Non-Subtractive Arterial Spin Labeling-Based (NSASL) Renal Magnetic Resonance Angiography (MRA): Development and...

Non-contrast renal MR angiography (MRA) is valuable for patients who cannot receive contrast agents or when avoiding radiation is desired. However, the conventional inflow inversion recovery (IFIR) method is limited by incomplete background suppression, venous contamination, and motion sensitivity.

To develop and evaluate a non-subtractive arterial spin labeling-based (NSASL) sequence for renal MRA and compare it with IFIR in healthy volunteers, with exploratory feasibility assessment relative to contrast-enhanced (CE)-MRA or computed tomography angiography (CTA) in patients.

Prospective.

Thirty healthy volunteers (10 male, 35.6  $\pm$  14.0 years) and six participants with renal diseases or high blood pressure (2 male, 62.7  $\pm$  9.03 years).

1.5 T; 3D stack-of-stars balanced steady-state free precession (bSSFP) NSASL MRA, 3D Cartesian bSSFP IFIR MRA, and CE-MRA.

Three radiologists independently rated image quality (main and branch renal arteries visualization, motion artifacts, vessel-to-background contrast, diagnostic confidence) on a 5-point scale. SNR efficiency (or SNR and time) and contrast ratio (CR) were also measured.

Intraclass coefficient (ICC), Shapiro-Wilk's test, paired Student's t-test, and Wilcoxon signed-rank test with Bonferroni correction, with p < 0.05 considered statistically significant.

ICC was good to excellent (ICC = 0.61-0.89) for average subjective scores. Compared with IFIR, NSASL showed significantly better vessel-to-background contrast (approximately fivefold increase in CR, Cohen's |d| = 2.54; +1 subjective score, |r| = 0.88), improved renal arteries visualization (+0.7 points, |r| = 0.67, corrected p   $\le$ 0.003), fewer motion artifacts (+0.6 points, |r| = 0.67, corrected p = 0.002), and higher diagnostic confidence (+0.6 points, |r| = 0.80, corrected p < 0.001). Acquisition time was reduced from 267.3 ± 69.0 s to 240.2 ± 51.3 s (Cohen's |d| = 0.54, corrected p = 0.018) while SNR efficiency was moderately lower (~26%, Cohen's |d| = 1.99, corrected p = 0.002). In participants with disease, NSASL yielded similar diagnostic confidence to CE-MRA (n = 4, +0.7 points, p = 0.194) and to CTA (n = 2, -0.2 points, p = 0.317).

NSASL significantly outperformed IFIR, with improved background suppression, vessel conspicuity, motion tolerance, and scan time in healthy volunteers.

2.

Stage 2.