Image analysis in patients with cancer studied with a combined PET and CT scanner

Purpose: To compare combined whole-body PET and CT images of different cancers with PET images alone. Materials and Methods: Thirty-two patients with known or possible cancers were examined using a combined positron emission tomographic (PET) and computed tomographic (CT) scanner. All data were acquired using this same combined scanner. After an injection of F-18 fluorodeoxyglucose (FDG), noncontrast helical CT imaging of the neck, chest, abdomen, or pelvis was performed. The spiral CT was followed by a PET scan covering the same axial extent as the CT. Results: Coregistered PET-CT images identified and localized 55 lesions. In 10 patients (31%), areas with variable amounts of normal physiologic FDG uptake were distinguished from potential uptake of FDG in a nearby neoplastic lesion. Improved localization was achieved in 9 patients (for a total of 13 lesions, or 24%). Conclusion: Combined PET-CT images appear more effective than PET images alone to localize precisely neoplastic lesions and to distinguish normal variants from juxtaposed neoplastic lesions.