Assessment of radionuclide impurities in [18F]fluoromethylcholine ([18F]FMCH).

PURPOSE: [18F]Fluoromethylcholine ([18F]FMCH) is a radiopharmaceutical used in positron emission tomography (PET) imaging for the study of prostate, breast, and brain tumors. It is usually synthesized in cyclotron facilities where 18F is produced by proton irradiation of [18O]H2O through 18O(p,n)18F reaction. Due to the activation of target materials, the bombardment causes unwanted radionuclidic impurities in [18O]H2O, that need to be removed during the radiopharmaceutical synthesis. Thus, the aim of this study is to quantify the radionuclide impurities in the 18F production process and in the synthesized [18F]FMCH, demonstrating the radionuclidic purity of this radiopharmaceutical. METHODS: Long-lived radionuclide impurities were experimentally assessed using high-resolution gamma and liquid scintillation spectrometries, while short-lived impurities were monitored analyzing the decay curve of the irradiated [18O]H2O with an activity calibrator. As spectrometric radionuclide library, a Geant4 Monte Carlo simulation of the 18F-target assembly was previously performed. RESULTS: 3H, 52,54Mn, 56,57,58Co, 95m,96Tc, 109Cd, and 184Re were found in the irradiated [18O]H2O, but no radionuclide was found in the non-irradiated [18O]H2O neither in the final [18F]FMCH solution with an activity concentration greater than the minimum detectable activity concentration. A total impurity activity <6.2 kBq was measured in the irradiated [18O]H2O, whereas a [18F]FMCH radionuclide purity >99.9999998% was estimated. Finally, the decay curve of the irradiated [18O]H2O revealed a very low maximum of 13N activity (<0.03% of 18F) even immediately after the end of bombardment. CONCLUSIONS: This study demonstrated the radionuclidic purity of [18F]FMCH according to the EU Pharmacopeia.

Natural radionuclides measurements and total dose indicative evaluation in drinking waters of an Italian central region.

A study of radioactivity content in drinking waters collected in some areas of geological interest in an Italian central region was performed to check the compliance with recent European regulations. Gross alpha and beta activities, 226Ra, 238U, 234U, 210Po and 3H concentrations were measured. Gross alpha and beta, 226Ra and 3H activities were determined using an ultra-low-level scintillation counter, 238U, 234U and 210Po by alpha spectrometry after radiochemical separation. Recommended WHO guideline activity concentrations for drinking water were exceeded in 6 cases for gross alpha activity and were not exceeded in any case for gross beta activity. Tritium concentration was always lower than MDA (6.75 Bq L(-1)); the concentrations (mBq L(-1)) of 226Ra, 238U, 234U and 210Po ranged from <1.80 to 23.00, from 1.20 to 140.00, from 1.60 to 120.00 and from 0.25 to 5.90, respectively. Due to the importance of the water in human diet, the doses were calculated for children and adults using the dose coefficient factors reported by EC Directive 96/29 EURATOM and annual water intake; all samples furnished a dose lower the reference level for drinking water (0.1 mSv y(-1)).

Radioactivity measurements and radiation dose evaluation in tap waters of Central Italy.

Consumption of drinking water is very important for human nutrition and its quality must be strictly controlled. A study of radioactivity content in tap water samples collected in the Central Italy was performed in order to check the compliance with recent European regulations. Gross alpha and beta activity, 226Ra, 238U and 234U concentrations were measured. Gross alpha and beta activities were determined by standard ISO 9696 and ISO 9697; for 226Ra determination liquid scintillation was used. 238U and 234U concentrations were determined by alpha spectrometry after separation from matrix by extraction chromatography and electroplating. Recommended WHO guideline activity concentrations for drinking water (0.1 and 1.0 Bq/L for gross alpha and gross beta activity, respectively) are exceeded in two cases for gross alpha activity and are not exceeded in any case for gross beta activity. The concentrations (mBq/L) of 226Ra, 238U and 234U ranged from <1.70 to 15.3, 0.65 to 48.8 and 0.780 to 51.5, respectively. Effective dose due to the uranium isotopes and radium was calculated for children and adults using the dose coefficients reported by EC Directive 96/29 EURATOM and annual water intake. For all class ages, the doses are quite similar and much lower than 0.1 mSv/year.