WO2016041062A1

WO2016041062A1 - Apparatus and method for producing a spectrally resolved image of a fundus of a subject

Info

Publication number: WO2016041062A1
Application number: PCT/CA2015/050856
Authority: WO
Inventors: Jean Philippe SYLVESTRE; David Lapointe; Sebastien Blais-Ouellette; Jean-Daniel ARBOUR; Daniel L. Farkas
Original assignee: Optina Diagnostics, Inc.
Priority date: 2014-09-19
Filing date: 2015-09-04
Publication date: 2016-03-24

Abstract

The present disclosure relates to an apparatus and a method for spectrally resolved imaging of a fundus of a subject. A tunable filter outputs monochromatic excitation light having high out-of-band rejection from light provided by a light source. An illuminating optic component directs the monochromatic excitation light towards the fundus of the subject. A collecting optic component collects light emanating from the fundus of the subject. A sensor senses the light emanating from the fundus of the subject. A processor iteratively selects wavelengths of the monochromatic excitation light and produces a spectrally resolved image of the fundus based on the sensed light emanating from the fundus of the subject.

Description

APPARATUS AND METHOD FOR PRODUCING A SPECTRALLY RESOLVED IMAGE OF A FUNDUS OF A SUBJECT

TECHNICAL FIELD

[0001] The present disclosure relates to the field of spectral imaging.

More specifically, the present disclosure relates to an apparatus and a method usable to obtain a spectrally resolved image of a fundus of a subject.

BACKGROUND

[0002] Techniques involving multispectral and hyperspectral imaging of the fundus are gaining interest to help for the detection and diagnosis of ocular and systemic diseases having manifestations in the eye, and for following progression of such diseases. Examples of illnesses that can be detected by examination of a subject's fundus include diabetes, cardiovascular diseases, and neurological disorders such as Alzheimer's disease (AD). Clinical applications of eye imaging generally include the detection eye disease, organ specific diseases and systemic diseases.

[0001] Fluorescence imaging of the fundus involves using light at a first wavelength to excite fluorophores present in the fundus. The fluorophores emit light at another wavelength, typically at a longer wavelength. Excitation is provided by short light pulses may produce fluorescence at shorter wavelengths. A given fluorophore may emit light at a specific wavelength when excited at another specific wavelength. Efficiency of fluorescence imaging thus depends on careful excitation wavelength selection and on careful fluorescence emission capture. Spectral information obtained from fluorescence emission can be used to detect presence of a specific fluorophore from a sample containing multiple fluorescence sources.

[0003] In the particular case of AD, amyloid plaques become present in the fundus, as an extension of the brain. Such plaques become biomarkers that possess characteristic spectral signatures. [0002] Fluorescence imaging using specific fluorescence dyes has been proposed. Conventional solutions rely on a small number of excitation wavelengths, for example two or three wavelengths excitation. Each excitation wavelength is usually associated with a specific emission wavelength filter. Such solutions fail to provide fluorescence information over a sufficient spectral range to allow unambiguous identification of specific biomolecules in the fundus. Other solutions suggest discriminating the emission light from the fundus by filtering light, using for example a point or line spectrometer, a diffractive grating or tunable filter placed in front of a light sensor. These would however require using very powerful excitation light. Concerns, related to safety and comfort of the subject, are undesirable aspects of these solutions.

[0003] Speed of acquisition is another relevant factor to consider.

Available time to acquire data in the fundus is limited by eye movement. For example spectrometers used to obtain spectral information of a point or line in the image can be affected by the eye movements.

[0004] Therefore, there is a need for an apparatus and a method capable of safely and efficiently producing a spectrally resolved image of a fundus of a subject, the apparatus and method being useful in detecting signs of Alzheimer's disease and like illnesses in the subject.

SUMMARY

[0005] According to the present disclosure, there is provided an apparatus for producing a spectrally resolved image of a fundus of a subject. The apparatus comprises a tunable filter to output monochromatic excitation light with high out-of-band rejection from light provided by a light source. Also included is an illuminating optic component configured to direct the monochromatic excitation light towards the fundus of the subject. A collecting optic component is configured to collect light emanating from the fundus of the subject. A sensor senses the light emanating from the fundus of the subject. A processor is operatively connected to the sensor and to the tunable filter. The processor iteratively selects wavelengths of the monochromatic excitation light. The processor also produces the spectrally resolved image of the fundus based on the sensed light emanating from the fundus of the subject.

[0006] According to the present disclosure, there is also provided a method for producing a spectrally resolved image of a fundus of a subject. Monochromatic excitation light with high out-of-band rejection is directed towards the fundus of the subject, the monochromatic excitation light having iteratively selected wavelengths. Light emanating from the fundus of the subject is collected. The light emanating from the fundus of the subject is sensed and the spectrally resolved image of the fundus is produced based on the sensed light emanating from the fundus of the subject.

[0007] The foregoing and other features will become more apparent upon reading of the following non-restrictive description of illustrative embodiments thereof, given by way of example only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Embodiments of the disclosure will be described by way of example only with reference to the accompanying drawings, in which:

[0009] Figure 1 is a schematic representation of monochromatic excitation light with high out-of-band rejection being swept across a spectral range of various fluorophores;

[0010] Figure 2 is an illustration showing impacts of using high out-of- band rejection of excitation light and a blocking filter of reflected light;

[0011] Figure 3 is a block diagram of an apparatus for producing a spectrally resolved image of a fundus of a subject according to a first embodiment;

[0012] Figure 4 is a block diagram of an apparatus for producing a spectrally resolved image of a fundus of a subject according to a second embodiment; and

[0013] Figure 5 is a sequence diagram showing operations of a method for block diagram of an apparatus for producing a spectrally resolved image of a fundus of a subject.

[0014] Like numerals represent like features on the various drawings.

DETAILED DESCRIPTION

[0015] Various aspects of the present disclosure generally address one or more of the problems related to safely and efficiently producing a spectrally resolved image of a fundus of a subject.

[0016] At the onset of Alzheimer's disease (AD), amyloid plaques become present in the fundus of a subject. Fluorescence imaging and reflectance imaging of the fundus are useful in initially detecting AD and in following progression of its effects on the subject. Other biomarkers indicative of other ailments are also detectable in the fundus; the disclosed method and apparatus are useful in detecting a broad variety of diseases and is not limited to applications to AD detection.

[0017] An apparatus and a method introduced herein use monochromatic light to excite the surface of a subject's fundus. Light is collected in vivo from the fundus, in a non-invasive manner. The collected light may comprise fluorescence emitted by biomarkers present in the fundus, the emission resulting from the excitation from the monochromatic light. Alternatively or in addition, the collected light may comprise a reflection from the fundus. Yet another type of light that may be collected, instead of or in addition to fluorescence and reflection emissions, include Ramans emissions resulting from excitation of biomarkers with the monochromatic light. The collected light is sensed after being optionally filtered, and an image of the subject's fundus is obtained. Wavelength selection of the monochromatic light allows identifying the spectral signature of specific biomarkers on the fundus. [0018] The following terminology is used throughout the present disclosure:

[0019] Fundus: the interior surface of the eye, or a part thereof, including the retina, optic disc, macula and fovea, and posterior pole.

[0020] Subject: a patient or a laboratory animal.

[0021] Tunable filter: a filter or a filter assembly capable of passing a signal in a selectable bandwidth according to control signal or to a manual selection.

[0022] Monochromatic light: light having a narrow bandwidth, compared to a signal to be measured, in the visible, ultraviolet or infrared ranges.

[0023] Illuminating and collecting optics: assemblies including lenses and/or optical fibers and/or similar components for purposes of directing light to and from an illuminated point.

[0024] Blocking filter: a filter having a narrow bandwidth for rejecting

(blocking) an undesired signal while passing another desired signal.

[0025] Sensor: in the context of the present disclosure, any device capable of detecting light, including without limitation a camera and a photosensor.

[0026] Processor: a computer, a processing device, or an assembly of computers and/or processing devices, the processor having or being connected to a non-transient memory for storing program instructions that are executable by the processor.

[0027] Hyperspectral imaging: producing an image from light collected over a large spectrum, for example beyond the visible range, with the objective of obtaining a spectrum for each pixel image.

[0028] Fluorophore: a chemical compound that can re-emit light upon light excitation.

[0029] Fluorescence signal: light emitted by a biomarker, for example a fluorophore, being subjected to an excitation signal, the fluorescence signal possibly having a different wavelength from a wavelength of the excitation signal.

[0030] Dichroic filter: a filter that can pass light in a specific bandwidth while reflecting other colors.

[0031] Spectral signature: a combination of wavelengths that are emitted (e.g. by fluorescence), absorbed or reflected, the combination being specific to a biomarker.

[0032] Broadband light source: a source of light having a large wavelength range, for example white light.

[0033] Supercontinuum light source: a type of broadband light source that uses nonlinear distortion to produce white light from a laser source.

[0034] Volume Bragg grating filter: a narrow band optical filter using refractive index modulation within the volume of a photosensitive material.

[0035] Image registration: alignment of image features to compensate for movements of the object being imaged.

[0036] Amyloid plaques: abnormal structures made of incorrectly folded proteins, generally found in spaces between the brain's nerve cells.

[0037] The present disclosure suggests using very "clean" monochromatic light to excite fluorophores present in the fundus of a subject. The monochromatic light is "clean" because it is produced using equipment having high out-of-band rejection. Sequentially adapting the monochromatic light by "sweeping" its wavelength over a predetermined range allows to successively excite a variety of distinct fluorophores and to discriminate various fluorescence signals or Raman emissions resulting from this excitation.

[0038] Referring now to the drawings, Figure 1 is a schematic representation of monochromatic excitation light with high out-of-band rejection being swept across a spectral range of various fluorophores. A narrow beam of excitation light 10 has high out-of-band rejection relative to noise floor 12. The noise 12 is spread over a spectral bandwidth 14 over which a wavelength of the excitation light 10 is swept. A graph 20 illustrates wavelengths at which various fluorophores 22-26 will react to the excitation light 10. Another graph 40 shows that the same fluorophores 22-26 emit fluorescence signals at other wavelengths. In the non-limiting examples of fluorophores 22-26, the fluorescence signal is at a longer wavelength compared to the wavelength of the corresponding excitation signal.

[0039] Considering for example the fluorophores 24 and 25, it can be observed that their excitation wavelengths overlap significantly and their peaks are separated by a narrow range. Likewise, their fluorescence signal wavelengths are close and have significant overlap. For this reason, the present disclosure uses monochromatic light, defined as light having a small bandwidth compared to the signal to be measured, with high out-of-band rejection of the excitation light 10 to maximize excitation of one fluorophore type while reducing excitation of other types of fluorophores, the wavelength of the excitation light 10 being swept over the spectral bandwidth 14 over a short period of time to successively excite and detect the fluorophores 22-26 in rapid succession.

[0040] Without limiting the present disclosure, it has been found that good experimental results can be obtained by sweeping the monochromatic excitation light in 0.1 to 10 nm increments over at least 50 nm within infrared, visible and ultraviolet ranges, i.e. over a 350 to 1000 nm wavelength range. Use of equipment providing full width at half maximum (FWHM) of 5 nm or less and an optical density (OD) of at least 4 at 20 nm from a wavelength at maximum output were led to favorable results.

[0041] Figure 2 is an illustration showing impacts of using high out-of- band rejection of excitation light and a blocking filter of reflected light. The eye 50 of a subject is illuminated, either by the narrow beam of excitation light 10 of Figure 1 , or by a wider conventional beam of excitation light 60. The conventional excitation light 60 has low out-of-band rejection relative to a fairly high noise floor 62.

[0042] In a first use case of Figure 2, the conventional excitation light

60 is used to illuminate the eye 50, for example the retina or any part of the fundus. The eye 50 emits a reflection 64 of the excitation light 60 and a fluorescence signal 16. A blocking filter 52 rejects at least in part (i.e. attenuates) the reflection 64 of the excitation light 60. The blocking filter 52 has a fluorescence signal window 54 for passing (i.e. providing minimal attenuation) of the fluorescence signal 16 within a fluorescence bandwidth 18. Light signals 16 and 64 coming out of the blocking filter 52, including within the fluorescence bandwidth 18, are received at a camera 56. The fluorescence signal 16 is perceived by the camera 56 with much less power than the reflection signal 64 within the fluorescence bandwidth 18, rendering it very difficult or impossible to detect. Additionally, the wide beam width of the conventional excitation light 60 may cause more than one fluorophore present in the eye 50 to fluoresce at the same time.

[0043] In a second use case of Figure 2, using the narrow beam of excitation light 10, any contamination from out-of-band noise 12 of that may pass through the fluorescence signal window 54 and reach the camera 56 has lower power than the fluorescence signal 16. The camera 56 can easily detect the fluorescence signal 16. Moreover, the narrow beam width of the excitation light 10 reduces risks that more than one fluorophore present in the eye 50 will fluoresce at the same time, this discrimination being highly effective when the excitation light 10 is centered at the peak of an excitation range of a given fluorophore, as seen on graphs 20 and 40.

[0044] Figure 3 is a block diagram of an apparatus for producing a spectrally resolved image of a fundus of a subject according to a first embodiment. An apparatus 100 can produce a hyperspectral image of the complete fundus or of any part thereof, for example an image of the retina or of the optical nerve. The apparatus 100 comprises a light source 1 10, a tunable filter 120, an illuminating optic component 130, a collecting optic component 140, an optional blocking filter 150, a sensor 160 and a processor 170. The apparatus 180 may further comprise a display 180. The light source 1 10 as shown produces light having a broad wavelength range, for example white light. The wavelength range of the light source 1 10 may further extend in the ultraviolet and/or infrared ranges. The tunable filter 120 has a high out-of-band rejection and extracts monochromatic excitation light 122 from the light source 1 10. The illuminating optic component 130 may comprise one or more lenses, one or more optic fibers, or an assembly thereof. It directs the monochromatic excitation light towards 122 the fundus 190 of the subject. The illuminating optic component 130 may illuminate at once the entire fundus 190 or a section of the fundus 190 under the control of an operator of the apparatus 100. Alternatively, the optic component 130 may comprise a scanning apparatus (not shown) effecting a raster scan of the fundus 190 by directing the monochromatic excitation light 122 to image the fundus 190 one pixel at a time. The collecting optic component 140 may comprise one or more lenses, one or more optic fiber, or an assembly thereof. It collects light emanating from the fundus 190 of the subject. This light includes a fraction 142 of the monochromatic excitation light 122 and an additional fluorescence signal 144 (or, alternatively, a Raman signal). The optional blocking filter 150, when present, filters (i.e. blocks, separates or removes) the fraction 142 of monochromatic excitation light 122 from the fluorescence signal 144 emanating from the fundus 190 of the subject. The blocking filter 150, if present, attenuates wavelengths in a range of the excitation light 122 while passing with minimal attenuation wavelengths of the fluorescence signal 144. The sensor 160 senses the fluorescence signal 144, which may have been filtered by the blocking filter 150. The processor 170 controls the tunable filter 120 to iteratively select wavelengths of the monochromatic excitation light 122. The processor 170 may cause the tunable filter 120 to output the monochromatic excitation light 122 by sweeping over a range extending from 350 to 1000 nm, or over a part of this range. The processor 170 produces the spectrally resolved image of the fundus 190 based on the fluorescence signal 144 (or Raman signal) that emanates from the fundus 190 of the subject. The display 180, if present, shows the spectrally resolved image of the fundus 180.

[0045] Without limitation, in an embodiment of the apparatus 100, the tunable filter 120 may be configured to attenuate out-of-band emission of the monochromatic excitation light 122 by a factor of at least 10,000 to 1 (OD 4) at 20 nm from the nominal wavelength.

[0046] The light emanating from the fundus 190 may comprise light

142 reflected by the fundus 190 or a fluorescence signal 144 emitted by the fundus, the reflected light or the fluorescence signal (or Raman signal) resulting from directing the monochromatic excitation light 122 towards the fundus 190 of the subject.

[0047] The apparatus 100 may include variants of its various components. In non-limiting examples, the sensor 160 may comprise a camera capable of capturing light in spectral ranges of the reflected light and of the fluorescence signal, the light source 1 10 may comprise a broadband light source, for example a supercontinuum light source, the tunable filter 120 may comprise a volume Bragg grating filter or other type of filter having high out-of- band rejection, and/or the blocking filter 150 may comprise a tunable blocking filter or a plurality of blocking filters, for example mounted on a filter wheel, and be configured to allow passing of the fluorescence signal 144 (or Raman signal) in a plurality of wavelengths, allowing fluorescence imaging in multiple spectral ranges. [0048] In another variant, the light source 1 10 may comprise a tunable light source emitting monochromatic light with high out-of-band rejection, the light source 1 10 having an OD of at least 4.0 or up to 4.7. US patent no. 7,557,990 B2, the disclosure of which is incorporated by reference herein, discloses a Bragg grating tunable filter that can be used to produce light with high out of band rejection. With such construction of the light source 1 10, characteristics of the tunable filter 120 may be relaxed, so long as the monochromatic light 122 with adequate high out-of-band rejection is obtained from the combination of the light source 1 10 and of the tunable filter 120.

[0049] Without limitation, the tunable filter 120 may be configured to output the monochromatic excitation light in a 350 to 1000 nm wavelength range, tunable in 0.1 to 10 nm increments. Also without limitation, the blocking filter 150 may be a bandpass filter having a bandwidth in a 20 to 100 nm range.

[0050] In addition to the above mentioned functions, the processor

170 may be programmed and configured to analyze the spectral image of the fundus 190. This type of analysis allows to identify spectral signatures within the spectrally resolved image of the fundus 190, to identify location and concentration of biomarkers on the spectrally resolved image of the fundus 190, to normalize the spectrally resolved image of the fundus 190, to correct the spectrally resolved image of the fundus 190 according to spectral characteristics of the apparatus 100 and its optical components, to perform registration of the spectrally resolved image of the fundus 190 to correct for eye movements of the subject, or to perform any combination of these functions. Use of distinct, associated processors or computers to perform the various tasks of the processor 170 is contemplated. In a non-limiting example, a first processor may control acquisition of the fluorescence signal 144 (or Raman signal), including control signals sent to the tunable filter 120, a second processor may form the spectrally resolved image of the fundus 190 and a third processor may perform further image analysis. [0051] Figure 4 is a block diagram of an apparatus for producing a spectrally resolved image of a fundus of a subject according to a second embodiment. An apparatus 200 can produce a hyperspectral image of the complete fundus or of any part thereof, for example an image of the retina or of the optical nerve. The apparatus 200 is similar to the apparatus 100 and shares many components and features, including many of its optional features. Generally, the light source 1 10, the tunable filter 120, the illuminating optic component 130 and the optional display 180 are similar or identical to those of the apparatus 100 or its variants, and perform the same functions. A collecting optic component 240 may be the same or slightly differ from the collecting optic component 140 in that it collects light emanating from the fundus 190 of the subject, including a similar fraction 242 of the monochromatic excitation light 122 as well as an additional light signal 244. The light signal 242 comprises light reflected by the fundus 190 resulting from directing the monochromatic excitation light 122 towards the fundus 190 of the subject. The light signal 244 comprises a fluorescence signal (or a Raman signal) emitted by the fundus 190 resulting from directing the monochromatic excitation light 122 towards the fundus 190 of the subject. A dichroic filter 250 separates the reflected light signal 242 from the fluorescence signal 244. A first sensor 260 senses the fluorescence signal 244 and a second sensor 265 senses the reflected light signal 242. In a variant, the first and second sensors 260, 265 may actually be the same, unique sensor receiving both light signals 242 and 244.

[0052] The processor 270 is similar to the processor 170 and performs the same functions described hereinabove. The processor 270 is different in that it is connected to both sensors 260 and 265 and combines their outputs to produce the spectrally resolved image of the fundus 190.

[0053] Either of the apparatus 100 and the apparatus 200 may be used for detecting amyloid plaques in the fundus of a subject and, in particular, for detecting signs of Alzheimer's disease in the subject. [0054] Figure 5 is a sequence diagram showing operations of a method for block diagram of an apparatus for producing a spectrally resolved image of a fundus of a subject. Operation of a sequence 300 shown on Figure 5 can produce a hyperspectral image of the complete fundus or of any part thereof, for example an image of the retina or of the optical nerve. The sequence 300 comprises a plurality of operations that may be executed in variable order, some of the operations possibly being executed concurrently, some of the operations being optional. The sequence 300 may be operated using either of the apparatus 100 and apparatus 200 introduced hereinabove, or using one of their variants. In operation 310, monochromatic excitation light having high out-of-band rejection is directed towards the fundus of the subject. The monochromatic excitation light has iteratively selected wavelengths and operations of the sequence 300 may be performed in any desired number of iterations. The monochromatic excitation light may for example be produced by filtering light from a broadband light source and may have a 350 to 1000 nm wavelength range selectable in 0.1 to 10 nm increments. Light emanating from the fundus of the subject is collected at operation 320. The monochromatic excitation light is optionally filtered, or removed, from the light emanating from the fundus of the subject at operation 330. Operation 330 may be performed using a bandpass filter having a bandwidth in a 20 to 100 nm range. Alternatively the bandpass filter may have a broader bandwidth or may be replaced by an edge filter. The collected and optionally filtered light emanating from the fundus, which results from directing the monochromatic excitation light towards the fundus of the subject, may include light reflected by the fundus, or a fluorescence signal (or a Raman signal) emitted by one or more fluorophores of interest present in the fundus, or both. If both are present, operation 340 may separate the reflected light and the fluorescence signal. Operation 350 comprises sensing the collected light emanating from the fundus of the subject, for example using a camera capable of capturing light in spectral ranges of the reflected light and/or of the fluorescence signal. If both the reflected light and the fluorescence signal are present, operation 350 may include separately sensing these distinct light signals, for example using distinct cameras. The sequence 300 continues at operation 360 with the production of the spectrally resolved image of the fundus based on the sensed filtered light emanating from the fundus of the subject, using one or both of the reflected light and fluorescence signal. Optionally, operation 370 comprises showing the spectrally resolved image of the fundus on a display.

[0055] In one or more variants, the production of the spectrally resolved image of the fundus at operation 360 may include one or more of an identification of spectral signatures within the spectrally resolved image of the fundus, an identification of location and concentration of biomarkers on the spectrally resolved image of the fundus, a normalization of the spectrally resolved image of the fundus or a registration of the spectrally resolved image of the fundus to correct for eye movements of the subject.

[0056] The method illustrated on Figure 5 and any of its variants may be used for detecting amyloid plaques in the fundus of a subject and, in particular, for detecting signs of Alzheimer's disease in the subject.

[0057] Those of ordinary skill in the art will realize that the description of the apparatus and method for spectrally resolved imaging of a fundus of a subject are illustrative only and are not intended to be in any way limiting. Other embodiments will readily suggest themselves to such persons with ordinary skill in the art having the benefit of the present disclosure. Furthermore, the disclosed apparatus and method may be customized to offer valuable solutions to existing needs and problems related to safely and efficiently producing a spectrally resolved image of a fundus of a subject.

[0058] In the interest of clarity, not all of the routine features of the implementations of the apparatus and method are shown and described. It will, of course, be appreciated that in the development of any such actual implementation of the apparatus and method, numerous implementation- specific decisions may need to be made in order to achieve the developer's specific goals, such as compliance with application-, system-, and business- related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that a development effort might be complex and time- consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the field of spectral imaging having the benefit of the present disclosure.

[0059] In accordance with the present disclosure, the components, process operations, and/or data structures described herein may be implemented using various types of operating systems, computing platforms, network devices, computer programs, and/or general purpose machines. In addition, those of ordinary skill in the art will recognize that devices of a less general purpose nature, such as hardwired devices, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), or the like, may also be used. Where a method comprising a series of operations is implemented by a computer or a machine and those operations may be stored as a series of instructions readable by the machine, they may be stored on a tangible medium.

[0060] Systems and modules described herein may comprise software, firmware, hardware, or any combination(s) of software, firmware, or hardware suitable for the purposes described herein. Software and other modules may reside on servers, workstations, personal computers, computerized tablets, personal digital assistants (PDA), and other devices suitable for the purposes described herein. Software and other modules may be accessible via local memory, via a network, via a browser or other application or via other means suitable for the purposes described herein. Data structures described herein may comprise computer files, variables, programming arrays, programming structures, or any electronic information storage schemes or methods, or any combinations thereof, suitable for the purposes described herein.

[0004] Although the present disclosure has been described hereinabove by way of non-restrictive, illustrative embodiments thereof, these embodiments may be modified at will within the scope of the appended claims without departing from the spirit and nature of the present disclosure.

Claims

WHAT IS CLAIMED IS:

1 . An apparatus for producing a spectrally resolved image of a fundus of a subject, comprising:

a tunable filter for outputting monochromatic excitation light with high out-of-band rejection from light provided by a light source;

an illuminating optic component for directing the monochromatic excitation light towards the fundus of the subject;

a collecting optic component for collecting light emanating from the fundus of the subject;

a sensor of the light emanating from the fundus of the subject; and

a processor operatively connected to the sensor and to the tunable filter for iteratively selecting wavelengths of the monochromatic excitation light and for producing the spectrally resolved image of the fundus based on the sensed light emanating from the fundus of the subject.

2. The apparatus of claim 1 , wherein the light emanating from the fundus comprises light reflected by the fundus resulting from directing the monochromatic excitation light towards the fundus of the subject, the sensor being configured to sense the reflected light.

3. The apparatus of claim 1 , wherein the light emanating from the fundus comprises a fluorescence signal emitted by the fundus resulting from directing the monochromatic excitation light towards the fundus of the subject, the sensor being configured to sense the fluorescence signal.

The apparatus of claim 1 , wherein the light emanating from the fundus comprises light reflected by the fundus and a fluorescence signal emitted by the fundus, the reflected light and the fluorescence signal resulting from directing the monochromatic excitation light towards the fundus of the subject.

The apparatus of claim 4, comprising a blocking filter for filtering the reflected light from the fluorescence signal.

The apparatus claim 5, wherein the sensor is configured to sense the fluorescence signal.

The apparatus of claim 5, wherein:

the blocking filter comprises a dichroic filter for separating the reflected light from the fluorescence signal; and

the sensor of the light emanating from the fundus of the subject comprises a sensor of the reflected light and a sensor of the fluorescence signal.

The apparatus of any one of claims 5 to 7, wherein the blocking filter is a bandpass filter having a bandwidth in a 20 to 150 nm range.

The apparatus of any one of claims 5 to 8, wherein the blocking filter comprises a plurality of blocking filters configured to allow passing of the light emanating from the fundus of the subject in a plurality of wavelengths.

The apparatus of any one of claims 5 to 9, wherein the blocking filter is tunable to allow passing of the light emanating from the fundus of the subject in a plurality of wavelengths.

The apparatus of any one of claims 5 to 7, wherein the blocking filter comprises an edge filter having a transmission bandwidth in a spectral range of fluorescence signals resulting from the selected wavelengths of the monochromatic excitation light.

12. The apparatus of any one of claims 1 to 1 1 , comprising the light source.

13. The apparatus of claim 12, wherein the light source is a broadband light source.

14. The apparatus of claim 13, wherein the broadband light source is a supercontinuum light source.

15. The apparatus of claim 12, wherein the light source is a tunable light source configured to emit monochromatic light with high out-of-band rejection.

16. The apparatus of claim 15, wherein characteristics of the tunable light source are selected from the group consisting of a full width at half maximum (FWHM) of 10 nm or less, an optical density (OD) of at least 4 at 20 nm from a wavelength at maximum output, tunability over a spectral range of at least 50 nm and any combination thereof.

17. The apparatus of any one of claims 1 to 15, wherein the tunable filter has an optical density (OD) of at least 4 at 20 nm from a wavelength at maximum output.

18. The apparatus of any one of claims 1 to 17, wherein the tunable filter is a volume Bragg grating filter.

19. The apparatus of any one of claims 1 to 18, wherein the tunable filter is configured to output the monochromatic excitation light ranges selected from a visible range, an infrared range, an ultraviolet range and a combination thereof.

20. The apparatus of any one of claims 1 to 19, wherein the tunable filter is tunable in 0.1 to 5 nm increments.

21 . The apparatus of any one of claims 1 to 20, wherein the illuminating optic component is configured to direct the monochromatic excitation light at once over the fundus of the subject.

22. The apparatus of any one of claims 1 to 20, wherein the illuminating optic component is configured to scan the fundus of the subject with the monochromatic excitation light.

23. The apparatus of any one of claims 1 to 22, comprising a display for showing the spectrally resolved image of the fundus.

24. The apparatus of any one of claims 1 to 23, wherein the processor is configured to identify reflectance and/or fluorescence signatures within the spectrally resolved image of the fundus.

25. The apparatus of any one of claims 1 to 24, wherein the processor is configured to identify location and/or concentration of biomarkers on the spectrally resolved image of the fundus.

26. The apparatus of any one of claims 1 to 25, wherein the processor is configured to normalize the spectrally resolved image of the fundus.

27. The apparatus of any one of claims 1 to 26, wherein the processor is configured to correct the spectrally resolved image of the fundus according to spectral characteristics of the apparatus.

28. The apparatus of any one of claims 1 to 27, wherein the processor is configured to perform registration of the spectrally resolved image of the fundus to correct for eye movements of the subject.

29. The apparatus of any one of claims 1 to 27, wherein the processor is configured to select wavelengths of the monochromatic excitation light over a range of 350 to 1000 nm, or over a part of this range.

30. The apparatus of any one of claims 1 to 28, wherein the sensor is a camera.

31 . The apparatus of claim 1 , wherein the light emanating from the fundus comprises a Raman signal emitted by the fundus resulting from directing the monochromatic excitation light towards the fundus of the subject, the sensor being configured to sense the Raman signal.

Use of the apparatus of any one of claims 1 to 31 for detecting amyloid plaques in the fundus of the subject.

Use of the apparatus of any one of claims 1 to 31 for detecting signs of Alzheimer's disease in the subject.

34. A method for producing a spectrally resolved image of a fundus of a subject, comprising:

directing monochromatic excitation light with high out-of-band rejection towards the fundus of the subject, the monochromatic excitation light having iteratively selected wavelengths;

collecting light emanating from the fundus of the subject;

sensing the light emanating from the fundus of the subject; and producing the spectrally resolved image of the fundus based on the sensed light emanating from the fundus of the subject.

35. The method of claim 34, wherein sensing the light emanating from the fundus of the subject is performed using a camera.

36. The method of any one of claims 34 or 35, wherein the light emanating from the fundus comprises light reflected by the fundus resulting from directing the monochromatic excitation light towards the fundus of the subject.

37. The method of any one of claims 34 or 35, wherein the light emanating from the fundus comprises a fluorescence signal emitted by the fundus resulting from directing the monochromatic excitation light towards the fundus of the subject.

38. The method of any one of claims 34 or 35, wherein the light emanating from the fundus comprises light reflected by the fundus and a fluorescence signal emitted by the fundus, the reflected light and the fluorescence signal resulting from directing the monochromatic excitation light towards the fundus of the subject.

39. The method of claim 38, comprising filtering the reflected light from the fluorescence signal.

40. The method of claim 39, comprising filtering the reflected light using a bandpass filter or an edge filter having a transmission bandwidth in an emission spectral range of one or more fluorophores of interest present in the fundus of the subject.

41 . The method of any one of claims 38 to 40, comprising separately sensing the reflected light and the fluorescence signal.

42. The method of any one of claims 34 to 41 , comprising showing the spectrally resolved image of the fundus on a display.

43. The method of any one of claims 34 to 42, comprising identifying spectral signatures within the spectrally resolved image of the fundus.

44. The method of any one of claims 34 to 43, wherein comprising identifying location and concentration of biomarkers on the spectrally resolved image of the fundus.

45. The method of any one of claims 34 to 43, comprising producing the monochromatic excitation light by filtering light from a broadband light source.

46. The method of any one of claims 34 to 45, wherein the monochromatic excitation light is in a 350 to 1000 nm wavelength range selectable in 0.1 to 5 nm increments.

47. The method of any one of claims 34 to 46, comprising normalizing the spectrally resolved image of the fundus.

48. The method of any one of claims 34 to 47, comprising registering the spectrally resolved image of the fundus to correct for eye movements of the subject.

49. The method of any one of claims 34 or 35, wherein the light emanating from the fundus comprises wherein the light emanating from the fundus comprises a Raman signal emitted by the fundus resulting from directing the monochromatic excitation light towards the fundus of the subject.

50. Use of the method of any one of claims 34 to 49 for detecting amyloid plaques in the fundus of the subject.

51 . Use of the method of any one of claims 34 to 49 for detecting signs of Alzheimer's disease in the subject.