Evaluation of pulmonary lesions with 18FDG CoDo PET: comparison with CT, MRI and clinical findings

Dual-head gamma camera coincidence (PET) is one of the recent approaches to overcome the problems of the dedicated PET scans such as high cost and limited availability. The purpose of this study was to evaluate the accuracy of 18FDG coincidence detection (CoDe) PET in differentiating benign from malignant lesions and staging malignancy. Thirty-one patients with pulmonary lesions underwent 18FDG CoDe PET. Patients were prepared for the study by overnight fasting. The images were acquired at about 1 hr postinjection of 3-10 mCi 18FDG intravenously using dual head gamma camera (Elscint, Varicam) equipped with 5/8 inch thick NaI crystal. The images were analyzed visually. Pathologic proof of diagnosis was obtained by aspiration biopsy in 24 patients and by operation in 7 patients. Among 25 patients with pathologically proven malignant lesions ( 11 adenocarcinoma, 3 non-small cell lung cancer, 5 squamous cell cancer, 4 small cell lung cancer, 1 invasive thymoma and 1 adenosquamous cell cancer), 18FDG CoDe PET could not detect only 1 lesion which was adenocarcinoma of less than 1 cm in size. In seven patients underwent lobectomy, 6 CoDe PET studies agreed with pathologic results. Whereas only 3 of 7 patients CT findings agreed with pathologic findings. However, 6 patients with benign lesions also showed positive FDG uptake. The false positive pathologies were due to tuberculosis, pneumonia, and granulomatous changes due to silicosis. 18FDG CoDe PET was sensitive in the evaluation of lung lesions but was not specific for malignancy. 18FDG CoDe PET was more sensitive than CT in nodal staging in limited number of patients studied thus far