Speaker
Description
In nuclear medicine, radiopharmaceuticals are subject to strict quality and purity controls to ensure both patient safety and the effectiveness of diagnostic or therapeutic procedures. A major concern is the presence of radioactive contaminants, unwanted isotopes that can deliver additional radiation doses. Gamma spectroscopy, typically performed with high-purity germanium (HPGe) detectors, is one of the most common techniques to identify these contaminants due to its excellent energy resolution (2–3% at 1 MeV). However, HPGe detectors are expensive, require cooling, and often need to detect contaminants with activity levels up to three orders of magnitude lower than the primary isotope. This requires long acquisition times to achieve acceptable statistics. Additionally, overlapping gamma peaks from different isotopes can further complicate the identification of contaminants. A promising alternative is beta-gamma coincidence spectroscopy, which allows to select the decaying of a particular isotope by detecting beta and gamma emissions from the same event in a short time window (of the order of ns). The BeGAM project aims to develop a portable and precise detector to identify beta emitters in radiopharmaceuticals through beta/gamma coincidence and anticoincidence measurements. The detector consists of GaGG scintillators for gamma spectroscopy and a central plastic scintillator for beta detection. The current prototype includes four GaGG scintillators arranged around a hollow plastic scintillator, allowing placement of the radioactive sample at the center to maximize the solid angle. Initial tests were performed using a $^{207}$Bi source to evaluate the detector’s ability to perform coincidence measurements between conversion electrons and gamma rays emitted by the source. These measurements served to characterize the system's timing and energy resolution. We are currently starting the commissioning of the prototype with measurements on $^{99}$Mo/$^{99m}$Tc solutions produced by our collaborator at the Azienda Ospedaliero-Universitaria Careggi (AOUC). Solutions with different concentrations of $^{99}$Mo will be prepared to characterize sensitivity and accuracy of the detector in determining low levels of $^{99}$Mo activity.
