Repeatability of Metabolic Imaging With Hyperpolarized Pyruvate: Back-to-Back Neuroimaging and Blood Analysis

Area of Science:

• Biomedical Imaging
• Metabolic Pathway Analysis
• Magnetic Resonance Imaging

Background:

• ¹³C MRI with hyperpolarized [1-¹³C]pyruvate noninvasively images metabolic pathways.
• Concerns exist regarding the influence of circulating ¹³C-pyruvate and ¹³C-lactate on subsequent metabolism after high-dose injections.
• Lack of guidance for consecutive pyruvate injections in hyperpolarized ¹³C MRI studies.

Purpose of the Study:

• Characterize blood pyruvate and lactate dynamics after [1-¹³C]pyruvate injection.
• Evaluate the repeatability of ¹³C neuroimaging using consecutive pyruvate injections.
• Establish guidance for multi-injection protocols in hyperpolarized ¹³C MRI.

Main Methods:

• Sixteen healthy adults underwent blood sampling or ¹³C/¹H MRI.
• Blood samples analyzed for pyruvate, lactate concentrations, and ¹³C enrichment via mass spectrometry.
• Participants received one or two injections of [1-¹³C]pyruvate (non-hyperpolarized or hyperpolarized) with varying intervals.

Main Results:

• Plasma ¹³C-pyruvate peaked within 30s, returning to baseline in 5-10 min; ¹³C-lactate peaked at 2-3 min.
• Higher lactate ¹³C enrichment observed in fasting vs. fed states; total blood lactate unchanged.
• Excellent repeatability for brain ¹³C-lactate/pyruvate ratio (ICC=0.9842); high voxel-wise correlation (0.72) between injections.

Conclusions:

• Consecutive hyperpolarized [1-¹³C]pyruvate injections provide repeatable metabolic measurements in humans.
• Supports the use of multi-injection protocols in ¹³C MRI studies.
• Validates the safety and efficacy of repeated pyruvate administration for metabolic imaging.