SNAPFLOW: A Novel Integrated MRI Sequence for Simultaneous Intracranial Vessel and Blood Flow Assessment

To develop and evaluate a single-acquisition integrated MRI sequence named SNAPFLOW for simultaneous assessment of intracranial arterial lumen morphology, vessel wall, and blood flow within a single acquisition.

SNAPFLOW integrates Simultaneous Non-contrast Angiography and intraPlaque hemorrhage (SNAP) imaging, pulsed arterial spin labeling (ASL)-MRA, and non-interleaved 3D phase-contrast (PC) flow imaging within a single intrinsically co-registered acquisition. SNAP-derived MRA and vessel wall images were reconstructed using phase-sensitive inversion recovery, ASL-MRA was generated by complex control-label subtraction, and PC velocity maps were obtained using phase-difference methods, respectively. SNAPFLOW was evaluated in 12 healthy volunteers and two patients with cerebrovascular disease and compared with conventional SNAP and 3D PC MRI.

Quantitative velocity measurements in SNAPFLOW showed good-to-excellent agreement with conventional 3D PC MRI, with ICCs ranging from 0.836 to 0.931 across encoding directions (RL: 0.836; AP: 0.931; FH: 0.922) and corresponding Bland-Altman biases of -0.87 cm/s (RL), -0.04 cm/s (AP), and -0.18 cm/s (FH). SNAPFLOW-based SNAP-MRA and ASL-MRA showed substantial overlap while providing distinct contrast mechanisms and total visible vessel lengths of 4521 ± 643 mm for reference SNAP, 4668 ± 459 mm for SNAPFLOW-derived SNAP-MRA, and 4616 ± 632 mm for SNAPFLOW-derived ASL-MRA (all p > 0.05). In representative cases, SNAPFLOW enabled inherently co-registered visualization of lumen, vessel-wall, and flow.

SNAPFLOW provides a single-acquisition framework for intrinsically co-registered cerebrovascular MRI and may facilitate comprehensive assessment of intracranial vascular pathology.