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Silicone-based polymer composites containing high atomic number additives are prioritized for the development of new materials for radiation shielding, due to their mechanical, thermal, electrical, and multifunctional properties. The X-ray attenuation properties, as well as mechanical properties, of the newly developed-lead-free multi-layered structures for radiation shielding, based on silicone composite layers containing tin, cerium oxide, tungsten oxide, and bismuth additives, are analyzed and discussed in this paper. It is shown that, by varying the additive concentrations in silicone composites, lead-free and flexible layered structures, exhibiting lead-equivalent X-ray shielding, can be fabricated.

Tungsten-cobalt (W-Co) alloy nanoparticles have been synthesized from aqueous electrolyte by the sonoelectrochemical method applying the pulsed potential mode and continuous ultrasound irradiation. Simple electrochemical synthesis technique with the integrated ultrasonic bath (ultrasonic frequency 38 kHz, effective ultrasonic power 80 W) as the ultrasound source was used for this purpose. The shape and surface morphology of the synthesized W-Co nanoparticles were determined by transmission and scanning electron microscopy, as well as composition of W-Co nanoparticles was assessed by energy dispersive X-ray spectroscopy. The size of synthesized W-Co nanoparticles was investigated in detail by photon correlation spectroscopy. It was found that the size of produced spherical W-Co nanoparticles varied from 100 to 500 nm, and the average atomic ratio of W and Co in nanoparticles was 23:4 correspondingly. The non-uniformity of synthesized particles in size and the reasons for that are discussed on the basis of the obtained results.

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National diagnostic reference levels (DRLs) are an essential tool for optimizing protocols and protecting patients from an unjustified radiation exposure. The aim of this study was to conduct a nationwide survey of adult patient doses received from nuclear medicine procedures and update national DRL values for most common procedures. Data on the radioactivity administered to standard adult patients was collected from all Lithuanian hospitals, using in practice nuclear medicine applications, between 2017 and 2022. Twelve of the most commonly performed nuclear medicine diagnostic procedures: myocardial perfusion scintigraphy (two parts), thyroid scintigraphy, lung perfusion scintigraphy, bone scintigraphy, dynamic renal scintigraphy (divided into two procedures), parathyroid scintigraphy, hepatobiliary scintigraphy, lymphoscintigraphy, neuroendocrine tumor scan, oncology PET/CT imaging were included. The 75th percentile of dose the distribution was estimated for establishing national DRLs. During data collection period, the nuclear medicine imaging equipment were upgraded. The procedures were completed with 12 SPECT and SPECT/CT gamma cameras (two with CZT detectors), 2 cardiac-centred gamma cameras with CZT detectors and 2 PET/CT scanners. Data was collected on 7979 administered activities to the patients. For each procedure, depending on its frequency, 50 to 580 administered radiopharmaceutical activities were selected. Based on the collected data, national DRLs were updated in 2021 for three procedures. A large part of procedures were performed with scanners manufactured between 2008 and 2011. In the past few years, the main Lithuanian hospitals that provide nuclear medicine services have updated their SPECT/CT systems. In the future, the data collection process should be continued in order to reassess DRLs with respect to new scanning systems (e.g. with a CZT detectors and newer PET/CT technology). Variations in the prescribed radiopharmaceutical activities showed that optimization and harmonization procedures may be performed in some hospitals.