Is whole body CT necessary for metabolic PET imaging of solitary pulmonary nodules?

18F-FDG PET is a noninvasive imaging metod for metabolic characterisation of the solitary pulmonary nodule (SPN) detected with other imaging metods. The CT part of PET/CT data that is used for attenuation correction of PET images, also provides information about the anatomical features of lessions.During PET/CT evaluation of SPN a whole body scan, from vertex to thigh is routinely done which casues whole-body X-ray exposure.The aim of the study is;To investigate the necessity of whole body CT imaging in SPN assessment and to evaluate if a thorax-only CT imaging causes a change in staging.To identify the frequency of clinically significant extrathoracic incidental findings.To identify the decrease of the patient radiation dose from CT when the CT imaging is limited to thorax.The study included patients referred to the Nuclear Medicine Department of Gazi University for diagnosis and metabolic characterization of a SPN. The CT images were examined and the extrathoracic incidental findings were categorized according to their clinical significance. Also the CT radiation doses for the whole body scan and the thoracic only scan were calculated for each patient.A total of 154 patients were involved to the study. According to the results obtained in our study we concluded that whole body PET imaging can be applied first. Then, if there is no extrathoracic 18F-FDG accumulation, a thoracic-only PET/CT imaging can be done. A whole body CT scan bears no additional clinical significance. This approach decreases CT radiation doses by a factor of 1/3.