Background: Respiratory gating is often used in 4D-flow acquisition to reduce motion artifacts. However, gating\nincreases scan time. The aim of this study was to investigate if respiratory gating can be excluded from 4D flow\nacquisitions without affecting quantitative intracardiac parameters.\nMethods: Eight volunteers underwent CMR at 1.5 T with a 5-channel coil (5ch). Imaging included 2D flow\nmeasurements and whole-heart 4D flow with and without respiratory gating (Resp(+), Resp(?)). Stroke volume\n(SV), particle-trace volumes, kinetic energy, and vortex-ring volume were obtained from 4D flow-data. These parameters\nwere compared between 5ch Resp(+) and 5ch Resp(?). In addition, 20 patients with heart failure were scanned using a\n32-channel coil (32ch), and particle-trace volumes were compared to planimetric SV. Paired comparisons were performed\nusing Wilcoxonâ��s test and correlation analysis using Pearson r. Agreement was assessed as bias �± SD.\nResults: Stroke volume from 4D flow was lower compared to 2D flow both with and without respiratory gating\n(5ch Resp(+) 88 �± 18 vs 97 �± 24.0, p = 0.001; 5ch Resp(?) 86 �± 16 vs 97.1 �± 22.7, p < 0.01). There was a good correlation\nbetween Resp(+) and Resp(?) for particle-trace derived volumes (R2 = 0.82, 0.2 �± 9.4 ml), mean kinetic energy (R2 = 0.86,\n0.07 �± 0.21 mJ), peak kinetic energy (R2 = 0.88, 0.14 �± 0.77 mJ), and vortex-ring volume (R2 = 0.70, ?2.5 �± 9.4 ml).\nFurthermore, good correlation was found between particle-trace volume and planimetric SV in patients for 32ch\nResp(?) (R2 = 0.62, ?4.2 �± 17.6 ml) and in healthy volunteers for 5ch Resp(+) (R2 = 0.89, ?11 �± 7 ml), and 5ch Resp(?)\n(R2 = 0.93, ?7.5 �± 5.4 ml), Average scan duration for Resp(?) was shorter compared to Resp(+) (27 �± 9 min vs 61 �±\n19 min, p < 0.05).\nConclusions: Whole-heart 4D flow can be acquired with preserved quantitative results without respiratory gating,\nfacilitating clinical use.
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