Free-Breathing Arterial Spin Labeling MRI of the Kidney Using Flow-Sensitive-Alternating Inversion Recovery With Golden-Angle Radial Sampling.

Renal function critically depends on adequate perfusion. Arterial spin labeling (ASL) MRI enables noninvasive perfusion quantification but is highly susceptible to respiratory motion artifacts in renal applications. In this work, we developed and validated a free-breathing renal ASL technique using flow-sensitive alternating inversion recovery with golden-angle radial sampling and motion-corrected reconstruction. Eleven healthy volunteers (25 ± 2.1 years, six male) and nine Stage 2 chronic kidney disease (CKD) patients (42 ± 17 years) were enrolled. Healthy subjects underwent repeat scans after a 1-week interval for test-retest assessment. A breath-hold turbo spin-echo ASL sequence served as the reference. Renal blood flow (RBF) in the cortex and medulla was quantified using the Buxton model. The proposed free-breathing approach showed strong agreement with the breath-hold reference (coefficient of variation [CoV] = 8.8%) and excellent scan-rescan repeatability (CoV = 7.7%). Mean bias between free-breathing and breath-hold RBF measurements was 13 ± 21 mL/100 g/min (p < 0.001). In healthy volunteers, cortical RBF was 249 ± 19 mL/100 g/min and medullary RBF 138 ± 20 mL/100 g/min; in CKD patients, these values were significantly reduced to 144 ± 34 and 75 ± 15 mL/100 g/min, respectively (p < 0.001). This free-breathing ASL technique provides a reliable and repeatable foundation for RBF assessment that does not require breath-holding, facilitating broader clinical applicability particularly in patients with limited respiratory capacity, and offers potential for investigating renal pathophysiology.