Eleventh international symposium on radiopharmaceutical chemistry: Abstracts

Abstract

11C]methyl]temozolomide human injection was 7 pg (range 4-15 pg). For rat studies 37 -11 1Mbq was injected. To support the PET studies a rapid and efficient metabolite analysis method had to be developedwhich took into consideration the difficultim associated with the chemical instabilities of tcrnozolomide and its metabolic products. Temozolomide is stable at acidic pH (<7) and decomposes to MTIC at pH >7; MTIC is stable alkaline pH and spontaneously decomposes to AIC at pH < 7.3 71 6 Symposium AbstractsFollowing i. v. injection of [ 3-N-[ 11C]methyl]temozolomide, serial arterial blood samples from either humans or Spraque-Dawley rats were taken and cell-free plasma was deproteinated using acetonitrile. The mixtures were centrifuged (2000 g , 3 min), supernatants concentrated by rotary evaporation. The residues were re-suspended in the mobile phase and filtered prior to HPLC analysis. A "p" Bondapak c 1 8 ( 30 x 0.78 cm i.d.) column was eluted with the mobile phase containing a mixture of ammonium acetate (0.05 M):acetonitrile (955 v/v) at a flow rate of 3 mL min-1. The eluate was monitored with on line radioactivity and UV detector connected to PC integrator system. Extraction of radioactivity from human or rat plasma into acetonitrile was >98%. Methanol could not be used for deproteinations as it acted as a nucleophile causing ring opening of temozolomide in vitro . Temperatures greater than 40°C during rotary evaporation also caused - 15.Oxygen-18 enriched water is used for the production of fluorine-18 as [18FJfluoride via the 180@,n)lnF nuclear reaction. The yield of 18F is dependent on the degree of enrichment of 1 8 0 in the target water. If the irradiated 180-water is purified and reused, then a gradual