Objective: We determined the glucose metabolism and computed tomographic (CT) density of the normal prostate gland in relation to age and prostate size on [F-18] fluorodeoxyglucose positron emission tomography (PET)-CT.
Methods: We determined the CT density (Hounsfield Units, HU) and glucose metabolism (standardized uptake value, SUV) of the normal prostate in 145 men (age range 22-97 years) on PET-CT scans which were performed for indications unrelated to prostate pathology. Correlations among SUV, HU, prostate size, and age were calculated using Pearson's correlation coefficients, scatter plots, and linear regression trend lines. The SUV and HU values were also compared among different primary cancer types using the Kruskal-Wallis test.
Results: The population average and range of the normal prostate size were 4.3 +/- 0.5 cm (mean +/- SD) and 2.9-5.5 cm, respectively. The population average of mean and maximum CT densities was 36.0 +/- 5.1 HU (range 23-57) and 91.7 +/- 20.1 HU (range 62-211), respectively. The population average of mean and maximum SUV was 1.3 +/- 0.4 (range 0.1-2.7) and 1.6 +/- 0.4 (range 1.1-3.7), respectively. Mean SUV tended to decrease as the prostate size increased (r = -0.16, P = 0.058). Higher mean HU was correlated with higher mean SUV (r = 0.18, P = 0.033). The strongest association was observed between age and prostate size. The prostate gets larger as age increases (r = 0.32, P < 0.001). Prostate mean SUV, max SUV, mean HU, and max HU were not significantly different among different types of primary cancers.
Conclusions: Although the normal prostate size increases with age, it does not significantly affect the gland's metabolism and CT density, and therefore age-correction of these parameters may be unnecessary.