Abstract. In the 'thermo-acoustic sensing technique' (TAST), a burst of sound, called the 'thermometer' beam, is passed through tissue and its transit time is measured. A focused sound field, called the heating field, then warms a small volume in the path of the thermometer beam, in proportion to the absorption. Finally, the thermometer beam burst is repeated and its transit time subtracted from that of the initial thermometer burst. This difference measures the velocity perturbation in the tissue produced by the heating field. Experiments on a fixed human brain showed an ability to distinguish between various tissue types combined with a spatial resolution of better than 3 mm. Should predictions based on the data and theory prove correct, TAST may become a non-invasive alternative to biopsy. The basic theory, predictions of signals from interesting tissues, potential applications and foreseeable problems are presented.

Print publication: Issue 2 (March 1977)