Systems and methods for optode imaging

Methods and systems disclosed herein may be operable to detect a presence or absence of an analyte in human tissue. An example method includes operating one or more light sources to illuminate a plurality of optodes with excitation light. Each optode is embedded in tissue at a respective location. The excitation light causes the optodes to emit emission light and the optodes are sensitive to at least one analyte such that the emission light emitted by the optodes is indicative of a presence or absence of at least one analyte in the tissue. An optical filter arrangement includes for each optode in the plurality of optodes a corresponding set of one or more optical filters. The method includes obtaining detector information from a detector arrangement optically coupled to the optical filter arrangement, and detecting the at least one analyte based on the detector information.

BACKGROUND

Medical diagnostic information about living tissue may be obtained by a variety of optical means. For example, an optical sensor, e.g. an optode, may be configured to provide a characteristic optical response when in proximity to an analyte in the tissue. The optical response may be read out by a detector.

SUMMARY

In an aspect, a system is provided. The system includes one or more light sources. The one or more light sources are operable to illuminate a plurality of optodes with excitation light. Each optode is embedded in tissue at a respective location. The excitation light causes the optodes to emit emission light. The optodes are sensitive to at least one analyte such that the emission light emitted by the optodes is indicative of a presence or absence of at least one analyte in the tissue. The system also includes an optical filter arrangement. The optical filter arrangement includes for each optode in the plurality of optodes a corresponding set of one or more optical filters. The system further includes a detector arrangement optically coupled to the optical filter arrangement. The detector arrangement includes for each optode in the plurality of optodes a corresponding set of one or more detectors operable to detect light received from the optode's respective location via the optode's corresponding set of one or more optical filters. The system yet further includes a controller having at least one processor. The controller is programmed to carry out operations. The operations include operating the one or more light sources to illuminate the plurality of optodes with excitation light. The system also includes operating the detector arrangement to obtain detector information. The detector information includes for each optode a respective optode signal indicative of light that has been emitted from the optode's respective location in response to the illumination from the one or more light sources, filtered through the optode's corresponding set of one or more optical filters, and detected by the optode's corresponding set of one or more detectors. The system yet further includes detecting the at least one analyte based on the detector information.

In an aspect, a method is provided. The method includes operating one or more light sources to illuminate a plurality of optodes with excitation light. Each optode is embedded in tissue at a respective location. The excitation light causes the optodes to emit emission light, and the optodes are sensitive to at least one analyte such that the emission light emitted by the optodes is indicative of a presence or absence of at least one analyte in the tissue. An optical filter arrangement includes for each optode in the plurality of optodes a corresponding set of one or more optical filters. The method also includes operating a detector arrangement to obtain detector information. The detector arrangement is optically coupled to the optical filter arrangement and the detector arrangement includes for each optode in the plurality of optodes a corresponding set of one or more detectors operable to detect light received from the optode's respective location via the optode's corresponding set of one or more optical filters. The detector information includes for each optode a respective optode signal indicative of light that has been emitted from the optode's respective location in response to the illumination from the one or more light sources, filtered through the optode's corresponding set of one or more optical filters, and detected by the optode's corresponding set of one or more detectors. The method yet further includes detecting the at least one analyte based on the detector information.

DETAILED DESCRIPTION

The systems and methods described herein may provide diagnostic information about tissue via optical means. For example, the systems may include an optode or another type of chemical sensor configured to change its optical properties while in proximity to a particular analyte.

Optodes may provide a characteristic optical response while in proximity to an analyte. In general, each optode may include a chemical configured to provide an optical response when in proximity to the analyte. For example, the chemical may have a given fluorescence spectrum that is at least partially quenched or attenuated when the analyte is nearby. Furthermore, the optodes may be incorporated into various physical structures, such as nanoparticles and/or polymer matrices. As such, the optodes may be interrogated as optical sensor devices that may measure a presence, concentration, and/or location of the analyte.

In such an example, the optode may be illuminated by an excitation light source. In response to receiving light at the excitation wavelength, certain chemicals such as fluorophores in the optode may emit emission light. When in proximity of the specific analyte, the emission behavior may be increased, decreased, or otherwise affected.

Optical filters may exhibit selective transmission of light based on polarization and/or wavelength. That is, optical filters may transmit light at some polarizations and/or wavelengths, but not at others. Additionally or alternatively, optical filters may provide varying degrees of attenuation based on the polarization and/or wavelength of incoming light. Furthermore, such optical filters may be placed in an optical path between a light source and detector so as to attenuate, modify, or otherwise filter light incident on the detector.

In an example embodiment, an optical filter plate may include a plurality of optical filters arranged to correspond spatially with the optode arrangement. The optical filter plate may be optically coupled to a detector array, such as an array of charge-coupled devices (CCD) and/or a focal plane array (FPA). In such a scenario, the optical filter plate may filter the light emitted from the optodes so as to provide a recognizable optical pattern to the detector array. Accordingly, the systems described herein may be used to detect a concentration, presence, or lack thereof of the specific analyte.

The systems and methods described herein may enable a variety of applications. In some example embodiments, the systems and methods herein may be used for intra-operative tumor imaging. For instance, an arrangement of optodes may be injected or otherwise applied to the skin tissue near a known cancer tumor site. The optodes may be configured to provide a characteristic optical response when in proximity to cancer cells or a specific marker that may bind to such cells. As such, the imaging of such optodes via the optical filter arrangement may provide information indicative of the surgical margins of the cancer tumor. Furthermore, such imaging may proceed during and after surgery to confirm complete resection of the tumor.

In an example embodiment, the systems described herein may be incorporated into a surgical robot. For example, the surgical robot may obtain information about tissue to be removed and tissue to be preserved via the present system. In the scenario above involving a cancer tumor, the surgical robot may periodically or continuously image the surgical site during surgery to identify cancerous tissue for removal (e.g. via laser cutting) and/or identify non-cancerous tissue for preservation.

The systems and methods described herein may be incorporated into a wearable device. For example, a wrist-mountable device may incorporate the light source, optical filter arrangement, and detector array as described herein. Additionally or alternatively, the wearable device may be worn elsewhere on the body. For example, the wearable device may be mountable or positionable on a back, a chest, an arm, a hand, a finger, a head, or other parts of the body.

In some embodiments, the present application may enable an optical biopsy. That is, by applying an array of optodes near or in a suspect skin growth or skin spot, information about the skin growth or spot may be obtained. As an example, the optodes may be configured to provide information about the presence of malignant melanoma cells. As such, the skin growth or spot may be interrogated without physical removal of tissue. It is understood that similar biopsy or medical diagnoses are possible via optical means with the present systems and methods.

Point of care applications are also possible. For example, an array of optodes may be applied to infected skin tissue, e.g. cellulitis. The optodes in such a scenario may be configured to provide a characteristic optical response when in proximity to a bacteria or a biomarker bound to such bacteria. Imaging the optodes via the optical filter arrangement may help visualize the progression of the infection and identify locations where medication (e.g. topical ointment, injection) may be delivered.

II. Example Systems

FIG. 1illustrates a system100, according to an example embodiment. System100includes at least one light source102, an optical filter arrangement106, a detector arrangement110, and a controller112. At least some of the elements of system100may be arranged in a wearable device. For example, system100may take the form of a smartwatch, necklace, armband, headband, chest strap, or another type of wearable device. In some embodiments, system100may be incorporated into clothing.

At least some of the elements of system100are configured to interact with and/or interrogate an optode array122embedded in tissue120, as described herein.

The at least one light source102may include a laser, such as a single-mode laser configured to provide excitation light104in the visible or near-infrared wavelengths. However, multi-mode lasers, wavelength-adjustable lasers, diode lasers, gas lasers, and broadband light sources such as light-emitting diodes (LEDs) are also contemplated. Furthermore, other wavelengths and wavelength ranges are considered herein. Specifically, the at least one light source102may be configured to provide excitation light104at one or more excitation wavelengths of at least one optode in the optode array122.

The at least one light source102may be configured or arranged in various positions so as to provide excitation light104to the optode array122. In an example embodiment, the at least one light source102may include a plurality of micro-LED arranged around the optical filter arrangement106. Other configurations are possible. For example, a plurality of micro-LEDs and/or lasers may be interspersed or interleaved around the filters of the optical filter arrangement106. For example, filters and light sources may be arranged in a checkerboard pattern. In another example embodiment, the light sources102may be disposed in an interleaved arrangement with respect to the detectors in the detector arrangement110. In a further embodiment, the light source102may include a scanning light source, such as a scanning laser. In such a scenario, light from the scanning laser may be directed toward a scanning galvanometer and towards a portion of the skin tissue120.

Additionally or alternatively, the system100may include a spatial light modulator. In such a scenario, the operations may include selecting a target optode from the plurality of optodes. The operations may further include controlling the spatial light modulator to direct the excitation light toward at the target optode in the plurality of optodes from the one or more light sources102.

WhileFIG. 1illustrates the at least one light source102as illuminating the optode array122from a location proximate to the optical filter arrangement106, other arrangements are possible. For example, the light source102may illuminate the optode array122from another location. In an example embodiment, the light source102may illuminate the optode array122from an opposite side of the tissue120. That is, the system100may allow transillumination of the excitation light through an earlobe, a nostril, or another soft tissue region of the body. Other arrangements of the light source(s)102, the optode array122and the optical filter arrangement106are contemplated herein.

In some embodiments, the system100may include a diffuser that may be configured to diffuse the light of the at least one light source102. For example, the one or more light sources102may be optically-coupled to the diffuser, which may be disposed around the detector arrangement110. That is, the diffuser may be disposed around an outer periphery of an optical path between the detector arrangement110and the optode filter arrangement106. Additionally or alternatively, the diffuser may be located elsewhere.

In an example embodiment, the optode array122may include one or more optodes. In turn, each optode may include a fluorophore or a dye configured to change its optical properties when near an analyte130. For example, each optode of the optode array122may be configured to change its respective optical properties in the presence of a different respective analyte. As such, each optode of the optode array122may be configured to sense a different analyte. Furthermore, various combinations of optodes may be combined, arranged, or ordered in the optode array122so as to improve the accuracy and/or repeatability of analyte detection.

The words “near”, “proximate”, or “nearby” as used herein with respect to an analyte may indicate a distance between the analyte and a given optode of the optode array122. In some embodiments, “near”, “proximate”, or “nearby” may relate to a distance of less than 50 microns. However, other distances are possible. For example, optodes may be sensitive to analytes present within distances up to 1 millimeter.

Furthermore, the optical response of a respective optode may be based on the concentration of the analyte. Namely, the optical response (e.g. fluorophore quenching) may scale with analyte concentration. The systems and methods described herein may be operable to detect very low analyte concentration levels. For example, such systems may be operable to detect 10 ng/mL or less of analyte in solution (e.g. blood and/or interstitial fluid).

The analyte130may represent one or more target analytes of interest that may be detected and measured in the human body. For example, the analyte130may include glucose, a biomarker, a particular cell type (e.g., a cancer cell), or another type of target analyte. As described above, the systems and methods described herein may be operable to detect several analytes in a single detection cycle. The analyte130could be present in interstitial fluid or other bodily fluid.

The optical filter arrangement106may include one or more optical elements. The one or more optical elements may include a bandpass filter, a longpass filter, a shortpass filter, a dichroic filter, a polarization filter, an interference filter, an absorptive filter, a dielectric stack, a bandstop filter, a lens, a diffuser, or another type of optical element. The optical filter arrangement106may be arranged substantially along a plane so that different spatial regions along the plane may have different light transmission characteristics depending upon where light impinges along the optical filter arrangement106.

The detector arrangement110may be optically coupled to the optical filter arrangement106. In an example embodiment, the detector arrangement110may include a focal plane array or an image sensor configured to sense light transmitted through the optical filter arrangement106. In other words, the detectors in detector arrangement110may be operable to detect light transmitted through the optical filter arrangement106from the optodes of optode array122.

The detector arrangement110may include one or more charge coupled devices (CCDs) or complementary metal oxide semiconductor (CMOS) detectors.

Controller112may be coupled to light source102and detector110. The controller112may include a memory in which to store instructions. The controller112may also include a processor configured to carry out various operations based on the instructions. Namely, the operations may include the controller112operating the one or more light sources102to illuminate the optode array122with excitation light.

The operations may also include operating the detector arrangement110to obtain detector information. Namely, the detector information may include for each optode a respective optode signal indicative of light that has been emitted from the optode's respective location in response to the illumination from the one or more light sources102, filtered through the optode's corresponding set of one or more optical filters in the optical filter arrangement106, and detected by the optode's corresponding set of one or more detectors.

Furthermore, the operations include detecting the at least one analyte based on the detector information. For example, detecting the at least one analyte may be based on a characteristic optical signal being received by one or more detectors of the detector arrangement110. The characteristic optical signal may include signals from a particular combination of optodes, an optical signal indicative of quenching, enhancement, or another modification of a given waveband or wavelength of an optode optical response. Other characteristic optical signals are possible.

System100may be configured to carry out operations related to filtering at least a portion of a background signal based on information provided from the detector information. In an example embodiment, the background signal may include a tissue autofluorescence signal. That is, tissues naturally emit light when illuminated by certain wavelengths of light. In such an embodiment, the controller112may be configured to adjust the detector information based on the background signal. Additionally or alternatively, the controller112may adjust one or more of the optode signals based on a corresponding portion of the background signal.

In yet another embodiment, the plurality of optode signals may each include an autofluorescence portion associated with tissue autofluorescence and an emission portion associated with emission light from the respective optodes. As such, the controller may be configured to adjust the emission light with respect to the corresponding autofluorescence portions.

Other ways of reducing the effect of tissue autofluorescence are contemplated herein.

FIGS. 2A-2Dillustrate a scenario200, according to an example embodiment. The elements of scenario200may be similar or identical to corresponding elements illustrated and described in reference toFIG. 1.

FIG. 2Aillustrates embedding a plurality of optodes211-215into tissue210via a skin surface216. That is, the plurality of optodes211-215may be injected or otherwise inserted into the tissue210. The plurality of optodes211-215may be arranged in a particular two-dimensional or three-dimensional arrangement or pattern. Specifically, the arrangement of optodes may be asymmetric so as to avoid alignment ambiguity. As illustrated,FIG. 2Ashows optodes211-215as disposed in two rows, with three and two columns in the respective rows. In such a configuration, the arrangement of optodes is less likely to be misread based on lateral or rotational misalignment between the optodes211-215and the readout device. The optodes211-215may be delivered to a depth of approximately 1 millimeter below the skin surface216(e.g., implanted in the dermis), however delivery to other skin depths is contemplated.

In an example embodiment, the plurality of optodes211-215may be configured to provide a change in an optical response based on a proximity to different analytes A through E. For example, optode211may be sensitive to analyte A, optode212may be sensitive to analyte B, and so on. In other embodiments, each optode may be sensitive to multiple analytes, or each of the optodes may be sensitive to the same analyte (e.g., analyte A).

In some example embodiments, a registration fiducial may be applied to the skin surface216or implanted into the skin. The registration fiducial may include a visible structure or mark, in the shape of a cross, a box, or another recognizable symbol. In such a scenario, the registration fiducial may be used by a robot or user to properly align the filter plate and detector array, as described below. In other embodiments, the registration fiducial may be invisible to the unaided eye. For example, the registration fiducial may include a characteristic arrangement of optodes configured to emit light at a characteristic wavelength or within a characteristic waveband.

FIG. 2Billustrates a filter plate220that may include a plurality of optical filters221-225. The plurality of optical filters221-225may be arranged along a surface of the filter plate220so as to spatially correspond to the plurality of optodes211-215. For example, optical filter221may arranged so as to correspond with optode211, optical filter222may be arranged so as to correspond with optode212, and so on.

In an example embodiment, each optical filter may have a different optical transfer function (OTF). That is, as a function of the wavelength of light, optical filter221may transmit light differently than optical filter222. For example, optical filter221may have an OTF configured to efficiently transmit a characteristic optical signal from optode211indicating a presence of analyte A. As a non-limiting example, optical filter221may include a bandpass filter. Specifically, the bandpass filter (A′) may be configured to transmit at least a characteristic portion of light emitted from optode211in the presence of analyte A. Optical filter222may include a bandpass filter (B′) that may be configured to transmit at least a characteristic portion of light emitted from optode212in the presence of analyte B. Furthermore, optical filter223may include a bandpass filter (C′) that may be configured to transmit at least a characteristic portion of light emitted from optode213in the presence of analyte C. Also, optical filter224may include a bandpass filter (D′) that may be configured to transmit at least a characteristic portion of light emitted from optode214in the presence of analyte D. Similarly, optical filter225may include a bandpass filter (E′) that may be configured to transmit at least a characteristic portion of light emitted from optode215in the presence of analyte E. In an example embodiment, the characteristic portion of light may correspond with a characteristic waveband or plurality of wavebands.

In an example embodiment, the characteristic waveband may include a characteristic long wavelength cutoff and a characteristic short wavelength cutoff. In such a scenario, the one or more optical filters may include a shortpass filter having a cutoff wavelength less than the characteristic short wavelength cutoff. Furthermore, the one or more optical filters may include a longpass filter with a cutoff wavelength greater than the characteristic long wavelength cutoff.

Additionally or alternatively, optical filter221may include a bandstop filter and/or a notch filter. In another embodiment, the optical filters may include a prism, a polarization filter, or another type of optical element configured to modify one or more properties of light. It is understood that other optical filters and optical elements or combinations of such elements are possible so as to minimize the optical transmission of background signals (e.g. tissue autofluorescence) and maximize optical transmission of characteristic emission light from the optodes.

AlthoughFIG. 2Billustrates a “one-to-one” relationship between the plurality of optodes211-215and the optical filters221-225, other relationships are possible. For example, more than one optical filter may correspond spatially to each optode. Additionally or alternatively, more than one optode may correspond to each optical filter. Furthermore, while optical filters221-225are illustrated as discrete filter elements, it is understood that one or more slowly varying optical filter elements may make up the optical filter. That is, the filter plate220may include one slowly varying optical filter (e.g. a gradient filter).

In addition to the elements described above,FIG. 2Cillustrates a detector array230. The detector array230includes detector elements231-235. The detector elements231-235may include detector pixels. In an example embodiment, the detector elements231-235include CCD or CMOS image sensor pixels. Detector elements231-235may include other types of devices configured to sense light, such as avalanche photodiodes, photoconductor, and other photo-sensitive devices.

As illustrated inFIG. 2C, the detector array230and the detector elements231-235may correspond spatially to the optical filters221-225and/or the optodes211-215. That is, the filter plate220may be fixed with respect to the detector array230such that the optical filters221-225provide transmitted light to one or more detector elements231-235. Furthermore, the filter plate220and detector array230may be aligned or registered to the optode array in tissue210. As described above, the registration may be performed via the registration fiducial.

In an example embodiment, emission light from the optode211may be filtered by optical filter221and sensed by detector element231. Likewise, emission light from optode212may be filtered by optical filter222and sensed by detector element232, and so on.

WhileFIG. 2Cillustrates a “one-to-one” correspondence between the detector elements231-235and the optical filters221-225, other relationships are possible. For example, a plurality of detector elements may correspond to a particular optical filter.

FIG. 2Dillustrates a light source240. As described herein, the light source240may include one or more lasers, LEDs, or other light-emitting devices. In an example embodiment, the light source240is configured to provide excitation light so as to cause light to be emitted by the optodes211-215. As illustrated, light source240may direct excitation light towards the optode213. In this example scenario, analyte C (246) is present within a detectable concentration level and/or a detectable distance from the optode213.

In response to receiving the excitation light from the light source240, optode213may emit emission light244. Furthermore, in response to analyte C (246) being nearby with a sufficient concentration, at least a portion of the emission light244may be quenched, enhanced, or otherwise modified. The emission light244may be filtered by optical filter223as filtered light248. Among other properties, filtered light248may include a relatively small portion of light at the excitation wavelength(s). In other words, the optical filter223may be selected and/or configured to filter at least a substantial portion of the excitation wavelengths from the emission light244.

The filtered light248may be sensed by detector element233. The detector element233may provide information indicative of sensing analyte C (246) to a controller, such as controller112as described in reference toFIG. 1.

FIG. 3illustrates a system300, according to an example embodiment. The elements of system300may be similar or identical to corresponding elements from scenario200and system100as illustrated and described in reference toFIGS. 1 and 2A-2D. In an example embodiment, system300may represent a portion of a wearable device having a lensed optical design.

An optode302may be injected or otherwise delivered to a location under a skin surface304. The optode302may be configured to emit emission light in response to excitation light having an excitation wavelength. System300may be aligned, registered, positioned, or otherwise disposed proximate to a skin surface304and the optode302.

System300may include at least one light source306. The at least one light source306may be configured to provide excitation light in an illumination beam308. The at least one light source306may include a laser diode configured to emit light with wavelengths between 630-640 nm at around 140 mW power. In some embodiments, one or more collimation lenses may be disposed proximate to the laser diode(s) so as to collimate the excitation light. For example, the collimation lenses may include a molded acrylic lens.

The system300may further include lenses310and314. In an example embodiment, lenses310and314may be configured to form an achromatic doublet lens set. For example, the achromatic doublet lenses may include a numerical aperture of 0.5 with f1.0 optics. The system300may also include an optical filter312. The optical filter312may be a bandpass filter configured to transmit light with wavelengths between 660-700 nm. Accordingly, the optical filter312may filter out the excitation light from the laser diode light source(s)306.

The doublet lenses310and314may collect light from near the skin surface304and focus it onto a detector array316. In an example embodiment, the detector array316may include a CMOS sensor with over 4 million pixels. The detector array316may be sensitive to light transmitted through the doublet lenses and the bandpass filter.

The excitation light in the illumination beam308may be transmitted, at least in part, to the optode302. The optode302may emit emission light, which may be collected via lens310. The emission light may be filtered by optical filter312. Specifically, light with wavelengths outside the optical filter pass band (e.g. excitation light) will be substantially rejected/filtered. The lens314may focus the emission light onto the detector array316.

FIG. 4illustrates a cross-sectional view of a system400, according to an example embodiment. The elements of system400may be similar or identical to corresponding elements illustrated and described in reference toFIGS. 1, 2A-2D, and 3. In an example embodiment, system400may represent a portion of a wearable device having a “lensless” optical design. As described herein, lensless optical designs may not include an imaging objective lens. Alternatively or additionally, lensless optical designs may include a lenslet array. The lenslet array may include a plurality of lenslet elements that correspond with, and are aligned to, a plurality of detector elements and/or pixels of an image sensor. In some embodiments, the lenslet array may improve light collection efficiency. It is understood that a variety of other types of lensless optical designs are possible, all of which are contemplated herein.

System400may be operable to detect emission light emitted from an optode402, which may be embedded beneath a skin surface404. The optode402may be configured to emit emission light in response to receiving excitation light.

System400includes a light source406. Light source406may include one or more laser diodes. The light source406may be optically coupled to a diffuser408. The diffuser may include a polymeric material, such as acrylic (polymethylmethacrylate). However, other materials configured to diffuse light are contemplated herein.

The system400may also include one or more of: a polarization filter412, an interference filter414, and an absorptive filter416. The combination of the polarization filter412, interference filter414, and the absorptive filter416may be termed the optical filter stack. Alternatively, any subset of the filters may make up the optical filter stack, e.g. a single absorptive filter416or a combination of an absorptive filter and an interference filter, etc. The physical order of the respective filters in the optical filter stack is interchangeable. That is, the polarization filter412, interference filter414, and the absorptive filter416may be arranged in different order within the optical filter stack. The optical filter stack may be configured to transmit at least a portion of the emission light from optode402while rejecting substantially all of the excitation light from light source406. The system400may also include an image sensor418. As described elsewhere herein, the image sensor418may include a CMOS or CCD image sensor.

In an example embodiment, one or more of the filters in the optical filter stack may be configured to have different optical transfer functions along a lateral dimension of the one or more filters. For example, the one or more filters of the optical filter stack may be patterned (e.g. via lithographic techniques) so as to have different optical transfer functions based on a location along a lateral dimension of the filter. The different optical transfer functions may include one or more of: a different wavelength/waveband, a different polarization, a different relative optical density, etc. Accordingly, different pixels of the image sensor418may receive light having been filtered according to the different optical transfer functions of the optical filter stack based on the respective location of the pixels along the lateral dimension of the image sensor418.

The system400includes a baffle420, which may be configured to block light from the light source406and diffuser408from directly entering the optical filter stack.

In an example embodiment, excitation light emitted by the light source406may be optically coupled to the diffuser408, which may diffuse the excitation light so as to spread it across the skin surface404. Furthermore, the excitation light may impinge on optode402. In response, the optode402may emit emission light. At least a portion of the emission light may be incident on the optical filter stack. Furthermore, at least some of the emission light may be transmitted through the polarization filter412, the interference filter414, and the absorptive filter416so as to be sensed by the image sensor418.

It is understood that a variety of other optical configurations are possible to provide excitation light to optodes embedded in tissue and detection of the emission light from the optodes. For example, an edge-emitting laser diode may be coupled into a light guide film. The light guide film may be configured to guide excitation light from the edge-emitting laser diode along a plane parallel to the image sensor. At least a portion of the excitation light may be reflected and/or refracted out of the plane and toward the skin surface (and the embedded optode(s)).

In another embodiment, a light source may transilluminate optodes from an “opposite side” of the skin surface. That is, the light source may be located on an opposing skin surface from the image sensor and optical filter(s). For example, the light source may transilluminate an optode embedded in an earlobe through a backside of the earlobe.

In yet another embodiment, the light source may be coupled to a dichroic prism. In such a scenario, the light source may emit excitation light that may be refracted towards the skin surface via a dichroic beam splitter or prism. That is, at least based on the wavelength of the excitation light, the excitation light may be diverted out of plane towards the skin surface and the embedded optode(s). The dichroic beam splitter/prism may be configured to transmit emission light from the optodes substantially through the beam splitter and towards the optical filter stack and image sensor.

In a further embodiment, a laser diode may illuminate a spatial light modulator with excitation light. The spatial light modulator may controllably direct the excitation light towards a dichroic beam splitter/prism. The dichroic beam splitter/prism may be configured to refract light at the excitation wavelength(s) out of plane towards the optodes embedded under the skin surface. In other words, a combination of a spatial light modulator and a dichroic beam splitter may enable spatially-controllable illumination of discrete optodes embedded in the skin surface.

In addition to a spatial light modulator, systems described herein may generally provide modulated light via other devices and systems in an effort to improve signal to noise ratio in the presence of physiometric noise, e.g. autofluorescence. For example, a laser diode may illuminate the tissue at a given pulse frequency. In such a scenario, various lock-in and/or heterodyne signal amplification/isolation techniques may be used in an effort to improve the signal to noise ratio of the desired signal (e.g. light output from the plurality of optodes) by substantially rejecting all other signals that are not at the pulse frequency.

FIGS. 5A-5Dillustrate various views of systems, according to several example embodiments.FIG. 5Aillustrates a top view of a system500. Elements of system500may be similar or identical to elements illustrated and described in reference toFIGS. 1, 2A-2D, 3, and 4. System500may include a plurality of light sources510, a primary detector array520, and a calibration detector array530. As described elsewhere herein, light sources510may include laser diodes configured to emit excitation light. As illustrated, the light sources510may be arranged around a perimeter of the primary detector array520. However, other arrangements are possible.

The primary detector array520and the calibration detector array530may include a plurality of detector elements522. As described herein, the detector element522may include one or more pixels of a CMOS image sensor.

In an example embodiment, the detector elements522of the primary detector array520may be arranged in a square array. In such a scenario, a center-to-center distance between respective detector elements522of the primary detector array520may be 0.7 millimeters. Other distances are contemplated.

In an example embodiment, the secondary detector array530may include a linear arrangement of detector elements522. The secondary detector array530may be operable to calibrate autofluorescence properties of tissue. That is, autofluorescence may vary substantially between individuals as well as between tissue locations. As such, a local calibration array may enable optical measurements with better rejection of autofluorescence signals.

FIG. 5Billustrates a cross-sectional view of a system550, according to an example embodiment. The cross-sectional view of system550may be provided along reference line532ofFIG. 5A. The system550may include a substrate552. In an example embodiment, the substrate552may include a printed circuit board, however other substrate materials are possible.

The system550may include baffles554that may provide an opaque barrier between individual detector elements522. The baffles554may also be operable to prevent stray excitation light produced by light sources510from directly impinging upon the detector elements522. The system550may also include an optical filter556, a lenslet array558, and a aperture plate560. The lenslet array558may provide optical power for discrete detector elements522and their corresponding portions of the optical filter556. The system550may also include an aperture plate560. The aperture plate560may be configured to provide coarse spatial dependence. That is, by providing an aperture for each relatively large detector element/channel, spatial information about a rough location of one or more optodes may be obtained.

In some embodiments, aperture plate560may include a plurality of slits. Additionally or alternatively, aperture plate560may include a plurality of aperture holes that correspond to locations of the detector elements522.

FIG. 5Cillustrates a cross-sectional view of a system560, according to an example embodiment. The elements of system560may be similar or identical to system550; however an arrangement of various elements may differ. For example, light sources510may be interleaved between detector elements522of the detector array. Furthermore, an optical channel for each detector element522may be baffled from other detector elements and the light sources510by a plurality of baffles554. The baffles554may be substantially opaque to excitation light. In an example embodiment, the baffles554include a metalized channel. Additionally or alternatively, an optical filter556(e.g. an absorbtive filter) may be present in each optical channel.

System560may provide higher intensity excitation light for the optodes and may enable simultaneous measurement of the autofluorescence background and an emission light signal.

FIG. 5Dillustrates a cross-sectional view of a system560, a top-view of light emissions580and representative detector signals590, according to an example embodiment. For purposes of illustration, system560may include two detector elements562and564. The detector elements562and564may have respective baffles554and respective optical filters556. The detector elements562and564may be arranged on a substrate552such that a plurality of light sources510may be arranged around and/or between the detector elements562and564.

In an example embodiment, system560may be in proximity to tissue570. For example, the system560may be a part of a mobile device, which may be moved into contact with a skin surface. Alternatively, contact with the skin surface need not be necessary. In such scenarios, optodes572and574may have previously been implanted in the tissue570. In some cases, a lateral spacing (e.g. along the x-direction) between the optodes572and574may correspond to a lateral spacing between the detector elements562and564.

As illustrated inFIG. 5D, the tissue570may include a suspect skin area578. In such a scenario, the suspect skin area578may include a suspicious skin spot, tissue mass, etc. As such, in some cases, the suspect skin area578may include a plurality of analytes (e.g. cancer cells or other types of cells indicative of a particular medical condition). The plurality of analytes may include analyte576. Optode574may provide a characteristic optical response579in response to being in proximity to the analyte576. In an example embodiment, the characteristic optical response579may include a characteristic optical response with wavelengths in the near-infrared. Other optical responses and wavelengths are possible.

In the scenario described above,FIG. 5Dmay illustrate a top view of light emissions580from the optodes572and574and/or the region around the optodes572and574. For example, light sources510may illuminate the tissue570near the optodes572and574. In response to the excitation light, the tissue570may autofluoresce. That is, the tissue570near the optodes572and574may naturally emit light in response to absorbing the excitation light from light sources510.

In some cases, optodes572and574may be configured to fluoresce when illuminated with excitation light and while in proximity to the analyte576. In such a scenario, the optode574may provide characteristic optical response586. Thus, detector562may receive light from an autofluorescence response582while detector564may receive light from an autofluorescence response584and characteristic optical response586.

Accordingly, the spectral waveforms of light received by detectors562and564may vary. For example, in the above example, detector562may provide detector signal592, which may correspond to the autofluorescence response582. Furthermore, detector564may provide a superposition of detector signal594and detector signal596. That is, a signal from detector564may include an autofluorescence response584and a characteristic optical response586.

In such scenarios, various noise-reduction techniques may be applied to improve signal-to-noise ratio. For example, detector signal592may be integrated versus wavelength to provide a baseline autofluorescence correction factor. As such, the autofluorescence correction factor may be subtracted from integrated detector signals594and596.

Other noise-reduction techniques based on wavelength and/or spatial locations are possible. As an example, noise-reduction techniques may be based on tissue optical properties and/or optode depth within the tissue.

It is understood that other optical arrangements are possible so as to determine spatial information about a presence or absence of an analyte in skin tissue using optodes. Such other optical arrangements are contemplated herein.

III. Example Methods

FIG. 6illustrates a method600, according to an example embodiment. The method600may include various blocks or steps. The blocks or steps may be carried out individually or in combination. The blocks or steps may be carried out in any order and/or in series or in parallel. Further, blocks or steps may be omitted or added to method600.

The blocks of method600may be carried out by various elements of the systems100,300,400,500,550, and560as illustrated and described in reference toFIGS. 1, 3, 4, 5A, 5B, 5C, and 5D.

Block602includes operating one or more light sources (e.g. light source102) to illuminate a plurality of optodes (e.g. optode array122) with excitation light. The one or more light sources may include a light-emitting diode and/or a laser diode. As described elsewhere herein, each optode may be embedded in tissue at a respective location. The excitation light may cause the optodes to emit emission light. For example, the optodes may include a chemical, such as a fluorophore, which may be configured to fluoresce in response to receiving the excitation light. Furthermore, the optodes are configured to change their optical properties in response to a presence or an absence of at least one analyte. That is, the optodes may exhibit optical sensitivity to the at least one analyte such that the emission light emitted by the optodes is indicative of a presence or absence of the at least one analyte in the tissue.

An optical filter arrangement (e.g. optical filter arrangement106) includes for each optode in the plurality of optodes a corresponding set of one or more optical filters. The optical filters may include at least one of: a bandpass filter, a longpass filter, a shortpass filter, a dichroic filter, a polarization filter, an interference filter, or an absorptive filter. Other types of optical filters or optical elements are possible.

Block604includes operating a detector arrangement (e.g. detector arrangement110) to obtain detector information. The detector arrangement is optically coupled to the optical filter arrangement. In some embodiments, the one or more light sources are disposed in an interleaved arrangement with respect to the detectors in the detector arrangement.

Furthermore, the detector arrangement includes for each optode in the plurality of optodes a corresponding set of one or more detectors operable to detect light received from the optode's respective location via the optode's corresponding set of one or more optical filters. The detector information includes for each optode a respective optode signal indicative of light that has been emitted from the optode's respective location in response to the illumination from the one or more light sources, filtered through the optode's corresponding set of one or more optical filters, and detected by the optode's corresponding set of one or more detectors.

Block606includes detecting the at least one analyte based on the detector information. In such a scenario, a presence or absence of the at least one analyte may be determined via the described method600.

The method600may optionally include determining a background signal based on the detector information. In such a scenario, the background signal may include a tissue autofluorescence signal. For example, a background signal may be obtained by illuminating skin tissue that does not have embedded optodes. The emitted light from such tissue may be indicative of a background autofluorescence signal. Additionally, the method600may include adjusting the detector information based on the background signal. That is, the background signal may be subtracted from the detector information in a wavelength- or spatially-dependent manner. For example, background subtraction and/or other noise reduction methods may be possible based on optical properties of tissue and optode depth within the tissue.

The method600may optionally include adjusting each of the optode signals based on a corresponding portion of the background signal. That is, the background signal may be subtracted from each optode signal in a wavelength dependent manner so as to reduce the influence of tissue autofluorescence on the analyte detection technique.

FIG. 7illustrates several waveforms700, according to an example embodiment. The several waveforms700may include an autofluorescence waveform710and an emission waveform720. Furthermore,FIG. 7includes several wavebands corresponding to several bandpass filters. For example, waveband730may correspond to a bandpass filter with a pass band substantially between 700 nm and 730 nm. Waveband740may correspond to a bandpass filter with a pass band substantially between 760 nm to 820 nm. Furthermore, waveband750may correspond to a bandpass filter with a pass band substantially between 875 nm and 900 nm. It is understood that such wavebands are provided for illustration only and other wavelengths and wavebands are possible.

In some example embodiments, an optode signal may include an emission portion (e.g. emission waveform720) and a corresponding autofluorescence portion (e.g. autofluorescence waveform710). In such a scenario, the emission portion may be indicative of light from the optode's location that is filtered by a first optical filter (e.g. a filter with waveband740) in the optode's corresponding set of optical filters. Likewise, the autofluorescence portion is indicative of light from tissue at the optode's location that is filtered by a second optical filter (e.g. a filter with waveband730or750) in the optode's corresponding set of optical filters. Thus, adjusting each of the optode signals based on a corresponding portion of the background signal may include adjusting the emission portions of the optode signals with respect to the corresponding autofluorescence portions.

In some embodiments, the emission light may represent a characteristic signal over a characteristic waveband. That is, emission waveform720may include certain identifying characteristics. For example, emission waveform720includes a characteristic signal shape having a peak wavelength around 800 nm and a characteristic waveband of approximately 760 nm to 820 nm. Other identifying characteristics are possible.

Such identifying characteristics may be utilized in cancelling or reducing the autofluorescence background signal. For example, an integrated signal from the three filter windows730,740, and750may be used to correct the autofluorescence background if functional forms (e.g. the autofluorescence and emission waveforms) are known, or may be at least approximated or predicted.

In such a scenario, several detector “channels” may be used, each with a different filter window in an effort to obtain optical information from a plurality of spectral windows. As such, a substantial portion of the background autofluorescence may be cancelled.

Other methods and systems are contemplated to reduce or eliminate background signals. For example, a spectral unmixing method may be used in conjunction with machine learning to find an optimal reduction in background noise for a given set of filters, spectral windows, and approximate emission and autofluorescence waveforms.

Furthermore, methods and systems that utilize lock-in amplification, phase-locked loops, homodyne detection, heterodyne detection, and/or other methods for reducing background signal noise are contemplated herein.

The computer readable medium can also include non-transitory computer readable media such as computer-readable media that store data for short periods of time like register memory, processor cache, and random access memory (RAM). The computer readable media can also include non-transitory computer readable media that store program code and/or data for longer periods of time. Thus, the computer readable media may include secondary or persistent long term storage, like read only memory (ROM), optical or magnetic disks, compact-disc read only memory (CD-ROM), for example. The computer readable media can also be any other volatile or non-volatile storage systems. A computer readable medium can be considered a computer readable storage medium, for example, or a tangible storage device.

While various examples and embodiments have been disclosed, other examples and embodiments will be apparent to those skilled in the art. The various disclosed examples and embodiments are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.