Acoustic microscopy

At this week’s First Pan American/Iberian Meeting on Acoustics in Cancun, researchers presented results on acoustic microscopy, a burgeoning technique that could provide new kinds of medically useful information on biological tissue. Unlike many other microscopy techniques, acoustical microscopy can be performed on living tissue and even inside the body, with the use of small ultrasound probes. And unlike optical microscopy of biological specimens, acoustic microscopy does not require tis sue staining.

In the technique, an ultrasound probe makes contact with a tissue sample, then yields an image based on how the tissue responds to the ultrasound. Although the resolution of acoustical microscopy is ultimately limited to about the cell level, rather than the molecular level (its maximum resolution is about 0.1 microns, about a hundredth of the width of a red blood cell), it can provide unique information on a biological tissue’s mechanical properties. For many materials, the mechanical properties have a wider range of values than the optical properties, so the technique could come in handy for characterizing Alzheimer’s plaques, to name one example. In principle, an acoustic microscope could also yield quick assessments on the pathology of skin lesions, without a biopsy and long before other techniques could provide information.

At the meeting, researchers described how acoustic microscopy is already advancing cardiology, specifically in the area of intravascular ultrasound (IVUS), in which a small ultrasound camera is threaded into the body to detect artery blockage. Using a scanning acoustic microscope to gather basic data on artery plaque, Yoshifumi Saijo of Tohoku University (saijo@idac.tohoku.ac.jp) and his colleagues are helping clinicians better interpret IVUS images. Employing knowledge from acoustical microscopy, Ton van der Steen (vandersteen@tch.fgg.eur.nl) of the Erasmus Medical Center in the Netherlands and colleagues have developed a clinical technique called IVUS elasticity imaging, which can detect vulnerable artery plaques, a hard-to-catch condition which kills up to 250,000 people every year in the US alone. (Session 1pBB at the meeting; Background information at http://www.acoustics.o rg/press/144th/Jones.htm and http://www.eur.nl/fgg/thorax/ela sto/)