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EP-4327741-B1 - PROCESS FOR IN SITU TESTING AN ANALYTE MONITOR, AND ANALYTE MONITOR

EP4327741B1EP 4327741 B1EP4327741 B1EP 4327741B1EP-4327741-B1

Inventors

  • MONPEURT, Cyrielle
  • BLANC, Romain

Dates

Publication Date
20260513
Application Date
20220827

Claims (9)

  1. Process for in situ testing an analyte monitor (1) based on photoacoustic or photothermal detection comprising: a) providing an analyte monitor (1) based on photoacoustic or photothermal detection at a measurement position relative to a target (2); b) setting an irradiation configuration (Cirrad) of a light source of the analyte monitor (1) comprising at least one triplet of irradiation parameters comprising a modulation frequency (fmod), a wavelength λ and an optical power P; c) irradiating the target (2) with the light source of the analyte monitor (1) configured with the irradiation configuration (Cirrad) at a plurality of irradiation time points and measuring for each time point at least an amplitude (A(fmod, λ, P)) and a phase (φ(fmod, λ, P)) of an acoustic or thermal wave generated in response to the irradiation for at least one triplet of irradiation parameters (fmod, λ, P) of the irradiation configuration (Cirrad); characterized in that the process comprises the following steps: d) calculating with a processor (13) of the analyte monitor (1) at least one correlation coefficient (R(fmod, λ, P)) between the amplitude (A(fmod, λ, P)) and the phase (φ(fmod, λ, P)) for at least one triplet of irradiation parameters (fmod, λ, P) of the irradiation configuration (Cirrad) over a window period (Twin) comprising at least two irradiation time points of said plurality of irradiation time points; e) comparing with the processor (13) of the analyte monitor (1) at least one of the at least one correlation coefficient (R(fmod, λ, P)) with at least one threshold value (Rthresh); f) providing with a processor (13) of the analyte monitor (1) a test result based on the result of the comparison.
  2. Process for in situ testing an analyte monitor (1) based on photoacoustic or photothermal detection according to claim 1 in which if the absolute value of at least one correlation coefficient (R(fmod, λ, P)) is higher than a threshold value (Rthresh), the test result is an authorisation to proceed with at least one subsequent measurement with the analyte monitor (1).
  3. Process for in situ testing an analyte monitor (1) based on photoacoustic or photothermal detection according to claim 1 or claim 2 in which if the absolute value of at least one correlation coefficient (R(fmod, λ, P)) is lower than a threshold value (Rthresh), the test result comprises displaying an alert chosen in the list: message on a user interface of the analyte monitor (1) or by emailing to check the positioning of the analyte monitor (1) and/or to check one or more components of the analyte monitor (1), optical alert, sound alert.
  4. Process for in situ testing an analyte monitor (1) based on photoacoustic or photothermal detection according to any of claims 1-3 comprising, if the absolute value of at least one correlation coefficient (R(fmod, λ, P)) is lower than a threshold value (Rthresh), between e) and f) at least one of: g1) updating the window period (Twin) and repeating d), e) and f) ; g2) updating the irradiation configuration (Cirrad) and repeating c), d), e) and f) ; g3) imposing a forced modification on the target (2) and/or the environment of the target (2) and/or the analyte monitor (1) and repeating b) c), d), e) and f).
  5. Process for in situ testing an analyte monitor (1) based on photoacoustic or photothermal detection according to claim 4 comprising both g1) and g2), and in which g2) is implemented only if g1) has been repeated imax times, imax being a predetermined positive integer associated with the window period updating.
  6. Process for in situ testing an analyte monitor (1) based on photoacoustic or photothermal detection according to claim 4 or claim 5 comprising both g2) and g3), and in which g3) is implemented only if g2) has been repeated jmax times, jmax being a predetermined positive integer associated with the irradiation configuration updating.
  7. Process for measuring an analyte level in the target (2) with an analyte monitor (1) based on photoacoustic or photothermal detection comprising the process for in situ testing the analyte monitor (1) according to any of claims 1 to 6 prior to at least one measurement step of the analyte level.
  8. Analyte monitor (1) based on photoacoustic or photothermal detection for measuring an analyte level in a target (2) comprising : - an intensity-modulation device, - a light emitter emitting an intensity-modulated light, - a light emitter controller for controlling at least one modulation frequency (fmod) at which said intensity-modulation device modulates the intensity of a light emitted by the light emitter, - at least one detection cell (12) comprising a sensor sensing directly or indirectly a thermal wave propagating out of the target (2) in response to an irradiation, - a processor module (13) configured to receive and process sensor data from the at least one detection cell (12), wherein the processor module (13) further comprises means adapted for : i) setting an irradiation configuration (Cirrad) comprising at least one triplet of irradiation parameters of a light source of the analyte monitor (1) comprising a modulation frequency (fmod), a wavelength (λ) and an optical power (P); ii) irradiating the target (2) with the light source of the analyte monitor (1) configured with the irradiation configuration (Cirrad) at a plurality of irradiation time points and measuring for each time point at least an amplitude (A(fmod, λ, P)) and a phase (φ(fmod, λ, P)) of an acoustic or thermal wave generated in response to the irradiation for at least one triplet of irradiation parameters (fmod, λ, P) of the irradiation configuration (Cirrad); characterized by : iii) calculating at least one correlation coefficient (R(fmod, λ, P)) between the amplitude (A(fmod, λ, P)) and the phase (φ(fmod, λ, P)) for at least one triplet of irradiation parameters (fmod, λ, P) of an irradiation configuration (Cirrad) over a window period (Twin) comprising at least two irradiation time points of with the light emitter; iv) comparing at least one of the at least one correlation coefficient (R(fmod, λ, P)) with at least one threshold value (Rthresh); v) providing a test result based on the result of the comparison.
  9. Computer program comprising instructions to cause the analyte monitor (1) of claim 8 to acquire measurement data obtained at step c) of claim 1 and execute steps d)-f) of the in situ testing process of claim 1 or the in situ testing process of any of claims 2 to 6.

Description

FIELD OF THE INVENTION The present invention relates to an analyte monitor based on photoacoustic or photothermal detection. More specifically, the invention relates to a process for testing in situ such an analyte monitor. TECHNOLOGICAL BACKGROUND In the field of sensors for human beings or animals, non-invasive sensors based on photoacoustic or photothermal detection are known. By way of an example, glycemia can be measured with a photoacoustic or a photothermal sensor, such as that of US 2022/257,154. A zone of interest of a medium to be analysed, called target, is irradiated by means of a laser beam of wavelength and modulation frequency chosen according to the parameter of interest to be measured. The laser beam is absorbed by the target to a depth which depends on the structuring of the target. The absorption of light energy leads to local heating of the target. In response to this heating, a thermal wave with a frequency equal to the modulation frequency of the laser is generated in the target. This wave propagates in the target and in particular to the outer surface of the target. In the case of a photothermal sensor, the thermal wave is directly detected and analysed. Photoacoustic detection exploits the fact that the thermal wave is associated with a pressure wave of frequency identical to the modulation frequency. In the case of indirect photoacoustic detection, the pressure wave generated in the fluid external environment is detected when the thermal wave generated in the target reaches, after propagation, the interface between the target and its fluid external environment. Photoacoustic detection has many advantages compared to other detection techniques, among which the fact that the transduction is orthogonal: the optical signal entering the medium to be analysed is converted into an acoustic signal which is very specific to the phenomenon to be observed and which makes it possible to use inexpensive and miniaturized sensors. The difficulty of photoacoustic or photothermal detection comes (among others) from: the number of parameters generally influencing the detected signal and,for certain analytes of interest present in low concentration in the medium to be analysed, the low proportion of the detected signal specific to each of these parameters of interest. In a stratified material, in order to be able to deduce from the photoacoustic or photothermal signal the concentration of a given layer in an analyte of interest, it is thus necessary to know all the other parameters influencing this signal. In particular, it is necessary to know the structuring of the material, i.e. the thicknesses of the different layers constituting the material, their respective physico-chemical compositions (with the exception of the parameter of interest to be measured), as well as possibly their thermal conductivities or even the thermal resistance associated with each interface between two successive layers. Calibrating once and for all (or at least for a significant period of use) a sensor based on photoacoustic or photothermal detection is only possible if only the parameter of interest varies in the target. On the other hand, when the characteristics of the stratified medium to be analysed vary, it is necessary to carry out a calibration of the sensor regularly to obtain a measurement with acceptable accuracy. This problem arises more particularly for sensors intended for use on living organisms. For example, in the case of a non-invasive interstitial blood glucose sensor, the calibration of a non-invasive sensor based on photoacoustic or photothermal detection can only be achieved with limited accuracy because the composition of the skin varies not only from one patient to another but also over time for a given patient. Before even thinking of calibrating the analyte monitor, it is necessary to test its correct operation, i.e. to check that there is for example no failure of one of its components or no problem with the positioning of the sensor. For example, in the case of a glycemia sensor comprising a cuff positioned on the arm of a patient, the cuff may not be tight on the arm or may move due to the patient movements so that its position doesn't allow measuring glycemia. The part of the signal associated with glycemia may in such cases be drowned in noise. In such cases, even if the glycemia sensor provides a measurement, this measurement is not reliable. As a consequence, an in situ testing process for repeatedly testing in situ an analyte monitor based on photoacoustic or photothermal detection is necessary. In the field of photoacoustic sensors, in general, a calibration procedure is carried out with a reference sample or a calibration unit. This calibration can at the same time be exploited as a testing procedure. US11275059 describes such an in situ calibration unit. In a particular embodiment, the calibration unit is integrated in the photoacoustic sensor. However, bearing in mind miniaturization, w