Off-resonance-robust velocity-selective magnetization preparation for non-contrast-enhanced peripheral MR angiography.

PURPOSE: To develop a new velocity-selective (VS) excitation pulse sequence which is robust to field inhomogeneity, and demonstrate its application to non-contrast-enhanced peripheral MR angiography (MRA).

METHODS: The off-resonance-robust VS saturation pulse is designed by incorporating 180° refocusing pulses into the k-space-based reference design and tailoring sequence parameters in a velocity region of interest. The VS saturation pulse is used as magnetization preparation for non-contrast-enhanced peripheral MRA to suppress background tissues but not arterial blood based on their velocities. Non-contrast-enhanced peripheral MRA using the proposed VS preparation was tested in healthy volunteers and a patient with arterial stenosis.

RESULTS: Calf angiograms obtained using the new VS preparation show more uniform background suppression than the reference VS preparation, as demonstrated by larger mean values and smaller standard deviations of artery-to-vein and artery-to-muscle contrast-to-noise ratios (71.0 ± 11.4 and 75.3 ± 12.1 versus 61.7 ± 22.7 and 58.5 ± 27.8). Two-station peripheral MRA using the new VS preparation identifies stenosis of the femoral and popliteal arteries in the patient, as validated by digital subtraction angiography.

CONCLUSION: Non-contrast-enhanced MRA using the new VS magnetization preparation can reliably provide high angiographic contrast in the lower extremities with significantly improved immunity to field inhomogeneity.