Elimination of residual blood flow-related signal in 3D volume-selective TSE arterial wall imaging using velocity-sensitive phase reconstruction

Purpose: To improve 3D volume-selective turbo spin-echo (TSE) arterial wall imaging by introducing velocity phase sensitivity to the sequence. Materials and Methods: Slow or recirculating blood may give incomplete nulling in 3D vessel wall imaging, hindering differentiation between arterial wall and lumen. Reconstructed phase images are used to reduce the residual blood signal with postprocessing. A volume-selective 3D TSE (1) sequence with increased velocity sensitivity perpendicular to the slab was developed. Sensitivity was introduced by modifying the gradient waveforms such that residual signal from slow or recirculating blood is distinguished from the wall by the phase shift introduced. This was tested on a pulsatile flow phantom and the carotid artery wall of six healthy volunteers and 17 patients. Images were acquired on a Siemens Magnetom Sonata 1.5T scanner, A quantitative comparison of the lumen/wall contrast was made using images acquired with and without modification. Results: Velocity sensitivity produces significantly reduced residual signal by intravoxel dephasing. Phantom "lumen/tissue" contrast improved by 0.10 (P < 0.01), with a similar change in vivo (0.69-0.73, P < 0.01). Postprocessing removal of the blood signal using phase signal provided further improvement. Conclusion: Introducing velocity sensitivity reduces unwanted, potentially misleading residual blood in 3D volume-selective vessel wall imaging.