Dosimetry audits in Taiwan radiotherapy departments.

Objectives: This study examines the practice of the regulation of Standards for Medical Exposure Quality Assurance (SMEQA) in Taiwan based on on-site quality audit for radiation therapy systems from 2016 to 2019. Methods: 81 radiation therapy departments, 141 linacs, 9 γ knife systems, 34 high dose rate brachytherapy systems, 20 Tomotherapys, and 6 Cyberknives were audited yearly. Data collection and analysis for each institute's documents including QA procedure, ion chamber and electrometer calibration reports, and a questionnaire relating to machine type and staffing, were requested first and reviewed by auditors. On-site SMEQA core item measurements, including beam output, beam profile and energy constancy for external beam therapy systems, and the source strength, positioning, and timer accuracy for brachytherapy systems were audited second. More than 300 photon beams and more than 400 electron beams were measured each year. Results: There were approximately 8.9 radiotherapy units per million population, and 1.2 medical physicists per unit in Taiwan. For the output measurements, more than 78 and 75% of the photon beams and electron beams, respectively, from linacs were with deviations within ±1.0%. Photon beams have lower beam quality measurement deviations than electron beams. Including in-plane and cross-plane measurements, more than 90 and 85% photon and electron beams, respectively, were with flatness consistency within 1.0%. All audit measurements were within the SMEQA acceptance criteria. Conclusions: According to SMEQA regulations on-site QA audits were successfully carried out from 2016 to 2019 for all Taiwan radiotherapy units. The measurement results showed high quality machine performance in Taiwan. Advances in knowledge: Dosimetry audits with directly acquired measurement readings have lower uncertainties; allow immediate feedback, discussion, and adjustment in a timely manner. In addition to regulation system establishment and education and training implementation, the machine quality is closely related to machine maintenance implementation.

Cu2O hollow spheres: synthesis, characterization and magnetic property.

Cu2O hollow spheres with thin shells were synthesized using poly(vinylpyrrolidone) (PVP) as the template in deionized water. In this process, CuAc2.H2O was reduced by acerbic acid in the presence of PVP and sodium hydroxide. Techniques, including XRD, XPS, TEM and HRTEM were used to characterize the morphology, structure and composition of the as-prepared nanomaterials. The results revealed that the average diameter of polycrystalline Cu2O hollow spheres is about 200 nm, with the shells as thin as approximately 10 nm. The formation mechanism, of these hollow spheres was studied. Magnetic property of the sample demonstrates a paramagnetic behavior at 15 K, and it might be attributed to the hollow-sphere structure of the diamagnetic Cu2O.

Marginal leakage of different temporary restorations in standardized complex endodontic access preparations.

This study compared the marginal leakage of temporary restorations using Cavit, IRM, zinc phosphate cement (ZPC), and copper bands cemented with ZPC. Standardized complex endodontic access preparations were made in 176 extracted human molars. The teeth were divided into six groups, including positive and negative controls. A Universal matrix system was placed over each tooth before restoration, except in the copper band group, in which teeth were restored with ZPC after copper band cementation. Marginal leakage was evaluated with a binocular microscope after the teeth were immersed in artificial saliva, colored with 2% methylene blue and buffered to neutral pH, at 37 degrees C for various time intervals after thermal cycling. In the experimental groups, the differences in the leakage scores of the Cavit group and the other groups were very marked. The Cavit group presented the least marginal leakage, irrespective of time, whereas more than half the specimens from the IRM, ZPC, and copper band groups displayed severe leakage from day 1.