RF imaging is best known in the context of radar systems, but RF diagnostic imaging and measurement systems have also been developed for medical applications. For example, U.S. Patent Application Publication 2008/0169961, whose disclosure is incorporated herein by reference, describes computerized tomography using radar, which may be used for generating an image of living tissue.
As another example, U.S. Patent Application Publication 2009/0299175, whose disclosure is incorporated herein by reference, describes a method and apparatus for determining and tracking the location of a metallic object in a living body, using a radar detector adapted to operate on a living body. Applications described in this publication include determination of the extent of in-stent restenosis, performing therapeutic thrombolysis, and determining operational features of a metallic implant.
Yet another example is U.S. Pat. No. 5,766,208, whose disclosure is incorporated herein by reference. This patent describes a non-acoustic pulse-echo radar monitor, which is employed in the repetitive mode, whereby a large number of reflected pulses are averaged to produce a voltage that modulates an audio oscillator to produce a tone that corresponds to the heart motion. The monitor output potential can be separated into a cardiac output indicative of the physical movement of the heart, and a pulmonary output indicative of the physical movement of the lung.
U.S. Pat. No. 4,926,868, whose disclosure is incorporated herein by reference, describes a method and apparatus for cardiac hemodynamic monitoring based on the complex field amplitudes of microwaves propagated through and scattered by thoracic cardiovascular structures, particularly the heart chambers, as a function of time during the cardiac cycle. The apparatus uses conformal microstrip antennas that operate in the UHF band. The basic measurement technique is vector network analysis of the power wave scattering parameter.
U.S. Patent Application Publication 2009/0240133, whose disclosure is incorporated herein by reference, describes a radio apparatus and method for non-invasive, thoracic radio interrogation of a subject for the collection of hemodynamic, respiratory and/or other cardiopulmonary related data. A radio transmitter transmits an unmodulated radio interrogation signal from an antenna into a subject, and a radio receiver captures, through the antenna, reflections of the transmitted radio interrogation signal returned from the subject. A Doppler component of the reflections contains the data that can be extracted from the captured reflections.