Deuterium Metabolic Imaging of the Human Abdomen at Clinical Field Strength.

OBJECTIVES

The aim of the study was to translate abdominal deuterium metabolic imaging (DMI) to clinical field strength by optimizing the radiofrequency coil setup, the administered dose of deuterium ( 2 H)-labeled glucose, and the data processing pipeline for quantitative characterization of DMI signals over time. This was assessed in the kidney and liver to establish a basis for routine clinical studies in the future.

MATERIALS AND

METHODS

5 healthy volunteers were recruited and imaged on 2 or 3 separate occasions, with varying doses of 2 H-glucose: 0.75 g/kg (high dose), 0.50 g/kg (medium dose), and 0.25 g/kg (low dose), resulting in a total of 13 DMI scan sessions. DMI was performed at 3 T using a flexible 20 × 30 cm 2 2 H-tuned transmit-receive surface coil. For quantitative comparisons across scans, the 2 H-glucose signal was normalized against the sum of 2 H-glucose and 2 H-water (GGW ratio). To quantify the time course of GGW, 3 novel metrics of metabolism were defined and compared between doses and organs: the maximum value across the time course (GGW max ), the sum over the whole time course (GGW AUC ), and the average signal across a defined plateau (GGW mean plateau ). The 2 H-lipid signal overlaps with 2 H-lactate; hence, the 2 signals were measured as the combined 2 H-lipid+lactate signal.

RESULTS

The careful positioning of a dedicated surface coil minimized unwanted gastric signals while maintaining excellent hepatic and renal measurements. The time courses derived from the liver and kidney were reproducible and comparable across different doses, showing the potential for dose reduction. The signal from the liver plateaued at approximately 30 minutes, and that from the kidney at approximately 40 minutes. The liver exhibited higher quantitative values for 2 H-glucose uptake compared to the kidney, a trend consistent across all 3 quantitative metrics and doses, for example, for the highest dose: GGW AUC liver  = 31 ± 3; GGW AUC kidney  = 27 ± 3; P  = 0.05. A trend toward lower quantitative measurements with decreasing dose was observed: this was significant between the high and the low dose for all 3 parameters and between the medium and low dose for GGW mean plateau and GGW AUC , but was not significant between the high and the medium dose for any of the 3 parameters. The hepatic 2 H-lipid+lactate signal increased over 70-90 minutes in 12/13 cases (mean: 39 ± 24%), while the renal lipid+lactate signal increased in only 8/13 cases (mean: 5 ± 17%). The hepatic 2 H-water signal increased in all 13 cases (mean: 18 ± 10%), and the renal 2 H-water signal increased in only 10/13 cases (mean: 10 ± 13%).

CONCLUSIONS

DMI of the human abdomen is feasible using a clinical magnetic resonance imaging system and the signal changes measured in the kidney and liver can serve as a reference for future clinical studies. The 2 H-glucose dose can be reduced from 0.75 to 0.50 g/kg to minimize gastric signal without substantially affecting the reliability of organ quantification. The increase in 2 H-lipid+lactate or 2 H-water signal over time could serve as direct and indirect measures of metabolism, respectively.