PROJECT SUMMARY: This proposal is devoted to the development, clinical implementation and evaluation of a novel, real-time, motion correction methodology for concurrent MR/PET acquisitions. Available methods for data acquisition and reconstruction in MR/PET scanners do not fully capitalize on the simultaneous imaging capabilities of the commercially available MR/PET instrumentation. These capabilities could be used to obtain real-time information for reducing motion artifacts and partial voluming bias from PET images without significantly affecting the workflow of the corresponding MRI examination. Our methodology builds on the track record of the multi-institutional research team with all aspects of MRI and PET data acquisition and reconstruction. The proposed methodology will lead to improved sensitivity and quantitative accuracy for PET scans when they are simultaneously acquired during the course of an MR/PET examination. Such improvements will lead to better detection, staging and surveillance of small (<1cm) abdominal lesions, which assessment is currently limited due to excessive signal loss from motion blur and partial voluming bias.