The radiometer is a sensitive, passive microwave receiver that is used to measure the natural emissions from the human body. The magnitude of those emissions, considered to be thermal noise, increases as the temperature increases. The radiometer senses these changes in emissions, and when compared with a built-in precision reference, provides an accurate measurement of temperature.
Conventional temperature sensors, such as thermocouples or thermistors, measure the material at the point of contact. These sensors, particularly when surface cooling is required, will not indicate the temperature of the target tissue during the ablation procedure. The microwave radiometer, on the other hand, measures the temperature at depth, namely the average temperature of the volume of tissue as defined by the pattern of the antenna.
The microwave receiving pattern of the antenna lies within the RF ablation heating field, i.e. the target tissue. Contained within the catheter tip is a unique and passive diplexer, which provides the ability to isolate, or separate, the sensitive receiver from the power associated with the RF transmitter. The diplexer allows the transmitter and the receiver to simultaneously share a common antenna.