5H-1 Effects of Fine Metal Oxide Particle Dopant on the Acoustic Properties of Silicone Rubber Lens for Medical Array Probe

The effects of fine metal oxide particles, particularly those of high density elements (7.7 to 9.7 times 10³ kg/m³), on the acoustic properties of silicone rubber have been investigated, in order to develop an acoustic lens with a low acoustic attenuation. Silicone rubber doped with Yb₂O₃ powder having nanoparticle size of 16 nm showed a lower acoustic attenuation than silicone rubber doped with powders of CeO₂, Bi₂O₃, Lu₂O₃ and HfO₂ . The silicone rubber doped with Yb₂O₃ powder showed a sound speed of 880 m/s, an acoustic impedance of 1.35 times 10⁶ kg/m²s, an acoustic attenuation of 0.93 dB/mmMHz and a Shore A hardness of 55 at 37degC. Although typical silicone rubber doped with SiO₂ (2.2 times 10³ kg/m³) shows a sound speed of around 1000 m/s, heavy metal oxide particles decreased the sound velocities to lower than 930 m/s. Therefore, an acoustic lens of silicone rubber doped with Yb₂O₃ powder provides increased sensitivity because it realizes a thinner acoustic lens than is conventionally used due to its low sound speed. Moreover, it has an advantage in that a focus point is not changed when the acoustic lens is pressed to a human body due to its reasonable hardness