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US 2014/0276166 A1Published application
Method of measuring bioimpedance
AssigneeCardioLogic Innovations Ltd.
InventorsOren DRORI, Shimon ARAD, Haim KRIEF
Life of this patent
Estimating the term…
Abstract
A method for measuring the impedance of a portion of a subject, by passing a known current provided by a current source unit between a first pair of electrodes contacting the skin surface of the subject. The measuring of a voltage with a voltage measuring instrument, between at least one second pair of electrodes contacting the skin surface of the subject when the current source unit is passing the known current through the first pair of electrodes; calculating the bio-impedance of the portion of the subject based on the known current and the calibrated voltage.
Claims20
A method for measuring the impedance of a portion of a subject:
- a. passing a known current provided by a current source unit between a first pair of electrodes contacting the skin surface of said subject;
- b. measuring a voltage with a voltage measuring instrument, between at least one second pair of electrodes contacting said skin surface of said subject when said current source unit is passing said known current through said first pair of electrodes;
- c. calculating the bio-impedance of said portion of said subject based on said known current and the calibrated voltage ;
- wherein said calibrated voltage is calculated according to the following calibration formula:
- Vc=Vm−(Am[(J(□)]{right arrow over (r)}′({right arrow over (r)}))α(r)d{right arrow over (r)}−Ac[(J(□)]{right arrow over (r)}′({right arrow over (r)}))α(r)d{right arrow over ()})
- wherein Am is the volume of said portion of said subject enclosed by said second pair of electrodes;
- Ac is the volume of a standard portion of a measured subject enclosed by said second pair of electrodes;
- α(r) is a function containing the resistivity of a body according to the radius the cross section of said subject;
- and J({right arrow over (r)}({right arrow over (r)})) is the Jacobian of coordinate transformation from Cartesian coordinates {right arrow over (r)}′ to elliptic coordinates {right arrow over (r)}:
- J
- (
- r
- ′
-
- (
- r
- ->
- )
- )
- =
- Det
-
-
-
- r
- ->
-
- (
- r
- ->
- )
-
- r
- ->
-
- further wherein said α(r) is calculated according to a solution of the poission equation:
- v
- ·
- (
- 1
- ρ
-
- ∇
- ϕ
- )
- =
- -
- l
- y
- ;
- said φ is the electric potential according as a function of position on the thorax of said subject;
- said ρ is the impedance as a function of position in said thorax;
- and lγ is zero except on the surface of said thorax.
50 more elements
A device configured to measure the impedance of a portion of a subject, comprising:
- a current source unit capable of passing a known current through said subject's chest through a first pair of electrodes;
- a voltage measuring unit capable of measuring a voltage between at least one second pair of electrodes when said current source unit is passing said known current through said portion of said subject through said first pair of electrodes, and when said first and said second pair of electrodes are placed on said subject;
- and
- a controller, comprising at least one processor, configured to determine the impedance of said portion of said subject based on said known current and calibrated voltage value based upon measured voltage;
- said calibrated voltage is calculated by the formula:
- Vc=Vm−(Am[(J(□)]{right arrow over (r)}′({right arrow over (r)}))α(r)d{right arrow over (r)}−Ac([J(□)]{right arrow over (r)}′({right arrow over (r)}))α(r)d{right arrow over ()})
- where Am is the volume of a portion of said subject enclosed by said second pair of electrodes;
- Ac is the volume of a standard portion of a measured subject enclosed by said second pair of electrodes;
- α(r) is a function containing the resistivity of a body according to the radius of a cross section of said subject;
- and J({right arrow over (r)}′({right arrow over (r)})) is the Jacobian of coordinate transformation from Cartesian coordinates {right arrow over (r)}′ to elliptic coordinates {right arrow over (r)}:
- J
- (
- r
- ′
-
- (
- r
- ->
- )
- )
- =
- Det
-
-
-
- r
- ′
-
-
- (
- r
- ->
- )
-
- r
- ->
-
- further wherein said α(r) is calculated according to a solution of the poission equation:
- ∇
- ·
- (
- 1
- ρ
-
- ∇
- ϕ
- )
- =
- -
- l
- g
- ;
- said φ is the electric potential according as a function of position on the thorax of said subject;
- said ρ is the impedance as a function of position in said thorax;
- and lγ is zero except on the surface of said thorax.
52 more elements
Dependencies are inferred from the claim text.