Supplement Project Summary/Abstract The Parent Grant, Hyperpolarized MRI Technology Resource Center (HMTRC; P41 EB013598; 2011-2027), aims to develop and disseminate optimal new HP 13C MR technologies with requisite training/documentation to advance significantly this emerging molecular imaging method. From the HP 13C MRI studies done to date, it is clear that HP 13C MR has outstanding research and clinical value, but also that all aspects of this technology (instrumentation, agent chemistry, DNP/dissolution methodology, MR acquisition, and data analysis) require specialized development to realize their full potential. Specialized C-13 MR phantom development has been a critical component of this P41 for HP technology development & testing. We believe that this supplement project fits the NOSI eligibility: “Parent grants that develop and use phantoms as part of their original scientific aims may be eligible for the supplemental funding under this NOSI. If the supplement proposes to include and perform additional steps but are needed to make the phantoms ready for dissemination. Applicants may propose to perform tasks along the optimization, validation, and calibration pipeline”. This supplement for optimizing, calibrating and disseminating C-13 MRI phantoms will benefit this NCBIB’s Dissemination & Training aspects and the TRD’s, and especially TRD1 that is responsible for “beyond state-of- the-art” polarizer and MRI hardware technologies for all HP 13C MRI studies performed & supported by this P41 Center’s TRDs, CPs and SPs. This TRD has been highly successful in developing novel technologies with 13C- phantom testing for HP MRI driving first-ever HP 13C studies in humans at 15 sites to date & expect 50+ by 2 years. We have found that unlike many MRI phantoms that are spherical or cylindrical with non-homogeneous internal structures, the most-useful HP C-13 phantoms currently are shaped like human anatomy and filled with a uniform solution with C-13 signals and doped to match human loading and MR relaxation times. The new phantom technology resources will be optimized & disseminated for use by the HP C-13 MRI community with feedback on performance, quality, and ease of dissemination. New MR hardware developments including these optimized phantoms are driven by the research needs of CPs together with TRDs2&3. TRD1 develops novel 13C RF exciters and detectors that require specialized phantom testing and also for the TRD3 development and testing of new methods for data reconstruction, visualization and analysis. These 13C MR phantoms, mimicking human anatomy, have been critical for testing coil & acquisition technology developments, driven by the CPs for metabolic imaging of brain cancer, abdominal/pelvic cancer, liver disease, and brain disorders. The major focus of this supplement project will be on optimizing our specialized HP C-13 phantoms for dissemination to advance HP 13C-MRI developments, benefit multi-site trials, and the training of new i...