DEVICE AND METHOD FOR DETERMINING AT LEAST ONE CHARACTERIZING PARAMETER OF MULTILAYER BODY TISSUE
A device for the non-invasive measurement of a glucose level, body hydration or another characterizing parameter of body tissue comprises at least two coplanar waveguides arranged on a common support. An AC signal is applied to the first ends of the coplanar waveguides, and the signal arriving at the second end is measured. The coplanar waveguides have differing gap widths, such that their electric fields have different reach into the body tissue. This allows obtain depth resolved information about the permittivities of individual tissue layers and to obtain more accurate results.
1 . A device for determining at least one characterizing parameter P of living body tissue, in particular a glucose level or water content, comprising
a number N>1 of coplanar waveguides, each coplanar waveguide comprising a center strip electrode between ground electrodes, wherein at least some of said coplanar waveguides have different gap widths between their center strip electrode and their ground electrodes for generating electrical fields of different reach,
a signal generator generating at least one AC signal, wherein first ends of said coplanar waveguides are connected to said signal generator,
a measuring unit, wherein a second ends of said coplanar waveguides are connected to said measuring unit for measuring N measured parameters m i ,
a control unit for determining said characterizing parameter P from at least part of said measured parameters m i .
2 . The device of claim 1 , comprising at least one coplanar waveguide having a gap width of 100 μm or less.
3 . The device of claim 1 , comprising at least one co-planar waveguide having a gap width of at least 1 mm, in particular between 1 and 4 mm.
4 . The device of claim 1 , comprising at least one co-planar waveguide having a gap width of at least 4 mm.
5 . The device of claim 1 , wherein said signal generator generates an AC signal having a frequency of at least 50 MHz.
6 . The device of claim 1 , wherein said ground electrodes are wider than said center strip electrodes.
7 . The device of claim 1 , further comprising a non-conductive cover layer covering said electrodes.
8 . Use of the device of claim 1 , for measuring a glucose level.
9 . Use of the device of claim 1 , for measuring a water content.
10 . A method for determining at least one characterizing parameter P of body tissue, in particular a glucose level or water content, comprising,
applying a number N>1 of coplanar waveguides to a skin region of said body tissue, each coplanar waveguide comprising a center strip electrode between ground electrodes, wherein at least some of said coplanar waveguides have different distances between their center strip electrode and their ground electrodes generating electrical fields of different reach by means of said coplanar waveguides by applying an AC signal to a first end of each coplanar waveguide,
measuring N measured parameters m i depending on a signal exiting from a second end of each coplanar waveguide,
determining said characterizing parameter P from at least part of said measured parameters m i .
11 . The method of claim 10 , wherein at least a first of the measured parameters m i1 of a layer i 1 depends on the characterizing parameter P as well as on a further parameter Q and at least a second of the measured parameters m i2 of a layer i 2 above said layer i 1 depends on said further parameter Q and to a lesser degree on the characterizing parameter P, said method further comprising the step of
combining the measured parameters m i 1 and m i 2 for obtaining a calculated value (∈ i 1 ) that depends less on the further parameter Q than said measured parameter m i 1 .
12 . The method of claim 11 , wherein said characterizing parameter P is a glucose level
13 . The method of claim 12 , wherein a coplanar waveguide i 1 with a distance between its center strip electrode and its ground electrodes of at least 1 mm is used for measuring said measured parameter m i 1 and a coplanar waveguide i 2 with a distance between its center strip electrode and its ground electrodes of less than 1 mm is used for measuring said measured parameter m i 2 .
14 . The method of claim 13 , wherein said coplanar waveguide i 1 has a distance between its center strip electrode and its ground electrodes of less than 4 mm.
15 . The method of claim 11 , wherein said characterizing parameter P is water content.
16 . The method of claim 15 , wherein a coplanar waveguide i 1 with a distance between its center strip electrode and its ground electrodes of at least 4 mm is used for measuring said measured parameter m i 1 and a coplanar waveguide m i 2 with a distance between its center strip electrode and its ground electrodes of less than 5 mm is used for measuring said measured parameter m i 2 .