Fig. 6: Image- and spectroscopy-based quantification of renal function.
a The accumulation of both [13C]urea (a) and Z-OMPD (c) in the renal cortex (blue curves and ROI) and pelvis (yellow curves and ROI) can be assessed by extraction of 3D-ROI-based (e, two example slices shown) signal time curves from the image series in Fig. 5b, c. Scale bars, 10 mm. b, d T1-decay correction and fitting of time curve sections, where temporal signal evolution is mainly driven by the renal filtration process. Additionally, for renal blood flow, cortex time curves are normalized by image-derived arterial input functions (AIFs, red ROIs in e) for [13C]urea (f) and Z-OMPD (g). h Single kidney GFR values for [13C]urea and Z-OMPD show good agreement, with Z-OMPD showing slightly faster renal clearance. i Comparison of renal blood flow values for [13C]urea and Z-OMPD also shows good agreement between both perfusion agents with renal blood flow measured by Z-OMPD being systematically higher compared to [13C]urea. j Axial slice positioning for non-imaging, spectroscopic assessment of renal filtration. Scale bars, 10 mm. k Waterfall plot of a dynamic slice-spectroscopy on both kidneys. Due to different pH milieus, the anatomical regions of the kidney, namely the renal cortex, medulla and pelvis are distinguishable as individual peaks for the C5-resonance of Z-OMPD. l tGFR values can be calculated from spectroscopic data only by fitting of the time curves of the cortex- and the pelvis peak integrals. Correlations for RBF (r = 0.90, p = 2 × 10-6) and GFR (r = 0.88, p = 4 × 10-5) between [13C]urea- and Z-OMPD-based measurements were assessed by linear regression.
