Patent ID: 12239441

DETAILED DESCRIPTION

FIG.1shows a functional spectroscopy system1(hereinafter, also referred to as fNIRS system1), which, without this implying any loss of generality, is assumed as implementing the continuous-wave detection method. Once again without this implying any loss of generality, it is assumed that the fNIRS system1is designed for analysis of brain activity.

In particular, the fNIRS system1comprises an optical detection system12and a processing and analysis system14, electrically coupled to one another.

In detail, the optical detection system12comprises a plurality of lighting devices2(just one of which is illustrated inFIG.1) that are the same as one another, and a plurality of detection devices3(just one of which is illustrated inFIG.1) that are the same as one another.

In general, each lighting device2comprises a first light source2A and a second light source2B that may be formed by corresponding LEDs. In particular, the first and second light sources2A,2B emit light radiation in the near infrared at different wavelengths. For instance, the first light source2A emits a first light radiation, having a wavelength shorter than 800 nm (for example, 735 nm), whereas the second light source2B emits a second light radiation, having a wavelength longer than 800 nm (for example, 850 nm). In this way, the processing and analysis system14may determine, among the parameters for the body tissue being investigated, the variations in time of the concentrations of oxygenated hemoglobin and of deoxygenated hemoglobin in the blood.

FIG.2shows a possible example of one lighting device2.

In detail, the lighting device2comprises a container20, for example of PVC (polyvinyl chloride), which is delimited at the top and at the bottom, respectively, by a first surface20A and a second surface20B, which define, respectively, a first plane of extension A and a second plane of extension B (which are illustrated dashed inFIG.2) both parallel to a plane XY of a Cartesian reference system XYZ.

Further, the container20has, for example, a hollow circular shape in top plan view, with axis of symmetry S parallel to a first axis Z of the reference system XYZ.

In greater detail, the container20delimits a main cavity24and a secondary cavity22, which are in communication with one another. In particular, the main cavity24has a cylindrical shape, gives out onto the first surface20A and overlies the secondary cavity22, which also has a cylindrical shape, has a diameter smaller than the diameter of the main cavity24, is aligned with the main cavity24along the axis of symmetry S, and gives out onto the bottom surface20B.

Present inside the main cavity24is a substrate30, which is delimited by a top surface30A and a bottom surface30B; in particular, the substrate30is made, for example, of FR4 and is of a flexible type. Further, the substrate30may have a cylindrical shape, with an axis coinciding with the axis of symmetry S and with a diameter comprised between the diameter of the main cavity24and the diameter of the secondary cavity22. Albeit not illustrated, extending within the substrate30are electronic circuits and conductive paths.

Extending on the top surface30A is a bicolor LED emitter32, which is functionally equivalent to the first and second light sources2A,2B and is electrically coupled to the electronic circuits and to the conductive paths formed in the substrate30, which are in turn electrically coupled to an electrical cable34that enables connection of the lighting device2to the processing and analysis system14for managing operation of the lighting device2in the various operating steps.

The lighting device2also comprises a cap26, arranged on the first surface20A of the container20so as to close the main cavity24at the top. The cap26is made of a dielectric material, such as, for example, polyimide (such as Kapton®) or polyethylene laminas (such as PEN/PET—polyethylene naphthalate/polyethylene terephthalate), so as to present a high transmittance in the near infrared (for example, higher than 90%); further, the cap26has a thickness (i.e., an extension along the first axis Z) of, for example, 0.2 mm.

As illustrated inFIG.3, the bicolor LED emitter32is electrically equivalent to a first LED35A and a second LED35B, each having respective anode and cathode terminals. Further,FIG.3shows a first resistor42and a second resistor44, each having a first terminal and a second terminal. The first and second resistors42,44are designed, in use, to polarize, respectively, the first and second LEDs35A,35B, and both have a resistance comprised, for example, in the range between 10Ω and 1 kΩ.

In particular, the anode terminals of the first and second LEDs35A,35B are connected to a control terminal40. On the other side, the cathode terminals of the first and second LEDs35A,35B are connected, respectively, to corresponding first terminals of the first and second resistors42,44. In addition, the second terminals of the first and second resistors42,44are respectively connected to a first supply terminal46and to a second supply terminal48, which are set in use, respectively, at a first supply voltage VCCRand a second supply voltage VCCIRThe control terminal40and the first and second supply terminals46,48are connected to the processing and analysis system14through the electrical cable34.

In use, the processing and analysis system14controls the first and second supply voltages VCCR, VCCIRand sends a driving signal DSon the control terminal40so that the first and second LEDs35A,35B are turned on in an alternating way, emitting, respectively, the first light radiation and the second light radiation. In this connection, having assumed that the fNIRS system1is of the continuous-wave type, the first and second LEDs35A,35B are alternatively turned on for a relatively long period of time (for example, for periods comprised between 1 μs and 10 ms).

FIG.4shows in detail a single detection device3of the fNIRS system1, which is now described limitedly to the differences with respect to the lighting device2. Components of the detection device3that are already present in the lighting device2are designated by the same references increased by 100, except where otherwise specified.

In detail, the detection device3comprises a photodetector92, formed, for example, by a silicon photomultiplier (SiPM), which is formed by an array of Geiger-mode avalanche photodiodes (GAPDs), also known as single-photon avalanche diodes (SPADs).

The photodetector92is arranged on the top surface130A of the substrate130and is electrically coupled to the electronic circuits and to the conductive paths of the substrate130(which are not illustrated), which are coupled to the processing and analysis system14through the electrical cable134. In this way, the processing and analysis system14receives an output signal Vsignal, generated by the photodetector92as a function of the light radiation reflected by the brain tissue, as described hereinafter.

The detection device3further comprises an optical filter90, which is arranged on the first surface120A of the container120so as to close the main cavity124and so as to overlay, at a distance, the photodetector92.

In greater detail, the optical filter90is made, for example, of a dielectric material, such as plastic (for example, polyester or polycarbonate, or an organic glass, such as CR39); further, the optical filter90is a high-pass filter for the frequencies in the near infrared with a cut-on wavelength of, for example, 700 nm. In this way, the optical filter90is able to let through the environmental radiation having a wavelength equal to or longer than 700 nm, filtering out, instead, the background light, which could introduce errors due to phenomena of optical interference.

The containers of the lighting devices2and of the detection devices3may be the same as one another.

As illustrated inFIG.5, the photodetector92is set in an electrical circuit comprising a first branch3A and a second branch3B, arranged in parallel with one another and arranged between a biasing terminal102, which in use is set at a biasing voltage Vbias, and a reference terminal108set at a reference voltage Vground.

The first branch3A comprises the photodetector92, the cathode terminal of which is connected to the biasing terminal102, and an output resistor106, having a first terminal and a second terminal, which are connected to the anode terminal of the photodetector92and to the reference terminal108, respectively. The anode terminal of the photodetector92and the first terminal of the output resistor106form an output node110. For instance, the output resistor106has a resistance of 1 kΩ. The biasing terminal102, the reference terminal108, and the output node110are electrically connected to the processing and analysis system14, through the conductive paths that extend in the substrate130and through the electrical cable134.

In use, the photodetector92is reversely biased by the biasing voltage Vbias, the latter being higher (in modulus) than the breakdown voltage of the photodetector92.

The second branch3B comprises a capacitor104, having a first terminal and a second terminal, which are respectively connected to the biasing terminal102and to the reference-potential terminal108; by way of example, the capacitor104has a capacitance of 100 nF. Further, the capacitor104acts, in use, as a voltage-filtering and voltage-stabilization element for the photodetector92.

Operatively, the photodetector92receives the reflected (or backscattered) radiation (more precisely, fractions thereof) coming from the brain tissue, as the first radiation or the second radiation emitted by the bicolor LED emitter32impinges upon the brain tissue, generating a corresponding current, with consequent generation, on the output node110, of the output signal Vsignal, which is received by the processing and analysis system14.

Once again with reference toFIG.1, the processing and analysis system14is described now in greater detail, with reference to the interaction with a single lighting device2and a single detection device3, except where otherwise specified. In other words, reference is made the corresponding analysis of a portion of the brain tissue, optically coupled to the lighting device2and to the detection device3considered.

This having been said, the processing and analysis system14comprises: a microcontroller5, electrically coupled to the lighting device2by the electrical cable34; a filtering and amplification block6, coupled to the detection device3by the electrical cable134; an ADC (analog-to-digital converter)7, electrically coupled to the filtering and amplification block6and to the microcontroller5; and an electronic analysis system9, coupled to the microcontroller5.

In use, the microcontroller5controls the bicolor LED emitter32so as to turn on the first and second LEDs35A,35B in an alternating way. For example, the microcontroller5controls the first and second LEDs35A,35B so that each has an ON time comprised in the range of, for example, 1 μs to 10 ms.

Considering either the first light radiation or the second light radiation, this impinges upon the brain tissue and propagates in the latter. Part of the light radiation is absorbed by the brain tissue, whereas the remaining portion is reflected after propagating for some centimeters within the brain tissue; a corresponding reflected radiation is thus generated. In particular, according to whether the first or second light radiation impinges upon the brain tissue, a first reflected radiation or a second reflected radiation, respectively, is generated, the first reflected radiation and the second reflected radiation being received, in an alternating way, by the photodetector92.

In particular, considering either the first reflected light radiation or the second reflected light radiation, this impinges upon the detection device3, which generates the aforementioned output signal Vsignal. For instance, the detection device3may operate in a free-running condition, i.e., so that detection of the reflected light radiation is made in a continuous way. Once again with reference to the output signal Vsignal, since the first light radiation and the second light radiation, and thus also the first reflected light radiation and the second reflected light radiation, are generated in an alternating way, said output signal represents, alternatively, the first reflected radiation or the second reflected radiation.

Next, the output signal Vsignalis sent to the filtering and amplification block6, which reduces the noise due to the electronic components and amplifies the output signal Vsignal. Consequently, at output from the filtering and amplification block6, an amplified output signal Vsignal_Ais present.

The amplified output signal Vsignal_Ais transmitted to the ADC7, which converts the amplified output signal Vsignal_Ainto a digital signal, referred to hereinafter as the analysis signal SA.

The analysis signal SAis subsequently sent to the microcontroller5, which in turn sends it to the electronic analysis system9by known interfacing systems. Then, the analysis signal SAis processed by the electronic analysis system9so as to determine parameters regarding the brain activity. For instance, if the analysis signal generated in response to the first reflected radiation and the second reflected radiation are referred to as first and second analysis signals SA1, SA2, the processing system9may process in a per se known manner the first and second analysis signals SA1, SA2to determine the concentrations of the oxygenated hemoglobin and of the deoxygenated hemoglobin.

As illustrated inFIG.6, the fNIRS system1further includes a wearable structure200in the form of a helmet or headset, which is arranged on the scalp of the patient under examination.

The wearable structure200comprises a plurality of housings201, each of which is designed to house indifferently a lighting device2or else a detection device3. In other words, considering any housing201, an operator may insert therein either a lighting device2or else a detection device3indifferently. Further, if by “probe device” is meant one of the lighting devices2or one of the detection devices3, considering any housing201, the mechanical coupling between the probe device and the housing is, for example, of the press-fit type, or else of an elastic type, and enables fixing of the probe device in the housing201in a releasable way. The probe device is thus arranged in contact with the scalp of the patient, to which it is temporarily fixed. In particular, in the case of a lighting device2, the corresponding cap26contacts the scalp. Instead, in the case of a detection device3, the scalp contacts the corresponding optical filter90.

Without this implying any loss of generality, the housings201are arranged according to a mesh-like arrangement; i.e., they are arranged at the nodes of a hypothetical mesh, which covers the entire wearable structure200.

For practical purposes, an operator may choose whether to connect the lighting devices2and the detection devices3in corresponding housings201so as to cover the entire scalp (i.e., by coupling all the housings201to corresponding probe devices), or else just a portion of scalp, so as to focus analysis on this portion. In addition, an operator may arrange the lighting devices2and the detection devices3in the corresponding housings201so that each lighting device2is operatively coupled to at least one corresponding detection device3, i.e., so that the detection device3is able to receive, following upon reflection by the brain tissue, at least part of the first light radiation and of the second light radiation emitted by the lighting device2. In other words, it is for example possible for each detection device3to be arranged in a corresponding housing201that is adjacent to a corresponding housing201that houses a lighting device2, where by “adjacent” is meant that it is arranged at a distance such as to enable optical coupling between the detection device3and the lighting device2.

The advantages that the present fNIRS system affords emerge clearly from the foregoing description.

In particular, the present fNIRS system enables a considerable reduction of the losses due to the optical coupling in so far as both the light sources and the photodetectors are arranged on the scalp of the patient being examined, without any need to resort to guiding structures, such as optical fibers. Further, the fNIRS system provides a high degree of flexibility for the operator, who may vary the relative arrangements, and thus also the distances, between the lighting devices and the detection devices.

Further, any interference due to the external environment is attenuated, since the present fNIRS system comprises a plurality of filters that are able to reduce considerably the disturbance deriving from the external environment.

In addition, the present fNIRS system is able to analyze the brain tissue to a greater depth in so far as not only is there a better optical coupling between light sources and photodetectors, but each photodetector (in particular, in the case of the silicon photomultiplier) has a high sensitivity. This advantage thus enables use of light sources that consume little power, such as low-power LEDs, without any significant losses in terms of quality of the analysis signals SA.

In addition, both the light sources and the photodetectors are electrically insulated from the body tissue, with consequent reduction of the risks for the patient.

Furthermore, it is clear that modifications and variations may be made to the system described and illustrated herein.

For instance, each photodetector may be of a type different from what has been described. In general, it is possible to use any photodetector with a gain higher than unity, such as single SPADs, or else photodiodes operating in the linear regime in the proximity of the breakdown voltage.

In addition, the number of light sources in each lighting device, as well as the corresponding wavelengths of emission, may be different from what has been described previously and may vary according to the functional parameters that are to be determined. For instance, systems are possible in which each lighting device includes a single light source, which in turn may generate radiation at different wavelengths.

Furthermore, in general, the wavelengths of the light sources may be different from what has been described and may, for example, fall within portions of the spectrum other than the near infrared.

Further possible are systems that enable spectroscopic analyses different from continuous-wave spectroscopy to be carried out.

In addition, systems are possible in which the housings are coated with blackened paints, so as to prevent any undesired light absorption.

The shape of the wearable structure may change, for example according to the type of body tissue that is to be analyzed, since, as explained previously, the present fNIRS system is not limited to the analysis of just the brain tissue.

All this having been said, embodiments are possible, in which the lighting devices and/or the detection devices are of the type shown, respectively, inFIGS.7and8.

In detail, as shown inFIG.7, the lighting device (here designated by302) further includes a top coating layer304, arranged on top of the cap26and made up of a conductive material such as graphene or a conductive polymer (such as poly(3,4-ethyelenedioxythiophene):poly(styrene sulfonate), known as PEDOT-PSS) or a random network of nanowires (e.g., carbon nanotubes, silver nanowires). The top coating layer304is substantially transparent (i.e., with an optical transmittance greater than 85%) in the near infrared; therefore, the optical behavior of the lighting device302stays the same, irrespective of the presence of the top coating layer304. In addition, the top coating layer304acts as an electrode, such as an electrode for electroencephalography (EEG) or electrocardiography (ECG) for the case of the PPG.

In greater detail, the top coating layer304includes a respective inner portion, which overlies, at a distance, the bicolor LED emitter32, and a peripheral portion, which overlies a portion of the cap26in direct contact with the container20; the top coating layer304is thus arranged in front of the bicolor LED emitter32. The lighting device302may further include a contact region306, arranged on the peripheral portion of the top coating layer304and made up of a layer of a metal such as gold, platinum or aluminum. In addition, the lighting device302may further include a conductive wire308, made up of copper. The conductive wire308has a corresponding first end, which contacts the contact region306. A first portion of the conductive wire308extends partially along the outer wall of the portion of the container20which delimits the main cavity24; in addition, a second portion of the conductive wire308extends through a hole310through the container20, this hole310giving out onto the secondary cavity22; a third portion of the conductive wire308extends in the secondary cavity22. The conductive wire308has a corresponding second end, which may be coupled, in use, to an EEG or ECG system312. Although not shown, embodiments are possible in which the first portion of the conductive wire308extends in the main cavity24.

As shown inFIG.8, the detection device (here designated by403) further includes a respective top coating layer404, arranged on the optical filter90and made up of a conductive material such as graphene or a conductive polymer (such as PEDOT-PSS) or a random network of nanowires (e.g., carbon nanotubes, silver nanowires). The top coating layer404is substantially transparent (i.e., with an optical transmittance greater than 85%) in the near infrared; therefore, the optical behavior of the detection device403stays the same, irrespective of the presence of the top coating layer404. In addition, the top coating layer404acts as an electrode, such as an EEG or ECG electrode in the case of the PPG.

In greater detail, the top coating layer404includes a respective inner portion, which overlies, at a distance, the photodetector92, and a peripheral portion, which overlies a portion of the optical filter90in direct contact with the container120; the top coating layer404is thus arranged in front of the photodetector92. The detection device403may further include a respective contact region406, arranged on the peripheral portion of the top coating layer404and made up of a layer of a metal such as gold, platinum or aluminum. In addition, the detection device403may further include a respective conductive wire408, made up of, e.g., copper. The conductive wire408has a corresponding first end, which contacts the contact region406. A first portion of the conductive wire408extends partially along the outer wall of the portion of the container120which delimits the main cavity124; in addition, a second portion of the conductive wire408extends through a hole410through the container120, this hole410giving out onto the secondary cavity122; a third portion of the conductive wire408extends in the secondary cavity122. The conductive wire408has a corresponding second end, which may be coupled, in use, to the EEG or ECG system, here designated by412.

The top coating layers304,404may also be disposable and applied on purpose onto the cap26and the optical filter90.

As shown inFIGS.9A and9B, a further embodiment is possible, which is described herein below with reference to the lighting device302, though the same features may apply to the detection device403.

In detail the contact region306has an annular shape, arranged on the peripheral portion of the top coating layer304. Therefore, the contact region306laterally delimits an aperture307, overlying, at a distance, the bicolor LED emitter32.

In addition, the lighting device302includes a plurality of metallic needles399, namely a plurality of metallic cones (namely, sharp elements), with bases arranged on the contact region306and axes parallel to the axis of symmetry S. The vertices of the cones are apt to contact the body of the patient, therefore the needles399and the contact region act as an electrode. The arrangement of the needles399shown inFIG.9a-9B is purely illustrative.

In the case of the embodiment shown inFIGS.9A-9B, the top coating layer (here designated by1304) may be made of a dielectric material, or it may even be absent, in which case (not shown), the contact region306is arranged on the cap26. The top coating layer1304may also be of the same type as shown inFIG.7.

As mentioned before, the needles may be present also in the case of the detection device403, as shown inFIG.10. In particular, the needles, here designated by499, are arranged on the contact region (here designated by406), which has the same shape shown inFIGS.9A-9B; the aperture, designated by407, overlies the photodetector92, at a distance. The top coating layer, designated by1404, may be of dielectric material, or it may even be absent, in which case (not shown), the contact region406is arranged on the optical filter90. The top coating layer1404may also be of the same type as shown inFIG.8.

As shown inFIGS.11A and11B, a further embodiment is possible, which is described here below with reference to the lighting device302, though the same features may apply also to the detection device403.

In detail, the contact region306has the shape of a layer with a plurality of apertures398, which give out onto corresponding portions of the top coating layer1304, which may be made of a dielectric material; the top coating layer1304may even be absent, in which case (not shown), the contact region306is arranged on the cap26and the apertures398give out corresponding portions of the cap26; at least one of the apertures398overlies the bicolor LED emitter32. The needles399are arranged on the contact region306, which has the same shape shown inFIGS.9A-9B.

In case the top coating layer1304is of the same type as shown inFIG.7and the apertures398are uniformly distributed, the overall transmittance of the assembly formed by the top coating layer1304and the contact region306is given, to a first approximation, by product of i) the transmittance of the top coating layer1304and ii) the ratio between the overall area of the apertures398and the overall area of the coating layer1304, in top plan view.

As shown inFIG.12, a further embodiment is possible, in which the needles (designated by499) are arranged on the contact region406of the detection device403, which may have the same shape shown inFIGS.11A-11B. In this case, the apertures398give out onto the top coating layer1404, which may be made of a dielectric material. The top coating layer1404may even be absent, in which case (not shown), the contact region406is arranged on the optical filter90. The top coating layer1404may also be of the same type as shown inFIG.8.

Put in other words, the embodiments shown inFIGS.7,8,9A-9B,10,11A-11B and12feature, each, a cover structure arranged on top of an active optical device. In particular, in the case shown inFIG.7, the cover structure includes the cap26and the top coating layer304; in the cases shown inFIGS.9A-9B and11A-11B, the cover structure includes the cap26, the top coating layer1304, the contact region306and the needles399. In the case shown inFIG.8, the cover structure includes the optical filter90and the top coating layer404; in the cases shown inFIGS.10and12, the cover structure includes the optical filter90, the contact region406and the needles499. In the case of the lighting devices302, the cover structure is crossed by the light generated by the bicolor LED emitter32; in the case of the detection devices403, the cover structure is crossed by the light to be detected by the photodetector92.

Although not shown, further embodiments are possible, in which the needles have rounded vertices, i.e., rounded end portions apt to contact the body.

Finally, it has to be noted that the present system may form a photopletysmography (PPG) system, rather than a fNIRS system.

The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.