It is difficult to image at high resolution using conventional optics to any reasonable depth below the skin. There are many ways to counteract this and one unique method is called photoacoustic imaging. This method was invented by Lihong Wang at Washington University in St Louis.
The phenomenon of acoustic imaging is fascinating use of engineering, biology and optics. The sample or animal is irradiated with a laser pulse. This is absorbed by the tissue and leads to thermal expansion in the tissue. This thermal expansion is enough to generate acoustic waves that can be detected by an ultrasonic detector. This can be thus used to detect signals from below the normal absorption depth of conventional light in tissue. The images are spectacular. Besides tissue, it is also possible to use photoacoustic imaging in microscopy and that generates beautiful images too.
The clinical applications have been commercialized by various companies including Endra. Philips, and Visualsonics.
Wang Lab :: Genetics, Washington University in St. Louis (wustl.edu)
