a method of examining the functioning of the gastrointestinal system by means of radio
telemetry. In gastrointestinal telemetry, a patient swallows a miniature radio transmitter, or endoradiosonde, which generates electromagnetic oscillations. As the endoradiosonde passes through the gastrointestinal tract, effects of physiological, physical, and chemical phenomena give rise to frequency modulation of the oscillations, which are detected by a radio receiver (Figure 1).
The oscillators of endoradiosondes operate in the frequency band from 300 to 450 kilohertz (kHz) or from 1,800 to 2,000 kHz. Endoradiosondes for the determination of temperature, pressure, or pH are manufactured (Figure 2).
The movement of an endoradiosonde makes it possible to observe processes that occur in all divisions of the gastrointestinal tract. A thread is sometimes attached to an endoradiosonde; the thread inhibits the movement of the device, for example, from the stomach to the duodenum. The location of an endoradiosonde is determined by means of fluoroscopy or radio direction finding.
Gastrointestinal telemetry does not disturb normal digestive processes.