Overview of Recent Advancement in Ultrasonic Imaging for Biomedical Applications

This paper discusses the application of acoustic microscopy to the detection of cancerous cells. Acoustic microscopy is a welldeveloped technique but the application to biological tissues is challenging. Acoustic microscopy images abnormality based on the difference in the acoustic impedance from the background. One of the difficulties in the biomedical applications is that since both normal and abnormal cells consist of mostly water, their acoustic impedance is quite close to each other. Consequently, the contrast of the image tends to be low. Another issue is concerning the spatial resolution. For higher resolution, the use of a short wavelength is essential. However, since the attenuation of an ultrasonic signal increases quadratically with the frequency, the reduction in the wavelength compromises the image quality. The present paper addresses these issues and describes various techniques to overcome the problems.