Advances in ultrasound: from microscanning to telerobotics.

This paper is in memory of W V Mayneord (1902-1988). Experiments conducted in Mayneord's laboratory were amongst the first to show that ultrasound had diagnostic potential. Now, one in every four imaging studies uses ultrasound. Amongst numerous contemporary advances, microscanning is concerned with imaging subcentimetre size volumes of tissue in three dimensions with 10-100 microns resolution. The traditional approach is by pulse echo imaging, with a focused ultrasonic beam in the frequency range 20-100 MHz. This approach may be complemented by ultrasonic CT (to correct for attenuation and speed variations), reflex transmission imaging (to provide attenuation data) and synthetic aperture scanning (to decrease imaging time). Harmonic microscanning may reduce artefacts, and elasticity imaging may also be possible. Microscanning is likely to have applications in pathology and in the operating room, for trackless microintervention, in molecular biology and drug studies, and in experimental imaging of small mammals including, in particular, the mouse. Robotics is the engineering science concerned with devices that are able to execute tasks usually performed by humans. Two procedures, ultrasonically guided biopsy and ultrasonic laparoscopy, are being used to demonstrate the feasibility of telerobotics. The approach is that of telepresence, as distinct from supervisory control or virtual reality. Problems associated with image compression and communications latency are identified. Although incremental developments in medical ultrasound have resulted from clinical pull, major advances have, in general, been due to technical push.