Extension of Rapid Phase-Contrast Magnetic Resonance Imaging Using BRISK in Multidirectional Flow

We developed BRISK–CON–VPS, a rapid phase-contrast cine approach that is a hybrid of the BRISK–VPS (Block Regional Interpolation Scheme for k-space) and conventional (CONV–VPS) scanning employing k-space views per segment (VPS). BRISK–CON–VPS allows data acquisition approximately four times faster than CONV–VPS imaging and has the advantage compared to BRISK–VPS that it can potentially be incorporated into real-time applications. In BRISK–CON–VPS contiguous regions of k-space are sampled using a views per segment factor that is varied as a function of distance from the k-space center. Computational fluid dynamics (CFD) data were used to simulate CONV–VPS, BRISK–VPS, and BRISK–CON–VPS. BRISK–CON–VPS was simulated by incrementing the VPS progressively with increasing distance from the k-space origin while BRISK–VPS was simulated using a uniform VPS applied to the sparse sampling scheme. Simulations showed that up to a base VPS of 5, both BRISK–CON–VPS and BRISK–VPS retained excellent axial-velocity accuracy. Secondary in-plane velocity flow fields were well represented with BRISK–CON–VPS and BRISK–VPS up to a base VPS of 3. CONV–VPS, BRISK–CON–VPS, and BRISK–VPS were applied in vivo and shown to provide comparable quantitative flow data. BRISK–CON–VPS accomplishes breath-hold acquisitions as efficiently as BRISK–VPS, but without requiring data interpolation or under-sampling k-space.