Research Article: Noninvasive MRA-derived fractional flow for intracranial stenosis: methodological evaluation and hemodynamic insights
Abstract:
Current fractional flow (FF) approaches in quantifying the hemodynamic severity of intracranial atherosclerotic stenosis (ICAS) are invasive or require angiography. This study primarily evaluated a noninvasive FF method derived from magnetic resonance angiography (MRA-FF) against established reference standards, with an exploratory assessment of its ability to reflect hemodynamically relevant impairment.
In this retrospective study of 50 patients with ICAS, MRA-FF was computed from 3D vascular models using patient-specific flow boundary conditions. Agreement with invasive pressure-wire-derived FF (PW-FF, n =?18) and angiography-based FF (DSA-FF, n =?50) was assessed using intraclass correlation coefficients (ICC). Equivalence to DSA-FF was evaluated using the two one-sided tests procedure (TOST; ? =?±0.05). An exploratory analysis examined the ability of MRA-FF to discriminate hypoperfusion using receiver operating characteristic (ROC) analysis in the subset of patients with available perfusion imaging ( n =?38).
MRA-FF showed moderate-to-good agreement with PW-FF (ICC?=?0.743; 95% CI, 0.437–0.895) and good agreement with DSA-FF (ICC?=?0.784; 95% CI, 0.649–0.871). Equivalence to DSA-FF was confirmed by TOST (90% CI of difference, ?0.016 to 0.035; p <?0.01). In the perfusion subset, MRA-FF was lower in patients with hypoperfusion than in those without ( p =?0.022). The area under the ROC curve for discriminating hypoperfusion was 0.723 (95% CI, 0.54–0.90). Within this dataset, the exploratory optimal cutoff value was 0.855.
MRA-FF demonstrates good agreement with invasive and angiographic reference methods and shows the ability to discriminate hypoperfusion in an exploratory analysis. These findings support the feasibility and potential clinical utility of a fully noninvasive FF approach for functional assessment and hemodynamic characterization, although further external validation is required.
Introduction:
Fractional flow (FF), defined as the ratio of distal to proximal pressure across a stenosis, provides a physiologic assessment of lesion-specific hemodynamic severity ( 1 ). It is a cornerstone of functional assessment in coronary artery disease ( 2 – 4 ). With increasing insight into cerebrovascular pathophysiology, the concept of FF has been extended to intracranial atherosclerotic stenosis (ICAS) ( 5 – 7 ). Prior studies show that patients with similar degrees of angiographic stenosis may exhibit markedly…
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