EXPRESS: Diagnostic Accuracy of Noninvasive Translesional Pressure Ratio Based on Magnetic Resonance Imaging for Intracranial Atherosclerotic Stenosis: A Validation Study

The anatomic stenosis severity of intracranial atherosclerotic stenosis (ICAS) does not reliably reflect lesion-specific hemodynamic impairment, and invasive pressure-wire assessment is technically challenging in the cerebral circulation. This study aimed to develop and validate MRI-derived pressure ratio (M-PR), a noninvasive functional assessment framework for ICAS. Compared with time-of-flight MRA (TOF-MRA)-based lumen reconstruction, high-resolution vessel wall imaging (HR-VWI) could provide more accurate vascular geometry for CFD, while phase-contrast MRA (PC-MRA) could further improve patient-specific boundary conditions. On this basis, we developed two M-PRs using the same PC-MRA-derived boundary conditions but different sources of vascular geometry: TOF-MRA for TOF-PR and HR-VWI for VWI-PR. Correlation with wire-based PR was assessed using Pearson or Spearman analysis, and agreement was evaluated by Bland-Altman analysis. Subgroup analyses stratified by stenosis severity were performed. In 42 patients with symptomatic ICAS (mean stenosis, 75.3% ± 7.8%), VWI-PR showed strong correlation (r = 0.87, P < 0.001) and close agreement (mean difference, 0.002 ± 0.09), whereas TOF-PR showed weaker correlation (r = 0.37, P = 0.016) and poorer agreement (−0.17 ± 0.25). TOF-PR underestimated PR in severe stenosis, whereas VWI-PR remained stable across stenosis grades. These findings support VWI-PR as an accurate hemodynamic biomarker for functional assessment of ICAS.