Acoustic Field of a Medical Ultrasound Probe Operated in Continuous-Wave Mode Investigated by TV Holography

Time-averaged TV holography has been shown to be a useful technique for investigating acoustic fields in transparent media. The theory of time-averaged TV-holography measurements of ultrasonic fields in water is described. Projections of the phase and the amplitude of a 3.25-MHz ultrasonic field from an annular ultrasound probe operated in cw mode are presented. Quantitative measurements with a spatial resolution of better than 100 mum have been obtained. A set of such projections may be processed into a three-dimensional mapping of the phase and the amplitude of the acoustic field by tomographic techniques. This process is described, and an example of a tomographic reconstruction of the same ultrasonic field is presented.