Four-dimensional phase contrast MRI with accelerated dual velocity encoding

To validate a novel approach for accelerated four-dimensional phase contrast MR imaging (4D PC-MRI) with an extended range of velocity sensitivity.

4D PC-MRI data were acquired with a radially undersampled trajectory (PC-VIPR). A dual V(enc) (dV(enc) ) processing algorithm was implemented to investigate the potential for scan time savings while providing an improved velocity-to-noise ratio. Flow and velocity measurements were compared with a flow pump, conventional 2D PC MR, and single V(enc) 4D PC-MRI in the chest of 10 volunteers.

Phantom measurements showed excellent agreement between accelerated dV(enc) 4D PC-MRI and the pump flow rate (R(2) ≥ 0.97) with a three-fold increase in measured velocity-to-noise ratio (VNR) and a 5% increase in scan time. In volunteers, reasonable agreement was found when combining 100% of data acquired with V(enc) = 80 cm/s and 25% of the high V(enc) data, providing the VNR of a 80 cm/s acquisition with a wider velocity range of 160 cm/s at the expense of a 25% longer scan.

Accelerated dual V(enc) 4D PC-MRI was demonstrated in vitro and in vivo. This acquisition scheme is well suited for vascular territories with wide ranges of flow velocities such as congenital heart disease, the hepatic vasculature, and others.