Uptake of 18 F-fluoro-2-deoxyglucose in the Healthy Testes of Young Men as Assessed by Positron Emission Tomography/Computed Tomography; Including the Inter- and Intra-observer Variation

Abstract

Knowledge of the physiological testicular accumulation of 18F-fluoro-2-deoxyglucose (FDG) is essential in order to discriminate between normal and pathological findings. In this study, the 18F-FDG-uptake in healthy testes of young men was assessed using positron emission tomography/computed tomography (PET/CT)-scans. A total of 40 testes of 20 men with a mean age of 26.5 ± 3.9 years were evaluated. 18F-FDG-uptake was expressed as the standardized uptake value (SUV). Testicular volume was measured on CT and PET. All scans were assessed by three researchers, one of whom assessed every scan twice. Laterality indices and inter- and intra-observer variation were evaluated. Correlation between the SUVmax and SUVpeak, between SUVmean and SUVpeak and between age and SUVpeak were assessed. Testes showed an average SUVmax of 3.42 ± 0.61, SUVpeak of 3.06 ± 0.54 and SUVmean of 2.44 ± 0.44. The average testicular volume on CT was 23.0 ± 6.4 ml, whereas on PET it was 18.0 ± 5.1 ml. Laterality indices were calculated of 0.077 ± 0.065 (SUVmax), 0.074 ± 0.066 (SUVpeak), 0.072 ± 0.063 (SUVmean), 0.245 ± 0.259 (CT), and 0.200 ± 0.188 (PET), respectively. Inter- and intra-observer reliability were found to be perfect for the SUVs (intraclass correlation coefficient [ICC] 0.992-1.0), but poor for testicular volumes (ICC 0.854-0.902). Testicular 18F-FDG uptake in young men can be measured accurately on PET/CT and shows high symmetry. Consequently, 18F-FDG PET/CT has the potential to become a useful instrument in the evaluation of the functioning of the individual testis.

Physiologic testicular uptake of 18-F fluorodeoxyglucose in the Indian population

“…Meij-de Vries et al . reported SUV of 3.42 ± 0.61 in a study done on 20 patients the age group of 18–32 years,[ 16 ] that is slightly higher than the SUV observed in our study, probably due to geographical variation. Testicular SUV values observed on 208 patients in the age groups of 41–50, 51–60, and 61–70 years in our study were 2.62 ± 0.0.67, 2.52 ± 0.0.67, and 2.52 ± 1.34, respectively [ Table 1 ].…”

“…reported a positive correlation ( r = 0.349, P < 0.0001) in a study done 20 males with mean of 26.5 ± 3.9 years. [ 16 ] Our study shows a mild positive correlation up to the age of 30 years and a mild negative correlation after the age of 31 years while comparing the age and testicular FDG uptake.…”

“…Varying levels of testicular uptake have been reported in various age groups in different studies. [ 9 15 16 17 18 19 ] Our study showed a testicular SUV of 2.52 ± 0.67 in the age group of 10–20 years [ Table 1 ]. Goethals et al .…”

“…was 22.1 ± 6.4 cm 3 (3.8–41.5)[ 15 ] and by Meij-de Vries was 23.0 ± 6.4 cm 3 (10.2–42.8). [ 16 ] Mean testicular volume reported by Gupta et al ., Huang et al ., Fui MNT et al ., and Anafa et al . was 16.73 cm 3 ,[ 23 ] 16.57 cm 3 ,[ 25 ] 18.0 cm 3 ,[ 26 ] and 18.57 cm 3 ,[ 14 ] respectively.…”

The Independent Functioning of the Orchidopexied Congenital Undescended Testis as Assessed by Positron Emission Tomography/Computed Tomography

“…In a previous study, the normative testicular SUV in 20 young men and found a mean SUV peak of 3.06 ± 0.54 (1.81-4.14) with a high symmetry for both testes was evaluated. [ 19 ]…”