Standardized uptake values of uterine leiomyoma with ¹⁸F-FDG PET/CT: Variation with age, size, degeneration, and contrast enhancement on MRI

Objective: To assess the effect of age, size, the degree of degeneration, and contrast enhancement on magnetic resonance imaging (MRI) on ¹⁸F-fluoro-2-deoxyglucose (¹⁸F-FDG) uptake in uterine leiomyomas using quantitative standardized uptake values (SUVs). Methods: A total of 61 leiomyomas of 41 patients, who underwent combined positron emission tomography/computed tomography (PET/CT) using ¹⁸F-FDG and contrast-enhanced MRI were included in this study. Sixty-one leiomyomas were divided into two groups: "non-degenerated" leiomyomas showing distinct low signal intensity on T2-weighted images and intermediate signal intensity on T1-weighted images, and "degenerated" leiomyomas showing other types of signal intensity. Sixty-one leiomyomas were also divided into two groups of "strongly enhancing" leiomyomas and "weakly enhancing" leiomyomas in terms of their degree of contrast enhancement on MRI. Results: The mean values of the maximum and average SUVs for the total of 61 leiomyomas were 2.34 ± 0.75 (range 1.59-5.15) and 1.74 ± 0.50 (0.66-3.95), respectively. There was a moderate negative correlation between the maximum and average SUVs and age (r = -0.43 and P = 0.00016, r = -0.31 and P = 0.029, respectively). Although there was a mild positive correlation between maximum SUV and size (r = 0.35 and P = 0.011), there was no significant difference between average SUV and size. Although there was no significant difference in average SUV between "degenerated" and "non-degenerated" leiomyomas, the maximum SUV of "degenerated" leiomyomas was significantly higher than that of "non-degenerated" leiomyomas (P = 0.0012). The degree of contrast enhancement on MRI was not significantly correlated with ¹⁸F-FDG uptake. Conclusions: Mild or moderate uptake of ¹⁸F-FDG is often observed in uterine leiomyoma and declines with age, and should not be confused with malignant accumulation.