Simultaneous hyperpolarized 13C-pyruvate MRI and 18F-FDG PET (HyperPET) in 10 dogs with cancer

Abstract

With the introduction of combined PET/MR spectroscopic (MRS) imaging, it is now possible to directly and indirectly image the Warburg effect with hyperpolarized13C-pyruvate and 18F-FDG PET imaging, respectively, via a technique we have named hyperPET. The main purpose of this present study was to establish a practical workflow for performing 18F-FDG PET and hyperpolarized13C-pyruvate MRS imaging simultaneously for tumor tissue characterization and on a larger scale test its feasibility. In addition, we evaluated the correlation between 18F-FDG uptake and13C-lactate production. Methods: Ten dogs with biopsy-verified spontaneous malignant tumors were included for imaging. All dogs underwent a protocol of simultaneous 18F-FDG PET, anatomic MR, and hyperpolarized dynamic nuclear polarization with13C-pyruvate imaging. The data were acquired using a combined clinical PET/MR imaging scanner. Results: We found that combined 18F-FDG PET and13C-pyruvate MRS imaging was possible in a single session of approximately 2 h. A continuous workflow was obtained with the injection of 18F-FDG when the dogs was placed in the PET/MR scanner.13C-MRS dynamic acquisition demonstrated in an axial slab increased13C-lactate production in 9 of 10 dogs. For the 9 dogs, the13C-lactate was detected after a mean of 25 s (range, 17-33 s), with a mean to peak of13C-lactate at 49 s (range, 40-62 s).13C-pyruvate could be detected on average after 13 s (range, 5-26 s) and peaked on average after 25 s (range, 13-42 s). We noticed concordance of 18F-FDG uptake and production of13C-lactate in most, but not all, axial slices. Conclusion: In this study, we have shown in a series of dogs with cancer that hyperPET can easily be performed within 2 h. We showed mostly correspondence between13C-lactate production and 18F-FDG uptake and expect the combined modalities to reveal additional metabolic information to improve prognostic value and improve response monitoring.