There were a variety of offshoots from the medical research. For example, some burglar alarms and fish locators make use of ultrasound. Medical uses other than for therapeutic purposes, says Porter, include pulse-echo diagnostic imaging, doppler shift detection of blood flow velocity, and surgical techniques such as cataract removal and tumor irradiation. There is a basic difference between sound waves employed in diagnostic ultrasound and those involved in therapeutic ultrasound. The fundamental difference, Porter explains, is that diagnostic equipment is designed to obtain information without intentionally producing a biological effect.
Therapeutic ultrasound is designed to intentionally produce certain biological effects.
The prime difference is in the frequency ranges. Ultrasound is measured in megahertz. One megahertz is one million cycles per second. This is a frequency, says Porter, which is ideal for sound absorption in body tissues. The frequency for diagnostic units might range up to 10 megahertz.