[18F]flor üretiminde kullanılan [18O]H2O'in saflaştırılması ve analizi

Abstract

[18F]fluoride is a positron emmitting radioisotope which is used in nuclear medicine for scanning. It is produced in particle accelerators (cyclotron) by proton bombardment of 18O enriched water (%95-97). [18F]fluoride obtained from the cyclotron is put in a chemical form which is taken up by the targeted organ in the body for imaging. Irradiation and chemical synthesis cause 18O enriched water to be polluted. These impurities can damage the cyclotron target and decrease the [18F]flor yield when it is used again for bombardment. Because of its high cost,using purified irradiated water is more advantageous than buying fresh [18O]H2O.In this study, analysis of organic impurities was performed by gas chromotography (GC), analysis of ionic impurities was performed by ion chromotography and atomic absorption spectroscopy (AAS) and analysis of radionuclidic impurities was performed by multi channel analyser (MCA). Results of the analysis show that amount of ionic impurities was in specification limits and radionuclidic impurities didn?t exist. For removing defined organic impurities in irradiated [18O]H2O, ozonation, ultrasonication, UV and distillation methods were used. These methods were applied separately and combined.The methods that were used for removing organic impurities, were applied to prepared model solutions. With four hours ozonation that applied to model solutions, complete acetone, 35 % of ethanol, 90 % of acetonitrile was removed. But when organic compounds were oxidized, CO2 and H2O were formed. Forming H2O is a disadvantage because it decreases O-18 concentration in [18O]H2O. To see the effects of ozonation to O-18 concentration, this method was applied to irradiated [18O]H2O. During the ozonation, in defined periods samples were taken. O-18 concentration in taken samples was determined by gravimetric analysis and it was decided that optimum ozonation period was 10 minutes. Ultrasonication method was applied to model solutions and 60 % of acetone, 10 % of ethanol and 40 % of acetonitrile were removed. Method was applied to irradiated [18O]H2O sample and determined O-18 concentration by gravimetric analysis. Results of the analysis showed that ultrasonication method didn?t change the O-18 concentration so much. Distillation method was applied to irradiated [18O]H2O samples. Due to material loss, distillation was applied after ozonation and ultrasonication for the impurities which can?t be removed by only ozonation and only ultrasonication. It was observed that all of the organic impurities were removed by ozone+distillation and ultrasonication+distillation methods but it requires that a serial distillation because of material loss. By ozone+ultrasonication method with a little decrease of O-18 concentration, acetone and acetonitrile removed completely and 30 % of ethanol removed.It is decided that ozone+ultrasonication is the most appropriate method to purify irradiated [18O]H2O. [18F]fluoride and [18F]FDG were produced by the [18O]H2O that is purified by this method. 69 % [18F]FDG yield was observed by purified [18O]H2O and 72 % [18F]FDG yield was observed by fresh [18O]H2O. These results show that irradiated [18O]H2O can be used after removing impurities.