Low-Attenuation Acoustic Silicone Lens for Medical Ultrasonic Array Probes

35 × 10 6 kg/m 2 sv s.Ztissue = 1.55 × 10 6 kg/m 2 s. In general, the ultrasound is reflected at the boundary with different Z. Moreover, a convex-shaped acoustic lens is attached on top of the acoustic matching layers to focus the ultrasound beam and to ensure good contact to the human body. Specifically, the acoustic lens is used for focusing of the short axis; the elevation dimension determines the effective slice thickness of the image plane. The ultrasound transmission is attenuated in acoustic matching layers, acoustic lens, and human tissue. The acoustic attenuation (α) of the acoustic lens is very important because it is usually thicker than the matching layers. Moreover, α becomes large with increasing frequency; the α of the acoustic lens has a great effect on the sensitivity of a medical ultrasonic probe as well. Silicone rubber has been the predominant acoustic lens material for external focusing since 1974 (Iinuma and Hashiguchi 1974, 1978) because it is safe to use