Imaging of pneumoconiosis by positron emission tomography using 18F-fluorodeoxyglucose and 11C-methionine

Abstract

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Objectives: Patients with pneumoconiosis are at high risk for acquiring lung cancer but it is difficult to differentiate lung cancer from benign pneumoconiosis on conventional imaging. FDG and C-11-methionine are commonly used tumor-seeking PET tracers, but accumulations of FDG are well known in granulomatous lesions. Comparative studies between the two PET tracers in pneumoconiosis for detecting lung cancer have not been reported. The aim of this study was to evaluate the clinical value of MET-PET in pneumoconiosis and to compare with FDG-PET.

Methods: Seven patients with pneumoconiosis received both whole body MET-PET and FDG-PET in a single day. MET-PET was obtained from 15-20min after injection of 361-533MBq of MET. One hour later, 161-220 MBq of FDG was administered to obtain FDG-PET from 40-60 min. The uptake scores of FDG and MET were visually graded from 0 (no uptake) to 2+ (intense uptake).

Results: CT studies identified 18 large nodules (>3cm in diameter) and many small lesions (<3cm) in six patients and only small lesions without large lesions in the remaining one patient. All of 18 large nodules showed positive FDG uptake. On the other hand, accumulation of MET was seen in 11 lesions. The FDG uptake score was higher than the MET uptake score in 15 of 18 large nodules. However, FDG and MET revealed similar uptake score (FDG 2+ = MET 2+) in 3 large nodules. Lung cancer existed in one of these 3 lesions. None of the small lesions were visualized by either tracer.

Conclusions: These preliminary study indicates that high accumulations of both FDG and MET may be observed in large benign nodules in pneumoconiosis. Among these lesions, those with similar intense uptake of both FDG and MET should be carefully observed due to high risk for lung cancer.