Abstract：Objective: To evaluate the clinical value of abnormalities that do not show increased 18F-FDG uptake on non-enhanced CT of integrated PET/CT in patients with non-small cell lung cancer. Materials and Methods: The study consisted of a retrospective analysis of consecutive PET/CT scans obtained at our PET center between May and December 2006. During the eight-month period, there were 119 patients had a diagnosis of non-small cell lung cancer. All scans were obtained with integrated PET/CT scanner(Siemens Biograph Sensation 16). Each case was interpreted independently by two experienced PET/CT physicians. All abnormalities with negative 18F-FDG uptake were recorded. The abnormalities were classified as being of major, moderate or minor significance according to the definitions previously by Ford. Results: There were 119 patients with non-small cell lung cancer underwent initial staging(66/119, 55.5%)， restaging or treatment monitoring(53/119, 44.5%) PET/CT imaging during the study period. The abnormalities were located in the head and neck(n=40), thorax(n=97), abdomen and pelvis(n=128), and bony skeleton(n=18). The clinical importance of these abnormalities was classified as major n=9(3%), moderate n=121(42%), or minor n=153(54%). Major abnormalities noted in the study included 4 cases of small lung nodules, 1 case of osteolytic lesion and 1 case of brain lesion suggestive of metastasis, as well as 1 case of liver mass and 2 cases of renal mass. Conclusions: CT scan in PET/CT can not be only a tool for attenuation correction and anatomic landmarks alone. Even low-dose CT can provide important diagnostic information. There is a high prevalence of CT abnormalities in non-small cell lung cancer that do not show 18F-FDG uptake, but small proportion of which has clinical significance. Diagnostic CT should be done to get more significant information in PET/CT interpretation.
2008, Vol. 19 
