PET and CT imaging were performed on the prototype combined CTI/Siemens PET/CT scanner which comprises an ECAT ART PET scanner, and a Somatom AR.SP CT scanner. We have performed over 200 whole-body combined FDG PET/CT studies for a variety of oncologic indications since July 1998. The PET/CT was performed approximately one hour following a 6-7 mCi i.v. injection of FDG, with acquisition of helical CT data (pitch 1.6) immediately preceding acquisition of 3D emission data (10 min. per bed position; 2-5 bed positions/subject). In 30 subjects, the CT was performed with dynamic injection of iv contrast (90 cc Optiray). The PET images were corrected for attenuation using coefficients obtained by scaling the CT numbers from the CT images to the PET energy (511 keV) (3). The helical CT scan was reconstructed into 512 x 512 images with a slice thickness of 3.4 mm to match that of the PET scan.

Images were evaluated by two neuroradiologists for the purpose of describing the pattern of physiologic FDG uptake and localizing it to specific normal anatomic structures on the co-registered CT.