Diagnostic performance of PWI/DWI MRI parameters in discriminating hyperacute versus acute ischaemic stroke: finding the best thresholds.

AIM: To determine the accuracy of the perfusion/diffusion-weighted imaging (PWI/DWI) parameters [time to peak (TTP), mean time to peak (MTT), relative cerebral blood volume (rCBV), and relative cerebral blood flow (rCBF) maps]; in the evaluation of acute versus hyperacute ischaemic stroke.

MATERIALS AND METHODS: Fifty-five patients with symptomatic hyperacute (first 6h) or acute (7-24h) ischaemic stroke underwent diffusion and perfusion evaluation. Statistical analysis included Student's t-test, receiver operating characteristics (ROC) analysis of apparent diffusion coefficient (ADC), TTP, MTT, CBV, and CBF; correlation, linear, and logistic regression analysis.

RESULTS: Area under receiver operating characteristics (AUROC) analysis identified the ADC cut-off value 385×10(-6)mm(2)/s, MTT at 109.5%, TTP at 3.05s, CBV at 129%, and CBF at 98.5% (the record of the time of onset was considered the reference standard). The best performance corresponded to TTP, which showed a sensitivity of 0.94 and specificity of 0.88 (p<0.001).

CONCLUSIONS: Based on the present findings, hyperacute penumbra is reliably defined with a TTP >3s with no visible changes in diffusion. ADC, rCBF, and rCBV are not useful for discriminating between acute and hyperacute ischaemic stroke.