Presentation Authors: Antoni Bochinski*, Arunan Sujenthiran, Majed Shabbir, Gilbert Fruhwirth, Ewelina Kurtys, Tet Yap, London, United Kingdom
Introduction: Positron emission tomography (PET) has traditionally been used in the staging of urological cancer. However, there is now greater interest in its use to evaluate benign conditions. As PET tracer uptake into tissues reflects glucose metabolism, PET imaging of the testis may reveal areas of most active spermatogenesis or hormone production. The aim of this pilot study was to develop a protocol for ï¿¼PET/CT in rats with relation to how this could be performed in further human studies and present data on the efficacy of the adopted imaging method.
Methods: PET aligned with computer tomography (PET/CT) was used to functionally assess the testes of healthy male rats (n=5). The rats were given an intravenous injection of FDG in 3 different doses, rested for 40 min and then scanned for up to 60 mins. Testes uptake was expressed as standardised uptake value (SUV), a widely-used tracer uptake unit, calculated using Vivoquant software (Invicro, Boston, USA). SUV in testes was compared to that of thigh muscles to determine feasibility of this mode of imaging.
Results: The tracer was non-uniformly distributed in all tested rats. SUV in both testes (Mean=2.09; range 1.87-2.54) was significantly higher than that in thigh muscles used as baseline uptake regions (Mean SUV=0.53; range 0.47-0.56)(p- < 0.05). Furthermore, based on the visual assessment of the FDG images, a higher uptake into the epididymis as compared to the remaining region of the testes has been observed, however SUV was not calculated for the epididymis alone.
Conclusions: This pilot study demonstrated tracer uptake into rat testes was significantly higher than into muscle suggesting increased glucose metabolism. It is unclear whether hormonal production and/or sperm cell metabolism are responsible for the uptake, however the visually higher epididymal uptake, where no hormonal production takes place may suggest that the latter is responsible. This is the first study to report such findings and has shown PET/CT to be a potentially ground-breaking tool in the metabolic evaluation of testes for spermatogenesis. It may be useful in targeting TESE surgery and conversely avoiding unnecessary surgery when there is a lack of activity. Plans for a prospective immunohistopathological study, potentially leading to proof-of-concept, as well as human study are described.