Establishing Normal Testicular 18F-FDG PET/CT SUVs

OBJECTIVE. Knowledge of normal testicular 18F-FDG PET/CT (FDG PET/CT) SUVs is crucial for accurate examination interpretation. The objective of this study was to establish normal testicular SUV ranges among adult men receiving health care in North America. MATERIALS AND METHODS. A retrospective review of an institutional electronic database identified adult men undergoing pretreatment clinical FDG PET/CT examinations from March 15, 2013, through March 15, 2018. An FDG PET/CT image review of 700 testicles in 350 male patients was performed. Data collected included testicular SUVmax, SUVmean, and visual PET pattern of uptake. RESULTS. Testicular SUVmean and SUVmax values (mean ± SD) by age group were as follows: 3.1 ± 0.7 and 3.8 ± 0.9 for the age group of 18-30 years; 3.2 ± 0.6 and 4.0 ± 0.8, 31-40 years; 3.1 ± 0.4 and 3.8 ± 0.5, 41-50 years; 3.0 ± 0.5 and 3.7 ± 0.7, 51-60 years; 2.9 ± 0.5 and 3.5 ± 0.7, 61-70 years; 2.8 ± 0.5 and 3.5 ± 0.7, 71-80 years; and 2.6 ± 0.5 and 3.3 ± 0.6, more than 80 years. A statistically significant difference exists between age groups for testicular SUVmean (p ≤ .001) and SUVmax (p < .001), with SUVs peaking in the 4th decade of life and subsequently declining with age. A small but significant negative correlation exists between blood glucose level and testicular SUVmean (r = -0.12). CONCLUSION. This study reports the largest currently known cohort of SUVs in normal testicles and may guide clinical interpretation of testicular FDG activity. Discrepancies in normal SUVs may exist because of differences in patient demographics and PET technology.