Implantable Telemetry System

Sometimes it is wanted to implant the telemetry or receiver subcutaneously. Implantable telemetry systems allow the measurement of physiological variables over long periods of time. Here no sensors need to be attached to the body surface. Implantable telemetry is mainly used in animal research and the equipment must be sheltered from the animals. In simple conditions the implantable telemetry system consists of a power supply, transducer which is connected to the transmitter. For long term telemetry, implant telemetry is more helpful. The whole electronic circuit is fully packed as a capsule and then implanted subcutaneously (under skin) or deep in the body. This is called encapsulation unit. Silicon encapsulation is commonly used.

The telemetry transmitters are as small as possible. The weight and size of the batteries must be minimal and the operating lights must be maximal. Once a unit is implanted its service depends on the battery capacity. So the power source is of great importance. Mercury and silver oxide main batteries are used commonly. Depending on the application, the size and capacity of implantable unit battery varies. To save the power, radio frequency switches can be used to turn the system ON and OFF on depending on need. The use of implanted unit also limits the distance of transmission of the signal.

Why PWM is used in multichannel telemetry system?

PWM systems has a high noise immunity.
Techniques are cheaper and less complex than FM system.
PWM is lower sensitive to temperature changes.

Disadvantages of Implant Telemetry

1. One disadvantage of implantable telemetry unit is that the range of the signal is affected by the body fluids and skin which greatly attenuate the signal. For implant telemetry the size and weight limitations are much more serious than other types as heavy units can make the subject comfortless.

2. Some patients may be allergic to external materials and this can also make problems with implantable telemetry.

3. Proper protection of the patients is also a vital factor to be considered. In any means the patient will not be affected by the battery power supply.

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