As the incidence of breast cancer increases, concerns about unnecessary exposure to radiation during mammography
are increasing. This study quantitatively evaluated the thickness and weight showing 95 % shielding
ability of silicon, lead, bismuth, and tungsten with a tube voltage of 30 kVp and a distance between the X-ray
tube and shield of 100 cm using Geant4 Application for Tomographic Emission (GATE). The absorbed dose to
the breast was derived when the optimal shield derived from GATE was used using Monte Carlo N-Particle
code. The optimal thickness was in the order of tungsten, lead, bismuth, and silicon, and the total weight was
found in the order of bismuth, lead, tungsten, and silicon. There was no difference in the absorbed dose to the
breast depending on the material. When considering the thickness and weight of the shield, lead appears to be
the best material. Lead can be an optimal shield with reduced thickness and weight if it is wrapped with a minimum
amount of silicon.