Sensitive measurement of positron emitters eluted from HPLC

For sensitive analysis of the radioactive-metabolite in human PET, a radio- HPLC system coupled to a newly designed positron detector was constructed. The detector had the advantages of low noise level (1.7 +/- 1.0 cpm) and hi gh sensitivity (32 +/- 1%) due to coincidence counting and large EGO crysta ls. Furthermore, the detector was easy to move, since a pair of the EGO hou sings coupled to photomultipliers was effectively arranged in parallel and a HPLC cell with different volume could be inserted between the EGO housing . This radio-HPLC system was useful for analyzing samples with low radioact ivity. It was applied to the measurement of [C-11]FLB457 in plasma, having high affinity and high selectivity with dopamine D2 receptors. Extremely lo w radioactivity of [C-11]FLB457 (2500 dpm) could be analyzed by using the r adio-HPLC system. The performance of this detector was compared with those of commercially available systems that had been used as sensitive detectors for HPLC. (C) 2001 Elsevier Science Ltd. All rights reserved.