Methods, devices and apparatus for measuring local muscle volume

Abstract

The present invention relates to a method for measuring the muscle cross-section of a body part, wherein the muscle cross-section (S) is measured as a function of: - at least two electrical resistance values ​​measured by different electrodes positioned at different locations on the body, with at least two electrodes positioned along said body part; - the conductivity constant of the muscle (σ); - the permittivity constant of the muscle (ε).

Description

[Technical Field]

[0001] The present invention relates to a method, device and apparatus for measuring muscle volume locally in a human or animal. The present invention falls within the fields of medicine, biology and physiology. In particular, the present invention relates to medical diagnostics. [Background technology]

[0002] Skeletal muscle wasting is associated with negative health care outcomes across the board, including decreased physical function, increased incidence of complications or comorbidities, reduced quality of life, and shortened survival.

[0003] Therefore, there is a strong need for a non-invasive and highly accurate method for assessing skeletal muscle mass / volume.Evaluation of skeletal muscle mass / volume is extremely important in the general population and in physical conditions involving primary and / or secondary muscle wasting and degeneration.Skeletal muscle mass / volume can be an indicator of primary and / or secondary muscle wasting and degeneration.

[0004] The prior art is known for the assessment of skeletal muscle mass by specialized techniques such as whole body counting with neutron activation, dual energy X-ray absorptiometry, computed tomography, and magnetic resonance imaging, which are currently considered standard methods for measuring skeletal muscle mass / body mass.

[0005] The above methods are expensive, time consuming, require a high level of expertise, and require patients to travel to specific large and cumbersome facilities.

[0006] Bioelectrical impedance analysis (BIA) is known, as described in detail in Salinari et al., Journal of Applied Physiology, (USA), 2003, vol. 94, pp. 1552-1556 and Salinari et al., American Journal of Physiology Endocrinology and Metabolism, (USA), 2002, vol. 282: E960-6. However, current BIA methods have significant limitations.

[0007] The assessment of skeletal muscle mass using conventional BIA methods is inaccurate. In fact, the model used for assessment is oversimplified to accommodate individual physiological differences. Furthermore, the model is highly population-specific, making it difficult to generalize. Summary of the Invention

[0008] The object of the present invention is to - to provide a method that overcomes at least one of the drawbacks of the prior art methods, and / or - provide a non-invasive method applicable to all types of populations; and / or - Providing a method that can be performed at the patient's bedside; and / or - To provide an accurate and population-nonspecific method.

[0009] For this purpose, according to the invention, there is provided a method for measuring the muscle cross section of a body part, the muscle cross section (S) comprising: - at least two electrical resistance values ​​measured by different electrodes positioned at different locations on the body, with at least two electrodes positioned along the body part; - the muscle conductivity constant (σ), - The dielectric constant of muscle (ε) A method is provided in which the temperature is measured as a function of

[0010] Preferably, the at least two electrodes positioned along the body part are included among different electrodes positioned at different locations on the body.

[0011] The method may include measuring and / or determining at least two electrical resistance values ​​from different electrodes positioned at different locations on the body. The step of measuring the at least two electrical resistance values ​​may be performed by a processing unit.

[0012] Preferably, the at least two electrodes positioned along the body part are positioned at different locations on the body part, separated from each other by a known distance.

[0013] According to the present invention, at least two electrical reactance values ​​may be measured together with or instead of at least two electrical resistance values, and the at least two electrical resistance values ​​according to the present invention may be substituted by or combined with at least two electrical reactance values.

[0014] The at least two electrical resistance values ​​may be measured by bioelectrical impedance analysis.

[0015] In this document, when the term "electrode" is used alone, it refers to a voltage electrode.

[0016] The different electrodes positioned at different locations on the body can include at least three electrodes, with at least one of the at least three electrodes positioned at a body part other than the body part along which the muscle cross-section (S) is measured and along which two of the at least three electrodes are positioned.

[0017] The method may include measuring an electrical potential at each of at least two electrodes positioned along the body part. The at least two electrodes positioned along the body part may be part of an electrode array adapted to measure electrical potentials. Preferably, the electrode array for measuring electrical potentials is positioned along the body part. The electrodes of the electrode array for measuring electrical potentials may be adapted to measure changes in electrical potential along the body part caused by current flowing through the body part.

[0018] The method may include injecting a current through the body part from one current injection electrode to another current injection electrode of two current injection electrodes forming a pair of current injection electrodes. The injected current may be an alternating current. The alternating current may be injected in a single pulse or continuously in several different pulses. Preferably, one of the two current electrodes is positioned on the body part, and one of the two current electrodes may be positioned at a different body part from the body part where the muscle cross-section (S) is measured.

[0019] The method may include measuring a change in electrical resistance between two of at least two electrodes positioned along the body part, and thus along the body part.

[0020] The muscle cross section can be determined for each electrical resistance value studied as a function of the product of the electrical resistance value studied and the dielectric constant of the muscle.

[0021] The muscle cross section can be determined for each electrical resistance value studied as a function of the ratio between the electrical resistance value studied and the conductivity constant of the muscle.

[0022] The muscle cross section can be measured for each electrical resistance value studied as a function of the conductivity term comprising the product of the electrical resistance value studied and the conductivity constant of the muscle.

[0023] The muscle cross section can be measured as a function of the correction term.

[0024] The correction terms may allow for correction of standard terms currently used for measuring muscle cross-sections.

[0025] A standard term currently used to measure muscle cross section may be the product of electrical resistance and the muscle conductivity constant.

[0026] The correction term may include the product of the square of the measurement frequency and the square of the muscle dielectric constant. The measurement frequency may be directly related to and / or proportional to and / or equal to the pulse load of the alternating current injected between the two current injection electrodes.

[0027] The correction term may include, for each considered electrical resistance value, the product of the considered electrical resistance value and the square of the dielectric constant of the muscle.

[0028] The correction term may include, for each considered electrical resistance value, the ratio of the considered electrical resistance value to the conductivity constant of the muscle.

[0029] The correction term may include, for each considered electrical resistance value, the product of the considered electrical resistance value and the square of the measurement frequency.

[0030] The muscle cross section is - the sum of the conductivity term and the correction term, and / or - the reciprocal of the sum of the conductivity term and the correction term can be measured as a function of

[0031] The muscle cross section is - at least one pair of electrical resistance values ​​measured at a single measurement frequency or at different measurement frequencies, and / or - several pairs of electrical resistance values, at least one pair of electrical resistance values ​​being measured at a measurement frequency different from the measurement frequency at which another pair of electrical resistance values ​​is measured, and / or - several pairs of electrical resistance values, at least one pair of electrical resistance values ​​being measured at a measurement frequency different from the respective measurement frequencies at which the other respective pairs of electrical resistance values ​​are measured; and each pair of electrical resistance values ​​preferably includes a first electrical resistance value measured at a first electrode positioned at a first location on the body part and a second electrical resistance value measured at a second electrode positioned at a second location on the body part.

[0032] Preferably, the pair of electrical resistance values ​​is comprised among at least two electrical resistance values ​​measured by different electrodes positioned at different locations on the body.

[0033] Each of the pair of electrical resistance values ​​is preferably included in at least two of the measured electrical resistance values.

[0034] The first and second electrodes are preferably included among at least two electrodes positioned along the body part.

[0035] A relative electrical resistance value may be determined from at least two measured electrical resistance values.

[0036] The relative electrical resistance may be determined from a pair of electrical resistance values. The relative electrical resistance may be the resistance of the body part between the first electrode and the second electrode.

[0037] The first or second location of a body part at which the first and second electrical resistance values ​​of one pair of electrical resistance values ​​are measured, respectively, may be the same as the first or second location of a body part at which the first and second electrical resistance values ​​of another pair of electrical resistance values ​​are measured, respectively.

[0038] The muscle cross section (S) is calculated using Equation 1, i.e. JPEG0007752107000001.jpg34170 where δR / δz is the electrical resistance gradient between two locations in the body part separated by a distance z, and ω is the pulse load at which at least two electrical resistance values ​​are measured, and the electrical resistance gradient δR / δz is measured from the at least two electrical resistance values.

[0039] The two locations on the body part separated by a distance z between which the electrical resistance gradient is measured may be first and second locations at which the first and second electrodes are positioned, respectively.

[0040] The electrical resistance gradient δR / δz can be measured from a pair of electrical resistance values.

[0041] The electrical conductivity constant and / or the permittivity constant of the muscle may be a function of the measurement frequency at which at least two electrical resistance values ​​are measured; the electrical conductivity constant of the muscle may be between 0.1 and 2 Siemens / meter (S / m), preferably between 0.4 and 1.5 S / m, more preferably between 0.6 and 1.2 S / m; and the permittivity constant of the muscle may be between 1 and 10 -8 ~1·10 -6 Farads per metre (F / m), preferably 5·10 -8 ~7·10 -7 Included in F / m.

[0042] More preferably: - the electrical conductivity constant of the muscle is between 0.6 and 1.1 S / m in the measurement frequency range between 40 and 60 kHz, and / or - the electrical conductivity constant of the muscle increases to be comprised between 0.7 and 1.2 S / m in the measurement frequency range comprised between 220 and 260 kHz, and / or - The electrical conductivity constant of muscle decreases in the measurement frequency range of 340-360 kHz to fall within the range of 0.65-1.15 S / m.

[0043] More preferably: - The dielectric constant of muscle is 7·10 in the measurement frequency range of 40–60 kHz.-7 ~3.7 10 -7 Included in F / m, and / or The dielectric constant of muscle is reduced to 3.5·10 in the measurement frequency range included in 180–220 kHz. -7 ~1·10 -7 be included in F / m, and / or The dielectric constant of muscle is reduced to 3·10 in the measurement frequency range of 340–360 kHz. -7 ~5·10 -8 It will be included in F / m.

[0044] The muscle conductivity constant σ is given by Equation 2, i.e. JPEG0007752107000002.jpg15170 and / or the dielectric constant ε can be defined as a function of the measurement frequency f according to Equation 3, i.e. JPEG0007752107000003.jpg17170 where the terms a, b, c, d, g, h, and k may be functions of frequency f or may be constants.

[0045] The measurement frequency can be comprised between 40 and 1000 kHz.

[0046] Preferably, the measurement frequency is in the range of 50 to 500 kHz.

[0047] More preferably, the measurement frequency may be included in the range of 100 to 300 kHz.

[0048] According to the present invention there is further provided a method for measuring muscle volume of a body part, wherein the muscle volume of the body part can be measured from one or more muscle cross-sections of the body part, each muscle cross-section of the body part being measured according to the present invention.

[0049] The muscle volume of a body part can be calculated by integrating the muscle cross section over the distance z separating the two most distantly separated electrodes of at least two electrodes positioned along the body part.

[0050] The volume of a portion of a body part can also be measured. The volume of a portion of a body part can be calculated by integrating one or more muscle cross-sections over a distance z separating at least two electrodes positioned along the body part between which the muscle cross-section is measured.

[0051] The muscle volume (V) of a body part or part of a body part is calculated using Equation 4 JPEG0007752107000004.jpg19170

[0052] where n is the cross-section S of at least two electrodes positioned along the body part, between which the muscle cross-section S is measured, extending along a distance z between the electrodes. n The number of cross sections, n, is an integer equal to or greater than 1.

[0053] According to the present invention there is further provided an apparatus comprising technical means arranged and / or configured and / or programmed to carry out the method of the present invention.

[0054] According to the present invention there is further provided a computer program product comprising instructions which, when executed by a computer, cause the computer to carry out the method of the present invention.

[0055] Further objects, features and advantages will become apparent from the following detailed description of several embodiments of the invention taken in conjunction with the drawings. [Brief explanation of the drawings]

[0056] [Figure 1]Schematic showing the experimental setup used to measure electrical resistance values ​​on human participants. [Figure 2] 1 is a graph showing the electrical resistance measured at each voltage electrode of an electrode array positioned along the thigh of a human subject as a function of measurement frequency. [Figure 3] 1 is a graph showing electrical resistance gradient as a function of the distance separating voltage electrodes of an electrode array configured along a thigh muscle of a human subject. [Figure 4] 2 is a graph showing muscle conductivity measured in accordance with the present invention as a function of measurement frequency. [Figure 5] 2 is a graph showing the dielectric constant of muscle measured in accordance with the present invention as a function of measurement frequency. [Figure 6] Graph showing muscle cross-section as a function of distance along the muscle, measured in accordance with the present invention and by magnetic resonance imaging. [Figure 7] Graph showing muscle cross-sections measured in accordance with the present invention at the center of the muscle of each individual from a group of human subjects compared to muscle cross-sections measured by magnetic resonance imaging at the center of the muscle of each individual from a group of human subjects. [Figure 8] 1 is a graph showing muscle volume measured according to the present invention for a group of human subjects versus muscle volume measured by magnetic resonance imaging for said group of human subjects. DETAILED DESCRIPTION OF THE INVENTION

[0057] The embodiments described hereinafter are not limiting, and other embodiments may be envisioned that include selected features from those described hereinafter. Selected features may include features separated from a set of features (even if the selected feature is separated in a sentence containing other features) if the selected feature is sufficient to provide a technical advantage or to distinguish the present invention from the prior art. The selected features include at least features that are preferably described by their technical function and are not accompanied by structural features, or are accompanied by some structural details if the selected feature is sufficient by itself to provide a technical advantage or to distinguish the present invention from the prior art.

[0058] Furthermore, the embodiments described herein below are non-limiting embodiments within the scope of the above Summary of the Invention, and thus any individual feature of the following embodiments may be considered in combination with any more general or functional step or feature of the above Summary of the Invention.

[0059] ≪Participant≫ The cohort of 20 human subjects included 8 healthy participants and 11 patients. Eleven patients had neuromuscular disorders associated with muscle wasting. Written informed consent was obtained from all participants.

[0060] According to the present invention, the muscle cross section of a body part is - at least two electrical resistance values ​​measured by different electrodes positioned at different locations on the body, with at least two electrodes positioned along the body part; and - the muscle conductivity constant σ, and - Dielectric constant of muscle ε It is measured as a function of

[0061] The step of measuring muscle cross-section, also known to those skilled in the art as contractile cross-sectional area (cCSA), is performed by a computer processor.

[0062] Figure 1 shows a schematic diagram of the experimental setup used to perform measurements on human participants. The setup is configured to perform bioelectrical impedance measurements to measure at least two electrical resistance values.

[0063] The experimental device includes a multi-frequency bioelectrical impedance analyzer 1, sold by Bioparhom under the trade name Zmetrix. The step of measuring at least two electrical resistance values ​​is performed by the analyzer's processor. The experimental device includes 12 different electrodes 2 positioned at different locations on the subject's body. Of these 12 electrodes, 10 are voltage electrodes 21 configured to measure electrical potential, and 2 are current electrodes 22 configured to inject 50-100 μA of alternating current through the subject's body. The electrodes are skin electrodes placed on the subject's skin along the longitudinal axis of the area to be tested. The injected current is injected as a single pulse or in several different pulses, as desired. The measurement frequency is directly related to the pulse of alternating current injected between the two current injection electrodes.

[0064] Of the ten voltage electrodes 21, nine electrodes 21 form an electrode array 211 arranged along the thigh where muscle cross-section (S) is measured in accordance with the present invention as described hereinbelow. The nine electrodes 21 of the electrode array 211 are numbered E1 through E9 and are referred to as Em, where m is the number of the considered electrode 21 of the electrode array 211. Electrode E1, 21 of the electrode array 211 is positioned on the thoracic side of the patient's thigh, and electrode E9, 21 of the electrode array 211 is positioned on the sural side of the patient's thigh.

[0065] The voltage electrodes 21 of the electrode array 211 are spaced apart at a known distance from one another. The final voltage electrode E0,21 is positioned on a body part other than the thigh, in accordance with the embodiment, on the hand. One of the current electrodes 222 is positioned at the subject's ankle, and the other 221 is positioned on the subject's hand, so that current flows through at least the subject's thigh.

[0066] Although the electrode array 211 in this embodiment includes nine electrodes, the electrode array can include a variety of numbers of electrodes as needed. For example, the electrode array 211 may be substituted with only two voltage electrodes 21 positioned at two different locations on the subject's muscle.

[0067] In practice, the muscle cross-section is measured from at least one pair of electrical resistance values. Each electrical resistance value of the pair is included in the at least two electrical resistance values ​​measured. Each electrical resistance value is measured by a pair of voltage electrodes 21. A pair of voltage electrodes 21 measures the electrical resistance value between the two electrodes 21 of that pair of voltage electrodes 21. According to an embodiment, each pair of voltage electrodes 21 includes a voltage electrode E0,21 positioned on the patient's hand and one voltage electrode Em,21 of an electrode array 211.

[0068] The voltage electrode E0,21 positioned on the patient's hand is used as a reference electrode, so that each electrical resistance value can be measured from a pair of voltage electrodes 21 including the voltage electrode E0,21 positioned on the hand and one voltage electrode Em,21 of the electrode array 211. Thus, each measured electrical resistance value is calculated based on the electrical resistance R measured at the location on the thigh where the voltage electrode Em,21 of the electrode array 211 is provided. Em-E0 It is considered to be.

[0069] Referring to FIG. 2, the electrical resistance R measured at each voltage electrode E m,21 of the electrode array 211 positioned along the thigh of a human patient is Em-E0 A graph illustrating as a function of measurement frequency f is shown, where the measurement frequency f is between 50 and 350 kHz in 10 kHz intervals.

[0070] Using the Levenberg-Marquardt algorithm to perform nonlinear regression, we find that a double exponential function provides a good fit to this measurement with a coefficient of determination of 0.997 ± 0.018.

[0071] The electrical resistance value of each pair is a first electrical resistance value R measured at a first voltage electrode Em1,21 of the electrode array 211 positioned at a first location on the thigh. Em1-E0 and a second electrical resistance value R measured at a second voltage electrode Em2,21 of the electrode array 211 positioned at a second location on the thigh. Em2-E0 The first and second locations on the thigh are separated by a distance z, and an electrical resistance gradient δR / δz therebetween can be measured. According to an embodiment, a second electrical resistance value R measured at the second location on the thigh is E9-E0 is the voltage electrode E9,21 of the electrode array 211.

[0072] The relative electrical resistance value Rm is defined as the electrical resistance of the thigh between a pair of electrodes 21 including a first electrode Em,21 and a second electrode E9,21. That is, the relative electrical resistance value Rm is the electrical resistance of the thigh between the location of the first electrode Em,21 of the pair of electrodes 21 and the location of the second electrode E9,21 of the pair of electrodes 21. In other words, the relative electrical resistance value Rm is the electrical resistance of a portion of the thigh depending on the distance z separating the electrodes 21 of a pair of electrodes 21 of the electrode array 211.

[0073] The relative electrical resistance value Rm is calculated using Equation 5 JPEG0007752107000005.jpg12170 It is measured from

[0074] The relative electrical resistance value Rm is R1 = R E1-E0 -R E9-E0 and R8=R E8-E0 -R E9-E0As a result, an electrical resistance gradient δR / δz between a first and second location separated by a distance z can be determined from at least two relative electrical resistance values ​​Rm. The electrical resistance gradient δR / δz indicates the change in electrical resistance and therefore the change in electrical potential along the thigh.

[0075] FIG. 3 shows the gradient of the relative electrical resistance δR / δz as a function of the distance z separating two voltage electrodes Em,21 of an electrode array 211 arranged along a thigh muscle.

[0076] Using an adaptive nonlinear least-squares algorithm to perform nonlinear regression, we find that a third-order polynomial function provides a good fit to this measurement with a coefficient of determination of 0.981±0.082.

[0077] It is worth noting that Rm ΔI inj =ΔVm, where ΔI inj is the injected current and ΔVm is the difference in potential measured between a first voltage electrode Em, 21 positioned at a first location on the thigh and a second voltage electrode E9, 21 positioned at a second location on the thigh. Rm=R Em-E0 -R E9-E0 Considering this, ΔVm=V Em -V E0 -V E9 +V E0 Therefore, with proper calibration, V E0 can be a predetermined constant that allows the electrical resistance gradient δR / δz to be measured directly from measurements of only two voltage electrodes 21 of the electrode array 211 arranged along the thigh.

[0078] 4, the muscle conductivity constant σ of the muscle is measured as a function of the measurement frequency in accordance with the present invention. The inventors calculated the muscle conductivity constant σ using the muscle cross section S of the thigh (right side only) measured by nuclear magnetic resonance imaging for healthy participants in the test group, the reactance value X measured by an analyzer between the pair of voltage electrodes E m,21 of the electrode array 211 used for the measurement, and the electrical resistance value R measured by an analyzer between the pair of voltage electrodes E m,21 of the electrode array 211. Em-E0 , and the distance z separating the two voltage electrodes Em,21 of a pair of electrodes 21 of the electrode array 211 arranged along the thigh muscle, is calculated using Equation 6. JPEG0007752107000006.jpg24170 Use.

[0079] The inventors have found that Equation 2, i.e. JPEG0007752107000007.jpg15170 They found that a second-order polynomial function given by the following equation gave a good fit to the muscle conductivity constant σ with a coefficient of determination of 0.995, where a, b, and c are constants and a is −2.41 10 -12 and b is 1.15 10 -6 and c is equal to 0.8.

[0080] The black line indicates the mean value of the muscle conductivity constant σ as a function of measurement frequency, and region 3 indicates the confidence interval (CI). The difference between the values ​​of the muscle conductivity constant σ is due to the influence of measurement frequency and the variability of the muscle conductivity constant σ resulting from physiological individual differences.

[0081] The conductivity constant σ is in region 3, between 0.6 and 1.2 siemens / meter (S / m). Given the fact that measurements were performed on a small number of human subjects, the conductivity constant σ can be considered to be in absolute terms between 0.1 and 2 S / m. The muscle conductivity constant σ is in the range of 0.6 and 1.1 S / m in the measurement frequency range between 40 and 60 kHz. The muscle conductivity constant σ then increases to between 0.7 and 1.2 S / m in the measurement frequency range between 220 and 260 kHz. The muscle conductivity constant then decreases to between 0.65 and 1.15 S / m in the measurement frequency range between 340 and 360 kHz.

[0082] 5, the inventors measured the permittivity constant ε of muscle as a function of measurement frequency in accordance with the present invention. The inventors calculated the permittivity constant ε of muscle from the reactance gradient δX / δz as a function of the distance z separating the two voltage electrodes Em,21 of the electrode array 211 arranged along the thigh muscle, the conductivity constant σ of muscle measured as described above, the measurement pulse load ω, and the gradient of relative electrical resistance δR / δz as a function of the distance z separating the two voltage electrodes Em,21 of the electrode array 211 arranged along the thigh muscle, using Equation 7: JPEG0007752107000008.jpg43170 where ω=2πf.

[0083] The black line indicates the mean value of the muscle permittivity constant ε as a function of the measurement frequency, and region 3 indicates the confidence interval (CI). The difference between the values ​​of the muscle permittivity constant ε is due to the influence of the measurement frequency and the variation of the muscle permittivity constant ε resulting from individual physiological differences.

[0084] The inventors have found that the compound of formula 3: JPEG0007752107000009.jpg17170 It was found that the double exponential function given by the formula (2) gave a good fit to the dielectric constant ε with a coefficient of determination of 0.999, where d, g, h, and k are constants and d is 1.012 10 -6, g is equivalent to -10.54, and h is equivalent to 2.641 10 -7 and k is equal to -13.49.

[0085] The dielectric constant ε is 5·10 in region 4. -8 ~7·10 -7 Given the fact that measurements were made on a small number of human subjects, the dielectric constant ε is in absolute terms 1·10 -8 ~1·10 -6 The dielectric constant ε of muscle is 7·10 in the measurement frequency range of 40 to 60 kHz. -7 ~3.7 10 -7 The dielectric constant ε of muscle then decreases to 3.5·10 in the measurement frequency range included in 180–220 kHz. -7 ~1·10 -7 The dielectric constant ε of muscle is further reduced to 3·10 in the measurement frequency range of 340–360 kHz. -7 ~5·10 -8 It will be included in F / m.

[0086] The measurement frequency is in the range of 50 to 350 kHz. The inventors have found that measurement frequencies below 100 kHz may lead to unreliable results, since these frequencies are expected to be insufficient to penetrate the intracellular lumen and to produce inconsistencies related to large changes in skin-electrode impedance. Conversely, measurement frequencies above 350 kHz, or even 300 kHz, may lead to unreliable results, since the phenomena occurring at the interface and the diffusion phenomena that prevail at this frequency become prominent.

[0087] Muscle cross section is measured as a function of the inverse of the sum of a conductivity term and a correction term. The standard term is the term currently used to measure muscle cross section. It is the product of the electrical resistance and the muscle conductivity constant. The correction term is intended to correct the standard term currently used to measure muscle cross section. The standard term can be written as {(δR / δz)·σ}.

[0088] The purpose of the correction term is to weight the effect of the measurement frequency on the muscle conductivity constant and the muscle permittivity constant. The correction term also aims to mitigate variations in electrical resistance caused by physiological individual differences. The correction term also weights the effect of the measurement frequency on variations in electrical resistance caused by physiological individual differences.

[0089] The muscle cross section (S) is calculated using Equation 1 JPEG0007752107000010.jpg34170 where δR / δz is the electrical resistance gradient between two locations in the body part separated by a distance z, and ω is the pulse load at which at least two electrical resistance values ​​are measured, and the electrical resistance gradient δR / δz is determined from the at least two electrical resistance values.

[0090] 6, a graph is shown in which the solid line illustrates the muscle cross-section measured according to Equation 6 from bioimpedance measurements made along the thigh muscle of a healthy subject. Also shown is a dotted line illustrating the muscle cross-section measured by nuclear magnetic resonance imaging (NMRI) along the thigh muscle of a healthy subject. NMRI is considered the standard method for measuring skeletal muscle mass. The bioelectrical impedance measurements were made at 150 kHz, and the value of the conductivity constant σ of the muscle used for the measurements was 0.916 S / m, and the value of the permittivity constant ε was 2.338e10. -7 F / m are from Figures 4 and 5, respectively. As illustrated in Figure 6, the cross-section measured by the present invention is consistent with that measured by NMRI, with the standard error of the measurement being about 5.94%.

[0091] 7 and 8, the points illustrate the muscle cross-sections, or muscle volumes calculated from the muscle cross-sections, for each person in the subject group (healthy participants and patients), as determined by Equation 1 from bioelectrical impedance measurements performed at the mid-thigh of each person in the group, and compared to the muscle cross-sections measured at the mid-thigh of each person in the group by magnetic resonance imaging. The bioimpedance measurements were made at 150 kHz, and the muscle used for the measurements had a conductivity constant σ value of 0.916 S / m and a permittivity constant ε value of 2.338e10. -7 F / m is taken from Figures 4 and 5, respectively. The vertical axis shows the muscle cross-section measured according to the present invention, and the horizontal axis shows the muscle cross-section measured by magnetic resonance imaging. Lines 9 and 10 were obtained by linear regression fitting of the measured muscle cross-section values. Areas 5 and 6 show the confidence interval (CI) of the muscle cross-section values.

[0092] Tables 1 and 2 relate to the statistical parameters obtained by linear regression of the muscle cross-sectional values ​​and muscle volume values ​​shown in Figures 7 and 8, respectively.

[0093] Tables 1 and 2 show the muscle cross-section (S) and muscle volume (V) of the mid-thigh measured by the present invention (cCSA, respectively). BIA (cm 2 ) and V BIA (cm 3 )) and those measured by NMRI (cCSA NMRI (cm 2 ) and V NMRI (cm 3 )), p-value of Student's t-test (a test of the location of two samples for the null hypothesis that the means of the two populations are equal), change in the mean (CIM(cm)) with 95% confidence interval 2 ) [95% CI]), standard error of measurement expressed as coefficient of variation with 95% confidence interval (SEM (%) [95% CI]), and cCSA BIA and cCSA NMRI Between (Table 1) and V BIA and V NMRI The interclass correlation coefficients with 95% confidence intervals ([95% CI]) between (Table 2) are shown.

[0094] [Table 1] [Table 2]

[0095] 7 and Table 1, one can see the good agreement between the muscle cross-section measured by the present invention and that measured by NMRI. The results show excellent agreement between lean muscle cross-section measurements using the present invention and standard magnetic resonance imaging.

[0096] According to the present invention there is further provided a method for measuring muscle volume of a body part from one or more muscle cross-sections of the body part, wherein each muscle cross-section of the body part is measured according to the present invention. According to an embodiment, the muscle volume (V) of a portion of the thigh can be calculated using Equation 4: JPEG0007752107000013.jpg19170 where n is the cross section S of the muscle extending along the distance z between two voltage electrodes Em,21 of the electrode array 211 along the thigh, between which the muscle cross section S is measured. n The number of cross sections, n, is an integer equal to or greater than 1.

[0097] The muscle volume of the entire thigh is calculated by integrating the muscle cross section over the distance z separating the two further apart voltage electrodes Em,21 of the electrode array 211, namely E1 and E9.

[0098] Referring to Figure 8, thigh muscle volume measured from muscle cross-sections measured in accordance with the present invention is illustrated compared to muscle volume measured from muscle cross-sections measured by magnetic resonance imaging. The dots represent thigh muscle volume measured in healthy participants and patients. Muscle volume was determined from muscle cross-sections using Equation 4. Line 10 was obtained by linear regression fitting of thigh muscle cross-section values ​​measured in healthy subjects in the group and patients in the group. Region 6 represents the thigh muscle volume measured in the group. Healthy subjects and patients The CI for the values ​​of the thigh muscle cross-sectional area measured at is shown.

[0099] 8 and Table 2, it can be seen that there is good agreement between muscle volume measured by the present invention and muscle cross-section measured by NMRI. This result demonstrates good agreement between lean muscle cross-section measurements using the present invention and standard magnetic resonance imaging.

[0100] The invention is not limited to the embodiments described above, and many adjustments can be made within the scope of the invention.

[0101] Furthermore, features, alternatives and embodiments of the invention may be combined if they are not mutually exclusive.

[0102] Thus, in possible alternative combinations of the above-described embodiments: - the body part where the muscle cross section (S) is measured by the method of the present invention is the calf or the forearm or the upper arm; and / or - at least two electrical reactance values ​​are measured by the analyzer together with or as a substitute for at least two electrical resistance values; and / or The at least two electrical resistance values ​​according to the present invention are determined by the formula 8 JPEG0007752107000014.jpg11170 may be used to substitute for or combine at least two electrical reactance values, where Z impis the impedance, R is the resistance, and X is the reactance, and / or - the muscle cross section (S) is measured from pairs of electrical resistance values ​​measured at several different frequencies, at least one pair of electrical resistance values ​​being measured at a frequency different from the frequency at which another pair of electrical resistance values ​​is measured; and / or - the muscle cross section (S) is measured from pairs of electrical resistance values ​​measured at several different measurement frequencies, and at least one pair of electrical resistance values ​​is measured at a measurement frequency different from the measurement frequency at which each of the other pairs of electrical resistance values ​​is measured; and / or - the muscle cross section is measured from either a single pair of electrical resistance values ​​or several pairs of electrical resistance values ​​as appropriate; and / or - muscle cross-sections are measured either from electrical resistance values ​​measured at a single frequency or from electrical resistance values ​​measured at several different frequencies, as appropriate; and / or - the first or second location on the thigh at which the first and second electrical resistance values ​​of one pair of electrical resistance values ​​are measured, respectively, is the same as the first or second location on the thigh at which the first and second electrical resistance values ​​of another pair of electrical resistance values ​​are measured, respectively; and / or - the muscle cross section is determined for each electrical resistance value studied solely from the product of the electrical resistance value studied and the dielectric constant of the muscle, or as a function of this product; and / or - the muscle cross section is determined for each electrical resistance value studied solely from the ratio of the electrical resistance value studied to the electrical conductivity constant of the muscle, or as a function of this ratio; and / or - the muscle cross section is measured for each considered electrical resistance value solely from or as a function of the electrical conductivity term comprising the product of the considered electrical resistance value and the muscle conductivity constant; and / or the correction term is the product of the square of the measurement frequency and the square of the dielectric constant of the muscle, and / or the correction term is, for each considered electrical resistance, the product of the considered electrical resistance and the square of the dielectric constant of the muscle; and / or - the correction term is, for each considered electrical resistance value, the ratio of the considered electrical resistance value to the electrical conductivity constant of the muscle; and / or - the correction term is, for each considered electrical resistance, the product of the considered electrical resistance and the square of the measurement frequency; and / or - the muscle cross section is measured as a function of the sum of a conductivity term and a correction term, and / or the invention relates to an apparatus comprising technical means arranged and / or configured and / or programmed to carry out the method according to the invention; and / or The invention also relates to a computer program product comprising instructions that cause the computer to carry out the method according to the invention when the program is executed by a computer.

Claims

1. A method for measuring muscle cross-sections of a body part, comprising: - at least two electrical resistance values ​​measured by different electrodes positioned at different locations on the body, with at least two electrodes positioned along said body part; - the muscle conductivity constant (σ), - The dielectric constant of muscle (ε) is measured as a function of The muscle cross-section is measured from at least one pair of electrical resistance values ​​as a function of the inverse of the sum of a conductivity term and a correction term for each pair of electrical resistance values; the conductivity term is the product of the electrical resistance gradient (δR / δz) measured from the at least one pair of electrical resistance values ​​and the muscle conductivity constant; The correction term is the ratio between the electrical resistance gradient δR / δz and the conductivity constant of the muscle; the product of the electrical resistance gradient δR / δz and the square of the dielectric constant of the muscle, Including, δR / δz is the electrical resistance gradient between two locations in a body part separated by a distance z; The method.

2. The method of claim 1 , wherein the correction term comprises the product of the square of the measurement frequency and the square of the dielectric constant of the muscle.

3. 3. The method according to claim 1, wherein the correction term includes, for each pair of electrical resistance values, the product of the electrical resistance gradient δR / δz and the square of the measurement frequency.

4. The muscle cross section is at least one pair of electrical resistance values ​​measured at a single measurement frequency or at different measurement frequencies, and / or several pairs of electrical resistance values, at least one pair of electrical resistance values ​​being measured at a measurement frequency that is different from the measurement frequency at which another pair of electrical resistance values ​​is measured, and / or - several pairs of electrical resistance values, at least one pair of electrical resistance values ​​being measured at a measurement frequency different from the respective measurement frequencies at which the other respective pairs of electrical resistance values ​​are measured; 4. The method of claim 1, wherein each pair of electrical resistance values ​​comprises a first electrical resistance value measured at a first electrode positioned at a first location on the body part and a second electrical resistance value measured at a second electrode positioned at a second location on the body part.

5. 5. The method according to claim 1, wherein the first or second location of the body part at which the first and second electrical resistance values ​​of one pair of electrical resistance values ​​are measured is the same as the first or second location of the body part at which the first and second electrical resistance values ​​of another pair of electrical resistance values ​​are measured, respectively.

6. The muscle cross section (S) is calculated using the formula 1 6. The method according to claim 1, wherein the resistance is measured as a function of ω, where ω is the pulse load at which the at least two electrical resistance values ​​are measured.

7. The electrical conductivity constant and / or the dielectric constant of the muscle are functions of the measurement frequency at which at least two electrical resistance values ​​are measured, and the electrical conductivity constant of the muscle is between 0.1 and 2 S / m, and the dielectric constant of the muscle is between 1.10 －８ ~1.10 －６ The method according to any one of claims 2 to 6, wherein F / m is included.

8. - The conductivity constant of the muscle is given by equation 2, i.e. is defined as a function of the measurement frequency f according to The dielectric constant is given by equation 3, i.e. The method according to any one of claims 2 to 7, wherein the frequency f is defined as a function of the measurement frequency f according to

9. The method according to any one of claims 2 to 8, wherein the measurement frequency is comprised between 40 and 1000 kHz.

10. 10. A method for measuring muscle volume of a body part, wherein the muscle volume of the body part is measured from one or more muscle cross-sections of the body part, and each muscle cross-section of the body part is measured according to any one of claims 1 to 9.

11. An apparatus comprising technical means arranged and / or configured and / or programmed to carry out the method according to any one of claims 1 to 10.

12. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method of any one of claims 1 to 10.

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