Solid standards for positron emitters

Abstract

HypothesisPositron Emission Tomography is a well establish technique to obtain physiological information of a patient or a process. In order to guarantee all the benefits of this technique it is important to establish quality control routines on the equipment utilized to perform radioactive measurements, the activimeter. In this way, this paper describes the procedure to obtain solid radioactive standard sources, based on sodium-22, which could be used on performance tests as well as to calibration purposes. The solid standards were prepared using the epoxy resin, as it presents advantages such as chemical stability, compressive strength and low toxicity. Initially, the compatibility between epoxy resins and curing agents with the radioactive materials was evaluated. It was verified that the combination between resin SQ2220 (Redelease) and curing agent SQ3154 (Redelease) was the most adequate in a 2:1 ratio. In addition, an anti-bubble solution (0.5%) was added. Fluorescent dyes were used in order to verify the deposition of the radioactive material throughout the extension of the source. The geometry chosen to prepare the radioactive standards was the penicillin-type glass bottle (10 ml). An analytical balance was used for the accurate determination of the mass of the radioactive material and a vortex mixer for homogenization. Liquid radioactive sources (master solutions) were provided by the National Laboratory of Ionizing Radiation Metrology (LNMRI), Institute of Radioprotection and Dosimetry (IRD/CNEN/Brazil). Through the procedure established on the present work was possible to prepare solid standard sources for positrons emitters adequate to measurements on activimeters. The activity values determined experimentally were compared to the certificated value.