MRI-based mismatch detection in acute ischemic stroke: Optimal PWI maps and thresholds validated with PET

Area of Science:

• Neurology
• Radiology
• Medical Imaging

Background:

• Perfusion-weighted (PW) magnetic resonance imaging (MRI) is crucial for identifying penumbral tissue in acute stroke.
• Optimal selection of PW-maps and thresholds for detecting tissue at risk remains debated.
• Validation of PW-MRI performance against positron emission tomography (PET) is needed.

Purpose of the Study:

• To validate the performance of different PW-MRI maps against 15O-water-PET in acute stroke patients.
• To determine optimal PW-MRI thresholds for detecting critical flow (CF) as defined by PET.
• To improve the accuracy of MR-based mismatch definition in acute stroke.

Main Methods:

• Comparative PET-MR study in acute and subacute stroke patients with simultaneous imaging.
• Validation of PW-maps (Tmax, TTP) against quantitative (q)CBF-PET and normalized non-quantitative (nq)CBF-PET.
• Receiver operating characteristic (ROC) curve analysis to determine optimal thresholds and accuracy.

Main Results:

• PW-Tmax >6.1s (AUC=0.94) and non-deconvolved PW-TTP >4.8s (AUC=0.93) demonstrated the highest accuracy in detecting the PET-defined CF threshold.
• These thresholds were validated in 53 patients with a mean stroke-to-imaging time of 9.8 hours.
• Both PW-Tmax and TTP showed strong predictive performance for MR-based mismatch definition.

Conclusions:

• PW-Tmax and TTP are highly effective in detecting critical flow thresholds in acute stroke.
• The identified thresholds (>6.1s for Tmax, >4.8s for TTP) enhance the accuracy of MR-based tissue-at-risk assessment.
• These findings support the use of specific PW-MRI parameters for optimizing acute stroke management.