Tissue Information from Ultrasound Scattering

Abstract

Medical ultrasound is now progressing beyond its initial, and successful, phase, wherein its principal purpose was to provide adequately high resolution (in both space and time) images of tissue structure. Increasing emphasis is now being placed on the widely accepted notion that tissue probing with either pulsed or continuous wave ultrasound fields potentially provides more information than is currently displayed in the pulse-echo image. Much justification for this viewpoint (which is commonly stated, without adducing firm evidence) stems from the realization that conventional medical ultrasound images are constructed from a data base which is only a subset of the full data ensemble that is, in fact, measured. Moreover, the measurements, in turn, comprise only a subset of the data that are, in principle, practicably addressed with present day technology. In this sense, ultrasound imaging is probably unique amongst medical imaging modalities. Of course, the mere realization that not all measured data are used for image construction does not, in itself, guarantee that the discarded data contain new, or non-redundant, information. Occasionally, there is also an understandable confusion between the achievement of a “better” (e.g. higher resolution, more displayed dynamic range, etc) image, and the development of techniques that generate perhaps even rather poor images with an intrinsically different (tissue) information content.