Hyperpolarized Carbon-13 MRI for Metabolic Imaging.

Hyperpolarized Carbon-13 (HP C-13) MR is an emerging molecular imaging technique that utilizes a stable-isotope agent polarized in a separate instrument at 5 T and 1 K that is then injected into the patient in a 3T MRI scanner to provide information on cellular metabolism, cancer aggressiveness and response to therapy. While similar to PET in that it uses an injected isotope, HP C-13 differs in several ways. This approach using nuclear spins as "quantum sensors" of not only tissue perfusion and uptake locations but also of enzymatic conversions measured by frequency conversion rates. Much effort has gone into improving the "quantum control" methods for creating spin states with ~50% of the spins aligned with the field instead of ppm.  Also, specialized hardware for hyperpolarization, C-13 MR excitors/detectors, and specialized acquisition methods has been developed as well as the substanital efforts on the formulations of sterile human doses of (~1.5g).

This has enabled new metabolic contrast agents that detect not only the isotope uptake but also its downstream metabolites enabling quantification of enzymatic conversion rates in biomedically-important metabolic pathways. C-13 is not radioactive, rather it is a stable isotope that is present in all naturally-occurring endogenous molecules such as ¹³C-pyruvate. It has an excellent safety profile in 1000+ patient and normal volunteer studies with fast dynamic acquisitions.  We developed and applied this technology to address unmet clinical needs in the management of prostate cancer, brain tumors, kidney disease, metastatic breast cancer, pancreatic cancer, and cardiac disease. These studies have shown the ability of HP C-13 MRI to detect biomarkers of cancer aggressiveness, biopsy guidance and response to therapy in a 2-minute acquisition added to MRI exams.