This application requests funds for a PerkinElmer Spectrum CT optical imaging system to support research being carried out at Tufts University and Tufts Medical Center (TMC). A group of 9 well-funded NIH investigators will be major users of the instrument and will account for approximately 80% of its use. Cutting edge projects in the areas of cancer, infectious disease and arthritis are described. Need for the instrument at this time is critical as the existing heavily- used IVIS 200 instrument, which will be replaced by the Spectrum CT, is no longer supported by PerkinElmer and is in a state of disrepair. The new system will be housed in the Tufts/TMC Small Animal Imaging/ Preclinical Testing Facility where it will complement other animal imaging instrumentation. The Dean of the Medical School has recently provided a newly renovated laboratory for the Facility which includes space for the instrument, has pledged funds for a year of service contract support after the warranty expires, and whatever support is needed in future years to cover the cost of operating and maintaining the instrument. The Facility is directed by the PI and the instrument will be managed and operated on a day-to-day basis by the Associate Director and Manager of the Facility, who will also train new users. The PI, Facility staff, and more than 30 users of the existing IVIS 200 instrument represent strong optical imaging expertise for the new instrument. The PI, Facility staff and two radiologists that serve as Facility consultants have micro-CT experience thereby providing strong expertise for the CT feature of the new instrument as well. An advisory committee consisting of the PI, representatives from Tufts University, Tufts Medical Center, the Department of Developmental, Molecular and Chemical Biology and the Division of Laboratory Animal Medicine, which include 3 previous users of the instrument, will oversee use of the Spectrum CT instrument and develop policies for use and equitable sharing of the instrument. The availability of the Spectrum CT optical imager will greatly enhance the quality NIH-funded research being carried out Tufts University and Tufts Medical Center and will stimulate translation research and collaboration among the various components of the Tufts research community.