Metabolic imaging with hyperpolarized [1-(13)C]-
pyruvate can rapidly probe tissue metabolic profiles in vivo and has been shown to provide
cancer imaging
biomarkers for
tumor detection, progression, and response to
therapy. This technique uses a bolus injection followed by imaging within 1-2 minutes. The observed metabolites include vascular components and their generation is also influenced by cellular transport. These factors complicate image interpretation, especially since [1-(13)C]
lactate, a metabolic product that is a
biomarker of
cancer, is also produced by red blood cells. It would be valuable to understand the distribution of metabolites between the vasculature, interstitial space, and intracellular compartments. The purpose of this study was to better understand this compartmentalization by using a perfusion and diffusion-sensitive stimulated-echo acquisition mode (
STEAM) MRSI acquisition method tailored to hyperpolarized substrates. Our results in mouse models showed that among metabolites, the injected substrate (13)C-pyruvate had the largest vascular fraction overall while (13)C-alanine had the smallest vascular fraction. We observed a larger vascular fraction of
pyruvate and
lactate in the kidneys and liver when compared to back muscle and prostate
tumor tissue. Our data suggests that (13)C-lactate in prostate
tumor tissue voxels was the most abundant labeled metabolite intracellularly. This was shown in
STEAM images that highlighted abnormal
cancer cell metabolism and suppressed vascular (13)C metabolite signals.