EP3258830A1

EP3258830A1 - Non-invasive method for measuring a physiological parameter via a confocal spectroscopic measurement device

Info

Publication number: EP3258830A1
Application number: EP16705102.8A
Authority: EP
Inventors: Sylvain ZORMAN; Pierre-Yves FROUIN
Original assignee: Bioserenity SAS
Current assignee: Bioserenity SAS
Priority date: 2015-02-17
Filing date: 2016-02-15
Publication date: 2017-12-27
Also published as: JP2018505750A; ZA201705428B; CN107427265A; CA2976691A1; TW201634008A; MX2017010614A; WO2016131763A1; RU2017129450A; FR3032606A1; JP6850257B2; AR103722A1; RU2712034C2; US10772545B2; RU2017129450A3; CN107427265B; TWI707664B; AU2016221865A1; BR112017017335A2; FR3032606B1; US20180042536A1

Abstract

The present invention relates to a method for measuring a physiological parameter of a subject via an optical measurement device wherein said method comprises the following steps: - the optical measurement device (1,1bis) is placed opposite a skin surface (10) of the subject, such that the primary focal point of the optical lens is positioned at a predetermined skin depth, - the photosensitive receiver (4) receives light rays from the first primary focal point, at the predetermined skin depth, - the light rays received by the photosensitive receiver (4) are analyzed, and the analysis results are compared with the known data, such as to determine the physiological parameter of the subject.

Description

Non-invasive method of measuring a physiological parameter using a confocal spectroscopic measuring device

FIELD OF THE INVENTION

The present invention relates to methods for measuring a physiological parameter of a subject.

STATE OF THE ART

Spectroscopy is a non-invasive method for the study, analysis or quantification of physico-chemical parameters. This type of approach, applied to human physiology, allows the non-invasive measurement of vital parameters such as temperature, heart rate, level of oxygen saturation in the blood or bilirubin level.

Spectroscopy is carried out by a sensor positioned near the skin that measures the optical properties of the superficial layers of the skin.

An important limitation of the measurement of physiological parameters by spectroscopy is that the heterogeneity of the superficial layers of the skin induces disturbances which degrade the measurement.

Several strategies have been proposed to limit the presence of parasitic radiation from layers of skin adjacent to the layer of the skin of interest. There may be mentioned the use of polarized light conjugated to a detector positioned at the Brewster angle as described in WO201 1 151744 A1, the use of numerical correction factors, as described in US5353790 A, or the use of optical fibers oriented and positioned to be coupled to different skin depth, as described in WO2014006827 A1.

SUMMARY OF THE INVENTION

An object of the invention is to provide a method for measuring a physiological parameter of a subject by means of an optical measuring device having improved accuracy. This object is achieved in the context of the present invention, by means of a method for determining a physiological parameter of a subject that can be implemented by means of an optical measuring device comprising:

an optical axis on which is arranged an optical objective comprising a first object focus and a first image focus,

a first plane comprising a pinhole centered on the first image focus of the optical objective so as to let only the light rays coming from the first object focus of the optical objective,

a photosensitive receiver intended to receive the light rays coming from the first image focus, downstream from the pinhole,

a control unit configured to analyze the light rays received by the photosensitive receiver, and to compare the results of the analysis with known data, said method comprising the steps of:

placing the optical measuring device facing a skin surface of the subject, so that the first object focus of the optical objective is positioned at a predetermined skin depth,

reception by the photosensitive receiver of the light rays coming from the first object focus, at the predetermined skin depth,

analyzing the light rays received by the photosensitive receiver, and determining said physiological parameter of the subject based on the characteristics of the light rays received.

The invention is advantageously supplemented by the following characteristics, taken individually or in any of their technically possible combinations.

The physiological parameter to be determined is the body temperature of a subject.

Light rays having an infrared wavelength between 700 nm and 1 mm are analyzed.

The predetermined skin depth is included in the dermis or hypodermis, preferably between 100μηι and 1.5mm deep.

the optical objective comprises a second object focus and a second image focus, the second image focus being coincident with the first object focus, the measuring device furthermore comprises:

at least one light source,

a second plane comprising a pinhole centered on the second object focus so as to let only the light rays emitted by the light source from the second object focus,

a semi-reflecting plane mirror, said mirror being configured to transmit the light rays emitted by the light source towards the optical objective, and to transmit the light rays coming from the first object focus towards the photosensitive detector.

The method further comprises the steps of:

- emission of light rays by the light source to the second image focus at the predetermined skin depth,

receiving the light rays emitted by the light source, reflected by the skin and from the first object focus, at the predetermined skin depth, by the photosensitive receiver,

measuring the rate of absorption by the skin of the light rays emitted by the light source (s) from the analysis of the light rays received by the photosensitive receiver, and determination of the physiological parameter of the subject from the absorption rate measured. The physiological parameter to be determined is the cutaneous level of bilirubin.

The light rays emitted by the light source (s) have a wavelength of between 400 and 800 nm.

The predetermined skin depth is included in the hypodermis, and is preferably greater than 1 mm.

The physiological parameter to be determined is the blood oxygen saturation rate and carbon monoxide.

The device comprises two light sources, each emitting light rays of different wavelengths, a first between 620 and 680 nm and a second between 780nm and 1 mm.

The predetermined skin depth is included in the dermis or hypodermis, and is preferably greater than 0.2mm. DESCRIPTION OF THE FIGURES

Other objectives, characteristics and advantages will come out of the detailed description which follows with reference to the drawings given by way of non-limiting illustration, among which:

- Figure 1 shows a device for implementing a method according to a first embodiment of the invention;

- Figure 2 shows a device for implementing a method according to a second embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

The method for measuring a physiological parameter of a subject according to a first embodiment of the invention is implemented by means of an optical measuring device 1 comprising:

a photosensitive receiver 4 intended to receive light rays originating from a first image focus, downstream of a first pinhole 1 1,

an objective 3 adapted to focus the radiation emitted by the biological tissue 10 on the detector 4,

a first pinhole 11 positioned in a first confocal plane cF1 which is the conjugate by the objective 3 of the focal plane F containing the tissue to be studied.

Objective 3 is typically a lens. Objective 3 combines the plane F containing the tissue to be studied with the confocal plane cF1 in which is placed the first pinhole 1 1. In other words, the first pinhole 11 is centered on the first image focus of the optical objective 3 so as to let only the light rays from the first object focus of the optical objective, which corresponds to the plane F containing the tissue to study. Thus, only the photons coming from the focal plane F pass the pinhole 11 and participate in the spectroscopic measurement. Light from planes adjacent to F is stopped by the edges of the hole. The optical measuring device 1 thus makes it possible to select the depth of the spectroscopically measured layer.

The optical measuring device 1 advantageously comprises a filter 15 positioned between the photosensitive receiver 4 and the first pinhole 1 1, said filter 15 being adapted to pass only the radiation belonging to the frequency band to be analyzed. The optical measuring device 1 further comprises a control unit configured to analyze the light rays received by the photosensitive receiver 4, and compare the results of the analysis with known data.

The method comprises the steps of:

placing the optical measuring device 1 opposite a skin surface 10 of the subject, so that the first object focus of the optical objective is positioned at a predetermined depth of skin,

reception by the photosensitive receiver 4 of the light rays coming from the first object focus, at the predetermined skin depth,

analyzing the light rays received by the photosensitive receiver 4, and comparing the results of the analysis with the known data, so as to determine the physiological parameter of interest of the subject.

In a particular embodiment, the physiological parameter to be determined is the body temperature of the subject. The body temperature of the subject is determined by analyzing the intensity of the light radiation having an infrared wavelength of between 700 nm and 1 mm emitted by the skin. The photosensitive receiver 4 is adapted to detect light rays having an infrared wavelength of between 700 nm and 1 mm. The predetermined skin depth is included in the dermis or hypodermis, preferably between 100μηι and 1 .5mm from the skin surface 10. More preferably, the predetermined skin depth is greater than 0.5mm from the skin surface 10.

In a second embodiment, the method according to claim 1 is implemented by a measuring device 1 bis, as illustrated in FIG.

The measuring device 1 bis comprises, in addition to the photosensitive receiver 4, the objective 3, the first pinhole 1 1 and the control unit previously described:

at least one light source 2, typically one or more lasers or diodes, a semi-reflecting mirror 5 positioned between the detector 4 and the tissue to be studied,

a second pinhole 21 positioned in a second confocal plane cF2 which is the conjugate, by the objective 3 and the semi-reflecting mirror 4, of the focal plane F containing the tissue to be analyzed.

The optical objective 3 comprises a second object focus and a second image focus, the second image focus coinciding with the first object focus. The second pinhole 21 is centered on the second object focus so as to pass only the light rays emitted by the light source or sources from the second object focus.

It will be understood that in this way the illumination is concentrated on the focal plane F. The semi-reflecting plane mirror 5 is configured to transmit the light rays emitted by the light source towards the optical objective, and to transmit the light rays originating from the first object focus to the photosensitive detector 4.

Thus, only the photons coming from the focal plane F pass the pinhole 11 and participate in the spectroscopic measurement. Light from adjacent (fuzzy) planes is stopped by the edges of the hole. It is thus possible to obtain a net optical section corresponding solely to the focal plane. There is therefore selection of the depth of the spectroscopically measured layer. The measuring device 1a may further comprise a first polarizing plate 12 positioned between the first pinhole 11 and the semi-reflecting mirror 5 and a second polarizing plate 22 between the second pinhole 21 and the half-reflecting mirror 5. The axes of polarization of the two blades 12 and 22 are perpendicular so that the photons from the light source 2 and from the reflection on the surface of the skin 10 do not reach the detector 4. In fact, the reflection does not change the polarization, these photons polarized by the polarizing plate 22 will be absorbed by the polarizing plate 12. On the contrary, the photons absorbed and reemitted in the plane F by the photoactive molecules of the skin 10, have their polarization modified and can cross the polarizing plate F . The method further comprises the steps of:

emission of light rays by the light source 2 to the second image focus, at the predetermined skin depth,

reception of the light rays emitted by the light source (s), reflected by the skin and originating from the first object focus, at the predetermined depth of skin, by the photosensitive receiver 4,

determination of the absorption rate by the skin of the light rays emitted by the light source from the analysis of the light rays received by the photosensitive receiver 4, and comparison of the determined absorption rate with the known data, so as to determine the physiological parameter of the subject.

It will be understood that to the extent that it controls the emission and reception of light rays to / from the focal plane F corresponding to the predetermined skin depth, it is possible to know the rate of absorption by the skin comparing the rays emitted by the light source or sources via the second pinhole 21 to the focal plane F and the rays emitted from the focal plane F to the receiver 4 via the first pinhole 11.

In a particular embodiment, the physiological parameter to be determined is the cutaneous level of bilirubin. In this case, the device 1 bis comprises at least three light sources each emitting radiation of different wavelengths between 400 and 800 nm. The wavelengths emitted are also specific to the identification of dopa-melanin of red blood cells and bilirubin. Preferably, the device 1 bis comprises from three to seven light sources. The predetermined skin depth is in this case to the dermis or hypodermis and is greater than 0.2mm.

In another particular embodiment, the physiological parameter to be determined is the oxygen saturation blood level and carbon monoxide. In this case, the device 1 bis comprises two light sources 2 each emitting radiation in different wavelengths, a first between 620 and 680nm (red) and a second between 780 and 1 mm (infrared). The predetermined skin depth is in this case the hypodermis and is greater than 1 mm. It will be understood that the method for measuring a physiological parameter of a subject as described above is particularly advantageous insofar as it allows by means of the objective 3 and the pinhole (s) 1 1 and 21 to receive only the light rays from the focal plane F placed at the desired skin depth, thereby considerably reducing the measurement inaccuracies that could be induced by parasitic light radiation.

Claims

A method of measuring a physiological parameter of a subject that can be implemented by means of an optical measuring device (1, 1 bis) comprising:

a first plane comprising a pinhole (21) centered on the first image focal point of the optical objective so as to let only the light rays coming from the first object focus of the optical objective,

a photosensitive receiver (4) intended to receive the light rays originating from the first image focus, downstream from the pinhole camera,

a control unit configured to analyze the light rays received by the photosensitive receiver (4), and to compare the results of the analysis with known data, said method comprising the steps of:

placing the optical measuring device (1, 1a) facing a skin surface (10) of the subject, so that the first object focus of the optical objective is positioned at a predetermined depth of skin,

reception by the photosensitive receiver (4) of the light rays coming from the first object focus, at the predetermined skin depth,

- Analysis of the light rays received by the photosensitive receiver (4), and determination of said physiological parameter of the subject from the characteristics of the light rays received.

2. The method of claim 1, wherein the physiological parameter to be determined is the body temperature of a subject.

3. Method according to claim 2, wherein the light rays having an infrared wavelength between 700nm and 1 mm are analyzed.

4. The method of claim 2 or claim 3, wherein the predetermined skin depth is included in the dermis or hypodermis, preferably between 100μηι and 1.5mm deep.

The method of claim 1, wherein:

the optical objective comprises a second object focus and a second image focus, the second image focus being coincident with the first object focus,

the measuring device (1a) further comprises:

at least one light source (2),

a semi-reflecting plane mirror (5), said mirror being configured to transmit the light rays emitted by the light source towards the optical objective, and for transmitting the light rays coming from the first object focus towards the photosensitive detector (4) ,

said method further comprising the steps of:

emitting light rays from the light source (2) to the second image focus at the predetermined skin depth,

receiving the light rays emitted by the light source, reflected by the skin and originating from the first object focus, at the predetermined skin depth, by the photosensitive receiver (4),

measuring the rate of absorption by the skin of the light rays emitted by the light source (s) from the analysis of the light rays received by the photosensitive receiver (4), and determination of the physiological parameter of the subject from the light level measured absorption.

6. The method of claim 5, wherein the physiological parameter to be determined is the cutaneous bilirubin rate.

7. The method of claim 6, wherein the light rays emitted by the light source (s) (2) have a wavelength between 400 and 800nm.

The method of claim 6 or claim 7, wherein the predetermined skin depth is within the hypoderm, and is preferably greater than 1 mm. The method of claim 5, wherein the physiological parameter to be determined is the oxygen saturation blood level and carbon monoxide.

0. The method of claim 9, wherein the light rays from two light sources are analyzed, each emitting light rays of different wavelengths, a first between 620 and 680 nm and a second between 780 nm and 1 nm. mm. 1. The method of claim 9 or claim 10, wherein the predetermined skin depth is comprised in the dermis or hypodermis, and is preferably greater than 0.2mm.