Hyperpolarized [1-13 C]pyruvate MRI can image the metabolic shift in cardiac metabolism between the fasted and fed state in a porcine model.

PURPOSE: Owing to its noninvasive nature, hyperpolarized MRI may improve delineation of myocardial metabolic derangement in heart disease. However, consistency may depend on the changeable nature of cardiac metabolism in relation to whole-body metabolic state. This study investigates the impact of feeding status on cardiac hyperpolarized MRI in a large animal model resembling human physiology. METHODS: Thirteen 30-kg pigs were subjected to an overnight fast, and 5 pigs were fed a carbohydrate-rich meal on the morning of the experiments. Vital parameters and blood samples were registered. All pigs were then scanned by hyperpolarized [1-13 C]pyruvate cardiac MRI, and results were compared between the 2 groups and correlated with circulating substrates and hormones. RESULTS: The fed group had higher blood glucose concentration and mean arterial pressure than the fasted group. Plasma concentrations of free fatty acids (FFAs) were decreased in the fed group, whereas plasma insulin concentrations were similar between groups. Hyperpolarized MRI showed that fed animals had increased lactate/pyruvate, alanine/pyruvate, and bicarbonate/pyruvate ratios. Metabolic ratios correlated negatively with FFA levels. CONCLUSION: Hyperpolarized MR can identify the effects of different metabolic states on cardiac metabolism in a large animal model. Unlike previous rodent studies, all metabolic derivatives of pyruvate increased in the myocardium of fed pigs. Carbohydrate-rich feeding seems to be a feasible model for standardized, large animal hyperpolarized MRI studies of myocardial carbohydrate metabolism.

Low-Noise Active Decoupling Circuit and its Application to 13C Cryogenic RF Coils at 3 T.

We analyze the loss contributions in a small, 50-mm-diameter receive-only coil for carbon-13 (13C) magnetic resonance imaging at 3 T for 3 different circuits, which, including active decoupling, are compared in terms of their Q-factors and signal-to-noise ratio (SNR). The results show that a circuit using unsegmented tuning and split matching capacitors can provide >20% SNR enhancement at room temperature compared with that using more traditional designs. The performance of the proposed circuit was also measured when cryogenically cooled to 105 K, and an additional 1.6-fold SNR enhancement was achieved on a phantom. The enhanced circuit performance is based on the low capacitance needed to match to 50 Ω when coil losses are low, which significantly reduces the proportion of the current flowing through the matching network and therefore minimizes this loss contribution. This effect makes this circuit particularly suitable for receive-only cryogenic coils and/or small coils for low-gamma nuclei.

Renal ischemia and reperfusion assessment with three-dimensional hyperpolarized 13 C,15 N2-urea.

PURPOSE: The aim of this work was to investigate whether hyperpolarized 13 C,15 N2 -urea can be used as an imaging marker of renal injury in renal unilateral ischemic reperfusion injury (IRI), given that urea is correlated with the renal osmotic gradient, which describes the renal function. METHODS: Hyperpolarized three-dimensional balanced steady-state 13 C magnetic resonance imaging (MRI) experiments alongside kidney function parameters and quantitative polymerase chain reaction measurements were performed in rats subjected to unilateral renal ischemia for 60-minute and 24-hour reperfusion. RESULTS: We revealed a significant reduction in the intrarenal gradient in the ischemic kidney in agreement with cortical injury markers neutrophil gelatinase-associated lipocalin and kidney injury molecule 1, as well as functional kidney parameters. CONCLUSION: Hyperpolarized functional 13 C,15 N2 urea MRI can be used to successfully detect changes in the intrarenal urea gradient post-IRI, thereby enabling in vivo monitoring of the intrarenal functional status in the rat kidney. Magn Reson Med 76:1524-1530, 2016. © 2016 International Society for Magnetic Resonance in Medicine.