Quantification of whole-organ individual and bilateral renal metabolic rate of oxygen

초록

Purpose: Renal metabolic rate of oxygen (rMRO(2)) is a potentially important biomarker of kidney function. The key parameters for rMRO(2) quantification include blood flow rate (BFR) and venous oxygen saturation (SvO(2)) in a draining vessel. Previous approaches to quantify renal metabolism have focused on the single organ. Here, both kidneys are considered as one unit to quantify bilateral rMRO(2). A pulse sequence to facilitate bilateral rMRO(2) quantification is introduced.Methods: To quantify bilateral rMRO(2), measurements of BFR and SvO(2) are made along the inferior vena cava (IVC) at suprarenal and infrarenal locations. From the continuity equation, these four parameters can be related to derive an expression for bilateral rMRO(2). The recently reported K-MOTIVE pulse sequence was implemented at four locations: left kidney, right kidney, suprarenal IVC, and infrarenal IVC. A dual-band variant of K-MOTIVE (db-K-MOTIVE) was developed by incorporating simultaneous-multi-slice imaging principles. The sequence simultaneously measures BFR and SvO(2) at suprarenal and infrarenal locations in a single pass of 21 s, yielding bilateral rMRO(2).Results: SvO(2) and BFR are higher in suprarenal versus infrarenal IVC, and the renal veins are highly oxygenated (SvO(2) >90%). Bilateral rMRO(2) quantified in 10 healthy subjects (8 M, 30 +/- 8 y) was found to be 291 +/- 247 and 349 +/- 300 (mu molO(2)/min)/100 g, derived from K-MOTIVE and db-K-MOTIVE, respectively. In comparison, total rMRO(2) from combining left and right was 329 +/- 273 (mu molO(2)/min)/100 g.Conclusion: The present work demonstrates that bilateral rMRO(2) quantification is feasible with fair reproducibility and physiological plausibility. The indirect method is a promising approach to compute bilateral rMRO(2) when individual rMRO(2) quantification is difficult.

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