High dynamic range detector for gingivitis detection

Abstract

A system (100) for detecting tissue inflammation, particularly gingivitis, comprises: a light emitter (102) configured to emit light at a tissue region within a user's mouth; at least four wavelength-sensitive photodetectors (110, 112, 114 and 116) configured to detect an optical signal diffusely reflected by the tissue region, each of the at least four wavelength-sensitive photodetectors comprising a filter (BPF1, BPF2, BPF3 and BPF4) and a photodiode (D1, D2, D3 and D4), wherein the photodiodes are stacked on top of each other to generate a current differential signal for an amplifier corresponding to the photodiode, wherein the generation of the current differential signal removes undesirable components from the optical signal before amplification; and an inflammation detection unit (136) configured to receive an output from the corresponding amplifier and detect inflammation at the tissue region.

Description

Technical Field

[0001] The present disclosure generally relates to a front end for detecting tissue inflammation, particularly gingivitis, using diffuse reflectance spectroscopy techniques. Background Art

[0002] Currently, gingivitis detection using diffuse reflectance spectroscopy (DRS) is performed using a small, angled probe that is configured around one or more optical fibers that transmit light due to the limited space in the oral cavity. Such small probes are useful for measuring in the interproximal area where gingivitis often originates. However, when in contact, such small probes may exert a large pressure on the tissue, pushing away the blood, thereby destroying the DRS measurement of blood properties. Therefore, DRS measurements are preferably performed in a non-contact mode, and the required non-contact mode also results in the detection of specularly reflected light in addition to the required diffusely reflected components. Since the diffusely reflected light (i.e., light propagating through the tissue) is highly attenuated, these specularly reflected components can become relatively large.

[0003] In addition, an important property of the probe is source-detection separation because it affects the sampling depth of the probe (i.e., the depth in the tissue from which the measured light originates). However, source-detection separation increases the risk of illuminating and / or detecting light from non-gingival tissue (e.g., teeth and / or dental implants). For example, since the papilla ends in a small pointed shape, the desired papilla signal may be at least partially contaminated by the enamel signal due to the fiber separation. Since teeth and / or dental implants / restorations appear primarily white / yellowish, erroneous tooth reflections will add a direct current (DC)-like offset to the DRS signal that does not contain information about gingivitis detection (i.e., hemoglobin concentration). This erroneous signal occupies a portion of the dynamic range. Typically, such erroneous signals are removed by appropriate signal processing after amplification and / or analog-to-digital conversion that requires a large dynamic range and requires the resolution of the analog-to-digital converter.

[0004] Therefore, there is a need in the art for creative oral healthcare systems and methods that enable accurate detection of tissue inflammation, particularly gingivitis, using a DRS front end that removes large offset portions prior to amplification and / or analog-to-digital (AD) conversion, thereby relaxing the requirements on the electronics. Summary of the invention

[0005] The present disclosure relates to inventive systems and methods for detecting tissue inflammation, particularly gingivitis, using diffuse reflectance spectroscopy (DRS). Various embodiments and implementations herein relate to a gingivitis detection system including a front end that provides a large dynamic range and directly removes (i.e., at the sensor, before the sensor front end electronics) specular reflection components and DC components. The gingivitis detection system includes a light emitter, four or more wavelength sensitive photodetectors, and a specialized configuration of the tissue inflammation detection system.

[0006] In general, in one aspect, a system for detecting tissue inflammation is provided. The system includes: a light emitter configured to emit light at a tissue region within a user's mouth; at least four wavelength-sensitive photodetectors configured to detect an optical signal diffusely reflected by the tissue region, each of the at least four wavelength-sensitive photodetectors including a filter and a photodiode, wherein the photodiodes are stacked on top of each other to generate a current differential signal for an amplifier corresponding to the photodiode, wherein the generation of the current differential signal removes undesirable components from the optical signal before amplification; and an inflammation detection unit configured to receive an output from a corresponding amplifier and detect tissue inflammation at the tissue region. In various embodiments, the tissue inflammation is gingivitis.

[0007] In one embodiment, the light emitter and at least four wavelength-sensitive photodetectors are implemented in a DRS probe having a source-detection distance between 300 μm-2000 μm.

[0008] In one embodiment, the system further comprises a splitter configured to distribute the reflected light onto at least four wavelength-sensitive photodetectors.

[0009] In various embodiments, the splitter is a fused fiber splitter, a dispersion splitter, or a light-guiding manifold.

[0010] In one embodiment, the light emitter is a phosphor converted white LED.

[0011] In one embodiment, the filter for each of the at least four wavelength-sensitive photodetectors is a bandpass filter.

[0012] In one embodiment, the amplitude of the current differential signal for the photodiode is increasing.

[0013] In one embodiment, the current differential signal for the photodiode includes a first current differential signal, a second current differential signal and a third current differential signal for the photodiode, respectively, wherein the second current differential signal is greater than the first current differential signal and the third current differential signal.

[0014] In one embodiment, the stacked photodiodes form a stack with a bottom photodiode, and the bottom photodiode is terminated with a current source controlled in a closed loop.

[0015] In one embodiment, the stacked photodiodes form a stack with a bottom photodiode, and the bottom photodiode generates a photocurrent at a level to minimize a maximum differential signal to be minimized.

[0016] In general, in another aspect, a method for detecting tissue inflammation is provided, including a front end. The method includes: emitting light to a tissue area in a user's mouth via a light emitter; detecting an optical signal diffusely reflected by the tissue area via at least four wavelength-sensitive photodetectors, each of the at least four wavelength-sensitive photodetectors including a filter and a photodiode, wherein the photodiodes are stacked on top of each other to generate a current differential signal for an amplifier corresponding to the photodiode, wherein the generation of the current differential signal removes undesirable components from the optical signal before amplification; inputting the output of the amplifier to an AD converter; and inputting the output of the AD converter to a tissue inflammation detection unit. In various embodiments, the tissue inflammation is gingivitis.

[0017] In one embodiment, the detecting step further comprises: using a splitter to distribute the reflected light onto at least four wavelength-sensitive photodetectors.

[0018] In one embodiment, the splitter is a fused fiber splitter, a dispersion splitter, or a light-guiding manifold.

[0019] As used herein for the purposes of the present disclosure, the term "controller" is generally used to describe various devices related to the operation of an imaging device, system, or method. A controller can be implemented in a variety of ways (e.g., such as using dedicated hardware) to perform the various functions discussed herein. A "processor" is an example of a controller that employs one or more microprocessors that can be programmed using software (e.g., microcode) to perform the various functions discussed herein. A controller can be implemented with or without a processor, and can also be implemented as a combination of dedicated hardware that performs some functions and a processor that performs other functions (e.g., one or more programmed microprocessors and associated circuitry). Examples of controller components that can be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field programmable gate arrays (FPGAs).

[0020] It should be understood that all combinations of the aforementioned concepts and the additional concepts discussed in more detail below (assuming that these concepts are not mutually contradictory) are considered to be part of the inventive subject matter disclosed herein. In particular, all combinations of the claimed subject matter appearing at the end of this disclosure are considered to be part of the inventive subject matter disclosed herein.

[0021] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the drawings, like reference numerals generally refer to like parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

[0023] Figure 1A is a graph of diffuse reflectance spectroscopy spectra measured at different probe-target angles according to one embodiment.

[0024] Figure 1B is a graph of calculated blood oxygenation blood values ​​according to one embodiment.

[0025] Figure 2 is a graph of a simulated change in a diffuse reflectance spectroscopy spectrum resulting from a change in tissue oxygenation from fully oxygenated to fully deoxygenated, according to one embodiment.

[0026] Figure 3 is a schematic representation of a tissue inflammation detection system according to one embodiment.

[0027] Figure 4 A schematic block diagram of a tissue inflammation detection system including four wavelength-sensitive photodetectors according to one embodiment is shown.

[0028] Figure 5 is a flow chart of a method for detecting tissue inflammation according to one embodiment. DETAILED DESCRIPTION

[0029] The present disclosure describes various embodiments of systems and methods for using diffuse reflected light to improve detection of tissue inflammation, particularly gingivitis. More generally, applicants have recognized and appreciated that it would be beneficial to provide a system that removes large offsets as early as possible after obtaining a diffuse reflected spectral signal. Therefore, the systems and methods described or otherwise contemplated herein provide an oral care device configured to obtain measurements of gingival tissue. The oral care device includes a light emitter and four or more wavelength sensitive photodetectors configured to detect the diffuse reflected light so that an associated amplifier receives the lowest possible current difference. By removing the large offset portion prior to amplification and / or analog-to-digital (AD) conversion, the requirements on the electronics are relaxed and more accurate gingivitis detection is enabled.

[0030] The embodiments and implementations disclosed herein or otherwise contemplated may be utilized with any suitable oral care device, such as a toothbrush, a dental floss device, an oral irrigator, a tongue cleaner, or other personal care device. However, the present disclosure is not limited to these oral care devices, and thus the disclosure and embodiments disclosed herein may encompass any oral care device.

[0031] Gingivitis, which is an inflammation of the gums characterized by swelling, puffiness and redness of the gums, is primarily caused by plaque buildup, mostly in the gingival sulci (pockets). This gum disease is often found in hard-to-reach areas, such as in the interproximal areas between teeth and around the back teeth.

[0032] In fact, it is estimated that 50%-70% of the adult population is affected by gingivitis. However, early signs of gingivitis are often undetectable by consumers. Typically, gingivitis progresses to the point where an individual notices that their gums bleed easily when brushing their teeth. Therefore, gingivitis can only be detected when the disease has already progressed and is significantly more difficult to treat. Although gingivitis can be easily reversed with improved oral hygiene, it is important to maintain good oral health and detect gingivitis as soon as possible because gingivitis can spread to irreversible periodontitis.

[0033] Gingivitis can be diagnosed visually by detecting redness and swelling of the gums. (See RR. Lobene et al., "A modified gingival index for use in clinical trials", Clin. Prev. Dent. 8:3-6, (1986), which describes a non-contact gingivitis index based on redness and inflammation of the gums). However, this has limited sensitivity and is highly dependent on the color rendering index of the light source used. Therefore, modern phosphor-converted LEDs may have a low CRI, resulting in poor visual judgment.

[0034] The redness of the gums is an acute inflammatory response to bacterial biofilm toxins from dental plaque in the gingival sulcus or along the gum line area. This inflammatory response causes vasodilation in the short term, where smooth muscle cells in the arterioles relax and widen the blood vessels to increase blood supply to the capillary beds. This results in redness of the gums and can cause a small temperature increase that is difficult to measure. In addition, the capillaries become more permeable, which results in increased fluid loss from the capillaries to the interstitial spaces, resulting in swelling of the gums. If the inflammation is chronic, additional redness occurs through increased vascularization of the tissue, where additional capillaries may form to cope with the additional blood demand of the tissue.

[0035] These factors enable the detection of gingivitis based on diffuse reflectance spectroscopy (DRS). DRS is an optical method that involves, for example, emitting white light toward a target and analyzing the spectral properties of the diffusely reflected (rather than specularly reflected) light. Due to different chromophores in the gingival tissue, the spectral properties of the diffusely reflected light are significantly different from those of the source light. As described in T. Hanioka et al., "Hemoglobin concentration and oxygen saturation of clinically healthy and inflamed gingiva in human subjects", J. Periodontal Res. 25: 93-98 (1990), it is possible to determine the increase in total hemoglobin concentration and the decrease in blood oxygenation associated with the detection of gingivitis. The method uses six fixed wavelengths and calculates deoxygenated, oxygenated, and total hemoglobin concentrations. The latter two are used to calculate oxygen saturation.

[0036] Figure 1A and Figure 1B DRS spectra of measurements using different probe-target angles are shown. Figure 1B In , blood oxygenation values ​​are calculated according to the example method described by Hanioka et al. For angles close to the surface normal, the specular reflection becomes approximately ten times larger than the diffuse reflection component. Therefore, Figure 1B As shown in , the oxygenation values ​​calculated according to this method produce large variations. The detected specular reflected light can lead to large errors.

[0037] refer to Figure 2 , it is apparent that oxygenation-dependent changes in the DRS signal can become very small (even in the absence of errors and / or specular reflections), especially when forced to use near-infrared (NIR) wavelengths due to sampling depth requirements. Figure 2 The simulated change in the DRS spectrum caused by a change in tissue oxygenation from fully oxygenated to fully deoxygenated (100% ==> 0%) is shown. In reality, the change will be much smaller: for gingivitis a reduction in oxygenation of about 10% is expected. There are no specular reflections.

[0038] According to an embodiment using wavelength detection, some systems include a spectrometer to analyze the spectral shape of the received light. Other systems include tunable filters (e.g., MEMS Fabry-Pérot filters) on the received light and / or the emitted light. Although it is desirable to use a spectrometer or tunable filter due to the large number of wavelengths that can be used for processing, currently available systems are too large and / or too expensive for consumer products. Alternatively, the received light can be separated into different paths, and a bandpass filter can be applied to achieve the desired spectral band. The aforementioned Hanioka method uses six wavelengths and can be easily implemented using an embodiment of separated light as long as the large offset is removed before AD conversion. If not removed, a huge dynamic range and analog-to-digital converter resolution are required.

[0039] Since the detection of gingivitis is based on changes in hemoglobin concentration, the signal generated by these changes includes a small modulation of a larger offset portion caused by other tissue scattered signals (gingival and tooth hard tissue) and specular reflections. The offset portion is due to movement rather than DC; for example, a very small angle change can result in a large specular reflection component. Therefore, the offset portion cannot be removed by high-pass frequency filtering. Due to the large offset, most of the dynamic range of the front-end amplifier and the resolution of the analog-to-digital (AD) converter are wasted.

[0040] Based on the above, a specific goal of certain embodiments of the present disclosure is to provide a DRS front end that can remove wasteful large offsets as early as possible in the signal chain.

[0041] refer to Figure 3 and Figure 4 In one embodiment, a system 100 for detecting tissue inflammation is provided. The system 100 is configured to remove large offsets before amplification and / or AD conversion. The system 100 includes a light emitter (e.g., an optical fiber) 102, a light detector (e.g., an optical fiber) 106, and a controller 130. In an example embodiment, the light emitter includes a light source 103, for example, a broadband light source 103, such as a phosphor-converted white light LED. The light source is coupled into a source optical fiber to deliver the emitted light to the gingival tissue 104. The light detector (e.g., an optical fiber) 106 is configured to pick up diffusely reflected light from the tissue 104 and deliver the light.

[0042] In one embodiment, the light emitter 102 and the light detector 106 are implemented with a diffuse reflectance spectroscopy (DRS) probe having a source-detector distance between 300 μm and 2000 μm. Conventional configurations include: a source fiber followed by a detection fiber, a central source fiber surrounded by multiple detection fibers, or a single fiber used as both source and detector. An important property of the probe is the source-detection separation because it affects the sampling depth of the probe (i.e., the depth in the tissue from which the measured light originates). For the detection of gingivitis, an average diffuse reflectance spectroscopy sampling depth of greater than 250 μm is required. To achieve this average, a minimum source-detector distance of approximately 300 μm is required, depending on the wavelength.

[0043] Since the DRS signal from the detector 106 is generally not a differential signal, an additional component is included. According to one embodiment, the detector 106 of the system 100 is configured to deliver the reflected light to a spectral analysis unit or splitter 108. The splitter 108 is configured to distribute the reflected light over four or more wavelength sensitive photodetectors 110, 112, 114, and 116, each with a different wavelength sensitivity. The splitter 108 can be a fused fiber splitter, a dispersion splitter (e.g., a prism or grating), a light guide manifold, or any suitable alternative.

[0044] Each wavelength sensitive detector 110, 112, 114 and 116 includes a band pass filter (BPF) in front of a photodiode. Figure 4 As shown in , detector 110 includes a bandpass filter BPF1 in front of photodiode D1. Similarly, detector 112 includes a bandpass filter BPF2 in front of photodiode D2, detector 114 includes a bandpass filter BPF3 in front of photodiode D3, and detector 116 includes a bandpass filter BPF4 in front of photodiode D4. Photodiodes are advantageous because they have an extended linear range and can therefore process signals that include large offsets without introducing errors. Although Figure 4 The embodiment includes four wavelength sensitive detectors, but other embodiments may include five wavelength sensitive detectors or more than five wavelength sensitive detectors.

[0045] The photodiodes D1, D2, D3 and D4 are stacked so that the associated amplifiers receive current differentially, ie they receive a much smaller current. This enables greater amplification which results in a higher and improved signal-to-noise ratio (SNR) for the detection of gingivitis.

[0046] According to one embodiment, the current I1 ... I n Arranged in increasing amplitude. Alternatively, the current I1 ... I nAccording to another embodiment, the current is arranged as follows I1 <i2> I3 <i4>I5, etc. (or in other ways). However, the currents are never arranged so that the maximum and minimum expected currents are stacked on top of each other. According to one embodiment, the bottom of the stack is terminated by a current source, which is optionally controlled in a closed loop via the controller 130. Alternatively, in the middle of the photodiodes, the bottom diode produces the lowest expected photocurrent. According to another embodiment, the bottom diode generates a photocurrent at a level that is selected to minimize the maximum difference among the differences to be minimized, for example, at a wavelength that is expected to give an output close to the average / median level.

[0047] refer to Figure 4 According to one embodiment, the current difference present at the current-to-voltage amplifier is nominally minimal and / or balanced around zero. According to another embodiment, in the case of a single-supply electronics device, the current differential is a predetermined offset. As shown, the output of each wavelength-sensitive photodetector is input to a corresponding amplifier. According to one embodiment, the output of the amplifier is fed to an AD converter (not shown), and because those signals also do not carry a large offset, the useful resolution is much higher. Alternatively, the AD converter may have a lower resolution, which is advantageously less expensive.

[0048] The output of the AD converter is input to a controller or analyzer having an appropriate gingivitis detection algorithm. According to one embodiment, the algorithm includes a gingivitis detection method based on a wavelength derivative (slope) signal. According to another embodiment, the algorithm includes a differential method for calculating tissue oxygenation, such as described in DE Myers et al., "Noninvasive method for measuring local hemoglobin oxygen saturation in tissue using widegap second derivative near-infrared spectroscopy", J. Biomed. Opt., Vol. 10 (3), (2005). In Myers, a simple continuous wave near infrared algorithm is described using a single deep attenuation measurement at 680nm, 720nm, 760nm and 800nm. However, the differential current configuration of the spectrum detector as described above does not necessarily deliver the same differential as required by the derivative method. For example, if these methods require attenuation measurements at 680nm, 720nm, 760nm and 800nm, the corresponding detectors do not necessarily have to be stacked on top of each other. Since the bottom current is known, all currents can be calculated internally and hence the new differential. This means that the stacking order can be chosen so that the current flowing into the amplifier is as low as possible. This enables a higher dynamic range.

[0049] refer to Figure 5 , in one embodiment, Figure 5 200 is a flow chart of a method 200 for detecting tissue inflammation, the method including a front end for directly removing specular reflection components and DC components. In other words, specular reflection and DC components are removed at the sensor and before the sensor front end electronics. In step S210, a system for detecting tissue inflammation, particularly gingivitis, is provided. The system can be any device or system described herein or otherwise contemplated. For example, the system can be system 100, among many other devices or systems. Typically, the system includes a light emitter 102, four or more wavelength sensitive photodetectors 106, and a controller 130, which is configured to implement the functionality described herein. Many other components and configurations are also possible.

[0050] At step S220 of the method, at least one light emitter 102 emits light, the beam of which strikes the tissue. The light emitted by the light emitter may include two or more wavelengths. Thus, the light emitter may include one or more light sources 103. The light emitter may emit light periodically or continuously, or may emit light only in response to a trigger. For example, the system detects gingival tissue and activates the light emitter 102 to emit light.

[0051] At step S230 of the method, the reflected light is distributed among four or more wavelength-sensitive photodetectors 106, each of which has a different wavelength sensitivity. According to one embodiment, the system 100 includes a splitter 108 configured to distribute the reflected light. The splitter 108 can be a fused fiber splitter, a light guide manifold, or any suitable alternative. The output of each wavelength-sensitive photodetector is input to a corresponding amplifier.

[0052] At step S240 of the method, the output of the amplifier is fed into an AD converter. As described above, since those signals also do not carry large offsets, the useful resolution is much higher.

[0053] At step S250 of the method, the output of the AD converter is input to the controller 130 or processor, which is configured to analyze the signal. According to one embodiment, the controller 130 receives the signal, wherein the signal is analyzed by the processor 132 and / or the gingivitis detection unit 136 and / or stored in the memory 134 for future analysis.

[0054] Advantageously, the inventive systems and methods described herein remove large offsets as early as possible after acquiring the diffuse reflectance spectroscopy signal so that the associated amplifier receives the lowest possible current differential. By removing large offset components prior to amplification and / or analog-to-digital (AD) conversion, the requirements on the electronics are relaxed and more accurate gingivitis detection is enabled.

[0055] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0056] As used herein in the specification and claims, the indefinite articles "a" and "an" should be understood to mean "at least one" unless clearly indicated to the contrary.

[0057] As used herein in the specification and claims, the phrase "and / or" should be understood to mean "either or both" of the elements so combined, i.e., elements that are present in combination in some cases and separately in other cases. Multiple elements listed with "and / or" should be interpreted in the same manner, i.e., "one or more" of the elements so combined. Other elements may optionally be present in addition to the elements specifically identified with the "and / or" clause, whether related or unrelated to those elements specifically identified.

[0058] "Or" as used herein in the specification and claims should be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" should be interpreted as inclusive, that is, including at least one of a number of elements or lists of elements, but also including more than one, and optionally, including additional unlisted items. Only terms that clearly indicate the contrary, such as "only one" or "only one" or when used in the claims, "consisting of..." will refer to the inclusion of only one element of a plurality of elements or lists of elements. In general, when preceded by an exclusive term (such as, "either", "one", "only one" or "only one"), the term "or" as used herein should only be interpreted as indicating a unique alternative (i.e., "one or the other but not both").

[0059] As used herein in the specification and claims, the phrase "at least one" referring to a list of one or more elements should be interpreted as meaning at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This limitation also allows that elements other than the elements specifically identified in the list of elements to which the phrase "at least one" refers may optionally be present, whether related or unrelated to those specifically identified elements.

[0060] It should also be understood that in any method claimed herein that includes more than one step or action, the order of the method steps or actions is not necessarily limited to the order in which the method steps or actions are described unless explicitly indicated to the contrary.

[0061] In the claims as well as in the above description, all transitional phrases, such as "comprising," "including," "carrying," "having," "containing," "involving," "maintaining," "consisting of," etc., shall be understood as open, i.e., meaning including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively.

[0062] Although several creative embodiments have been described and illustrated herein, it will be readily contemplated by those skilled in the art that various other methods and / or structures are used to perform functions and / or obtain results and / or one or more of the advantages described herein, and each of such variations and / or modifications is considered to be within the scope of the creative embodiments described herein. More generally, it will be readily appreciated by those skilled in the art that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and that actual parameters, dimensions, materials, and / or configurations will depend on one or more specific applications in which the creative teachings are used. In the case of using only routine experiments, those skilled in the art will be aware of or be able to find many equivalents of the specific creative embodiments described herein. Therefore, it should be understood that the aforementioned embodiments are presented only by way of example, and within the scope of the appended claims and their equivalents, the creative embodiments may be practiced differently from the specific description and claims. The creative embodiments of the present disclosure are directed to each independent feature, system, article, material, toolbox, and / or method described herein. In addition, if such features, systems, articles, materials, kits and / or methods are not mutually inconsistent, then any combination of two or more such features, systems, articles, materials, kits and / or methods is included within the inventive scope of the present disclosure. < / i2>

Claims

1. A system (100) for detecting tissue inflammation, comprising: a light emitter (102) configured to emit light at a region of tissue (104) within a user's mouth; at least four wavelength-sensitive photodetectors (110, 112, 114, and 116) configured to detect an optical signal diffusely reflected by the tissue region, each of the at least four wavelength-sensitive photodetectors comprising a filter (BPF1, BPF2, BPF3, and BPF4) and a photodiode (D1, D2, D3, and D4), wherein the photodiodes are stacked on top of each other to generate a current differential signal for an amplifier corresponding to the photodiode, wherein the generation of the current differential signal removes undesirable components from the optical signal prior to amplification; as well as An inflammation detection unit (136) is configured to receive the output from the corresponding amplifier and detect tissue inflammation at the tissue region.

2. The system of claim 1, wherein the tissue inflammation detected is gingivitis.

3. The system of claim 1, wherein the light emitter and the at least four wavelength-sensitive photodetectors are implemented in a diffuse reflectance spectroscopy (DRS) probe having a source-detection distance between 300 μm-2000 μm.

4. The system of claim 1, further comprising a splitter (108) configured to distribute the reflected light over the at least four wavelength-sensitive photodetectors.

5. The system of claim 4, wherein the splitter is a fused fiber splitter, a dispersion splitter, or a light guide manifold.

6. The system of claim 1, wherein the light emitter is a phosphor-converted white LED.

7. The system of claim 1, wherein the filter for each of the at least four wavelength-sensitive photodetectors is a bandpass filter.

8. The system of claim 1, wherein the current differential signals for the photodiodes (D1, D2, D3, and D4) are increasing in amplitude.

9. The system according to claim 1, wherein the current differential signal for the photodiodes (D1, D2, D3 and D4) respectively includes a first current differential signal, a second current differential signal and a third current differential signal for the photodiodes (D1, D2 and D3), wherein the second current differential signal is greater than the first current differential signal and the third current differential signal.

10. The system of claim 1, wherein the stacked photodiodes form a stack with a bottom photodiode, and the bottom photodiode is terminated with a current source controlled in a closed loop.

11. The system of claim 1, wherein the stacked photodiodes form a stack with a bottom photodiode, and the bottom photodiode generates a photocurrent at a level to minimize a maximum differential signal to be minimized.

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