We have recently developed an isotropic angular projection acquisition technique (VIPR) that allows for large angular undersampling factors for situations in which the contrast signals of interest dominate. The technique is especially promising for phase contrast (PC) imaging where the excellent background suppression eliminates non-vascular streak artifacts. The high speed of VIPR can be used to produce several PC implementations 4-25 times faster than conventional PC when large imaging volumes are used and with scan times and isotropic spatial resolution comparable to 3D Time-of Flight (TOF). We wish to test the hypothesis that 3D VIPR-PC can provide anatomical information equivalent to and sometimes better than 3D TOF while also providing the opportunity for retrospective measurement of flow in all major vessels in the 3D volume with accuracy comparable to multiple 2D PC scans. We propose three implementations of VIPR-PC: (1) A Basic VIPR-PC version that will use a single velocity encoding (VENC) and provide significantly higher spatial resolution than conventional 3DPC. We will test its ability to measure average flow retrospectively for all vessels in the imaging volume. It will also be compared to 3D TOF for the purpose of providing anatomical information. (2) A velocity resolved non-gated method for providing velocity and speed distributions within voxels and for generation of angiographic images which have higher SNR than obtainable with a single VENC, and (3) A cardiac phase-resolved (CINE) version to provide the opportunity for retrospective determination of flow waveforms within all vessels in a large FOV without the need to acquire separate 2D scans for each vessel. We propose to develop and optimize the proposed methods and to test their feasibility using simulations, phantoms, and a series of studies using volunteers and patients.
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