Patent ID: 8805480

Claim:
A tissue classifying apparatus comprising: a microwave radiation source which outputs microwave radiation having a single stable frequency in the range of 5 to 60 GHz; a cable having a high phase stability under flexure which connects at a first end to the microwave radiation source; a probe which is connected to a second end of the cable, which is fitted with a distal end made from a rigid low loss ceramic which distal end penetrates into biological tissue to deliver the microwave radiation from the microwave radiation source to a region of tissue in direct contact with the distal end of the probe and which produces a reflected signal from the microwave radiation reflected back from the region of the tissue in direct contact with the distal end of the probe; a mixer which receives the reflected signal and a reference signal which is a portion of the output microwave radiation of the microwave radiation source, and which mixer reduces the frequency of the reflected signal and reference signal, the mixer having a first input selectively connected to receive the reflected signal or the reference signal, a second input connected to receive a mixing down signal, and an output for a mixed down reference signal and a mixed down reflected signal; a reflected radiation detector connected to the output of the mixer to receive the mixed down reflected signal and the mixed down reference signal, where the detector detects the magnitude and phase of both the mixed down reflected signal and the mixed down reference signal; and a tissue classifier which: classifies the region of tissue in direct contact with the distal end of the probe into a tissue type or tissue state based on a complex impedance of the region of tissue in direct contact with the distal end of the probe calculated from the magnitude and phase of the mixed down reflected and reference signals detected by the detector, and on a calibration value, obtained by measuring the impedance at the distal end of the probe for a known impedance, to which the calculated complex impedance is referenced, and displays the tissue type or tissue state of the region of tissue in direct contact with the distal end of the probe on a display.