WO2015168732A1

WO2015168732A1 - Methods and apparatus for characterisation of body tissue

Info

Publication number: WO2015168732A1
Application number: PCT/AU2015/050212
Authority: WO
Inventors: Warren Smith
Original assignee: Ti2 Medical Pty Ltd
Priority date: 2014-05-05
Filing date: 2015-05-05
Publication date: 2015-11-12

Abstract

Methods and apparatus for determining bioimpedance in a body are disclosed that use at least two current electrodes and at least two voltage sensing electrodes. At least one of the electrodes is connected to a biologically active points on an arm or leg of the body. In one configuration, bioimpedance at a region of interest is determined from a combination of voltages measured between different pairs of the electrodes, each pair including at least one of the current electrodes. In another configuration, at least one of the voltage sensing electrodes is positioned on an arm or leg distally of a current electrode.

Description

Methods and apparatus for characterisation of body tissue

Technical Field

[0001] The present disclosure relates to analysis and/or monitoring of bioimpedance properties of a patient's body.

Background

[0002] Bioimpedance analysis involves the measurement of the response of a living organism to externally applied electrical current. Bioimpedance parameters such as resistance, reactance and phase angle can be recorded for the purposes of determining blood flow and body composition (e.g., water and fat content). Nonetheless, there exists an accumulating body of evidence that the phase angle parameter of bioimpedance analysis has applications beyond its general use in body composition determination, as an indicator of general health status and as a promising prognostic tool. Phase angle is generally recognized to be an indicator of cell membrane integrity and the distribution of fluid in the intra- and extracellular spaces at the cellular level, for example.

Ongoing research indicates that phase angle may also reflect other biologic properties.

[0003] Bioimpedance analysis apparatus can employ two electrodes, the electrodes being positioned at either end of a body segment under analysis, the electrodes being used to deliver an electrical signal across the body segment and to measure the response of the body to that electrical signal. However, variations in the contact arrangement between the electrodes and the body can alter the measured bioimpedance levels, leading to inaccurate results.

[0004] Bioimpedance measurement apparatus can also include four electrodes. A pair of outer electrodes provides a drive circuit, and a pair of inner electrodes provides a sensing circuit.

Electrical current is applied between the drive electrodes and voltage is measured between the sensing electrodes and used to determine bioimpedance of tissue between the sensing electrodes.

[0005] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application. Summary

[0006] According to one aspect, the present disclosure provides a method of determining bioimpedance in a body, the method comprising:

connecting a first current electrode (A) to a first arm or leg of the body;

connecting a second current electrode (D) to a second arm or leg of the body;

connecting a first voltage sensing electrode (B) and a second voltage sensing electrode (C) at spaced apart positions of the body, separate from the first and second current electrodes; wherein at least one of the first current electrode (A) and the first voltage sensing electrode (B) is connected to a biologically active point on the first arm or leg of the body, the method further comprising:

applying at least one electrical signal between the first and second current electrodes; measuring, in response to the at least one electrical signal applied between the first and second current electrodes, voltage between at least two different pairs of the electrodes (A, B, C, D), wherein each pair includes at least one of the first and second current electrodes (A, D); and determining, from a combination of the measured voltages, the bioimpedance of a region of interest of the body that is located along a path between the first and second current electrodes.

[0007] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0008] In this Summary section, reference letters in brackets, e.g. (A, B, C, D), have been used to aid recognition of electrodes under discussion, in accordance with reference lettering used in the accompanying Figures and discussions thereof. Nevertheless, the apparatus and methods are not limited to any arrangement as shown in the Figures.

[0009] According to another aspect, the present invention provides apparatus for determining bioimpedance in a body, the apparatus comprising:

a first current electrode (A) adapted to connect to a first arm or leg of the body;

a second current electrode (D) adapted to connect to a second arm or leg of the body; a first voltage sensing electrode (B) and a second voltage sensing electrode (D) adapted to connect to the body at spaced apart positions of the body, separate from the first and second current electrodes;

wherein at least one of the first current electrode (A) and the first voltage sensing electrode (B) is adapted to connect to a biologically active point of the body, and wherein the apparatus is adapted to:

apply at least one electrical signal between the first and second current electrodes (A,D); and

measure, in response to the at least one electrical signal applied between the first and second current electrodes, voltage between at least two different pairs of the electrodes (A, B, C,- D), wherein each pair includes at least one of the first and second current electrodes (A, D).

[0010] In one embodiment, the apparatus comprises a processor adapted to determine, from a combination of the measured voltages, the bioimpedance of a region of interest of the body that is located along a path between the first and second current electrodes.

[0011] Since voltages are measured across different combinations of electrodes, and thus at regions that can be beyond the region of interest, an increase in contributions to the bioimpedance measurement from deeper current pathways arising outside of the region of interest of the body can be achieved. Bioimpedance properties of regions beyond the region of interest can be incorporated into the bioimpedance determination for the region of interest. Empirically this has been found to lead to more readily identifiable differences in bioimpedance measurements (increased resolution) between different surface-defined meridian pathways, for example. In some embodiments, one of the voltage measurements is made between the first and second current electrodes, enabling bioimpedance to be determined across the total current path. By incorporating, into the determination of the bioimpedance of the region of interest, bioimpedance across the total current path itself, resolution can be further enhanced. Further, through use of a combination of measurements between different electrodes, any error in the bioimpedance determination at the region of interest that might be caused by electrode-to-tissue contact impedances may be reduced or eliminated.

[0012] The biologically active point may be points that are known to show distinct electrical properties, e.g., they may be points on skin tissue that have increased conductance, reduced impedance and resistance, increased capacitance, and/or elevated electrical potential compared to surrounding skin tissue. The biologically active points may be acupuncture points.

[0013] By connecting the first current electrode (A) or the first voltage sensing electrode (B) to a biologically active point such as an acupuncture point on the first arm or leg, bioimpedance measurements across at least a portion of a preferential electrical pathway of the body, such as a meridian-defined electrical pathway, may be obtained. [0014] The first current electrode (A) may be connected at a position that is at, or distal to, the elbow or knee of the first arm or leg. For example, the first electrode (A) may be connected at a position on a first arm or foot, or first wrist or ankle, that forms part of the first arm or leg. The first voltage sensing electrode (B) may or may not be connected to the first arm or leg. The first voltage sensing electrode (B) may be connected at a position on the first arm or leg that is proximal to the connection position of the first electrode (A) or distal to the connection position of the first electrode (B). When the first voltage sensing electrode (B) is located on the first arm or leg and is distal to the first current electrode (A), the first voltage sensing electrode may be connected to the biologically active point. Otherwise, the first current electrode (A) may be connected to the biologically active point.

[0015] The second current electrode (D) may be connected at a position that is at, or distal to, the elbow or knee of the second arm or leg. For example, the second current electrode (D) may be connected at a position on a second arm or foot, or second wrist or ankle, that forms part of the second arm or leg. The second voltage sensing electrode (C) may or may not be connected to the second arm or leg. The second voltage sensing electrode (C) may be connected at a position on the second arm or leg that is proximal to the connection position of the second current electrode (D) or distal to the connection position of the second current electrode (D).

[0016] One of the second current electrode and the second voltage sensing electrode may be connected to a biologically active point such as an acupuncture point, a nail or tip of a finger or toe, or other region.

[0017] In one embodiment, the first and second current electrodes (A, D) provide outer electrodes and the first and second voltage sensing electrodes (B,C) provide inner electrodes. In another embodiment, the first and second voltage sensing electrodes (B, C) provide outer electrodes and the first and second current electrodes (A, D) provide inner electrodes. In yet another embodiment, the first voltage sensing electrode (B) and the second current electrode (D) provide outer electrodes and the first current electrode (A) and the second voltage sensing electrode (C) provide inner electrodes. In yet another embodiment, the first current electrode (A) and the second voltage sensing electrode (C) provide outer electrodes and the first voltage sensing electrode (B) and the second current electrode (D) provide inner electrodes. The outer and inner electrodes may be provided across a pathway that extends between the hand and the foot on a unilateral side of the body, e.g. on the right side of the body or on the left side of the body.

[0018] Nevertheless, in some embodiments, one or both of the voltage sensing electrodes may be connected at an opposite side of the body to the other electrodes, e.g., to enable bioimpedance measurement over a specific body segment. One or both of the first and second voltage sensing electrodes may be connected to an arm or leg that is different from the first arm or leg and the second arm or leg.

[0019] The first voltage sensing electrode (B) may be spaced at least 5 cm from the first current electrode (A) and the second voltage sensing electrode (C) may be spaced at least 5 cm from the second current electrode (D). Spacing the voltage sensing electrodes at such distances from the current electrodes can allow position dependent analysis with respect to the meridian-defined segments, while reducing the contributions from the voltage electrode - current electrode spacing on measured bioimpedance. In some embodiments, the spacing may be at least 7 cm, at least 10 cm or otherwise.

[0020] In one example, when the at least one electrical signal having current (I) is applied between the first and second current electrodes (A,D),

a voltage (V(AC)) is measured between the first current electrode (A) and the second voltage sensing electrode (C);

a voltage (V(BD)) is measured between the first voltage sensing electrode (B) and the second current electrode (D); and

a voltage (V(AD)) is measured between the first current electrode (A) and the second current electrode (D).

[0021] In this example, the bioimpedance (Zj) of the region of interest may be determined using Equation 1:

V(AC) V(BD) V(AD)

[0022] In another example, when the at least one electrical signal having current (I) is applied between the first and second current electrodes (A, D),

a voltage (V(AC)) is measured between the first current electrode (A) and the second voltage sensing electrode (C); and

a voltage (V(AB)) is measured between the first current electrode (A) and the first voltage sensing electrode (B).

[0023] In this example, the bioimpedance (Zj) of the region of interest may be determined using Equation 2a: [0024] Z, ₌ ) _ W

[0025] In a similar example, when the at least one electrical signal having current (I) is applied between the first and second current electrodes (A, D),

a voltage (V(CD)) is measured between the second voltage sensing electrode (C) and the second current electrode (D).

[0026] In this example, the bioimpedance (Zj) of the region of interest may be determined using Equation 2b:

[2b]

[0028] According to another aspect, the present disclosure provides a method of determining bioimpedance in a body, the method comprising:

connecting a first current electrode (A) to a first arm or leg of the body;

connecting a second current electrode (D) to a second arm or leg of the body;

connecting a first voltage sensing electrode (B) and a second voltage sensing electrode (C) at spaced apart positions of the body, separate from the first and second current electrodes; wherein:

the first voltage sensing electrodes (B) is connected to the first arm or leg at a position that is distal to the first current electrode (A); and/or

the second voltage sensing electrode (C) is connected to the second arm or leg at a position that is distal to the second current electrode (D); and

wherein one of the first current electrode (A) and the first voltage sensing electrode (B) is connected to a biologically active point on the first arm or leg of the body,

the method further comprising:

applying at least one electrical signal between the first and second current electrodes; measuring, in response to the at least one electrical signal applied between the first and second current electrodes, voltage between the first and second voltage sensing electrodes; and determining, from the voltage measurement, the bioimpedance of a region of interest of the body that is located along a path between the first and second current electrodes. [0029] According to another aspect, the present invention provides apparatus for determining bioimpedance in a body, the apparatus comprising:

a second current electrode (D) adapted to connect to a second arm or leg of the body; a first voltage sensing electrode (B) and a second voltage sensing electrode (C) adapted to connect to spaced apart positions of the body, separate from the first and second current electrodes; wherein:

the first voltage sensing electrodes (B) is adapted to connect to the first arm or leg at a position that is distal to the first current electrode (A); and/or

the second voltage sensing electrode (C) is adapted to connect to the second arm or leg at a position that is distal to the second current electrode (D); and

wherein one of the first current electrode (A) and the first voltage sensing electrode (B) is adapted to connect to a biologically active point on the first arm or leg of the body, wherein the apparatus is adapted to:

apply at least one electrical signal between the first and second current electrodes; and measure, in response to the at least one electrical signal applied between the first and second current electrodes, voltage between the first and second voltage sensing electrodes.

[0030] In one embodiment, the apparatus comprises a processor adapted to determine, from the measured voltage, the bioimpedance of a region of interest of the body that is located along a path between the first and second current electrodes.

[0031] By connecting the first current electrode or first voltage sensing electrode to a biologically active point such as an acupuncture point, bioimpedance measurements across at least a portion of a preferential electrical pathway of the body, such as a meridian-defined electrical pathway, may be obtained.

[0032] The first current electrode (A) may be connected at a position that is at, or distal to, the elbow or knee of the first arm or leg. For example, the first electrode (A) may be connected at a position on a first arm or foot, or first wrist or ankle, that forms part of the first arm or leg. The first voltage sensing electrode (B) may or may not be connected to the first arm or leg. The first voltage sensing electrode (B) may be connected at a position on the first arm or leg that is proximal to the connection position of the first electrode (A) or distal to the connection position of the first electrode (B). When the first voltage sensing electrode is located on the first arm or leg and is distal to the first current electrode, the first voltage sensing electrode may be connected to the biologically active point. Otherwise, the first current electrode (A) may be connected to the biologically active point. [0033] The second current electrode (D) may be connected at a position that is at, or distal to, the elbow or knee of the second arm or leg. For example, the second current electrode (D) may be connected at a position on a second arm or foot, or second wrist or ankle, that forms part of the second arm or leg. The second voltage sensing electrode (C) may or may not be connected to the second arm or leg. The second voltage sensing electrode (C) may be connected at a position on the second arm or leg that is proximal to the connection position of the fourth electrode (D) or distal to the connection position of the fourth electrode.

[0034] One of the second current electrode (D) and the second voltage sensing electrode (C) may be connected to a biologically active point such as an acupuncture point, a nail or tip of a finger or toe, or other region of the second arm or leg.

[0035] In one embodiment, the first and second voltage sensing electrodes (B, C) provide outer electrodes and the first and second current electrodes (A, D) provide inner electrodes. In another embodiment, the first voltage sensing electrode (B) and the second current electrode (D) provide outer electrodes and the first current electrode (A) and the second voltage sensing electrode (C) provide inner electrodes. In yet another embodiment, the first current electrode (A) and the second voltage sensing electrode (C) provide outer electrodes and the first voltage sensing electrode (B) and the second current electrode (D) provide inner electrodes. The outer and inner electrodes may be provided across a pathway that extends between the hand and the foot on a unilateral side of the body, e.g. on the right side of the body or on the left side of the body.

[0036] Nevertheless, in some embodiments, one of the voltage sensing electrodes may be connected at an opposite side of the body to the other electrodes, e.g., to enable bioimpedance measurement over a specific body segment. One of the first and second voltage sensing electrodes may be connected to an arm or leg that is different from the first arm or leg and the second arm or leg.

[0037] Again, the first voltage sensing electrode (B) may be spaced at least 5 cm from the first current electrode (A) and the second voltage sensing electrode (C) may be spaced at least 5 cm from the second current electrode (D). Spacing the voltage sensing electrodes at such distances from the current electrodes can allow position dependent analysis with respect to the meridian- defined segments, while reducing the contributions from the voltage electrode - current electrode spacing on measured bioimpedance. In some embodiments, the spacing may be at least 7 cm, at least 10 cm or otherwise. [0038] The at least one electrical signal can have a waveform or waveform spectrum suitable for electrical bioimpedance measurement, such as a controlled current AC waveform. Further, by inclusion of phase-sensitive electronics in the apparatus, impedance Z may be resolved into real (resistive) and imaginary (reactive) components.

[0039] In any of the aspects disclosed herein, the biologically active points may comprise Jing- Well points or Yuan-Source points. The term "Jing-Well point" is intended to refer to an anatomically well-defined acupuncture point (also known as Tsing, Sei, and Well point) listed in Table 1 below. Similarly, the term "Yuan-Source point" is intended to refer to an anatomically well-defined acupuncture point (also known as source point) listed in Table 2 below. The Jing- Well points and Yuan-Source points, are points on the skin which have been reported to have higher conductivity than surrounding skin or nail, and are arranged in lines known as "meridians". The Jing-Well points lie at the extremities of each of the 12 bilateral regular meridians.

Table 1 - Detailed Anatomical Location of the Jing-Well points

Data from: A Proposed Standard International Acupuncture Nomenclature: Report of a WHO Scientific Group, WHO Headquarters in Geneva, 1991; "Illustration of Acupoints" by Haruto Kinoshita, Ido-No-Nippon-Sha, Tokyo, Japan, 1976; and "Essentials of Chinese Acupuncture" Foreign Languages Press, Beijing, China, 1980

Table 2 - Detailed Anatomical Location of the Yuan-Source points

Data from: A Proposed Standard International Acupuncture Nomenclature: Report of a WHO

Scientific Group, WHO Headquarters in Geneva, 1991; "Illustration of Acupoints" by Haruto Kinoshita, Ido-No-Nippon-Sha, Tokyo, Japan, 1976; and "Essentials of Chinese Acupuncture" Foreign Languages Press, Beijing, China, 1980)

[0040] In any of the aspects, determining the bioimpedance of the body may include determining the phase angle. It has been have found that placement of current electrodes at certain positions of the hands and feet, particularly at Jing-Well, Yuan-Source, and/or sites at the tips of fingers or toes, gives rise to position-dependent phase angle measurement, even when voltage sensing electrodes are located at a significant distances from current electrodes. This is considered indicative of the different electrical statuses of meridian-defined body segments, and recent findings that there exist preferential pathways (including networks of pathways) in the body for current flow. By measuring along different meridian-defined body segments, a detailed analysis and/or monitoring of the body composition and/or health status of a patient may be achieved. Since phase angle is theoretically largely insensitive to differences in the shapes and cross-sectional areas of measured regions, it is a particularly useful parameter for comparing body composition and/or health status of left and right body segments. Thus, even if one segment of the body is larger than the other (one arm or leg may be more dominant, for example, and thus have a larger girth than the other) phase angle (given by the relationship Θ = atan(X/R)) will be largely unaffected by such geometrical differences.

[0041] The methods and apparatuses disclosed herein may be employed for body composition determination and/or as treatment monitoring or assessment aids in conventional medicine bioimpedance analysis applications. Additionally or alternatively, particularly since electrical signals can be applied across one or more meridian-defined body segments, the methods and apparatuses may be employed in traditional Chinese and integrative medicine-based assessments and treatments. The methods and apparatuses may bridge the sometimes disparate technologies of conventional-medicine bioimpedance analysis and acupuncture based principles of health diagnosis, providing enhanced diagnostic tools in either area.

[0042] Reference is made to determination of the phase angle parameter of bioimpedance in the present description. It is intended, however, that reference to phase angle measurement may include not only measurement of phase angle per se, but additionally combined phase angle and impedance measurement, with the combined data being used to define a bioimpedance vector. From this, resistance and reactance values can be calculated if required. Alternatively, phase angle measurement may include measurement of resistance and reactance, with phase angle (and optionally impedance magnitude and associated bioimpedance vector) being calculated from these two parameters.

[0043] In general, phase angle has been considered as an indicator of general health status, and has shown promise as a prognostic tool, for an ever growing number of conditions. Examples of such prognostic applications have been reported for patients that have cirrhosis of the liver, bacteraemia, are undergoing haemodialysis, have chronic obstructive pulmonary disease, amyotrophic lateral sclerosis, trauma, sepsis and/or various cancers (colorectal, breast, lung and pancreatic). By providing for more detailed analysis of bioimpedance across a wide range of meridian-defined body segments, the apparatus and methods of the present disclosure may provide enhanced health assessment and/or prognostic tools in these areas.

[0044] In one embodiment, when the first current electrode (A) is to be connected to a biologically active point on the first arm or leg of the body, a plurality of first current electrodes

(A) are provided, each first current electrode being be connected at a different biologically active point. In another embodiment, when the first voltage sensing electrode (B) is to be connected to an acupuncture point on the first arm or leg of the body, a plurality of first voltage sensing electrodes

(B) are provided, each first voltage sensing electrode being connected at a different biologically active point. Multiple bioimpedances may be determined according to the method disclosed herein using the plurality of first current electrodes or the plurality of first voltage sensing electrodes. This can permit a number of meridian-based segments of the body to be analysed or monitored sequentially without requiring reconfiguration of the electrode arrangement. Nonetheless, as an alternative approach, a single first current electrode (A) or a single voltage sensing electrode (B) may be provided that is moveable to permit various different positions, e.g. different biologically active points, to be probed successively, allowing a similar analysis to be made. For example, the first electrode (A) or first voltage sensing electrode (B) may be configured as a probe, moveable to connect at one Jing-Well point of the first hand or foot and, after analysis of a meridian-defined pathway related to that Jing-Well point, it may movable to connect at another Jing-Well point of the first hand or foot, to permit analysis of another meridian-defined pathway, and so forth.

[0045] In accordance with the traditionally defined longitudinal orientations of the twelve bilateral regular meridians, the first and second current electrodes may be positioned ipsilaterally, i.e. on the same side of the body. For example, the first current electrode (A) may be connected to the right arm (e.g. to the right hand) and the second current electrode (D) to the right leg (e.g. to the right foot), or vice versa. Similarly, the first current electrode (A) may be connected to the left arm (e.g. the left hand) and the fourth electrode (D) to the left leg (e.g. the left foot), or vice versa. However, it is conceived in some circumstances that the first and second current electrodes may be positioned contralaterally, i.e. on different sides of the body. This may be possible if low current levels are used, limiting current supply across the chest region, for example. With this in mind, the first current electrode (A) may be connected to any arm or leg and the second current electrode to any other arm or leg. For example, the first electrode current (A) may be connected to the left leg (e.g. the left foot) and the second current electrode (D) to the right leg (e.g. the right foot), or vice- versa. As another example, the first current electrode (A) may be connected to the left arm (e.g. the left hand) and the second current electrode (D) to the right arm (e.g. the right hand), or vice- versa. As another example, the first current electrode (A) may be connected to the left arm (e.g. the left hand) and the second current electrode (D) to the right leg (e.g. the right foot), or vice-versa

[0046] In one embodiment, the first current electrode (A) or the first voltage sensing electrode (B) is connected to any one of the following Jing-Well points of the right or left foot: SP1, LR1, ST45, GB44, Klla, BL67 and KI1, and the second current electrode (D) or the second voltage sensing electrode (C) is connected to any one or more fingernails, tips of fingers, acupuncture points or non-acupuncture points of the hand on the ipsilateral side under test. Yuan-Source points may also be used in place of Jing-Well points.

[0047] In another embodiment, the first current electrode (A) or the first voltage sensing electrode (B) is connected to any one of the following Jing-Well points of the right or left hand: LU11, LI1, PC9, TE1, HT9 and SI1, and the second voltage sensing electrode (C) or the second current electrode (D) is connected to any one or more of toenails, tips of toes, acupuncture points or non-acupuncture points of the foot on the ipsilateral side under test. Yuan-Source points may also be used in place of Jing-Well points.

[0048] The methods and apparatuses disclosed herein may therefore be used to obtain information on the status of any one or more of the 12 regular acupuncture meridians on the left and right sides of the body: the six regular meridians of the legs (SP, LR, ST, GB, KI and BL); and the six regular meridians of the arms (LU, LI, PC, TE, HT and SI).

[0049] To measure bioimpedance along substantially the whole length of the body portion between the connection positions of the first and second current electrodes, the first voltage sensing electrode (B) can be connected adjacent the first current electrode (A) and the second voltage sensing electrode (C) can be connected adjacent the second current electrode (D).

[0050] However, additionally or alternatively, substantially shorter segments of the body between the connection positions of the first and second current electrodes may be measured. This may be achieved by connecting one or both of the voltage sensing electrodes at a greater distance from the respective current electrode, e.g. on a different arm or leg.

[0051] For example, the first current electrode and the second current electrode may be connected to the right hand and right foot respectively. Accordingly, electrical signals can be applied between the right hand and right foot, via the right leg, torso, and right arm, enabling bioimpedance to be determined all along that path. By connecting one of the voltage sensing electrodes to the right ankle, and another voltage sensing electrode to the left leg or ankle, the sensing electrodes can be used to determine bioimpedance across a meridian-defined segment of the right leg. Additionally or alternatively, by connecting one of the voltage sensing electrodes to the right wrist, and another of the voltage sensing electrodes to the left arm or wrist, the sensing electrodes can be used to determine bioimpedance across a meridian-defined segment of the right arm. Additionally or alternatively, by connecting one of the voltage sensing electrodes to the left arm or wrist, and another of the voltage sensing electrodes to the left leg or ankle, the sensing electrodes can be used to determine bioimpedance along the right side of the torso. Various other connection points are conceivable to achieve similar segment analysis. The arrangements may be translated to the left side of the body for analysis of the left leg, the left arm and the left side of the torso. [0052] The analysis of the various different body regions may be performed in 'real-time', allowing continuous monitoring of the various meridian-defined body segments set out above. Optionally, analysis and monitoring can be performed on different body regions at the same time, through the use of multi-channel sensing arrangements.

[0053] Notably, despite the potentially large distances between the current electrodes and voltage sensing electrodes when placing the sensing electrodes on the other side of the body from the current electrodes, rather than bioimpedance data reaching a single plateau, independent of which current electrode is selected, differences in the bioimpedance data for each pathway analysed is observable. This is indicative of the different electrical statuses of preferential electrical pathways, such as the meridian-defined pathways, and is consistent with findings that point to the existence of preferential pathways in the body for current flow.

[0054] As discussed above, the methods and apparatus of the present disclosure may allow bioimpedance analysis along multiple preferential electrical pathways, e.g. meridian-defined pathways and segments thereof. The result of such detailed analysis may extend the application of body composition analysers beyond the realm of providing a very general health assessment of the individual through the generation of a single phase angle reading. Rather, a matrix of phase angles may be generated, one for each combination of body pathway and segment analysed. The data generated can be used, for example, to identify corresponding left and right meridian-defined segments of selected regions that have poor left -right balance and/or meridian-defined segments that are associated with excessively high or low phase angles. As a result, the methods and apparatus may provide an assessment tool or aid for healthcare providers (acupuncturist, physical therapist etc.) to specify treatment protocols for that individual. Furthermore, the methods and apparatus may be used during the treatment itself, as a means of achieving a detailed, non-invasive, monitoring of the response of the body to treatment, in real time if required, to allow objective assessment of the efficacy of the treatment.

[0055] The apparatus may be set up to determine bioimpedance on one side of the body only, but may then be moved to determine bioimpedance on the other side of the body. Alternatively, the apparatus may be duplicated, with two different sets of the electrodes being provided (i.e., at least 8 electrodes in total), allowing analysis and/or monitoring on both sides of the body without requiring reconfiguration.

[0056] In any of the aspects of the present disclosure, the current electrodes can be connected to drive apparatus for controlling the electrical signals, e.g. controlling the current or voltage level of the electrical signal, the pattern of electrical signals (e.g. pulsed signals (voltage or current pulsed)) and/or the sequence of electrical signals. The drive apparatus may include a computer interface for automatic control of the electrical signals, and/or to permit a user (e.g. the patient, or a clinician, doctor, or other health worker) to control the electrical signals prior to and/or during analysis or monitoring. The drive apparatus may be powered by batteries or by mains power. A.C. electrical signals may be used.

[0057] Electrodes that are used to measure voltage, which can include the current electrodes in addition to the voltage sensing electrodes, can be connected to voltage sensing apparatus, for sensing the electrical signals across the electrodes and for providing corresponding raw data, for processing the raw data, and for providing an output of the processed data in a suitable form for the end user. For example, the apparatus may include voltage detection circuitry, a multiplexer and a computer interface with appropriate software. The drive apparatus and sensing apparatus may be combined to allow feedback between the two systems.

Brief Description of Drawings

[0058] By way of example only, embodiments are now described with reference to the accompanying drawings, in which:

[0059] Figs. 1 and lb show electrode positions in a method and apparatus according to an embodiment of the present disclosure;

[0060] Fig. 2 shows a schematic illustration of the electrode positions of Figs, la and lb in relation to a skin surface;

[0061] Fig. 3 shows a probe used in a method and apparatus according to an embodiment of the present disclosure;

[0062] Fig. 4a and 4b show electrode positions in a method and apparatus according to another embodiment of the present disclosure;

[0063] Figs. 5a and 5b show location positions of Jing-Well and Yuan-Source points, respectively, in addition to standard BIA sites;

[0064] Fig. 6a and 6b shows schematic illustrations of apparatus according to embodiments of the present disclosure; [0065] Figs. 7a to 7d show electrode positions in methods and apparatus according to embodiments of the present disclosure to achieve analysis of different body regions and segments.

[0066] Fig. 8 shows electrode positions in methods and apparatus according to embodiments of the present disclosure to achieve analysis of a body segment.

[0067] Fig. 9 shows electrode positions in a method and apparatus according to an embodiment of the present disclosure;

[0068] Fig. 10 shows a schematic illustration of the electrode positions of Fig. 9 in relation to a skin surface;

[0069] Fig. 11 shows electrode positions in a method and apparatus according to an embodiment of the present disclosure;

[0070] Fig. 12 shows a schematic illustration of the electrode positions of Fig. 11 in relation to a skin surface;

[0071] Fig. 13 shows electrode positions in a method and apparatus according to an embodiment of the present disclosure;

[0072] Fig. 14 shows a schematic illustration of the electrode positions of Fig. 13 in relation to a skin surface;

[0073] Fig. 15 shows a phase angle profile graph for different electrical pathways of a body obtained in an example of the present disclosure;

[0074] Fig. 16 shows a phase angle profile graph for different electrical pathways of a body obtained in another example of the present disclosure; and

[0075] Fig. 17 shows an RXc graph of bioimpedance data obtained in an example of the present disclosure.

Description of Embodiments

[0076] Various apparatus and methods discussed in the following description of embodiments have electrodes positioned for analysis and monitoring of one of the right side and the left side of a body. However, in each embodiment, it will be understood the electrodes can be positioned, mutatis mutandis, for analysis and monitoring of the other side of the body. Further, reference is made in the discussions to connection of various electrodes to acupuncture points, although other types of biologically active points may be used in place of acupuncture points.

[0077] With reference to Figs, la and lb, according to an embodiment of the present disclosure, bioimpedance measurement apparatus is provided that includes a first current electrode A connected to an acupuncture point on a right hand 21 of a body 2, a first voltage sensing electrode B connected to the wrist of the right hand 21 midway between the ulna and radial styloid processes, a second voltage sensing electrode C connected to an ankle of a right foot 22 on the dorsum of the right ankle between the medial and lateral malleoli and a second current electrode D connected to a tip of a toe of the left foot 22. In this embodiment, the first and second current electrodes can be considered outer electrodes and form part of a drive circuit and the first and second voltage sensing electrodes can be considered inner electrodes and form part of a voltage sensing circuit. The first and second current electrodes can also form part of the voltage sensing circuit.

[0078] At least one electrical signal is applied between the first and second current electrodes A, D. In response to the electrical signal, voltage is measured between at least two different pairs of the electrodes A, B, C, D, wherein each pair includes at least one of the current electrodes A, D. From a combination of the measured voltages, the bioimpedance Zj of a region of interest of the body that is located along a path between the current electrodes A, D is determined.

[0079] To further aid understanding, a schematic illustration of the electrode positioning is provided in Fig. 2. The electrodes A, B, C, D are shown located connected to a skin surface 23 of the body. Tissue regions along the current path between the first and second current electrodes A, D can be considered to have respective bioimpedances, represented using resistor symbols (black rectangles). The tissue region of interest, having a bioimpedance Zj that is to be determined, is identified by reference numeral 24.

[0080] In this embodiment, the at least one electrical signal (having current (I)) is applied between the first and second current electrodes A,D. Voltage (V(AC)) is then measured between the first current electrode A and the first voltage sensing electrode C; voltage (V(BD)) is measured between the first voltage sensing electrode B and the second current electrode D; and voltage (V(AD)) is measured between the first current electrode A and the second current electrode D. The bioimpedance (Zj) of the region of interest 24 is determined using Equation 1 : _ V(AC) V(BD) V(AD)

I I I [1]

[0081] In this embodiment, voltages and bioimpedances are therefore measured across tissue located between different combinations of electrodes, including tissue located across the entire electrical signal (current) path. This contrasts, for example, with a possible alternative approach in which voltage (V(BC)) is measured between the first voltage sensing electrode B and the second voltage sensing electrode C, and the bioimpedance (Zj) of the region of interest 24 is determined using comparative Equation 1 ' :

V(BC)

Comparative [ ]

[0082] By incorporating, into the determination of the bioimpedance Zj across the region of interest using Equation 1 , bioimpedance measurement across the total current path itself, contributions to the bioimpedance measurement from deeper current pathways arising outside of the region of interest of the body can be achieved. Further, through use of a combination of measurements between different electrodes, any error in the bioimpedance determination at the region of interest that might be caused by electrode-to-tissue contact impedances may be reduced or eliminated.

[0083] As an alternative to the voltage measurements set forth above, voltage (V(AC)) can measured between the first current electrode A and the second voltage sensing electrode C; and voltage (V(AB)) measured between the first current electrode A and the first voltage sensing electrode B and the bioimpedance (Zj) of the region of interest may be determined using Equation 2a:

[2a]

[0084] As another alternative, voltage (V(BD)) can be measured between the first voltage sensing electrode B and the second current electrode D; and voltage (V(CD)) measured between the second voltage sensing electrode C and the second current electrode D and the bioimpedance (Zj) of the region of interest may be determined using Equation 2b:

₇ V(BD) V(CD)

Z, =— - -— [2b] [0085] In this embodiment, the first current electrode A is connected to an acupuncture point of the right arm and the second current electrode D is connected to a tip of a toe of the right leg (or alternatively a nail, an acupuncture point, a non-acupuncture point/or a skin zone of the right leg). Nevertheless, the configuration may be reversed such that the first current electrode A is connected to an acupuncture point of the right leg and the second current electrode D is connected to a tip of a finger of the right arm (or alternatively a nail, an acupuncture point, a non-acupuncture point/or a skin zone of the right arm).

[0086] Example acupuncture points include the anatomical locations of various Jing-Well points as referenced in Fig. 5a or the anatomical locations of various Yuan-Source points as referenced in Fig. 5b. Thus, in one example the first current electrode A can be connected to a specific Jing-Well point on the right hand, such as LI1, near the radial base of the nail of the index finger of the right hand. Meanwhile, the second current electrode D can be connected to the tip of the first toe of the right foot. In an alternative example, the first current electrode A can be connected to a specific Jing-Well point of the right foot, such as ST45, near the lateral base of the nail of the second toe. Meanwhile, the second current electrode D can be connected to the tip of the middle finger of the right hand.

[0087] By connecting the first and second current electrodes A, D to different limbs, e.g., at Jing-Well, Yuan-source or tips of digits, electrical signals may be transmitted across one or more different preferential electrical pathways of the body. Electrical signals may be transmitted along one or more meridian-defined preferential electrical pathways of the body.

[0088] Bioimpedance across a number of different preferential electrical pathways of the body may be determined by moving the first current electrode A between different connection positions. The first current electrode A may take the form of a mobile probe, which can be sequentially pressed against different points, e.g. Jing-Well or Yuan-Source points, whilst bioimpedance data for each probe point/meridian is recorded. The probe may be configured as shown in Fig. 3, for example, the probe having a handle section 10, which can be held by the user to allow

manipulation of the probe, and a removable contact section 11. The handle section 10 is connected to a wire 103 at its proximal end 101, for supplying electrical current thereto. At the distal end 102 of the handle section 10, a recess is provided (not shown) for receiving a conductive stud (e.g. of stainless steel material) located on one side of the contact section 11 in a snap-fit or click-fit manner. On the opposing side of the contact section 11 , a hydrogel electrolyte coating or a suitable dry electrode material is provided to ensure good releasable electrical contact between the probe and the patient's skin or nail. Once the analysis has been carried out, the contact section 11 can be removed and cleaned or replaced. A number of variations of the probe are conceivable, including having the contact section integral with the main section and forming the contact section of material that is relatively easy to clean or disinfect in situ, e.g. gold plating.

[0089] Although only one first current electrode is employed in the apparatus of Figs, la and lb, in other embodiments a plurality of first current electrodes can be provided. Thus, first current electrodes A can be connected at the same time to various positions, such as Jing-Well or Yuan- Source points, of the arm or leg. An electrical signal may be applied between each combination of the first and second current electrodes sequentially, whilst the bioimpedance data of an associated region of interest can be recorded. By taking this approach, a plurality of pathways can be analysed or monitored without requiring reconfiguration of the electrode arrangement.

[0090] Following from this, as shown in Fig. 4a, six first current electrodes A may be provided, for example, each connected to a respective Jing-Well point of the six regular meridians. As another alternative, as shown in Fig. 4b, six first electrodes A may be provided, for example, each connected to a respective Yuan-Source point of the six regular meridians.

[0091] In addition to or as an alternative to determining bioimpedance across a number of different preferential electrical pathways of the body using multiple first current electrodes A, or using a current electrode A in the form of a mobile probe, bioimpedance across a number of different preferential electrical pathways may be determined by moving the second current electrode D. For example, where multiple first current electrodes A are provided, an electrical signal may be applied sequentially between each of the first current electrodes A and the second current electrode D, the second current electrode D being located in a first position. Associated bioimpedance may be recorded. Subsequently, an electrical signal may be applied sequentially between each of the first current electrodes A and the second current electrode D, the second current electrode D being located in a second position different from the first position. Again, associated bioimpedance may be recorded. Each different position of the first current electrode D may be on the same hand or same foot, for example, and/or may be on different parts of the body. Bioimpedance data sets for each position of the second current electrode D may be compared with each other, e.g., for diagnostic purposes or otherwise.

[0092] Each first current electrode A and second current electrode D can form part of bioimpedance measurement apparatus shown schematically in Fig. 6a, for example. The apparatus comprises integrated drive and voltage sensing circuitry 71, the circuitry 71 being connected to the second current electrode B and the first and second voltage sensing electrodes, C, D, and connectable, via a multiplexer 72, to any one of the plurality of the first current electrodes A, enabling current to be delivered, from a power supply, to any combination of the electrodes, and voltage to measure measured across any combination of the electrodes. The circuitry 71 and multiplexer 72 are controlled by a controller 75 and integral user interface and data processor 76. The user interface allows the patient or clinician to control, through a graphical interface 77 connected thereto, the order in which current is applied to different electrodes, for example. The circuitry 71 is arranged to receive voltage readings from different pairs of the electrodes and deliver the voltage readings to the data processor 76 which is configured to generate corresponding bioimpedance data and present the data to the user via the graphical interface 77. The user interface and data processor 76, and graphical interface 77, may form part of a general purpose computer, or a custom-built device.

[0093] With reference to Fig. 9, according to an alternative embodiment of the present disclosure, bioimpedance measurement apparatus is provided that includes a first voltage sensing electrode B connected to an acupuncture point on a right hand 21 of a body 2, a first current electrode A connected to the wrist of the right hand 21 , a second current electrode D connected to an ankle of a right foot 22 of the body and a second voltage sensing electrode C connected to a tip of a toe of the left foot 22. In this embodiment, the first and second voltage sensing electrodes can be considered outer electrodes forming part of a voltage sensing circuit and the first and second current electrodes can be considered inner electrodes, forming part of a drive circuit. The first and second current electrodes can also form part of the voltage sensing circuit.

[0094] Again, at least one electrical signal is applied between the first and second current electrodes A, D. In response to the electrical signal, voltage is measured between at least two different pairs of the electrodes A, B, C, D, wherein each pair includes at least one of the current electrodes A,D. From a combination of the measured voltages, the bioimpedance Zj of a region of interest of the body that is located along a path between the current electrodes A, D is determined.

[0095] To further aid understanding, a schematic illustration of the electrode positioning is provided in Fig. 10. The electrodes A, B, C, D are shown connected to a skin surface 23 of the body. Tissue regions along the current path between the first and second current electrodes A, D can be considered to have respective bioimpedances, represented using resistor symbols (black rectangles). The tissue region of interest, having a bioimpedance Zj that is to be determined, is identified by reference numeral 24.

[0096] In this embodiment, the at least one electrical signal (having current (I)) is applied between the first and second current electrodes A,D. Again, voltage (V(AC)) is then measured between the first current electrode A and the first voltage sensing electrode C; voltage (V(BD)) is measured between the first voltage sensing electrode B and the second current electrode D; and voltage (V(AD)) is measured between the first current electrode A and the second current electrode D. The bioimpedance (Zj) of the region of interest 24 is again determined using Equation 1:

_ V(AC) V(BD) V(AD)

[i]

[0097] In this embodiment, voltages and bioimpedances are therefore measured across tissue located between different combinations of electrodes, including tissue located across the entire electrical signal (current) path, offering advantages as discussed above with respect to the preceding embodiment.

[0098] As an alternative to the voltage measurements set forth above, voltage (V(AC)) can measured between the first current electrode A and the second voltage sensing electrode C; and voltage (V(AB)) measured between the first current electrode A and the first voltage sensing electrode B and the bioimpedance (Zj) of the region of interest may be determined again using Equation 2a:

[2a]

[0099] As another alternative, voltage (V(BD)) can be measured between the first voltage sensing electrode B and the second current electrode D; and voltage (V(CD)) measured between the second voltage sensing electrode C and the second current electrode D and the bioimpedance (Zj) of the region of interest may again be determined using Equation 2b:

[2b]

[0100] As another alternative, voltage V(BC) can be measured between the first voltage sensing electrode (B) and the second voltage sensing electrode (C) and bioimpedance (Zj) of the region of interest may be determined using Equation 3:

[0101] In this embodiment, the first voltage sensing electrode B is connected to an acupuncture point of the right arm and the second voltage sensing electrode C is connected to a tip of a toe of the right foot (or alternatively a nail, an acupuncture point, a non-acupuncture point/or a skin zone of the right foot/leg). Nevertheless, the configuration may be reversed such that the first voltage sensing electrode A is connected to an acupuncture point of the right leg and the second voltage sensing electrode C is connected to a tip of a finger of the right hand (or alternatively a nail, an acupuncture point, a non-acupuncture point/or a skin zone of the right hand/arm).

[0102] Example acupuncture points include those discussed with respect to the preceding embodiments e.g Jing-Well points or Yuan-Source points. Again, electrical signals may be transmitted across one or more different preferential electrical pathways of the body. Particularly, electrical signals may be transmitted along one or more meridian-defined preferential electrical pathways of the body.

[0103] With reference to Fig. 11 , according to an alternative embodiment of the present disclosure, bioimpedance measurement apparatus is provided that includes a first voltage sensing electrode B connected to an acupuncture point on a right hand 21 of a body 2, a first current electrode A connected to the wrist of the right hand 21, a second voltage sensing electrode C connected to an ankle of a right foot 22 of the body and a second current electrode D connected to a tip of a toe of the left foot 22.

[0104] Again, at least one electrical signal is applied between the first and second current electrodes A, D. In response to the electrical signal, voltage is measured between at least two different pairs of the electrodes A, B, C, D, wherein each pair includes at least one of the current electrodes A,D. From a combination of the measured voltages, the bioimpedance Zj of a region of interest of the body that is located along a path between the current electrodes A, D is determined.

[0105] To further aid understanding, a schematic illustration of the electrode positioning is provided in Fig. 12. The electrodes A, B, C, D are shown connected to a skin surface 23 of the body. Tissue regions along the current path between the first and second current electrodes A, D can be considered to have respective bioimpedances, represented using resistor symbols (black rectangles). The tissue region of interest, having a bioimpedance Zj that is to be determined, is identified by reference numeral 24.

[0106] In this embodiment, the at least one electrical signal (having current (I)) is applied between the first and second current electrodes A,D. Again, voltage (V(AC)) is measured between the first current electrode A and the first voltage sensing electrode C; voltage (V(BD)) is measured between the first voltage sensing electrode B and the second current electrode D; and voltage (V(AD)) is measured between the first current electrode A and the second current electrode D. The bioimpedance (Zj) of the region of interest 24 is again determined using Equation 1 : V(AC) V(BD) V(AD)

[0107] In this embodiment, voltages and bioimpedances are therefore measured across tissue located between different combinations of electrodes, including tissue located across the entire electrical signal (current) path, offering advantages as discussed above with respect to the preceding embodiments.

[0108] As an alternative to the voltage measurements set forth above, voltage (V(AC)) can measured between the first current electrode A and the second voltage sensing electrode C; and voltage (V(AB)) measured between the first current electrode A and the first voltage sensing electrode B and the bioimpedance (Zj) of the region of interest may be determined again using Equation 2a:

[2a]

[0109] As another alternative, voltage (V(BD)) can be measured between the first voltage sensing electrode B and the second current electrode D; and voltage (V(CD)) measured between the second voltage sensing electrode C and the second current electrode D and the bioimpedance (Zj) of the region of interest may again be determined using Equation 2b:

[2b]

[0110] As another alternative, voltage V(BC) can be measured between the first voltage sensing electrode (B) and the second voltage sensing electrode (C) and bioimpedance (Zj) of the region of interest may be determined using Equation 3:

[0111] In this embodiment, the first voltage sensing electrode B is connected to an acupuncture point of the right arm and the second current electrode D is connected to a tip of a toe of the right foot (or alternatively a nail, an acupuncture point, a non-acupuncture point/or a skin zone of the right foot/leg). Nevertheless, the configuration may be reversed such that the first voltage sensing electrode A is connected to an acupuncture point of the right leg and the second current electrode D is connected to a tip of a finger of the right hand (or alternatively a nail, an acupuncture point, a non-acupuncture point/or a skin zone of the right hand/arm).

[0112] Example acupuncture points include those discussed with respect to the preceding embodiments, e.g Jing-Well points or Yuan-Source points. Again, electrical signals may be transmitted across one or more different preferential electrical pathways of the body. Particularly, electrical signals may be transmitted along one or more meridian-defined preferential electrical pathways of the body.

[0113] With reference to Fig. 13, according to an alternative embodiment of the present disclosure, bioimpedance measurement apparatus is provided that includes a first current electrode A connected to an acupuncture point on a right hand 21 of a body 2, a first voltage sensing electrode B connected to the wrist of the right hand 21, a second current electrode D connected to an ankle of a right foot 22 of the body and a second voltage sensing electrode C connected to a tip of a toe of the left foot 22.

[0114] Again, at least one electrical signal is applied between the first and second current electrodes A, D. In response to the electrical signal, voltage is measured between at least two different pairs of the electrodes A, B, C, D, wherein each pair includes at least one of the current electrodes A, D. From a combination of the measured voltages, the bioimpedance Zj of a region of interest of the body that is located along a path between the current electrodes A, D is determined.

[0115] To further aid understanding, a schematic illustration of the electrode positioning is provided in Fig. 14. The electrodes A, B, C, D are shown connected to a skin surface 23 of the body. Tissue regions along the current path between the first and second current electrodes A, D can be considered to have respective bioimpedances, represented using resistor symbols (black rectangles). The tissue region of interest, having a bioimpedance Zj that is to be determined, is identified by reference numeral 24.

[0116] In this embodiment, the at least one electrical signal (having current (I)) is applied between the first and second current electrodes A,D. Again, voltage (V(AC)) is measured between the first current electrode A and the first voltage sensing electrode C; voltage (V(BD)) is measured between the first voltage sensing electrode B and the second current electrode D; and voltage (V(AD)) is measured between the first current electrode A and the second current electrode D. The bioimpedance (Zj) of the region of interest 24 is again determined using Equation 1 : V(AC) V(BD) V(AD)

[0117] In this embodiment, voltages and bioimpedances are therefore measured across tissue located between different combinations of electrodes, including tissue located across the entire electrical signal (current) path, offering advantages as discussed above with respect to the preceding embodiments.

[0118] As an alternative to the voltage measurements set forth above, voltage (V(AC)) can measured between the first current electrode A and the second voltage sensing electrode C; and voltage (V(AB)) measured between the first current electrode A and the first voltage sensing electrode B and the bioimpedance (Zj) of the region of interest may be determined again using Equation 2a:

[2a]

[0119] As another alternative, voltage (V(BD)) can be measured between the first voltage sensing electrode B and the second current electrode D; and voltage (V(CD)) measured between the second voltage sensing electrode C and the second current electrode D and the bioimpedance (Zj) of the region of interest may again be determined using Equation 2b:

[2b]

[0120] As another alternative, voltage V(BC) can be measured between the first voltage sensing electrode (B) and the second voltage sensing electrode (C) and bioimpedance (Zj) of the region of interest may be determined using Equation 3:

[0121] In this embodiment, the first current electrode A is connected to an acupuncture point of the right arm and the second voltage sensing electrode C is connected to a tip of a toe of the right foot (or alternatively a nail, an acupuncture point, a non-acupuncture point/or a skin zone of the right foot/leg). Nevertheless, the configuration may be reversed such that the first current electrode A is connected to an acupuncture point of the right leg and the second voltage sensing electrode C is connected to a tip of a finger of the right hand (or alternatively a nail, an acupuncture point, a non-acupuncture point/or a skin zone of the right hand/arm).

[0122] Example acupuncture points include those discussed with respect to the preceding embodiments, e.g Jing-Well points or Yuan-Source points. Again, electrical signals may be transmitted across one or more different preferential electrical pathways of the body. Particularly, electrical signals may be transmitted along one or more meridian-defined preferential electrical pathways of the body.

[0123] The embodiments discussed with reference to Figs. 9 to 14 may employ bioimpedance measurement apparatus substantially as shown in Fig. 6a, but with different electrode positioning on the body. However, in the embodiments discussed with reference to Figs. 9 to 12, where it is the voltage sensing electrode B that is connected to the acupuncture point, rather than the more proximally located first current electrode A, a plurality of voltage sensing electrodes B may be employed in place of a plurality of current electrodes A, as illustrated in Fig. 6b, for example. The voltage sensing electrodes B may be multiplexed using the multiplexer 72 in order to obtain voltage measurements, and thus determine bioimpedances, across different electrical pathways.

[0124] The electrode arrangements positioned on the body as represented in Figs, la, lb, 9, 11 and 13, for example, may be used to determine bioimpedance across substantially a 'whole body region' (e.g. between ankle and wrist) of each electrical pathway. Additionally or alternatively, electrodes may be positioned so that bioimpedance across body segments may be determined. This may be achieved by connecting one or both of the voltage sensing electrodes, or additional voltage sensing electrodes, to the arm, wrist, leg or ankle associated with the other hand and foot to that having the first and second current electrodes connected thereto.

[0125] A 'whole body' analysis arrangement, with electrodes positioned in accordance with the embodiment discussed with reference to Figs, la and lb, is further represented in Fig. 7a. The first current electrode A, and the second current electrode D, are connected to the right hand and right foot respectively. Accordingly, electrical signals can be transmitted between the right hand and right foot, via the right leg, torso, and right arm, and voltage drop across that path, indicated generally by an unbroken line 3, will take place. Voltage measurements are made using, inter alia, the voltage sensing electrodes B, C, located on the right wrist and right leg respectively, across a path indicated generally by a broken line 4. Thus, the section for which bioimpedance can be determined in this arrangement is substantially a whole body region between the first and second current electrodes A, D. [0126] However, with reference to Fig. 7b, by connecting the first voltage sensing electrode B to the right wrist, and the second voltage sensing electrode C to the left wrist, voltages can be determined including along a path, indicated by unbroken line 41, extending across the right arm, upper torso and left arm. Since the region between the upper part of the right shoulder and the second voltage sensing electrode C is at the same potential (because there is substantially no current flow between these two sites), voltage drop and bioimpedance calculations will only relate to the right arm (along path 31). Thus, the apparatus can be configured in this manner to determine bioimpedance of the right arm only, again using Equation 1.

[0127] Similarly, with reference to Fig. 7c, by connecting the first voltage sensing electrode B to the right ankle, and the second voltage sensing electrode D to the left ankle, voltages can be determined including along another path, indicated by broken line 42, extending across the right leg, lower torso and left leg. Since the region between the voltage sensing electrode B and the upper part of the right leg is at the same potential (because there is substantially no current flow between these two sites), voltage drop and bioimpedance calculations will only relate to the right leg (along path 32) between the first and second current electrodes A, D. Thus, the apparatus can be configured in this manner to determine bioimpedance of the right leg only, again using Equation 1.

[0128] Similarly, with reference to Fig. 7d, by connecting the first voltage sensing electrode B to the left wrist, and the second voltage sensing electrode C to the left ankle, the voltages can be determined including along yet another path, indicated by broken line 43, extending across the left arm, torso and left leg. Since the region between the first voltage sensing electrode B and the upper part of the right arm is at the same potential (because there is no current flow between these two sites), and the region between the second voltage sensing electrode C and the upper part of the right leg is at the same potential (because there is also no current flow between these two sites either) voltage drop and bioimpedance calculations will only relate to the right torso (along path 33) between the first and second current electrodes A, D. Thus, the apparatus can be configured in this manner to determine bioimpedance of the right torso only, again using Equation 1.

[0129] The apparatus discussed with reference to Figs. 7a to 7d may be adapted for analysis of particular portions of the left side of the body in a similar manner. Further, the apparatus may be adapted to include electrode configurations, similar to those discussed with reference to Figs. 10 and 12, where the first current electrode (A) is positioned proximally of the first voltage sensing electrode (B), the first voltage sensing electrode (B) being connected to the acupuncture point (as represented in Fig. 8, for example). Bioimpedance may be determined again using Equation 1 , for example. [0130] In the arrangement of Fig. 8, by connecting the first voltage sensing electrode B to an acupuncture point of the right hand, and the second voltage sensing electrode the left wrist, voltages can be determined including along a path, indicated by unbroken line 44, extending across the right arm, upper torso and left arm. Since the region between the upper part of the right shoulder and the second voltage sensing electrode C is at the same potential (because there is substantially no current flow between these two sites), voltage drop and bioimpedance calculations will only relate to the right arm (along path 34). Thus, the apparatus can be configured in this manner to determine bioimpedance of the right arm only.

[0131] A method of determining bioimpedance using the apparatus substantially as illustrated in Fig. 6a, for example, will now be described.

a. The whole -body phase angle on the right side of the body is determined using Equation 1 with the first current electrode A connected to a standard BIA (non-acupuncture) point on the right hand, the second current electrode D positioned on the dorsal surface of the third metatarsal of the right foot, and the first and second voltage sensing electrodes B, C connected to the wrist of the right arm and the ankle of the right leg, respectively.

b. With a plurality of the first current electrodes A connected to the six Jing-Well points of the right hand, the second current electrode D positioned on the dorsal surface of the third metatarsal of the right foot, and the first and second voltage sensing electrodes B, C connected to the wrist of the right arm and the ankle of the right leg, respectively, the phase angle associated with each of the six Jing-Well point-defined meridians of the right hand is determined using Equation 1.

c. With a plurality of the first current electrodes A connected to the six Jing-Well points of the right foot, the second current electrode positioned on the dorsal surface of the third metacarpal of the right hand, and the first and second voltage sensing electrodes B, C connected to the ankle of the right leg and the wrist of the right arm, respectively, the phase angle associated with each of the six Jing-Well point-defined meridians of the right foot (plus Klla), is determined using Equation 1.

d. The whole -body phase angle on the left side of the body is determined using Equation 1 with the first current electrode A connected to a standard BIA (non-acupuncture) point on the left hand, the second current electrode D positioned on the dorsal surface of the third metatarsal of the left foot, and the first and second voltage sensing electrodes B, C connected to the wrist of the left arm and the ankle of the left leg, respectively.

e. With a plurality of the first current electrodes A connected to the six Jing-Well points of the left hand, the second current electrode D positioned on the dorsal surface of the third metatarsal of the left foot, and the first and second voltage sensing electrodes B, C connected to the wrist of the left arm and ankle of the left leg, respectively, the phase angle associated with each of the six Jing-Well point-defined meridians of the left hand is determined using Equation 1.

c. With a plurality of the first current electrodes A connected to the six Jing-Well points of the left foot, the second current electrode D positioned on the dorsal surface of the third metacarpal of the left hand, and the first and second voltage sensing electrodes B, C connected to the ankle of the left leg and wrist of the left arm, respectively, the phase angle associated with each of the six Jing-Well point-defined meridians of the left foot (plus Klla), is determined using Equation 1.

g. The ratio of the phase angle of each meridian on the right side of the body to the whole -body phase angle on the right side of the body is calculated. Likewise, the ratio of the phase angle of each meridian on the left side of the body to the whole-body phase angle on the left side of the body is calculated.

h. The left-side percentage difference in raw phase angle between left -right matched meridians is determined.

i. The left-right percentage difference in ratios of meridian phase angle to whole- body phase angle between left -right matched meridians is determined.

j. Results are output graphically and/or numerically.

[0132] To carry out this method or alternative methods of using the electrode apparatus of the present invention, in one embodiment the drive circuit and sensing circuit are connected to a power supply and control apparatus, e.g. as shown in Fig. 6a. The control apparatus comprises a controller, which controls the current or voltage level of the electrical signal, the pattern of electrical signals (e.g. pulsed signals) and the sequence of electrical signals sent to different current electrodes of the circuit; a patient interface, which allows a user to set appropriate electrical signal control, e.g. so that a user can select a particular meridian-defined segment for analysis, or the electrical signal parameters prior to and/or during analysis; and data processor, which receives the raw data such as phase angle and impedance magnitude from the sensing circuit, and processes the raw data; and a graphical interface, which provides an output of the processed data in a suitable form for interpretation by the end user. The methods of the present invention may be implemented using computer software, e.g. arranged to execute the method steps a to j, or variations thereof, set out above.

[0133] In general, when an electrode is connected to the wrist, it may be connected at a standard bioimpedance analysis site midway between the ulna and radial styloid processes, or otherwise. Further, when an electrode is connected to the ankle, it may be connected at a standard

bioimpedance analysis site on the dorsum of the right ankle between the medial and lateral malleoli, or otherwise. [0134] Various further non-limiting arrangements, configurations, parameters and techniques that may be used in embodiments of the apparatus and methods of the present invention are set out below.

Electrical Signals

[0135] The electrical signals delivered by the drive circuit electrodes may be AC (sinusoidal signals). The signals may have a frequency range of 100 Hz to 100 MHz, preferably 3 kHz to 1 MHz. Signals may be in the form of a single frequency, a set of frequencies (i.e. multi -frequency) or a continuous sweep (spectrum) of frequencies. For controlled current drive, applied current may be 0.2 μΑ to 2 mA, preferably 5 uA to 250 uA. For controlled voltage drive, the applied voltage may be 0.05V to 5.0 V, preferably 0.2 V to 2.0 V. A constant current drive may be preferable to counteract slight variations in the skin or nail surface profile / quality of electrode contact at the current electrode connection points.

[0136] The electrical signals may be pulsed, e.g. a voltage pulse or a current pulse. Principle Outcome Measures

[0137] Principle outcome measures may be in the form of impedance magnitude, resistance, reactance, or their reciprocals (admittance magnitude, conductance, susceptance), phase angle, reactance divided by resistance or as derived quantities such resistance divided by patient height, reactance divided by patient height etc. Furthermore, these quantities can be related to a single applied frequency, a range of applied frequencies, or a continuous sweep of applied frequencies.

Electrodes

[0138] In any embodiment described herein, one or more of the current and voltage sensing electrodes may use a wet-type contact (e.g. using a conductive paste or hydrogel etc.). The contact may be adhesive or non-adhesive. Alternatively or additionally, any one or more of the current and voltage sensing electrodes may use a dry-type contact (e.g. using metal, metal oxide, conductive textile, conformal "tattoo-like" thin-film, microstructured carbon or ultrafine microneedle arrays etc.). Any one of more of the electrodes can be active electrodes which have small or unit amplification close to the electrode. This may allow the electrodes to be used without electrode gel, for example. Any one or more of the electrodes may rely on an adhesive contact with the patient, and/or tattoo-like van der Waal's contact and/or may be held in position using straps, bands, gloves, socks or belts or patient pressure (e.g. through a patient gripping or standing or resting on the electrodes). [0139] The electrodes may be comprised in an automated probe system, where contact is made between the electrode and the patient through movement of, for example, a robotic arm carrying the electrode. An automated system such as this may be used for remote analysis or monitoring of a patient.

[0140] Any one more of the electrodes may be fixed to the patient or moveable.

[0141] Any one or more of the electrodes may take the form of metal plates, discs, strips, ellipses, heart-shapes, or other irregular shapes. The discs for the current or voltage sensing electrodes that are to be connected to acupuncture points may have a diameter of between 0.1 and 15 mm, preferably 2 mm to 10 mm. The discs for current or voltage sensing electrodes that are to be connected elsewhere may have a diameter of between 0.1 and 30 mm, preferably 8 mm to 25 mm. Where strips are used, electrodes may have a width of 2 mm to 10 mm and/or a length of 2 mm to 40 mm. For example, the strip may be about 5 mm wide and 20 mm long. The strips may have a width of 2 mm to 30 mm and/or a length of 2 mm to 40 mm. Nonetheless, the sizes may be adjusted, e.g., outside of the ranges provided, as appropriate for contacting different regions of the patient's skin or nail.

[0142] To make electrical contact with the patient's skin or nail, pressure may be applied to the skin or nail that is sufficient to ensure stable and reproducible electrode-skin or electrode -nail contact.

[0143] Physical contact is preferably avoided between the examiner and the patient during measurement to prevent the introduction of short-circuit contributions into the electrical measurement. The examiner may wear insulating gloves to prevent this possibility.

[0144] All or part of any one of the electrodes may be disposable, and discarded following testing to reduce the likelihood of cross-infection between patients. Alternatively, any one or more of the electrodes may be disinfected after use, and suitably dried.

[0145] Standard medically-approved leads and cables may be used to connect the electrodes to the control apparatus, multiplexer and power supply etc. The leads may be directly connected into the multiplexer, or connected to a wireless transmission unit for wireless transfer of data and/or electrical signals.

Body Positioning [0146] During analysis, the patient's body may be located in the supine position, or they may be standing, or seated with hands and feet resting on a suitable insulating surface. The patient may be resting or standing on a non-conducting surface with arms and legs not touching each other or the patient's torso.

[0147] The patient's skin or nails may be wiped with disinfecting alcohol prior to electrode contact, with a sufficient, e.g. 5 minute, drying period subsequently. Body hair on the legs or arms is preferably not removed unless excessive.

[0148] The patient's palms may be facing down on an insulating surface with fingers gently extended and not touching each other.

[0149] If necessary, insulating material (e.g. cotton, foam etc.) may be inserted between the fingers or toes to act as spacers to prevent inter -digit contact.

Example 1 - Methods & Instrumentation

[0150] Testing was carried out on a healthy male subject, seated in a chair, with arms extended and resting on a table with palms face downwards, and with digits of fingers not touching each other.

[0151] After allowing the subject to remain rested in a seated position for more than 5 minutes, electrodes were connected to the subject. In particular, six first current electrodes (8-mm diameter aluminium-foil adhesive gel electrodes) were attached to the various Jing-Well points of the left hand of the subject and a further first current electrode (20 mm x 20 mm electrode) was positioned at a standard bioimpedance analysis site (Std) on the dorsal surface of the left hand; a first voltage sensing electrode (20 mm x 20 mm electrode) was attached at a standard bioimpedance analysis site on the left wrist, a second voltage sensing electrode (20 mm x 20 mm electrode) was attached at a standard bioimpedance analysis site on the left ankle; and a second current electrode (20 mm x 20 mm electrode), was attached to a standard bioimpedance site on the dorsal surface of the left foot of the subject. Once the electrodes were in position, each of the first electrodes A were subjected to the application of electrical signals according to the sequence: Std, LU, LI, PC, TE, HT, SI and voltage measurements between electrodes were made as required by Equation 1 and comparative Equation Γ above. Electrical signals were delivered at a frequency of 50 kHz AC, with constant current value of 50 μΑ.

Example 1 - Results & Discussion [0152] Fig.15 shows the average phase angle profiles (for the whole -body region) associated with the meridian-defined segments of the left arm superimposed on the standard phase angle (Av. PhA_Std BIA) value. Phase angles profiles based on single voltage measurements as defined by comparative Eqn. Γ (Av.PhA_Jing-Well) and combinational voltage measurements as defined by Eqn. 1 (Av.hPhA_Jing-Well) were determined. Each point is the average of four determinations at each test site obtained from the six measurement sequences. The dotted lines represent ± 1 standard deviation.

[0153] Referring to the profiles, it is evident that more readily identifiable differences (greater resolution) in phase angles between surface-defined meridians are seen using the combinational measurement approach.

[0154] Fig. 17 provides a further representation of the data obtained in Example 1, in which bioimpedance measurement of surface-defined meridians is represented by plotting bioimpedance parameters resistance (R) and reactance (Xc) as bivariate vectors in an RXc graph. This enables comparison of the meridian-related vectors by qualitative visual inspection and also by quantitative analysis using established statistical methods.

[0155] In this approach, sets of meridian data are plotted in the RXc graph as a mean vector and the vector distribution is represented by its associated 95% confidence interval (confidence ellipse). Two mean vectors from two independent sets of meridian data can be compared by Hotelling's T2 test, for example. In general, if the 95% confidence intervals of set means do not overlap, the sets will be significantly different (P < 0.05).

[0156] Fig. 17 shows the 95% confidence ellipses (in the (h)R(h)X graph) drawn for meridian sets whose Av.hPhA profiles are shown in Fig. 15. Clearly LU is statistically different (P < 0.05) from LI, PC & HT, for example.

[0157] This powerful method can be used for comparing not only meridian-defined segments within a limb but also between different limbs. Furthermore, this approach can be developed to allow comparison of an individual's meridian data with that of a standard healthy reference population (so called tolerance ellipses).

Example 2 - Methods & Instrumentation

[0158] Testing was carried out on a healthy male subject, seated in a chair, with arms extended and resting on a table with palms face downwards. [0159] After allowing the subject to remain rested in a seated position for more than 5 minutes, various bioimpedance electrodes were connected to the subject. In particular, a first voltage sensing electrode with dimensions 20 mm x 20 mm was attached at a site on the TE meridian 1 cm distal to the olecranon of the ulna analysis sites on the left wrist and a second voltage sensing electrode was attached at the standard bioimpedance site on the left ankle; and a circular second current electrode with diameter 7.5 mm, was attached to the standard bioimpedance site on the dorsal surface of the left foot of the subject. First current electrodes consisting of a 7.5 mm diameter circular electrode were positioned at the six Yuan-Source points near the wrist of the left arm .

[0160] Once the electrodes were in position, the various first current electrodes were probed in six measurement cycles according to the sequence: HT, PC, LU, LI, TE, SI. Voltage

measurements between electrodes were made as required by Equation 1 and comparative Equation Γ above. Electrical signals were delivered at a frequency of 50 kHz AC, with constant current value of 50 μΑ.

Example 2 - Results & Discussion

[0161] Fig. 16 shows the average phase angle profiles (for the region from the left elbow to left ankle) associated with the meridian-defined segments of the left arm. Phase angles profiles based on single voltage measurements as defined by comparative Equation 1 ' (Av.PhA_Yuan) and combinational voltage measurements as defined by Equation 1 (Av.hPhA_Yuan) were determined. Each point is the average of four determinations at each test site obtained from the six measurement sequences. The dotted lines represent ± 1 standard deviation.

[0162] Referring to the profiles, it is evident that greater resolution in phase angle between surface-defined meridians is achieved using the new combinational approach.

[0163] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above -described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

Claims:

1. A method of determining bioimpedance in a body, the method comprising:

connecting a first current electrode (A) to a first arm or leg of the body;

connecting a second current electrode (D) to a second arm or leg of the body;

connecting a first voltage sensing electrode (B) and a second voltage sensing electrode (C) at spaced apart positions of the body, separate from the first and second current electrodes;

wherein at least one of the first current electrode (A) and the first voltage sensing electrode (B) is connected to a biologically active point on the first arm or leg of the body, the method further comprising:

2. The method of claim 1 , wherein the biologically active point is an acupuncture point.

3. The method of claim 2, wherein the acupuncture point is a Jing-Well or a Yuan-Source point.

4. The method of claim 1, 2 or 3, wherein the first current electrode (A) is connected to the first arm, and the second current electrode (D) is connected to the first leg, the first arm and the first leg being ipsilateral.

5. The method of claim 1, 2 or 3, wherein the first current electrode (A) is connected to the first leg, and the second current electrode (D) is connected to the first arm, the first arm and the first leg being ipsilateral.

6. The method according to any one of the preceding claims, wherein the first current electrode (A) and the first voltage sensing electrode (B) are both connected to the first arm or leg.

7. The method of claim 6, wherein the first current electrode (A) is connected distally of the first voltage sensing electrode (B).

8. The method of claim 6, wherein the first voltage sensing electrode (B) is connected distally of the first current electrode (A).

9. The method of claim 6, 7 or 8, wherein the second current electrode (D) and the second voltage sensing electrode (C) are both connected to the second arm or leg.

10. The method of claim 9, wherein the second current electrode (D) is connected distally of the second voltage sensing electrode (C).

11. The method of claim 9, wherein the second voltage sensing electrode (C) is connected distally of the second current electrode (D).

12. The method of any one of the preceding claims, wherein at least one electrical signal having current (I) is applied between the first and second current electrodes (A,D);

a voltage (V(AD)) is measured between the first current electrode (A) and the second current electrode (D); and

bioimpedance (Zj) of the region of interest is determined using Equation 1 :

V(AC) V(BD) V(AD)

Z, =

I I I Equation [1].

13. The method of any one of the preceding claims, wherein at least one electrical signal having current (I) is applied between the first and second current electrodes (A, D);

a voltage (V(AB)) is measured between the first current electrode (A) and the first voltage sensing electrode (B); and

bioimpedance (Zj) of the region of interest is determined using Equation 2a:

V(AC) V(AB)

Z, =

I I Equation [2a].

14. The method of any one of the preceding claims, wherein at least one electrical signal having current (I) is applied between the first and second current electrodes (A, D);

a voltage (V(CD)) is measured between the second voltage sensing electrode (C) and the second current electrode (D); and

bioimpedance (Zj) of the region of interest is determined using Equation 2b:

Equation [2b].

15. The method of any one of the preceding claims, wherein the first voltage sensing electrode (B) is connected at a position at least 5 cm from the connection position of the first current electrode (A).

16. The method of any one of the preceding claims, wherein the second voltage sensing electrode (C) is connected at a position at least 5 cm from the connection position of the second current electrode (D).

17. A method of determining bioimpedance in a body, the method comprising:

connecting a first current electrode (A) to a first arm or leg of the body;

connecting a second current electrode (D) to a second arm or leg of the body;

wherein:

the method further comprising:

applying at least one electrical signal between the first and second current electrodes; measuring, in response to the at least one electrical signal applied between the first and second current electrodes, voltage between the first and second voltage sensing electrodes; and determining, from the voltage measurement, the bioimpedance of a region of interest of the body that is located along a path between the first and second current electrodes.

18. The method of claim 17, wherein the biologically active point is an acupuncture point.

19. The method of claim 18 wherein the acupuncture point is a Jing-Well or a Yuan-Source point.

20. The method of claim 17, 18 or 19, wherein the first current electrode (A) and the first voltage sensing electrode (B) are connected to the first arm, and the second sensing electrode (C) and the second current electrode (D) are connected to the first leg, the first arm and the first leg being ipsilateral.

21. The method of claim 17, 18 or 19, wherein the first current electrode (A) and the first voltage sensing electrode (B) are connected to the first leg, and the second sensing electrode (C) and the second current electrode (D) are connected to the first arm, the first arm and the first leg being ipsilateral.

22. The method according to any one of claims 17 to 21 , wherein the first voltage sensing electrode (B) is connected distally of the first current electrode (A) on the first arm or leg.

23. The method according to any one of claims 17 to 22, wherein the second voltage sensing electrode (C) is connected distally of the second current electrode (D) on the second arm or leg.

24. The method of any one of claims 17 to 23, wherein the first voltage sensing electrode (B) is connected at a position at least 5 cm from the connection position of the second current electrode (A).

25. The method of any one of claims 17 to 24, wherein the second voltage sensing electrode (C) is connected at a position at least 5 cm from the connection position of the second current electrode (D).

26. Apparatus for determining bioimpedance in a body, the apparatus comprising:

a second current electrode (D) adapted to connect to a second arm or leg of the body;

a first voltage sensing electrode (B) and a second voltage sensing electrode (D) adapted to connect to the body at spaced apart positions of the body, separate from the first and second current electrodes;

wherein the first current electrode (A) or the first voltage sensing electrode (B) is adapted to connect to a biologically active point of the body, and

wherein the apparatus is adapted to:

measure, in response to the at least one electrical signal applied between the first and second current electrodes, voltage between at least two different pairs of the electrodes (A, B, C,- D), wherein each pair includes at least one of the first and second current electrodes.

27. The apparatus of claim 26, comprising a processor adapted to determine, from a combination of the measured voltages, the bioimpedance of a region of interest of the body that is located along a path between the first and second current electrodes.

28. The apparatus of claim 27, wherein upon applying at least one electrical signal, having current (I), between the first and second current electrodes (A,D), the apparatus is adapted to: measure voltage (V(AC)) between the first current electrode (A) and the second voltage sensing electrode (C);

measure voltage (V(BD)) between the first voltage sensing electrode (B) and the second current electrode (D); and

measure voltage (V(AD)) between the first current electrode (A) and the second current electrode (D); and

the processor is adapted to determine bioimpedance (Zj) of the region of interest using Equation 1:

V(AC) V(BD) V(AD)

Z, =

I I I Equation [1].

29. The apparatus of claim 27 or 28, wherein upon applying at least one electrical signal, having current (I), between the first and second current electrodes (A,D), the apparatus is adapted to:

measure voltage (V(AC)) between the first current electrode (A) and the second voltage sensing electrode (C); and

measure voltage (V(AB)) between the first current electrode (A) and the first voltage sensing electrode (B); and

the processor is adapted to determine bioimpedance (Zj) of the region of interest using Equation 2a: V(AC) V(AB)

I I Equation

30. The apparatus of claim 27, 28 or 29, wherein upon applying at least one electrical signal, having current (I), between the first and second current electrodes (A, D), the apparatus is adapted to:

measure voltage (V(CD)) between the second voltage sensing electrode (C) and the second current electrode (D); and

the processor is adapted to determine bioimpedance (Zj) of the region of interest using Equation 2b:

₇ V(BD) V(CD)

Z_j = Equation [2b].

31. Apparatus for determining bioimpedance in a body, the apparatus comprising:

32. The apparatus of claim 31 , comprising a processor adapted to determine, from the measured voltage, the bioimpedance of a region of interest of the body that is located along a path between the first and second current electrodes.