Acoustic microscopy in medicine

At last December’s First Pan American/Iberian Meeting on Acoustics in Cancún, Mexico, researchers presented results on this burgeoning technique, which could provide new kinds of medically useful information on biological tissue. To achieve microscopic resolution, acoustic frequencies of 1 GHz or higher are needed; the more familiar medical ultrasound imaging is typically done at 30 MHz or less. Unlike optical microscopy, which uses stains to examine the chemical nature of biological specimens and usually requires tissue removal, acoustic microscopy examines the mechanical nature of tissue and can even be performed inside the living body. The mechanical properties of many materials, including biological tissue, have a wider range of values than the optical properties, so the technique could come in handy for quickly assessing tissue pathologies without the need for biopsy. 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 Japan’s Tohoku University and his colleagues are helping clinicians better interpret IVUS images. Meanwhile, at the Erasmus Medical Center in the Netherlands, Ton van der Steen and his colleagues have developed a clinical technique called IVUS elasticity imaging, which can detect vulnerable artery plaques, a hard-to-catch condition that kills up to 250 000 people every year in the US alone.