Objective: The aim of this project is to quantify renal perfusion at 3 T with arterial spin labeling (ASL) images and to evaluate the feasibility of this measurement at 0.6 T.

Background: Chronic kidney disease (CKD) affects over one in ten individuals worldwide and has a high mortality rate. As renal microvascular dysfunction plays a key role in CKD progression, accurate and non-invasive quantification of renal perfusion is valuable. ASL magnetic resonance imaging (MRI) enables the measurement of renal perfusion without exogenous contrast agents and has been validated at 1.5 T and 3 T. However, its feasibility at 0.6 T has not yet been investigated.

Methodology: Data from the NEO-2 study acquired at 3 T was analyzed using a pipeline that included image registration, segmentation, and quantitative perfusion mapping. Midfield scanners have a lower signal-to-noise ratio and altered relaxation times. Therefore, the existing renal ASL sequence used in 3 T was adjusted. The sequence parameters that were modified included the repetition time (TR), the number of control–label pairs, voxel size, post-label delay (PLD), and background suppression (BGS) pulse timings. After choosing the optimal parameters, a healthy volunteer was scanned back-to-back at both field strengths for direct comparison.

Results: At 3~T, cortical perfusion values ranged between 180 and 286 mL/100g/min, consistent with literature. Optimal parameters at 0.6 T were: TR = 4000 ms, 25 control–label pairs, in-plane resolution of 4×4 mm^2, slice thickness of 10 mm, and PLD = 1400 ms with BGS pulses at 700 & 1100 ms. With these settings applied at 0.6 T, the cortical perfusion values were 215.34 ± 67.92 and 236.80 ± 66.33 mL/100 g/min in the left and right cortex, respectively. Using the 3 T acquisition protocol, the corresponding values were 241.89 ± 76.55 and 250.75 ± 70.82 mL/100g/min, respectively. Values at 3 T were approximately 5–10% higher.

Conclusion: The results show that renal ASL at 0.6~T can produce quantitative perfusion estimates that are similar to those at 3 T.