Sonomicrometry

Sonomicrometry was originally applied in the study of cardiac function in research animals by Dean Franklin in 1956, and was quickly adopted by biologists working in biomechanics as well as other physiological organ systems and structures (gastro-intestinal, uro-genital and musculo-skeletal).

The primary criteria for making sonomicrometer measurements is that the intervening space or material between the crystals must be capable of ultrasonic sound conduction in the frequency range of 100 kHz to at least several MHz.

In biological settings, almost all tissues have a speed of sound in the range of 1550 to 1600 meters per second, which is satisfactorily uniform to give accurate measurements to within 3% to 4%, and more typically to within 1%.

For example, when making measurements in biological tissue at body temperature (velocity = 1,590 m/s), a digital sonomicrometer operating with a clock speed of 128 MHz will have a spatial resolution of 12 micrometres.

Sonomicrometry crystals are most commonly implanted within skeletal or cardiac muscle tissue to track length changes during an activity (heartbeat, flapping a wing, chewing, etc.).