Assessment of testicular uptake in flourine-18 fluorodeoxyglucose positron emission tomography/computed tomography

The testis shows physiologic uptake in flourine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET). The purpose of this study was to examine the degree of FDG uptake of normal testis on PET/computed tomography (CT), especially in relationship to various clinical parameters. We obtained the maximum standardized uptake value (SUVmax) and the mean standardized uptake value (SUVmean) of each testis from PET/CT of 166 healthy men. We also calculated the testis-to-muscle (T/M) ratio, defined as the SUVmean of the testis divided by the SUVmean of the right thigh muscle. Subjects completed a questionnaire on their medical history and sexual habits, including frequency of sexual intercourse, latest date of sexual intercourse, and vasectomy history. We then evaluated the association between imaging parameters and sexual habits. The mean age of subjects was 48 +/- 10 years (range, 21-74), and the mean volume of each testis was 17.1 +/- 4.5 cm(3) (range, 7.4-32.4). The mean SUVmax was 3.6 +/- 0.5 (range, 2.2-5.5), the mean SUVmean was 2.5 +/- 0.4 (range, 1.6-3.8), and the mean T/M ratio was 4.2 +/- 0.8 (range, 2.3-7.3). Of the 166 subjects, 51 reported having sexual intercourse zero times per month and 109 had sexual intercourse at least per month. The interval between the latest date of sexual intercourse and PET/CT was less than 3 days in 48 subjects; between 3 days and 1 month in 58; and greater than 1 month in 60. Twenty subjects were currently vasectomized. The T/M ratio was significantly correlated with age (P = 0.040) but not with sexual habits. On the PET/CT, normal testicular FDG uptake decreased as age increased. (c) 2012 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 22, 245249, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ima.22029