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

Abstract

Many ischaemic stroke patients are ineligible for thrombolytic therapy due to unknown onset time. Quantitative MRI (qMRI) is a potential surrogate for stroke timing. Rats were subjected to permanent middle cerebral artery occlusion and qMRI parameters including hemispheric differences in apparent diffusion coefficient, T<sub>2</sub>-weighted signal intensities, T<sub>1</sub> and T<sub>2</sub> relaxation times (qT<sub>1</sub>, qT<sub>2</sub>) and <i>f</i><sub>1</sub>, <i>f</i><sub>2</sub> and <i>V</i><sub>overlap</sub> were measured at hourly intervals at 4.7 or 9.4 T. Accuracy and sensitivity for identifying strokes scanned within and beyond 3 h of onset was determined. Accuracy for <i>V</i><sub>overlap</sub>, <i>f</i><sub>2</sub> and qT<sub>2</sub> (>90%) was significantly higher than other parameters. At a specificity of 1, sensitivity was highest for <i>V</i><sub>overlap</sub> (0.90) and <i>f</i><sub>2</sub> (0.80), indicating promise of these qMRI indices in the clinical assessment of stroke onset time.