Impedance-calibrated diagnostic medical devices
Various embodiments set forth medical devices. In some embodiments, the medical device includes an impedance bridge, an instrument head that includes one or more electrode pairs and a calibration impedance, and one or more wire pairs that couple the impedance bridge to the one or more electrode pairs and the calibration impedance. The disclosed medical devices compensate for impedance caused by extraneous factors arising from manufacturing and materials variances while measuring the impedance of tissue.
1 . A method for determining a property of tissue, the method comprising:
recording, at one or more frequencies across an impedance bridge, one or more calibration impedance measurements that indicate an impedance of a first circuit that includes at least the impedance bridge, a calibration impedance load that is included in an instrument head of a medical device, and a first wire pair that passes within a catheter of the medical device and that is electrically coupled to the calibration impedance load;
recording, at one or more frequencies across the impedance bridge, one or more impedance measurements that indicate an impedance of a second circuit that includes at least the impedance bridge, one or more electrode pairs that are included in the instrument head, and a second wire pair that passes within the catheter and that is electrically coupled to the one or more electrode pairs;
determining one or more compensated impedance measurements based on the one or more calibration impedance measurements and the one or more impedance measurements; and
performing at least one action based on the one or more compensated impedance measurements.
2 . Method of claim 1 , wherein the calibration impedance load includes one or more additional impedance loads, and recording the one or more calibration impedance measurements includes at least one of:
a phase offset based on a calibration impedance measurement of a phase offset calibration impedance load included in the one or more additional impedance loads,
a coarse gain based on a calibration impedance measurement of a coarse gain calibration impedance load included in the one or more additional impedance loads,
a fine gain based on a calibration impedance measurement of a fine gain calibration impedance load included in the one or more additional impedance loads, or
a phase based on a calibration impedance measurement of a phase calibration impedance load included in the one or more additional impedance loads.
3 . The method of claim 1 , wherein recording the one or more calibration impedance measurements includes one or both of:
recording one or more of the one or more calibration impedance measurements during a factory calibration process, or
recording one or more of the one or more calibration impedance measurements during a surgical calibration process, wherein the instrument head is contacting the tissue during the surgical calibration process.
4 . The method of claim 1 , wherein:
recording the one or more calibration impedance measurements comprises measuring the one or more calibration impedance measurements of the calibration impedance at each frequency included in a first set of frequencies,
recording the one or more impedance measurements comprises measuring the one or more impedance measurements associated with the one or more electrode pairs at each frequency included in a second set of frequencies,
and
the second set of frequencies is different than the first set of frequencies.
5 . The method of claim 1 , wherein recording the one or more impedance measurements comprises:
recording a first impedance measurement based on a first current associated with a first electrode pair and the second wire pair, wherein the second wire pair is electrically coupled to the first electrode pair; and
recording a second impedance measurement based on a second current associated with a second electrode pair and a third wire pair that that passes within the catheter and that is electrically coupled to the second electrode pair.
6 . The method of claim 1 , wherein determining the one or more compensated impedance measurements includes one or both of:
subtracting the one or more calibration impedance measurements from the one or more impedance measurements, or
dividing the one or more impedance measurements by the one or more calibration impedance measurements.
7 . The method of claim 1 , wherein performing at least one action based on the one or more compensated impedance measurements comprises determining a Cole relaxation frequency of the tissue.
8 . The method of claim 7 , wherein the Cole relaxation frequency corresponds to a frequency associated with a greatest compensated impedance measurement included in the one or more compensated impedance measurements.
9 . The method of claim 8 , wherein performing at least one action based on the one or more compensated impedance measurements further comprises determining a tissue type of the tissue based on the Cole relaxation frequency of the tissue.
10 . The method of claim 1 , wherein performing at least one action based on the one or more compensated impedance measurements comprises:
determining a tumor tissue type of the tissue based on a Cole relaxation frequency of the tissue being above a threshold frequency; or
determining a non-tumor tissue type of the tissue based on the Cole relaxation frequency of the tissue being below the threshold frequency.
11 . The method of claim 1 , further comprising presenting, by the medical device, an output based on the one or more compensated impedance measurements, wherein the output comprises at least one of a visual output or an audio output.
12 . The method of claim 1 , wherein:
performing at least one action based on the one or more compensated impedance measurements comprises controlling a tool of the instrument head based on the property of the tissue, and
the tool comprises at least one of a therapeutic drug delivery tool, an energy delivery tool, or a tissue sample extraction tool.
13 . The method of claim 1 , wherein the first wire pair is a twisted wire pair, and wherein the second wire pair is a twisted wire pair.