TY - JOUR T1 - Comparison of 18Fcholine and 18Fhomocholine analogues as oncologic PET tracers JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1701 LP - 1701 VL - 53 IS - supplement 1 AU - Dominique Slaets AU - Filip De Vos Y1 - 2012/05/01 UR - http://jnm.snmjournals.org/content/53/supplement_1/1701.abstract N2 - 1701 Objectives 18FCholine is a radiotracer mainly used for prostate cancer imaging. Despite the advantage of a more favorable half-life compared to 11C, 18FCho is more prone to oxidative metabolisation with high urinary clearance as result. In this work, we evaluated 3 new fluorinated Cho analogues as possible oncologic PET tracers, thereby attempting to limit oxidative metabolism. Methods Radiolabeling was performed by adding 18FCH2Br in dry ACN to the precursors (5µL). The reaction was stopped by adding 6%NH4OH and purified on a WCX cartridge. Elution was performed with saline. The reaction yields were calculated and (radio)chemical purity was determined by HPLC. The tracer uptake was evaluated in PC3 cell suspension and data is expressed relative to 18FDG uptake. A tracer uptake inhibition experiment was performed by co-incubation of the radiotracers with a 15mM Cho solution. Then, a tracer release experiment was performed by re-incubation of the cells with a hypoosmotic solution. Finally, a biodistribution experiment was performed on xenograft mice. Results 18Fhomocholine ([18F]FHCho) shows an uptake (125.7%) higher than 18FDG (100%) and 18FCho (55.3%). Incorporation of alfa and beta-substituents on the propyl chain negatively affected uptake. Co-incubation of radiotracers with a choline solution significantly inhibited 18FCho (0.08%) and 18FHCho (3.7%) uptake, indicating that both tracers are substrates for the choline transporter. A betaine release experiment with a hypoosmotic solution was set up to determine the affinity of the tracer for choline oxidase and to determine the amount of tracer metabolically trapped in the cells. These experiments supported a higher affinity of 18FHCho (42.7%, compared to 27.6% for 18FCho) for the oxidase. Biodistribution studies however indicated no significant differences between both tracers, as even tumor/blood or muscle ratios were not significantly different. Conclusions Therefore, it can be concluded that, despite the large in vitro differences, 18FHCho is not superior than 18FCho for tumor visualization in vivo ER -