , 7 , 8 ]. In rat focal ischaemia, the spatial distribution and volume of abnormal qT 1 or qT 2 tissue is initially smaller than total ischaemia volume (delineated by decreased ADC) but increases with ischaemia duration [ 5 , 7 ]. We therefore proposed qMRI surrogates for stroke timing including f 1 , f 2 and V overlap , where f 1 and f 2 are the volume of tissue with elevated qT 1 or qT 2 as a percentage of total ischaemia volume, respectively, and V overlap is the volume with both elevated qT 1 and qT 2 normalised by the whole brain volume [ 7 ].…”

“…High sensitivity is also important to stratify as many patients as possible for thrombolysis. Accuracy of the above qMRI surrogates for stroke assessment has been reported in preclinical and clinical settings [ 3 , 4 , 5 , 6 , 7 , 8 ]. The objective of this study was to compare the accuracy and sensitivity of ADC, T 2 -w, qT 1 , qT 2 , f 1 , f 2 and V overlap in a defined rat model of ischaemic stroke.…”