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| Item Type: | Article |
|---|---|
| Title: | 4D flow imaging with UNFOLD in a reduced FOV |
| Creators Name: | Wink, C., Bassenge, J.P., Ferrazzi, G., Schaeffter, T. and Schmitter, S. |
| Abstract: | PURPOSE: Two-dimensional selective excitation (2DRF) allows shortening 4D flow scan times by reducing the FOV, but the longer 2DRF pulse duration decreases the temporal resolution, yielding underestimated peak flow values. Multiple k-space lines per cardiac phase, n(l) ≥ 2, are commonly applied in 4D flow MRI to shorten the inherent long scan times. We demonstrate that 2DRF 4D flow with n(l) ≥ 2 can be easily combined with UNFOLD (UNaliasing by Fourier-encoding the Overlaps using the temporaL Dimension), a technique that allows regaining nominally the temporal resolution of the respective acquisition with n(l) = 1, to assure peak flow quantification. METHODS: Two different 2DRF pulses with spiral k-space trajectories were designed and integrated into a 4D flow sequence. Flow phantom experiments and 7 healthy control 4D flow in vivo measurements, with and without UNFOLD reconstructions, were compared with conventional reconstruction and 1D slab-selective excitation (1DRF) by evaluating time-resolved flow curves, peak flow, peak velocity, blood flow volume per cardiac cycle, and spatial aliasing. RESULTS: Applying UNFOLD to 4D flow imaging with 2DRF and reduced FOV increased the quantified in vivo peak flow values significantly by 3.7% ± 2.3% to 5.2% ± 2.4% (P < .05). Accordingly, the peak flow underestimation of 2DRF scans compared with conventional 1DRF scans decreased with UNFOLD. Finally, 2DRF combined with UNFOLD accelerated the 4D flow acquisition 3.5 ± 1.4 fold by reducing the FOV and increasing the effective temporal resolution by 6.7% compared with conventional 1D selective excitation, with 2 k-space lines per cardiac phase. CONCLUSION: Two-dimensional selective excitation combined with UNFOLD allows limiting the FOV to shorten 4D flow scan times and compensates for the loss in temporal resolution with 2DRF (Δt = 64.8 ms) compared with 1DRF (Δt = 43.2 ms), yielding an effective resolution of Δt(eff) = 40.5 ms to enhance peak flow quantification. |
| Keywords: | 4D Flow, Fast Imaging, Reduced FOV, Reduced FOX, Spatially Selective 2D RF Excitation, UNFOLD |
| Source: | Magnetic Resonance in Medicine |
| ISSN: | 0740-3194 |
| Publisher: | Wiley |
| Volume: | 84 |
| Number: | 1 |
| Page Range: | 327-338 |
| Date: | July 2020 |
| Official Publication: | https://doi.org/10.1002/mrm.28120 |
| PubMed: | View item in PubMed |
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