Acoustics in Medical Devices: From Diagnostic to Therapeutic

By Peter Cameron, Research & Development Engineer

As a Research and Development (R&D) Engineer, I’m a lot more of the “R” than the “D.” This explains why you’d find me at the 161st meeting of the Acoustical Society of America (ASA) in Seattle this May (For proceedings, see J. Acoust. Soc. Am., Vol. 129, No. 4, Pt. 2, April 2011). Leading researchers in the field from around the world attend the conference. While the scope of the ASA journal covers a wide variety of topics, a significant portion is devoted to biomedical acoustics. Acoustics is a branch of physics dealing with sound and sound waves. In addition to covering the range of audible frequencies, the term “acoustics” covers infrasonic and ultrasonic signals that have frequencies below and above the audible spectrum, respectively.

In the constant endeavor to improve patient safety and comfort, and reduce recovery time, techniques using sound have been sought after for decades now — sound waves propagate in soft tissues and in bone, reaching areas inside the body noninvasively. The pressure oscillations associated with sound can directly affect cells, and the secondary effects of heat and cavitation play significant roles.

What this means for the medical device industry

We all know about ultrasonic imaging of the heart and of unborn babies. While research to improve the quality and capability of ultrasound imaging gets significant attention, the more exciting research is in new therapeutic applications. For example, focused ultrasound has applications in tissue ablation for treating tumors. In this technique, energy in the wave is dissipated in the tissue as heat or at high enough levels that can cause cavitation resulting in mechanical destruction.

In some more recent developments, acoustic technologies have facilitated transdermal drug delivery, localized drug delivery, and have achieved temporary disruption of the blood-brain barrier facilitating drug delivery to the brain. Ultrasound has been used to help dissolve blood clots, remove unwanted fatty tissue, and to heal wounds and fractured bones.

In the future, we’ll see many more therapeutic ultrasound techniques in devices receiving FDA approval. Samir Mitragotri takes a deep dive into this topic in his article, “Healing Sound: The Use of Ultrasound in Drug Delivery and Other Therapeutic Applications,” published in the March 2005 issue of Nature Reviews Drug Discovery. Written a few years back, the article still provides a comprehensive look at the therapies used and explored today. (Copyright forbids us from providing the full article, so you have to pay for anything more than the abstract. While I think the article is worth every dime, this is by no means a promotion to purchase it.)

Aside from other benefits, ultrasound devices can be portable and relatively low cost. They don’t subject the patient to harmful radiation (as X-rays do), and there are no restrictions associated with strong magnetic fields (as with MRIs). So doctors want to keep using them.

In addition to other ongoing research and advancements to improve ultrasound image quality and capabilities, shear-wave elastography received some attention at the ASA meeting. This technique can produce an image indicating the softness or hardness of the tissue, which can be overlaid on a traditional ultrasound image, enabling a doctor to virtually palpate internal tissues.

Super harmonic imaging and photoacoustic imaging were other topics discussed.

Overall, many new biomedical acoustic techniques hold great promise for the medical device industry. Providing concepts through scientific research is the first step. Execution to develop a working device suitable for clinical use is where these new technologies will ultimately take shape and become a reality in improving the health of patients.

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