Clinically-Feasible Non-Contrast Abdominopelvic MRA using 3D Radial Stack-of-Stars k-space Sampling and Compressed Sensing

Marc D Lindley^{1,2}, Daniel Kim^{2}, Kristi Carlston^{2}, Leif Jensen^{2}, Daniel Sommers^{2}, Ganesh Adluru^{2}, Edward VR DiBella^{2}, Christopher J Hanrahan^{2}, and Vivian S Lee^{2}

All imaging was performed on a 3T scanner (Tim Trio, Siemens). To determine limits of acceleration factors (R), we performed a numerical simulation experiment, where a fully sampled data set was retrospectively undersampled according to Figure 1. We tested three different acceleration strategies: (i) radial with R = 5.3, (ii) radial with R = 10.7, and (iii) radial with R = 16. We note that QIR requires a consistent inversion time for each kz plane, so we designed R to be multiples (sans small rounding) of previously published R = 2.7 using parallel imaging. For image reconstruction performed offline in Matlab, for each sampling pattern, coil sensitivity maps were self-calibrated from the densely sampled center of k-space (3). CS reconstruction was performed using non-local means (NLM) (4,5), which is a popular denoising filter that is applicable for CS. Image reconstruction was performed with 50 iterations with normalized NLM weight of 0.7 and normalized fidelity weight of 0.7, where normalization is based on maximum value. These weights were determined empirically based on visual inspection of training data. Based on visual inspection of images shown in Figure 1, prospective acceleration was limited to R=5.3 and 10.6.

For prospective imaging, 6 healthy volunteers (3 male, 3 female, mean age = 39+/-13) and 4 patients (2 male, 2 female, mean age = 63+/-8) with diagnosed aortoiliac disease were imaged after obtaining IRB-approved informed consent, with the original QIR with R = 2.7 and accelerated QIR with R=5.3 and 10.6. Other than the acceleration factors, all QIR NC-MRA pulse sequences used identical parameters: spatial resolution 1.3 x 1.3 x 1.7 mm, TR = 1 respiratory cycle, flip angle = 100°, inversion time = 1600 ms, and respiratory gating. Arterial vessel dimensions were measured at 4 locations as shown in Figure 2 (see arrows). Vessel dimensions were compared using analysis of variance (ANOVA), and with Bonferroni correction to compare each pair with original QIR as control. We also measured normalized signal difference [(vessel-background)/vessel] as a surrogate for contrast-to-noise ratio (CNR) at these locations. Note that true CNR is not easily measurable from GRAPPA and CS reconstructed data.

This work was supported in part by the following grants:

NIH- 5R01DK063183-11

NIH- 5R01HL116895-02

AHA - 14GRNT18350028

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Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)

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