MRI-based quantification of whole-organ renal metabolic rate of oxygen.

During the early stages of diabetes, kidney oxygen utilization increases. The mismatch between oxygen demand and supply contributes to tissue hypoxia, a key driver of chronic kidney disease. Thus, whole-organ renal metabolic rate of oxygen (rMRO 2 ) is a potentially valuable biomarker of kidney function. The key parameters required to determine rMRO 2 include the renal blood flow rate (RBF) in the feeding artery and oxygen saturation in the draining renal vein (SvO 2 ). However, there is currently no noninvasive method to quantify rMRO 2 in absolute physiologic units. Here, a new MRI pulse sequence, Kidney Metabolism of Oxygen via T 2 and Interleaved Velocity Encoding (K-MOTIVE), is described, along with evaluation of its performance in the human kidney in vivo. K-MOTIVE interleaves a phase-contrast module before a background-suppressed T 2 -prepared balanced steady-state-free-precession (bSSFP) readout to measure RBF and SvO 2 in a single breath-hold period of 22 s, yielding rMRO 2 via Fick's principle. Variants of K-MOTIVE to evaluate alternative bSSFP readout strategies were studied. Kidney mass was manually determined from multislice gradient recalled echo images. Healthy subjects were recruited to quantify rMRO 2 of the left kidney at 3-T field strength (N = 15). Assessments of repeat reproducibility and comparisons with individual measurements of RBF and SvO 2 were performed, and the method's sensitivity was evaluated with a high-protein meal challenge (N = 8). K-MOTIVE yielded the following metabolic parameters: T 2  = 157 ± 19 ms; SvO 2  = 92% ± 6%; RBF = 400 ± 110 mL/min; and rMRO 2  = 114 ± 117(μmol O 2 /min)/100 g tissue. Reproducibility studies of T 2 and RBF (parameters directly measured by K-MOTIVE) resulted in coefficients of variation less than 10% and intraclass correlation coefficients more than 0.75. The high-protein meal elicited an increase in rMRO 2 , which was corroborated by serum biomarkers. The K-MOTIVE sequence measures SvO 2 and RBF, the parameters necessary to quantify whole-organ rMRO 2 , in a single breath-hold. The present work demonstrates that rMRO 2 quantification is feasible with good reproducibility. rMRO 2 is a potentially valuable physiological biomarker.