Verena Pichler1, Thomas Zenz2, Cécile Philippe2, Chrysoula Vraka2, Neydher Berrotéran-Infante2, Sarah Pfaff2, Lukas Nics2, Marius Ozenil2, Oliver Langer3, Matthäus Willeit4, Tatjana Traub-Weidinger2, Rupert Lanzenberger4, Markus Mitterhauser5, Marcus Hacker2, Wolfgang Wadsak6. 1. Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria. Electronic address: verena.pichler@meduniwien.ac.at. 2. Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria. 3. Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria; Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria; Center for Health and Bioresources, AIT Austrian Institute of Technology GmbH, Seibersdorf, Austria. 4. Department of Psychiatry and Psychotherapy, Division of General Psychiatry, Medical University of Vienna, Vienna, Austria. 5. Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria; Ludwig-Boltzmann-Institute Applied Diagnostics, Vienna, Austria. 6. Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria; CBmed GmbH - Center for Biomarker Research in Medicine, Graz, Austria.
Abstract
INTRODUCTION: Radiochemists/radiopharmacists, involved in the preparation of radiopharmaceuticals are regularly confronted with the requirement of continuous high quality productions in their day-to-day business. One of these requirements is high specific or molar activity of the radiotracer in order to avoid e.g. receptor saturation and pharmacological or even toxic effects of the applied tracer for positron emission tomography. In the case of 11C-labeled radiotracers, the reasons for low molar activity are manifold and often the search for potential 12C-contaminations is time-consuming. METHODS: In this study, diverse 12C-contaminations were analyzed and quantified, which occurred during >450 syntheses of six PET tracers using [11C]CO2 or [11C]CH3I generated via the gas phase method in a commercially available synthesizer. Additionally, non-radioactive syntheses were performed in order to identify the origins of carbon-12. RESULTS: The manifold contributions to low molar activity can be attributed to three main categories, namely technical parameters (e.g. quality of target gases, reagents or tubings), inter/intralaboratory parameters (e.g. maintenance interval, burden of the module, etc.) and interoperator parameters (e.g. handling of the module). CONCLUSION: Our study provides a better understanding of different factors contributing to the overall carbon load of a synthesis module, which facilitates maintenance of high molar activity of carbon-11-labeled radiopharmaceuticals.
INTRODUCTION: Radiochemists/radiopharmacists, involved in the preparation of radiopharmaceuticals are regularly confronted with the requirement of continuous high quality productions in their day-to-day business. One of these requirements is high specific or molar activity of the radiotracer in order to avoid e.g. receptor saturation and pharmacological or even toxic effects of the applied tracer for positron emission tomography. In the case of 11C-labeled radiotracers, the reasons for low molar activity are manifold and often the search for potential 12C-contaminations is time-consuming. METHODS: In this study, diverse 12C-contaminations were analyzed and quantified, which occurred during >450 syntheses of six PET tracers using [11C]CO2 or [11C]CH3I generated via the gas phase method in a commercially available synthesizer. Additionally, non-radioactive syntheses were performed in order to identify the origins of carbon-12. RESULTS: The manifold contributions to low molar activity can be attributed to three main categories, namely technical parameters (e.g. quality of target gases, reagents or tubings), inter/intralaboratory parameters (e.g. maintenance interval, burden of the module, etc.) and interoperator parameters (e.g. handling of the module). CONCLUSION: Our study provides a better understanding of different factors contributing to the overall carbon load of a synthesis module, which facilitates maintenance of high molar activity of carbon-11-labeled radiopharmaceuticals.