Abstract Positron emission tomography (PET, including PET/CT and PET/MRI) with 18F-fluorodeoxyglucose (FDG) plays a key role in diagnosing and staging a wide variety of malignant tumors, assessing tumor grade, and evaluating response to therapy. The advent of other recently approved tracers, particularly those with theranostic partners, is opening a new era of imaging where the uptake of PET tracers can directly predict the effectiveness of certain targeted therapies. Such theranostic tracers image different aspects of tumor function than traditional diagnostic tracers (e.g. FDG), and they provide complementary images with different detection and staging performance across different levels of tumor differentiation and grade. The ability to routinely image multiple PET tracers in each patient would provide increased diagnostic performance, improved grading and staging information, and combine predictive theranostic imaging with the diagnostic workup. However, current technology requires that separate scans be performed for each tracer—usually on separate days—resulting in high cost, scheduling and logistical challenges, and undue burden on the patient. We propose to remove these obstacles by developing rapid dual-tracer PET tumor imaging techniques—providing accurate images of two PET tracers in a single scan, and making these techniques available for general clinical use. Multifunctional Imaging LLC (MFI) has previously developed a software medical device, mfiVerse™, which enables single-scan rest+stress myocardial perfusion PET imaging. This SBIR project will expand the software's capabilities to also support dual-tracer PET cancer imaging—a much broader set of applications that will serve many more clinical needs. We will first develop the capability to image FDG and Ga68 DOTATATE in a single, dual- tracer PET exam, which will provide improved imaging performance for both well- and poorly-differentiated neuroendocrine tumors, and simultaneously predict response to targeted radionuclide therapy with Lu177 DOTATATE. This Phase I project will establish a fully working prototype for dual-tracer PET tumor imaging, establish its initial operating performance, and set the stage for full product development and validation under a subsequent Phase II project. The device will also be expanded to support other tracer combinations in Phase II. Completion of this project will create a first-of-its-kind device for dual-tracer cancer PET imaging, enabling routine use of dual-tracer PET for a wide variety of cancer imaging indications.