Lukas M. Gottwald^{1}, Eva S. Peper^{1}, Qinwei Zhang^{1}, Bram F. Coolen^{2}, Gustav J. Strijkers^{2}, R. Nils Planken^{1}, Aart J. Nederveen^{1}, and Pim van Ooij^{1}

In this study, 8-fold pseudo spiral compressed sensing (CS) accelerated aortic 4D flow MRI was compared with 8-fold k-t principal component analysis (k-t PCA) acceleration. Scan times were approximately 7 minutes at 50% respiratory navigator efficiency. Image quality of the peak systolic phase contrast magnitude images was scored slightly higher for CS than for k-t PCA and time-resolved velocity pathline trajectories were similar. Quantitative hemodynamic differences in velocity and wall shear stress were found but these were small and can be attributed to a combination of acquisition strategy and physiological variation. CS can be used to accelerate 4D flow MRI.

[1] Pedersen H, Kozerke S, Ringgaard S, Nehrke K, Kim WY. k-t PCA: Temporally constrained k-t BLAST reconstruction using principal component analysis. Magn Reson Med 2009;62:706–716

[2] Giese D, Wong J, Greil GF, Buehrer M, Schaeffter T, Kozerke S. Towards highly accelerated Cartesian time-resolved 3D flow cardiovascular magnetic resonance in the clinical setting. J Cardiovasc Magn Reson 2014;16:42

[3] Martin Uecker, Frank Ong, Jonathan I Tamir, Dara Bahri, Patrick Virtue, Joseph Y Cheng, Tao Zhang, and Michael Lustig, Berkeley Advanced Reconstruction Toolbox, Annual Meeting ISMRM, Toronto 2015, In Proc. Intl. Soc. Mag. Reson. Med. 23:2486

[4] Bock J, Kreher W, Hennig J, Markl M. Optimized pre-processing of time-resolved 2D and 3D Phase Contrast MRI data. Proc. Intl. Soc. Mag. Reson. Med. 2007;15:3138.

[5] Potters W V, van Ooij P, Marquering HA, VanBavel E, Nederveen AJ. Volumetric arterial wall shear stress calculation based on cine phase contrast MRI. J Magn Reson Imaging 2015;Feb; 41:505–516

[6] Sigfridsson A, Petersson S, Carlhäll C-J, Ebbers T. Four-dimensional flow MRI using spiral acquisition. Magn Reson Med 2012;68:1065–1073

Figure 1. Schematics of
k-space sampling over time for a) CSENSE and b) k-t PCA

Figure 2. Example of
peak systolic phase contrast magnitude images for a) CS and b) k-t PCA. The total
score for edge sharpness, signal and noise over the ascending aorta, arch,
descending aorta and supra-aortic arteries revealed a slightly higher score for
CS.

Figure 3. An example of
a pathline movie for CS (left) and k-t PCA (right). For this subject, it
appears that higher velocities were present in the k-t PCA scan. In the CS
movie, however, the low velocity pathlines obscure the high velocity ones, see
Figure 4.

Figure 4. Quantitative
analysis for velocity and WSS shown for the same subject as Figure 3. A) The
k-t PCA data is co-registered and interpolated to the CS data for both velocity
and WSS. Mean velocity and WSS is calculated for the six regions indicated, and
Bland-Altman, orthogonal regression and angle differences analysis is performed
for all six regions combined. The results for this example are shown in b.

Table 1. Top: Mean
velocity and WSS in the six aortic regions for CSENSE and k-t PCA. Significant
differences (shown in bold) were defined with a Wilcoxon rank sum test with
P<0.05 considered significant. Bottom:
results of the Bland-Altman, orthogonal regression and angle difference
analyses.