Funds are being requested to purchase an Inveon PET (positron emission computed tomography) and dockable CT (transmission computed tomography) scanner (Siemens Medical Solutions USA, Inc, Knoxville, TN) for non-invasively and longitudinally monitoring cancer and other disease processes, trafficking of cancer, immune, and stem cells, cellular responses to therapy and other interventions, genetic pathway expression, and tumor targeting and biodistribution of new radiodiagnostic and radiotherapeutic agents in small-animal (i.e. mouse and rat) models. This state-of-the-art instrument, to be installed in our existing Small- Animal Imaging Core Facility, will be a critical, broadly used resource for the pre-clinical and translational oncology research program at Memorial Sloan-Kettering Cancer Center (MSKCC). The Inveon microPET- microCT (dockable) will replace our R4 microPET and microCAT II microCT. The R4 microPET was installed in 2000 and is now over 10 years old while the microCAT II was installed in 2003 and is now over 8 years old. Importantly, as of June 30, 2011, the R4 microPET is no longer supported, and, as of January 1, 2012, the microCAT II microCT will no longer be supported by the manufacturer, Siemens Medical Solutions USA, because the necessary replacement parts are no longer available for these instruments;this is documented in Section 12. Therefore, should either or both of these instruments require service support and replacement parts, they will simply not be available and these heavily used, critical resources will be immediately and permanently unavailable, a potentially devastating blow to our pre-clinical research program. Funds for a new, fully supported, and more functional microPET-microCT system, the Inveon microPET-microCT (dockable), are therefore urgently requested to maintain, enhance and expand our in vivo radionuclide and radiographic imaging capabilities. In addition to maintaining manufacturer service and applications support, among the critical advantages of the Inveon microPET-microCT (dockable) over our now-outdated R4 microPET and microCAT II microCT are: (1) superior spatial resolution - 1.4 mm full-width half-maximum (FWHM) for PET and 20 ?m for CT;(2) higher PET sensitivity - >10%;and (3) the unique ability to use the microPET-microCT as a fully integrated multi-modality system for transparent, near-perfect registration of PET and CT studies or as stand-alone microPET and microCT systems for independent imaging of separate animals. This docking feature eliminates the capital and operating expenses for a separate CT scanner. In addition to numerous new and ongoing funded projects in place to use the Inveon microPET-microCT (dockable), our Facility and our Center have well-established technical and scientific expertise to continue to fully and productively utilize this instrument upon its installtion and a highly efficient administrative and financial infrastructure in place to support and maintain this instrument and its effective use long-term.