Work

MRI ‐based quantification of whole‐organ renal metabolic rate of oxygen during free‐breathing

Year: 2025

Type: article

Abstract: Purpose Renal metabolic rate of oxygen (rMRO 2 ) reflects the kidney's metabolic efficiency, making it a potential biomarker for early‐stage kidney disease. This study introduces an ungated, free‐breathing MRI sequence in comparison to its breath‐hold counterpart to noninvasively measure whole‐organ rMRO 2 . Methods Free‐breathing (FB) K‐MOTIVE sequence (kidney metabolism of oxygen via T 2 and interleaved velocity encoding) was developed to simultaneously measure renal blood flow rate (BFR) and T 2 of blood water using the conservation of mass. T 2 is converted to venous oxygen saturation (SvO 2 ) using a calibration curve. Compared to previous versions, FB K‐MOTIVE minimizes respiratory motion artifacts by acquiring fully sampled velocity maps with spiral readout instead of partially collecting radial views at each T 2 weighting. Healthy participants ( n = 15, 32 ± 9 years) were imaged at 3 T at the renal veins to quantify individual rMRO 2 , and at the suprarenal and infrarenal inferior vena cava to indirectly quantify bilateral rMRO 2 (the total metabolism from both kidneys). Results Renal venous blood was highly oxygenated (SvO 2 91% ± 3%) and exhibited high BFR of 460 ± 90 mL/min per kidney. Further, total rMRO 2 of the two kidneys (160 ± 80 (μmol O 2 /min)/100 g) was statistically comparable to the indirect bilateral rMRO 2 (250 ± 120 (μmol O 2 /min)/100 g, p = 0.066). Using Lin's concordance correlation coefficient, there was good agreement between breath‐hold and free‐breathing acquisitions at the individual kidneys for SvO 2 (>0.75), BFR (>0.96), and rMRO 2 (>0.75). Conclusion FB K‐MOTIVE is a feasible approach to estimate rMRO 2 , yielding reproducible and physiologically plausible metabolic parameters. Free‐breathing acquisition can enhance patient comfort by eliminating the need for breath‐holding.

Source: Magnetic Resonance in Medicine

DOI: 10.1002/mrm.30583