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MRI-based mismatch detection in acute ischemic stroke: Optimal PWI maps and thresholds validated with PET
Olivier Zaro-Weber1,2,3, Walter Moeller-Hartmann4, Dora Siegmund1
11 Max-Planck-Institute for Neurological Research, Cologne, Germany.
Abstract:
Perfusion-weighted (PW) magnetic resonance imaging (MRI) is used to detect penumbral tissue in acute stroke, but the selection of optimal PW-maps and thresholds for tissue at risk detection remains a matter of debate. We validated the performance of PW-maps with 15O-water-positron emission tomography (PET) in a large comparative PET-MR cohort of acute stroke patients. In acute and subacute stroke patients with back-to-back MRI and PET imaging, PW-maps were validated with 15O-water-PET. We pooled two different cerebral blood flow (CBF) PET-maps to define the critical flow (CF) threshold, (i) quantitative (q)CBF-PET with the CF threshold <20 ml/100 g/min and (ii) normalized non-quantitative (nq)CBF-PET with a CF threshold of <70% (corresponding to <20 ml/100 g/min according to a previously published normogram). A receiver operating characteristic (ROC) curve analysis was performed to specify the accuracy and the optimal critical flow threshold of each PW-map as defined by PET. In 53 patients, (stroke to imaging: 9.8 h; PET to MRI: 52 min) PW-time-to-maximum (Tmax) with a threshold >6.1 s (AUC = 0.94) and non-deconvolved PW-time-to-peak (TTP) >4.8 s (AUC = 0.93) showed the best performance to detect the CF threshold as defined by PET. PW-Tmax with a threshold >6.1 s and TTP with a threshold >4.8 s are the most predictive in detecting the CF threshold for MR-based mismatch definition.
Insights
Perfusion-weighted MRI maps, specifically time-to-maximum (Tmax) and time-to-peak (TTP), accurately detect critical flow thresholds in acute stroke patients. These findings aid in defining tissue at risk using magnetic resonance imaging (MRI).
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.
