Is the optimal Tmax threshold identifying perfusion deficit volumes variable across MR perfusion software packages? A...

Area of Science:

• Neurology
• Radiology
• Medical Imaging

Background:

• Accurate quantification of ischemic core and penumbra is crucial for late-presenting acute ischemic stroke.
• Differences in MR perfusion software suggest variability in optimal Time-to-Maximum (Tmax) thresholds.

Purpose of the Study:

• To assess the optimal Tmax threshold for two MR perfusion software packages (RAPID and OleaSphere).
• To compare perfusion deficit volumes with final infarct volumes as ground truth.

Main Methods:

• Analysis of the HIBISCUS-STROKE cohort of acute ischemic stroke patients treated with mechanical thrombectomy.
• Post-processing of MR perfusion using RAPID and OleaSphere with Tmax thresholds of ≥6s, ≥8s, and ≥10s.
• Comparison of perfusion deficit volumes to day-6 final infarct volumes.

Main Results:

• Increasing Tmax thresholds (≥6s to ≥10s) significantly reduced perfusion deficit volumes for both packages.
• For RAPID, Tmax ≥6s and ≥8s moderately overestimated final infarct volume, with Tmax ≥8s showing closer agreement.
• For OleaSphere, Tmax ≥10s demonstrated closer agreement with final infarct volume compared to Tmax ≥6s.

Conclusions:

• The optimal Tmax threshold for defining ischemic penumbra appears to be ≥6s for RAPID and ≥10s for OleaSphere.
• The commonly recommended Tmax threshold of ≥6s may not be universally optimal across all MR perfusion software.
• Further validation studies are needed to establish optimal Tmax thresholds for each specific software package.