Whole-Abdomen Metabolic Imaging of Healthy Volunteers Using Hyperpolarized [1-¹³C]pyruvate MRI

Background: Hyperpolarized ¹³C MRI quantitatively measures enzyme-catalyzed metabolism in cancer and metabolic diseases. Whole-abdomen imaging will permit dynamic metabolic imaging of several abdominal organs simultaneously in healthy and diseased subjects. Purpose: Image hyperpolarized [1-¹³C]pyruvate and products in the abdomens of healthy volunteers, overcoming challenges of motion, magnetic field variations, and spatial coverage. Compare hyperpolarized [1-¹³C]pyruvate metabolism across abdominal organs of healthy volunteers. Study Type: Prospective technical development. Subjects: A total of 13 healthy volunteers (8 male), 21–64 years (median 36). Field Strength/Sequence: A 3 T. Proton: T₁-weighted spoiled gradient echo, T₂-weighted single-shot fast spin echo, multiecho fat/water imaging. Carbon-13: echo-planar spectroscopic imaging, metabolite-specific echo-planar imaging. Assessment: Transmit magnetic field was measured. Variations in main magnetic field (ΔB₀) determined using multiecho proton acquisitions were compared to carbon-13 acquisitions. Changes in ΔB₀ were measured after localized shimming. Improvements in metabolite signal-to-noise ratio were calculated. Whole-organ regions of interests were drawn over the liver, spleen, pancreas, and kidneys by a single investigator. Metabolite signals, time-to-peak, decay times, and mean first-order rate constants for pyruvate-to-lactate (k_PL) and alanine (k_PA) conversion were measured in each organ. Statistical Tests: Linear regression, one-sample Kolmogorov–Smirnov tests, paired t-tests, one-way ANOVA, Tukey's multiple comparisons tests. P ≤ 0.05 considered statistically significant. Results: Proton ΔB₀ maps correlated with carbon-13 ΔB₀ maps (slope = 0.93, y-intercept = −2.88, R² = 0.73). Localized shimming resulted in mean frequency offset within ±25 Hz for all organs. Metabolite SNR significantly increased after denoising. Mean k_PL and k_PA were highest in liver, followed by pancreas, spleen, and kidneys (all comparisons with liver were significant). Data Conclusion: Whole-abdomen coverage with hyperpolarized carbon-13 MRI was feasible despite technical challenges. Multiecho gradient echo ¹H acquisitions accurately predicted chemical shifts observed using carbon-13 spectroscopy. Carbon-13 acquisitions benefited from local shimming. Metabolite energetics in the abdomen compiled for healthy volunteers can be used to design larger clinical trials in patients with metabolic diseases. Evidence Level: 2. Technical Efficacy: Stage 1.