Assessment of the usefulness of the standardized uptake values and the radioactivity levels for the preoperative diagnosis of thyroid cancer measured by using 18F-FDG PET/CT dual-time-point imaging

The purpose of this study was to assess and compare the changes in the SUV (standardized uptake value), the F-18-FDG (F-18-fluorodeoxyglucose) uptake pattern, and the radioactivity level for the diagnosis of thyroid cancer via dual-time-point F-18-FDG PET/CT (positron emission tomographycomputed tomography) imaging. Moreover, the study aimed to verify the usefulness and significance of SUV values and radioactivity levels to discriminate tumor malignancy. A retrospective analysis was performed on 40 patients who received F-18-FDG PET/CT for thyroid cancer as a primary tumor. To set the background, we compared changes in values by calculating the dispersion of scattered rays in the neck area and the lung apex, and by comparing the mean and SD (standard deviation) values of the maxSUV and the radioactivity levels. According to the statistical analysis of the changes in F-18-FDG uptake for the diagnosis of thyroid cancer, a high similarity was observed with the coefficient of determination being R-2 = 0.939, in the SUVs and the radioactivity levels. Moreover, similar results were observed in the assessment of tumor malignancy using dual-time-point. The quantitative analysis method for assessing tumor malignancy using radioactivity levels was neither specific nor discriminative compared to the semi-quantitative analysis method.