Method and device for determining a parameter of living tissue
A device for measuring a glucose level or some other parameter of living tissue that affects the dielectric properties of the tissue is disclosed. The device comprises an electrode arrangement ( 5 ) having a plurality of electrodes ( 5 - i ). The signal from a signal source ( 31 ) can be applied to the electrode arrangement via a switching assembly ( 39 ). The switching assembly ( 39 ) is designed to selectively connect a first and a second pattern of the electrodes ( 5 - i ) to the signal source, thereby generating a first and a second electrical field with different spatial distribution in the tissue. By using a differential method which relies on measuring the impedance of the electrode arrangement ( 5 ) for each field and on suitable subtraction of the measured results, surface effects can be reduced and the focus of the measurement can be offset to a point deeper inside the tissue.
1. A device for measuring a parameter of living tissue, which parameter affects a response of said tissue to an electric field, comprising
an electrode arrangement ( 5 ),
a signal source ( 31 ) generating an electrical signal to be applied to said electrode arrangement ( 5 ) for generating an electrical field in said tissue, and
a detector ( 37 , 38 ) for measuring a response from said tissue to said electrical field and for determining at least one parameter therefrom,
wherein said device is adapted to generate at least two spatially different electrical fields (E 1 , E 2 ) in said tissue, and wherein said detector is adapted to determine said parameter from a difference of the responses of said tissue to said spatially different electrical fields,
and further comprising a switching assembly ( 39 ) arranged between said signal source ( 31 ) and said electrodes ( 5 - i ) for selectively connecting at least a first and a second pattern of said electrodes ( 5 - i ) to said signal source ( 31 ).
2. The device of claim 1 , wherein said parameter is a glucose level in the tissue.
3. A device for measuring a parameter of living tissue, which parameter affects a response of said tissue to an electric field, comprising
an electrode arrangement ( 5 ),
a signal source ( 31 ) generating an electrical signal to be applied to said electrode arrangement ( 5 ) for generating an electrical field in said tissue, and
a detector ( 37 , 38 ) for measuring a response from said tissue to said electrical field and for determining at least one parameter therefrom,
wherein said device is adapted to generate at least two spatially different electrical fields (E 1 , E 2 ) in said tissue, and wherein said detector is adapted to determine said parameter from a difference of the responses of said tissue to said spatially different electrical fields,
wherein said electrode arrangement ( 5 ) comprises a plurality of electrodes ( 5 - i ) arranged side by side, and
wherein said device is adapted to selectively apply
in a first mode of operation, a first voltage pattern to said electrodes ( 5 - i ), wherein in said first voltage pattern the electrodes of each pair of neighboring electrodes carry different voltages, and
in a second mode of operation, a second voltage pattern to said electrodes ( 5 - i ), wherein in said second voltage pattern the electrodes of a first part of the pairs of neighboring electrodes carry equal voltages and the electrodes of a second part of the pairs of neighboring electrodes carry different voltages.
4. The device of claim 3 , wherein said electrode arrangement ( 5 ) comprises at least four electrodes ( 5 - i ) arranged side by side.
5. The device of claim 3 , wherein said parameter is a glucose level in the tissue.
6. A device for measuring a parameter of living tissue, which parameter affects a response of said tissue to an electric field, comprising
an electrode arrangement ( 5 ),
a signal source ( 31 ) generating an electrical signal to be applied to said electrode arrangement ( 5 ) for generating an electrical field in said tissue, and
a detector ( 37 , 38 ) for measuring a response from said tissue to said electrical field and for determining at least one parameter therefrom,
wherein said device is adapted to generate at least two spatially different electrical fields (E 1 , E 2 ) in said tissue, and wherein said detector is adapted to determine said parameter from a difference of the responses of said tissue to said spatially different electrical fields,
wherein detector ( 37 , 38 ) is adapted to measure a first value s 1 indicative of the response of said tissue to a first electrical field and a second value s 2 indicative of the response of said tissue to a second electrical field, wherein said first and said second electrical fields are spatially different, and
to calculate a weighted difference k 1 ·s 1 −k 2 ·s 2 with weights k 1 and k 2 , wherein the weights are chosen such that a non-constant contribution of the di-electric response of an epidermis of the tissue to the weighted difference is minimized.
7. The device of claim 6 , wherein said parameter is a glucose level in the tissue.