Ultrasound therapy

The beginning of ultrasound therapy came with some experiments by Paul Langevin when he noticed the destruction of a school of fish in the sea when he developed the first commercially available sonar, and pain in his hand when submerged in a water tank that was energized with high intensity ultrasound. He found that the frequency of ultrasound was critical to the application. Raimar Pohlman demonstrated the therapeutic affects of ultrasonic waves at lower frequencies on human tissue in 1938. He introduced ultrasonic physiotherapy in Berlin, noting that the transducer should be limited to 5 W/cm^2, the transducer must be in motion and the bones must be avoided.

During the 1940's ultrasound therapy was claimed by some to be a cure all with no scientific evidence. Some of the claims included conditions such as arthritic pains, gastric ulcers, eczema, asthma, thyrotoxicosis, hemorrhoids, urinary incontinence, and even angina pectoris. Cynicism also abounded and development of it as a cure was delayed for years for more study. The intensity affects on different tissue depths can be found from the equation: I = Ioe^(-alphax) where I is the intensity in tissue at depth x, Ioe is the intensity on the surface, and alpha is the coefficient of absorption. The frequency of the ultrasonic waves will also have an effect on the generation of heat. As the frequency increases, so does the heat. Another equation was discovered: f = 1/T where T is the time period as in simple harmonic motion. Bone and muscle tissue were discovered to absorb more energy, and the longitudinal waves of ultrasound are reflected and transformed into transverse waves, creating a heating effect.

The experiments showed that the frequency range should be kept between 0.8 to 3 megahertz (800 to 3,000 kilohertz). Lower frequencies provide better penetration, up to about two inches depending on the density of the tissue. The sound waves cause tissue to vibrate, creating heat. This deep penetrating heat allows the healing of muscles, tendons, ligaments, joint capsules and bone. This is a type of thermotherapy (heat treatment) that helps relieve some types of acute and chronic pain, and promotes tissue relaxation, therefore it is useful in treating muscle tightness and spasms. It may also be used to treat conditions such as musculoskeletal injuries, arthritis and fibromyalgia. It can stimulate healing without causing irritation, speed metabolism and improve circulation, break up and soften scar tissue and adhesions, reduce chronic inflammation or swelling, enhance the body’s natural healing process, and reduce irritation to nerve roots. It can increase mobility in the joints as well.

Although ultrasound therapy is considered generally safe, potential for burns is possible and consulting a physician is recommended. Possible problems can occur if used too close to a pacemaker, near the abdomen of a woman who is pregnant, over the scull, eyes, heart or reproductive organs. It should be avoided in areas that have cancerous tissue.

Thanks to:

Laura Inverarity, D.O.

Vikas Garg, M.D., MSA

M. Bud Lateef, M.D.

Excerpts from Andre Denier: Les Ultra-sons appliques a la medecine. 1951.