Ultrasound for Small Things: Imaging and Interention at the Cellular Level

Ultrasound scanning is very well established for routine medical imaging: with a minimum wavelength of the order of 100 m, observation of most gross anatomy is possible. However, at smaller wavelengths, ultrasound offers useful tradeoffs between penetration and resolution for many more detailed observations ranging from small animal anatomy and structure of human epithelia down to subcellular features. Its technological realisation also has potential benefits compared with other imaging techniques, though still with many outstanding challenges in microengineering. This talk will first review the state of the art in technology and imaging at high resolution. Recently, ultrasound has also found growing interest in intervention, i.e. its use for remote actuation and surgery at a distance. Here, the same path from low to high resolution is being followed, and technological advantages and challenges are being identified. Focused ultrasound surgery will be discussed first in this area, then the focus of the talk will move to ultrasonic tweezing and targeted drug delivery. For both imaging and intervention, as the ultrasonic wavelength is shortened, the parallels and interaction with optical techniques become clearer; the talk will finish with discussion about how far this process can go.