A Comparison of T Relaxation-Based MRI Stroke Timing Methods in Hyperacute Ischemic Stroke Patients: A Pilot Study.

BACKGROUND

T relaxation-based magnetic resonance imaging (MRI) signals may provide onset time for acute ischemic strokes with an unknown onset. The ability of visual and quantitative MRI-based methods in a cohort of hyperacute ischemic stroke patients was studied.

METHODS

A total of 35 patients underwent 3T (3 Tesla) MRI (<9-hour symptom onset). Diffusion-weighted (DWI), apparent diffusion coefficient (ADC), T-weighted (Tw), T-weighted (Tw), and T relaxation time (T) images were acquired. T-weighted fluid attenuation inversion recovery (FLAIR) images were acquired for 17 of these patients. Image intensity ratios of the average intensities in ischemic and non-ischemic reference regions were calculated for ADC, DWI, Tw, T relaxation, and FLAIR images, and optimal image intensity ratio cut-offs were determined. DWI and FLAIR images were assessed visually for DWI/FLAIR mismatch.

RESULTS

The T relaxation time image intensity ratio was the only parameter with significant correlation with stroke duration ( = 0.49,  = .003), an area under the receiver operating characteristic curve (AUC = 0.77,  < .0001), and an optimal cut-off (T ratio = 1.072) that accurately identified patients within the 4.5-hour thrombolysis treatment window with sensitivity of 0.74 and specificity of 0.74. In the patients with the additional FLAIR, areas under the precision-recall-gain curve (AUPRG) and F scores showed that the T relaxation time ratio (AUPRG = 0.60, F = 0.73) performed considerably better than the FLAIR ratio (AUPRG = 0.39, F = 0.57) and the visual DWI/FLAIR mismatch (F = 0.25).

CONCLUSIONS

Quantitative T relaxation time is the preferred MRI parameter in the assessment of patients with unknown onset for treatment stratification.