What question did this study set out to answer?

To develop DynaTOF, a noncontrast MR angiography technique for visualizing cerebrovascular hemodynamics.

May 13, 2026Open Access

DynaTOF : Time‐Resolved Noncontrast Cerebral MR Angiography Using Spatially Modulated RF Saturation

Key Points

To develop DynaTOF, a noncontrast MR angiography technique for visualizing cerebrovascular hemodynamics.
Implemented varying flip angle and repetition time to encode inflow timing.
Five healthy volunteers and five AVM patients underwent scans with DynaTOF and PASL MRA.
Analyzed arterial flow and SNR/CNR using short-TR acquisitions and deep-learning reconstruction.
DynaTOF showed predictable inflow behavior and qualitative agreement with PASL imaging.
In AVM patients, DynaTOF accurately depicted arterial, nidus, and early venous transitions consistent with DSA.
Achieved efficient single-slab imaging with voxel size of 0.5 × 0.7 × 0.8 mm in approximately 1 min.

Abstract

ABSTRACT Purpose To develop a time‐resolved extension of three‐dimensional time‐of‐flight MR angiography, termed Dynamic TOF (DynaTOF), that exploits intrinsic RF saturation behavior to enable noncontrast visualization of cerebrovascular hemodynamics. Methods DynaTOF was implemented by varying flip angle, repetition time (TR), and slab‐selective RF excitation profile to modulate longitudinal magnetization saturation and encode relative inflow timing. Data were acquired using a short‐TR protocol combined with deep‐learning reconstruction to ensure scan efficiency. Five healthy volunteers underwent DynaTOF and pulsed arterial spin labeling (PASL) MRA. Five patients with intracranial arteriovenous malformations (AVMs) were scanned to evaluate clinical feasibility and compare temporal patterns with digital subtraction angiography (DSA). Analyses included inflow‐time characterization, cross‐correlation with PASL, region‐of‐interest assessment of arterial, nidus, and venous structures, as well as apparent SNR and contrast‐to‐noise ratio (CNR) quantification. Results In healthy volunteers, DynaTOF exhibited predictable parameter‐dependent inflow behavior and qualitative agreement with PASL‐derived inversion‐time dynamics. Apparent arterial SNR and CNR maxima were slice‐position dependent, shifting from higher flip angles (20°–30°) at the slab entrance to lower angles (7°–15°) distally. In AVM patients, DynaTOF delineated arterial‐to‐nidus‐to‐early‐venous transitions consistent with DSA, while venous depiction was attenuated for horizontal or curved‐flow vessels due to the directional dependence of TOF‐based inflow contrast. Short‐TR acquisition with deep‐learning reconstruction enabled single‐slab imaging with a voxel size of 0.5 × 0.7 × 0.8 mm 3 in approximately 1 min, supporting flexible parameter sweeps within routine clinical time constraints. Conclusion DynaTOF offers a noninvasive approach for time‐resolved characterization of cerebrovascular flow while preserving TOF‐like spatial resolution.

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