Rapid Cardiovascular Flow Quantitation Using Slice-Selective Spiral Fourier Velocity Encoding

J. L. Carvalho, K. S. Nayak Department of Electrical Engineering, University of Southern California, Los Angeles, CA, United States Introduction: Accurate flow quantitation is important for the evaluation of many cardiovascular conditions including valvular abnormalities, congenital defects, and coronary artery disease. In cardiac MRI, speed is of particular importance because low time resolution may cause underestimation of peak velocities, and acquisition time is typically limited to the duration of a breath-hold. Conventional 2DFT phase contrast (PC) [1] is inadequate because scan time would be prohibitive and because partial voluming is problematic when flow is highly localized and/or turbulent. We propose the use of Fourier Velocity Encoding (FVE) [2] with low spatial resolution spiral readouts to reduce acquisition time. The use of FVE instead of PC makes it possible to resolve the full velocity distribution within each voxel, avoiding problems related to partial voluming. In the heart, because of the large vessel sizes, low spatial resolution is sufficient to separate vessels and we were able to adequately sample kx,ky using a singleshot spiral acquisition. Balancing time and velocity resolutions, we were able to acquire time and spatially-resolved velocity distributions in a single 8-second breath-hold. In the neck, where breath-holding is not required, we used 4 spiral interleaves to achieve higher spatial resolution. The sequence was tested on phantoms and normal volunteers, and the results were compared with Doppler ultrasound.