MRI-Based Regional Kidney Blood Flow Mapping Is More Accurate Using Kidney-Specific Arterial Spin Labeling Model

Background: Arterial Spin Labeling (ASL) is a noncontrast MRI technique using magnetically labeled water to map renal blood flow (RBF). ASL is widely used in brain but to a lesser degree in the kidneys due to motion and inaccuracy. RBF quantification relies on kinetic models converting measured signals into perfusion (ml/min/100g). The single-compartment Buxton model is commonly used but lacks thorough kidney-specific validation. This study proposes an improved kinetic model incorporating an arterial outflow term for enhanced accuracy and physiological relevance. Methods: Healthy subjects underwent MRI (Siemens 3T Vida) under IRB approval: labeling duration=1.5s; delays=0.5,0.75,1,1.25,1.5,2,2.5s; TR/TE=6000/16ms; 10 dynamics; single-shot 3D TGSE readout. Two studies were performed: A: Baseline-11 subjects had renal ASL and phase-contrast (PC) MRI. B: Stress test-5 subjects underwent renal ASL and PC MRI before and after an oral protein-load inducing RBF changes. RBF was estimated using Buxton and our model: dΔM/dt = f/λ[I(t)-OFFe-OFT/T1I(t-OFT)]-1/T1ΔM where ΔM=ASL difference signal, f=RBF, λ=partition coefficient, I(t)=arterial input function, OFT/OFF=outflow delay/fraction, T1=longitudinal relaxation time. Results: A: Fig1 illustrates arterial outflow contrasts (OFF, OFT) introduced by our model. Fig2A shows compared to Buxton, our model improves RBF estimation accuracy (397.87±68.42 vs. 167.59±63.07), better matching PC measurements (612.06±64.03). AIC favors our model. B: Fig2B shows our model accurately detects RBF changes post-protein-load, correlating strongly with PC (r=0.62, p=0.27), whereas Buxton fails (r=-0.31, p=0.62). Conclusion: Including arterial outflow in the ASL model enhances physiological relevance and improves RBF estimation. Funding: NIDDK Support - NIDDK Support, NIDDK SupportIllustrative images from our model.Statistical analyses.