Real-time interactive duplex MR measurements: Application in neurovascularimaging.

OBJECTIVE. Real-time interactive duplex MR imaging is a new phase-contrast MR imaging technique that enables the quantification and display of flow ve locities in real time without the need for cardiac gating. We investigated the feasibility and reliability of the technique to assess hemodynamic info rmation both in vitro and in vivo in the carotid arteries and in the venous sinuses. SUBJECTS AND METHODS. Real-time interactive duplex MR measurements (TR/TE, 53/27; flip angle, 90 degrees; encoding velocity, 100 or 150 cm/sec) were p erformed in vitro with a steady-flow phantom and in 10 healthy volunteers i n whom common and internal carotid artery velocities were measured. In eigh t volunteers, velocity measurements were also performed in the superior sag ittal sinus during both normal breathing and hyperventilation. Time-velocit y plots were analyzed qualitatively and quantitatively and compared with fi ndings from conventional segmented k-space phase-contrast MR imaging and Do ppler sonography. RESULTS. Velocity determinations for real-time duplex MR and conventional p hase-contrast MR imaging showed an in vitro correlation of 0.99 and an in v ivo correlation of 0.83 (carotid arteries) and 0.76 (venous sinus). Velocit y measurements in the carotid arteries with real-time MR imaging were signi ficantly lower than those obtained with conventional phase-contrast MR (ave raged, 7.8%; p = 0.003) or sonography (23.7%, p < 0.001), likely because of volume averaging. Small but significant velocity changes occurring in the venous sinus during hyperventilation were reliably identified with both MR techniques. CONCLUSION. Real-time interactive duplex MR imaging can be effectively appl ied in neurovascular imaging to obtain hemodynamic information.