5D Flow MRI: A Fully Self-gated, Free-running Framework for Cardiac and Respiratory Motion–resolved 3D Hemodynamics

Using 5D flow MRI to decode the effects of rhythm on left atrial 3D flow dynamics in patients with atrial fibrillation

“…This pattern was segmented into multiple interleaves, each initiated with a superior‐inferior (SI) projection for self‐gating. The 5D flow imaging protocol used in this study was similar to a previous study, 26,29 where each interleaf consisted of six total radial k‐space trajectory angles corresponding to 21 total readouts (1 SI projection + 5*[4 velocity encodes]). Sequential interleaves were rotated by the golden angle (137.51°) throughout the entire scan 30 .…”

“…Cardiac and respiratory motion signals were extracted from SI projections using a previously validated principal component analysis (PCA) approach. 21,26,[30][31][32] Using a chosen temporal resolution of ~40 ms (temporal resolution = 8*repetition time [TR]), cardiac signals were used to bin the acquired k-space lines into the appropriate cardiac time frame. Each line was also tagged with the length of the heartbeat, RR Length , within which it was acquired ( Figure 1B,C).…”

“…These weights were empirically determined based on previous studies in CS-accelerated 4D flow MRI and 5D MRI. 21,26,27 Respiratory bins were divided such that the same number of radial k-space views were mapped in each bin. The 5D respiration-resolved reconstruction resulted in four reconstructed 1C).…”

“…[14][15][16][17][18][19][20][21][22][23][24] Recently, a fully self-gated free-running 5D flow framework was introduced. 19,21,23,25,26 This framework featured a continuous, free-running, 3D radial sequence, with interleaved three-directional velocity encoding as well as inherent self-gating projections to encode cardiac and respiratory motion without external gating signals. 21 The self-gating signal was used to retrospectively bin the flow-encoded 3D data of the heart into cardiac-temporal (4th dimension) and respiratory-resolved (5th dimension) bins.…”

“…Recently, a fully self‐gated free‐running 5D flow framework was introduced 19,21,23,25,26 . This framework featured a continuous, free‐running, 3D radial sequence, with interleaved three‐directional velocity encoding as well as inherent self‐gating projections to encode cardiac and respiratory motion without external gating signals 21 .…”