Whole-Heart MRI

Respiratory navigator-gated, ECG-triggered, contrast-enhanced, 3D whole-heart balanced SSFP MRI with fat saturation and T2 preparation pulse was acquired in transverse plane at the ES and the ED, separately (n = 89) or simultaneously (n = 21) during free breathing. Imaging parameters that were used for the 3D whole-heart imaging were as follows: TR/TE, 3.8 ms/1.9 ms; flip angle, 60°; turbo field echo factor, 8–15; the number of cardiac phases, 1 or 2; temporal resolution, 30–100 ms; the number of signal averages, 1; voxel size, 1.3–1.8 mm × 1.3–1.8 mm × 1.3–1.8 mm; 130 slices; and SENSE factor, 1.5–2.0 in anteroposterior direction. Field of view was adjusted individually according to patient size. The acceptance window of pencil beam navigator placed on the diaphragmatic dome was adjusted to the range of 3–7 mm to achieve optimal navigator gating efficiency of approximately 60% depending on a patient's respiratory pattern. Eighty-phase four-chamber cine imaging was used to determine the timing and duration of the ES and ED phases independently of each other in 89 patients. In dual-phase whole-heart MRI sequence enabling simultaneous acquisition of the two cardiac phases (6), a shorter duration between the two was selected to avoid image degradation of a shorter, usually ES, phase in the remaining 21 patients. Since the true trigger delay for the ED phase determined by 80-phase four-chamber cine imaging was technically difficult to be incorporated in whole-heart MRI protocol, the actual ED trigger delay was set to be the longest allowable. The total scan time for the 3D whole-heart MRI including both ES and ED phases was variable depending on imaging parameters and navigator efficiency, and was approximately 10–12 minutes. Single dose (0.1 mmol/kg) of a gadolinium-based contrast agent (gadoterate meglumine; Guerbet, Villepinte, France) was intravenously administered immediately prior to whole-heart MRI.