Relationship Between Blood Flow Velocity and Blood Suppression Inversion Time for Optimal Visualization of Renal Artery in Spatial Labeling with Multiple Inversion Pulses: In Vitro Study

Improving imaging quality of non-contrast enhanced magnetic resonance angiography (NCE-MRA) is essential to those renal function impairment patients especially patients with renal segmental branch disease in the renal parenchyma. To investigate the relation between blood flow velocity (BFV) and blood suppression inversion time (BSP TI) for optimal visualization of the renal artery in NCE-MRA by spatial labeling with multiple inversion pulses (SLEEK) sequence. Patients and Methods: A catheter (simulated renal artery) was used to perform SLEEK with various BSP TI when injected saline with different velocity (simulated BFV). The relationship between BFV and BSP TI was evaluated by measuring signal-to-noise ratio (SNR) and was confirmed in nine hypertensive patients. A negative relationship was found in vitro study between BFV and BSP TI with SLEEK sequence (r = -0.977, P = 0.023). For BSP TI = 200 ms, the simulated renal artery displayed hyper-intensity when simulated BFV = 96 - 128 cm/s and the maximum SNR was found when BFV = 128 cm/s (SNR = 0.927). For BSP TI = 500 ms, high signal appeared with BFV = 64 - 128 cm/s and the greatest SNR was found with BFV = 96 cm/s (SNR = 1.732). For BSP TI = 800 ms and 1100 ms, hyper-intensity arose with BFV = 16 - 128 cm/s and BFV = 6.4 - 128 cm/s separately, the highest SNR was described when BFV = 32 cm/s (SNR = 2.256) and BFV = 16 cm/s (SNR = 1.875). The different optimal BSP TI with best image quality was discovered in nine hypertensive patients. An optimal BSP TI based on BFV can improve the ability of delineating renal artery in SLEEK sequence.