Rationale: We believe that FDG PET/CT can be used to accurately diagnose the presence, extent, and acuity of VTE. It is unrealistic to assume that FDG-PET could or should become the primary imaging modality for evaluating VTE. The cost, compared to Doppler ultrasound, would be prohibitive, and would involve unnecessary radiation of the patient. We intend to establish the value of FDG PET, instead, as an alternative modality for the diagnosis of VTE. Clinical situations where this might prove useful include: 1) the presence of old clot, when the distinction between new and old may be important; 2) evaluation of abdominal, pelvic and thoracic thrombus, where Doppler is difficult-to-impossible because of patient obesity; 3) Complicated anatomy due to the presence of tumor or post-therapeutic changes.