Natively fat‐suppressed 5D whole‐heart MRI with a radial free‐running fast‐interrupted steady‐state (FISS) sequence at 1.5T and 3T

Abstract

Purpose To implement, optimize, and test fast interrupted steady‐state (FISS) for natively fat‐suppressed free‐running 5D whole‐heart MRI at 1.5 tesla (T) and 3T. Methods FISS was implemented for fully self‐gated free‐running cardiac‐ and respiratory‐motion‐resolved radial imaging of the heart at 1.5T and 3T. Numerical simulations and phantom scans were performed to compare fat suppression characteristics and to determine parameter ranges (number of readouts [NR] per FISS module and TR) for effective fat suppression. Subsequently, free‐running FISS data were collected in 10 healthy volunteers and images were reconstructed with compressed sensing. All acquisitions were compared with a continuous balanced steady‐state free precession version of the same sequence, and both fat suppression and scan times were analyzed. Results Simulations demonstrate a variable width and location of suppression bands in FISS that were dependent on TR and NR. For a fat suppression bandwidth of 100 Hz and NR ≤ 8, simulations demonstrated that a TR between 2.2 ms and 3.0 ms is required at 1.5T, whereas a range of 3.0 ms to 3.5 ms applies at 3T. Fat signal increases with NR. These findings were corroborated in phantom experiments. In volunteers, fat SNR was significantly decreased using FISS compared with balanced steady‐state free precession (P < 0.05) at both field strengths. After protocol optimization, high‐resolution (1.1 mm3) 5D whole‐heart free‐running FISS can be performed with effective fat suppression in under 8 min at 1.5T and 3T at a modest scan time increase compared to balanced steady‐state free precession. Conclusion An optimal FISS parameter range was determined enabling natively fat‐suppressed 5D whole‐heart free‐running MRI with a single continuous scan at 1.5T and 3T, demonstrating potential for cardiac imaging and noncontrast angiography.

Free‐running 5D coronary MR angiography at 1.5T using LIBRE water excitation pulses

“…The LIBRE pulse was compared to a 1‐2‐1 WE pulse that was available on the scanner, and, apart from an RF excitation angle optimization, no further optimization of this pulse was performed. Recent work has demonstrated that fast interrupted steady‐state (FISS) can be exploited for fat‐saturated 5D free‐running cardiac imaging, and a comparison with the present approach would be very instructive. The reconstruction pipeline, including regularization weights, was identical for LIBRE, SP, WE, and IFR, although optimal regularization weights are expected to vary as each acquisition will have slightly different noise levels and residual aliasing.…”

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

“…All data were binned and reconstructed using the following two strategies: 2.1.1 | Respiratory-resolved 5D reconstruction Prior 5D flow methods focus on resolving respiration as the 5th dimension. 18,19,21,23,27 This respiratory-resolved reconstruction scheme was based on strategies reported in a number of prior studies. 21,27,28 Data were binned into a cardiac timepoint-and respiratory-resolved 5D flow data set (kx-ky-kz-flow-cardiac-respiration).…”

“…Recent explorations into multi-dimensional and self-gated imaging have pushed the boundaries of "conventional" cardiac imaging towards more efficient scan times and operator ease-of-use. [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.…”

Non-contrast coronary magnetic resonance angiography: current frontiers and future horizons

“…4) are also available options for fat suppression on coronary MRA. Another approach to fat suppression, the fast interrupted steady-state (FISS) sequence, uses an RF excitation pulse to natively suppress the fat signal without the need for periodical application of fat suppression and ramp-up pulses, and is reported to present a strong suppression of pericardial fat signal [60,61]. The fat suppression technique is more challenging in radial imaging with higher magnetic field strengths, since the field inhomogeneities are typically accentuated.…”