¹⁸F-FDG PET/CT검사에서 지연영상을 이용한 갑상선 우연종 감별의 유용성 평가

Evaluate Utility of Thyroid Incidentaloma Discrimination by ¹⁸F-FDG PET/CT Delay Scan Images

Purpose: To evaluate the degree of malignancy of incident thyroid lesion found in ¹⁸F-FDG PET/CT findings and the usefulness of the method suggested in this study, we applicate the Delay Scan Method that differentiate a false positive benign tumor, inflammation and malignancy, as well as make the criteria of SUV. Materials and Methods: A retrograde study was conducted of 800 patients who were admitted in E hospital to receive ¹⁸F-FDG PET/CT examination. One patient who was diagnosed as primary thyroid cancer and received ¹⁸F-FDG PET/CT examination was excluded. The number of final patients of this study was 799, the reasons of ¹⁸F-FDG PET/CT examination of these patients were follow-up of old cancer or suspicious tumorous lesion in 696 and disease screening in 103. ¹⁸F-FDG PET/CT image photographing was taken in Biograph-Duo made by SIEMENS, after taking normal ¹⁸F-FDG PET/CT image (1 hr) and then 1 hr later we took the thyroid 1 beddelayed image for the patients who showed abnormal thyroid ¹⁸F-FDG uptake and above 2.0 SUV for 2 minutes every 1 bed. For the patients who showed abnormal thyroid uptake and above 2.0 SUV, 1 hr later, we took a 1 bed-delayed image and then made a comparative study between measured SUVmax of 1 hr-abnormal uptake image and that of 2 hr-delayed image. Results and Conclusion: In this ¹⁸F-FDG PET/CT study among the patients who showed incidental ¹⁸F-FDG thyroidal uptake the number of thyroid incidentaloma was 5 (0.63%), all of then showed benign findings. And in the case of incidental ¹⁸F-FDG uptake in thyroid, SUVmax variance obtained from 2 hr delayed image can be a indirect criteria in differentiating benign tumor from malignancy and decrease finding error. In the cases found thyroid incidentaloma when 1) SUVmax of focal thyroid lesion is above 5.0 and 2) SUVmax variance between normal ¹⁸F-FDG PET/CT exam and 2 hr delayed is 1.0±0.5, they are suspected as malignancy and confirming biopsy is to be followed. Otherwise, I also think that distinct follow-up PET or CT image study is a reasonable diagnostic method.