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

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