Development of the radiopharmaceutical ¹⁸F-acetate for detection of primary tumours through PET/CT

PET / CT (positron emission tomography / computed tomography) is a device that combines the features of diagnostic nuclear medicine (PET) and Radiology (CT) superimposing metabolic (PET) and anatomical (CT) images. By combining the two technologies examinations, the PET/CT scan allows physicians to diagnose more accurately and identify cancer, heart disease and brain disorders. The radiopharmaceutical ¹⁸F-FAc (fluoroacetate) is promising for application in detection of primary tumors of prostate and breast, using PET-CT techniques. Recent studies are showing the efficacy of the ¹⁸F-FAc in the detection of tumors that have low uptake of ¹⁸F-FDG (fluorodeoxyglucose). The fluoroacetate is a substrate for the enzyme acetyl-CoA synthase that metabolizes acid fluorcitric that, not being metabolized, causes inhibition of aconitase and inhibition of tricarboxylic acid. The aim of this work was to develop a positron emitting radiopharmaceutical, ¹⁸F-FAc at IPEN-CNEN/SP in agreement with Hospital AC-Camargo/ São Paulo. The ¹⁸F-fluoride ion was produced using the Cyclone 30 and 18 cyclotrons from IBA located at IPEN-CNEN/SP, by irradiating enriched ¹⁸O water with protons with integrated dose 30μAh. The labelling of ¹⁸F-FAc was performed in a synthesis module TRACERlab MXFDG (GE), using kits purchased from ABX. The radiochemical quality control of ¹⁸F-FAc was performed by Thin Layer Chromatography using TLC-SG 25 aluminium sheets strips (1.5 x 12 cm) and chloroform:methanol (1:1) as the solvent. For the radionuclidic quality control, samples of ¹⁸F-FAc and ¹⁸F-Fluoride were analysed by gamma-ray spectroscopy. The evaluation of the residual solvents was performed by gas chromatography and the analysis of kryptofix was performed by TLC using TLC-SG strips, methanol:chloroform (9:1) as solvent and kryptofix 2.2.2 standards. Biodistribution studies were performed with ¹⁸F-FAc injected into healthy Swiss mice. A reliable procedure was developed for preparation of ¹⁸F-FAc with a labelling yield of 37% (uncorrected) and 52% (corrected for decay) and stability of 19 hours. The quality control analysis showed that the product had the proper requirements for use, with radiochemical purity exceeding 99.9%.The biodistribution studies in healthy animals showed the expected uptake results in all the measured organs with intestinal and renal elimination. (author)