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Fig. 1 | Journal of Cardiovascular Magnetic Resonance

Fig. 1

From: Highly accelerated 4D flow cardiovascular magnetic resonance using a pseudo-spiral Cartesian acquisition and compressed sensing reconstruction for carotid flow and wall shear stress

Fig. 1

The pseudo-spiral sampling strategy for Cartesian 3D k-space sampling, with two phase encoding directions (ky,kz) and one fully sampled frequency encoding direction (kx). a In a regular Cartesian sampling strategy (ky,kz)-profiles are acquired line-by-line. b Additionally, in regular retrospectively triggered cardiac scans, each (ky,kz)-profile is repeated within each cardiac cycle to ensure complete filling of k-t-space and a fully sampled time dimension for each (ky,kz)-profile. The segments of 4xTR length indicate all 4 flow encoding segments of a 4D flow CMR scan, with the dark segments indicating the reference scan. c This distribution shows all pseudo-spiral (ky,kz)-coordinates sampled within one scan session. The pseudo-spiral trajectory creates a variable density distribution with an oversampled center. d In a pseudo-spiral sampling strategy, (ky,kz)-profiles are sampled from the center of k-space to the outside, however still on a Cartesian grid. e To achieve undersampling in the temporal domain, (ky,kz)-profiles are updated continuously within each cardiac cycle in addition to the pseudo-spiral sampling trajectory. f After retrospective cardiac binning, this results in a sampling mask of white (sampled) and black (not sampled) (ky,kz)-coordinates, with unique, incoherent sampling patterns per cardiac frames (see color coding in e)

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