EVALUATION OF PATIENTS WITH ROUND ATELECTASIS USING 2-[F-18]FLUORO-2-DEOXY-D-GLUCOSE PET

Purpose: Our goal was to determine the spectrum of 2-[F-18]fluoro-2-de oxy-D-glucose (FDG) PET findings in patients with round atelectasis (R A). Method: All patients from 1992 to 1997 with radiologic features of RA and FDG-PET scans were evaluated. There were nine men ranging in a ge from 52 to 75 years (mean 65 years). All had chest radiographs and CT scans that were correlated with FDG-PET. FDG-PET was considered pos itive if lesion activity was greater than mediastinal activity and neg ative if lesion activity was the same as or less than mediastinal acti vity. Results: Nine patients had 10 lesions, ranging in size from 1.2 to 5.0 cm (mean 3.1 cm). Lesion locations were right lower lobe (n = 5 ), left lower lobe (n = 4), and lingula (n = 1). All lesions were homo geneous and of soft tissue attenuation on CT. None contained air bronc hograms or calcification All had in-curving vessels and bronchi (comet tail sign), adjacent pleural thickening, and volume loss on CT. All l esions were negative on FDG-PET. Four lesions were percutaneously biop sied and showed chronic inflammation consistent with RA. Two lesions w ere unchanged on 2 and 3 year follow-up CT and were presumed to be RA as were four other lesions with characteristic CT features and negativ e FDG-PET. Conclusion: Our experience suggests that RA is not metaboli cally active on FDG-PET imaging. Thus, FDG-PET scans can play a role i n differentiating RA from malignancy when there are few or atypical fe atures of RA on chest radiographs and CT.