Yttrium-90 (90Y) has been widely used in therapeutic nuclear medicine including in the selective internal radiation therapy with 90Y-microsphere. In the procedure 90Y source is protected within the radiation shielding apparatus made of perspex. However, bremsstrahlung radiation may be generated when 90Y interacts with matter. The aim of this study was to evaluate bremsstrahlung radiation produced from radiation shielding apparatus using a scintillation detector and Monte Carlo simulation. The 90Y source in glass vial was placed in the radiation shielding apparatus. Bremsstrahlung measurement and spectrum were performed and recorded using thallium-doped sodium iodide (NaI(Tl)) scintillation detector. Counting time and distance between the detector and apparatus were varied to obtain the optimal condition for bremsstrahlung measurement. Monte Carlo N-Particle (MCNP) 5 was used to simulate bremsstrahlung radiation with the same geometry used in the measurement. For experimental measurement results, the optimal distance and counting time were 10 cm and 120 s, respectively. Although the result of bremsstrahlung spectrum from the detector and simulation exhibited similar trend, markedly greater count rate was observed in simulations than in detector measurements. In conclusion, 90Y bremsstrahlung can be produced from radiation protection apparatus and this can be evaluated by either measurement or simulation.

Selective internal radiation therapy using an 90Y labelled microsphere is increasingly used to treat hepatocellular carcinoma. Based on its properties, 90Y can produce bremsstrahlung radiation which is essential for post-treatment localisation and dosimetry. However, bremsstrahlung radiation could lead to an increase of radiation exposure of radiation workers. The aim of this work was to determine the 90Y bremsstrahlung radiation produced from the polymethyl methacrylate radiation shielding apparatus using the Monte Carlo simulation. A scintillation detector with a 137Cs standard source was used to validate the Monte Carlo simulation. After validation, the 90Y bremsstrahlung photons spectrum produced from the radiation shielding apparatus was simulated. The radiation equivalent dose rates to the head, neck, body, lower extremities at a distance of 30 centimeters, and finger (contact with the knob) were estimated to be 4.9 ? 0.6, 6.2 ? 0.1, 18.9 ? 0.4, 13.1 ? 0.6, and 3900 ? 50 ?Svh?1, respectively. The corresponding annual doses exceeded the limit when radiation workers performed 2631, 1563, 769, and 515 cases per year with contact the knob 3, 5, 10, and 15 minutes per case, respectively. The simulation result showed that radiation exposure of radiation workers and the number of selective internal radiation therapy procedures performed should be considered.