October 17, 2000 8:30—8:45

The purpose of the study was to evaluate a new technology of simultaneous transmission and F-18 FDG emission tomography (FDG-TET) in tumor imaging and its impact on patient management.

Emission and transmission devices were installed on the same gantry. 167 patients with histologically proven malignancy were evaluated at diagnosis or during follow up. Eight mCi of FDG were injected for PET and a low dose X-ray tube was used for CT. The FDG and CT were first interpreted independently, without knowledge of findings in other imaging modality. Subsequently fusion images were analyzed.

FDG-TET changed the interpretation of PET or CT in 75 patients (45%). In 60 patients TET allowed for correct localization of lesions on the PET studies. In 15 patients, FDG uptake was found in sites of physiologic activity. In 12 patients lesions previously missed on CT were retrospectively identified. In 21 patients, TET detected 34 previously unknown sites of disease.

FDG-TET changed the clinical management of 29 patients (17%). The stage of disease was changed in 9 patients. Early diagnosis of recurrence was made in 8 patients. Seven patients were referred for previously unplanned surgery. In 6 patients surgery was cancelled. Fifteen patients received additional chemo- or radiotherapy.

Diagnosis of cancer on CT is based on a change in size or attenuation of a mass. PET shows the metabolic status of a lesion but lacks anatomical landmarks. FDG-TET improves the diagnostic accuracy in cancer and may have a significant impact on patient management.