A combined PET/CT scanner for clinical oncology

The availability of accurately aligned, whole-body anatomical (CT) and func tional (PET) images could have a significant impact on diagnosing and stagi ng malignant disease and on identifying and localizing metastases. Computer algorithms to align CT and PET images acquired on different scanners are g enerally successful for the brain, whereas image alignment in other regions of the body is more problematic. Methods: A combined PET/CT tomograph with the unique capability of acquiring accurately aligned functional and anato mical images for any part of the human body has been designed and built. Th e PET/CT scanner was developed as a combination of a Siemens Somatom AR.SP spiral CT and a partial-ring, rotating ECAT ART PET scanner. All components are mounted on a common rotational support within a single gantry, The PET and CT components can be operated either separately, or in combined mode. In combined mode, the CT images are used to correct the PET data for scatte r and attenuation. Fully quantitative whole-body images are obtained for an axial extent of 100 cm in an imaging time of less than 1 h. When operated in PET mode alone, transmission scans are acquired with dual Cs-137 sources . Results: The scanner is fully operational and the combined device has bee n operated successfully in a clinical environment. Over 110 patients have b een imaged, covering a range of different cancers, including lung, esophage al, head and neck, melanoma, lymphoma, pancreas, and renal cell. The aligne d PET and CT images are used both for diagnosing and staging disease and fo r evaluating response to therapy. We report the first performance measureme nts from the scanner and present some illustrative clinical studies acquire d in cancer patients. Conclusion: A combined PET and CT scanner is a practi cal and effective approach to acquiring co-registered anatomical and functi onal images in a single scanning session.