Quantitative Characterization of Tissue Using Ultrasound

Present medical ultrasound systems are based on energy detection methods and therefore only utilize echo intensity information. However, phase, as well as spectral, information is recorded by the transducer, which is a pressure sensitive device, but is not utilized in present display or measurement schemes. This additional information may be of diagnostic significance since the interaction between sound and tissue is exceedingly complex, since many types of tissue can be categorized in terms of their acoustical properties, and since changes in tissue acoustical properties can be correlated with specific pathological states. Thus, in principle, in vivo techniques could be devised which would extract and separate the medically significant features of the ultrasound interactions with tissue and would display ultrasonic tissue signatures appropriate for a differential diagnosis. The development of such quantitative techniques for the measurement of ultrasonic tissue parameters and/or the display of ultrasonic tissue signatures is known as ultrasonic tissue characterization. In this paper we review the physical and clinical basis for ultrasonic tissue characterization, describe several characterization schemes currently being explored, and attempt to assess the importance such techniques may play in the future of diagnostic medicine.