Ultrasound Computed Tomography: From the Past to the Future

摘要

Current focus in ultrasonic imaging, particularly for medical applications, is to develop procedures adding functionality in addition to the morphology contained in the images conventionally obtained. In this context, it has always been the goal of ultrasonic imaging to grade lesions when tissue had been detected as being suspicious for cancer. New strategies for advanced ultrasonic applications include quantification on a rather molecular level (molecular imaging), determination of blood flow through vessels oriented arbitrarily in space and not aligned along the axis of the interrogating ultrasound beam. Furthermore, estimating tissue perfusion by means of ultrasonic contrast agents is within the focus of current research. These goals for more functionality can only be achieved, if appropriate parameters can be mapped quantitatively in 2D maps or 3D volumes. Since computed tomography (CT) a priori reveals material properties quantitatively it appears worthwhile to revisit ultrasound computed tomography (UCT) in context with these future tasks. However, this presentation to follow does not intend to be a complete summary of the various attempts to solve this ambitious problem and its various degrees of abstraction and assumptions made to succeed, it rather intends to sketch some procedural basics which where developed during the phase of implementing UCT as a diagnostic tool allowing to obtain quantitative images. With some exemptions the presentation is confined to the quantitative estimates of sound field parameters such as attenuation and velocity obtained by transmission tomography. It is hoped, that looking back to an exciting decade of UCT research may assist in solving upcoming problems.