(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`(19) World Intellectual Property
`Organization
`International Bureau
`
`(43) International Publication Date
`3 July 2014 (03.07.2014)
`
`P O P C T
`
`(10) International Publication Number
`WO 2014/105521 Al
`
`(51) International Patent Classification:
`A61C 19/04 (2006.01)
`A61B 6/14 (2006.01)
`
`(21) International Application Number:
`
`(22) International Filing Date:
`
`PCT/US2013/075736
`
`17 December 2013 (17. 12.2013)
`
`HN, HR, HU, ID, IL, IN, IR, IS, JP, KE, KG, KN, KP, KR,
`KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD, ME,
`MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ,
`OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA,
`SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM,
`TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM,
`ZW.
`
`(25) Filing Language:
`
`(26) Publication Language:
`
`(30) Priority Data:
`61/747,477
`3 1 December 2012 (3 1. 12.2012)
`61/754,698
`2 1 January 2013 (21.01.2013)
`
`English
`
`English
`
`US
`US
`
`(84) Designated States (unless otherwise indicated, for every
`kind of regional protection available): ARIPO (BW, GH,
`GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, SZ, TZ,
`UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ,
`TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK,
`EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV,
`MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM,
`TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW,
`KM, ML, MR, NE, SN, TD, TG).
`(72) Inventor: ISLAM, Mohammed N.; 1718 Newport Creek Declarations under Rule 4.17 :
`Drive, Ann Arbor, Michigan 48103 (US).
`— as to applicant's entitlement to apply for and be granted a
`patent (Rule 4.1 7(H))
`(74) Agents: BIR, David S. et al; Brooks Kushman P.C., 1000
`Town Center, Twenty-Second Floor, Southfield, Michigan — as to the applicant's entitlement to claim the priority of the
`48075 (US).
`earlier application (Rule 4.1 7(in))
`(81) Designated States (unless otherwise indicated, for every Published:
`kind of national protection available): AE, AG, AL, AM,
`AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, — with international search report (Art. 21(3))
`BZ, CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM,
`DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT,
`
`(71) Applicant: OMNI MEDSCI, INC. [US/US]; 1718 N ew
`port Creek Drive, Ann Arbor, Michigan 48103 (US).
`
`(54) Title: SHORT-WAVE INFRARED SUPER-CONTINUUM LASERS FOR EARLY DETECTION OF DENTAL CARIES
`
`FIG. 4
`
`o (57) Abstract: A system and method for using near-infrared or short-wave infrared (SWIR) sources such as lamps, thermal sources,
`
`laser diodes, and super-continuum light sources for early detection of dental caries measure
`LED's, laser diodes, super-luminescent
`transmission and/or reflectance. In the SWIR wavelength range, solid, intact teeth may have a low reflectance or high transmission
`o with very few spectral features while a carious region exhibits more scattering, so the reflectance increases in amplitude. The spectral
`o for applying SWIR light to one or more teeth may include a C-clamp design, a mouth guard design, or hand-held devices that may
`dependence of the transmitted or reflected light from the tooth may be used to detect and quantify the degree of caries. Instruments
`
`augment other dental tools. The measurement device may communicate with a smart phone or tablet, which may transmit a related
`signal to the cloud, where additional value-added services are performed.
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`SHORT-WAVE INFRARED SUPER-CONTINUUM LASERS FOR EARLY DETECTION OF
`DENTAL CARIES
`
`CROSS-REFERENCE TO RELATED APPLICATIONS
`
`[0001]
`
`This application claims the benefit of U.S. provisional application Serial No.
`
`61/747,477 filed December 31, 2012 and U.S. provisional application Serial No. 61/754,698 filed
`
`January 21, 2013, the disclosures of which are hereby incorporated by reference in their entirety.
`
`[0002]
`
`This application is related to U.S. provisional application Serial No. 61/747,472 filed
`
`December 31, 2012; Serial No. 61/747,481 filed December 31, 2012; Serial No. 61/747,485 filed
`
`December 31, 2012; Serial No. 61/747,487 filed December 31, 2012; Serial No. 61/747,492 filed
`
`December 31, 2012; and Serial No. 61/747,553 filed December 31, 2012, the disclosures of which
`
`are hereby incorporated in their entirety by reference herein.
`
`[0003]
`
`This
`
`application is being filed concurrently with International Application
`
`entitled Near-Infrared Lasers For Non-Invasive Monitoring Of Glucose, Ketones,
`
`HBAIC, And Other Blood Constituents (Attorney Docket No. OMNIOIOIPCT); U.S. Application
`
`entitled Focused Near-Infrared Lasers For Non-Invasive Vasectomy And Other
`
`Thermal Coagulation Or Occlusion Procedures
`
`(Attorney Docket No. OMNI0103PUSP);
`
`International Application
`
`entitled Short-Wave Infrared Super-Continuum Lasers
`
`For Natural Gas Leak Detection, Exploration, And Other Active Remote Sensing Applications
`
`(Attorney Docket No. OMNI0104PCT); U.S. Application
`
`entitled Short-Wave
`
`Infrared Super-Continuum Lasers For Detecting Counterfeit Or Illicit Drugs And Pharmaceutical
`
`Process Control (Attorney Docket No. OMNI0105PUSP); U.S. Application
`
`entitled Non-Invasive Treatment Of Varicose Veins (Attorney Docket No. OMNI0106PUSP); and
`
`U.S. Application
`
`entitled Near-Infrared Super-Continuum Lasers For Early
`
`Detection Of Breast And Other Cancers (Attorney Docket No. OMNI0107PUSP), the disclosures of
`
`which are hereby incorporated in their entirety by reference herein.
`
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`TECHNICAL FIELD
`
`[0004]
`
`This disclosure relates to lasers and light sources for healthcare, medical, dental, or
`
`bio-technology applications, including systems and methods for using near-infrared or short-wave
`
`infrared light sources for early detection of dental caries, often called cavities.
`
`BACKGROUND AND SUMMARY
`
`[0005]
`
`Dental care and the prevention of dental decay or dental caries has changed in the
`
`United States over the past several decades, due to the introduction of fluoride to drinking water, the
`
`use of fluoride dentifrices and rinses, application of topical fluoride in the dental office, and
`
`improved dental hygiene. Despite these advances, dental decay continues to be the leading cause of
`
`tooth loss. With the improvements over the past several decades, the majority of newly discovered
`
`carious lesions tend to be localized to the occlusal pits and fissures of the posterior dentition and the
`
`proximal contact sites. These early carious lesions may be often obscured in the complex and
`
`convoluted topography of the pits and fissures or may be concealed by debris that frequently
`
`accumulates in those regions of the posterior teeth. Moreover, such lesions are difficult to detect in
`
`the early stages of development.
`
`[0006]
`
`Dental
`
`caries may be
`
`a dynamic disease
`
`that
`
`is
`
`characterized by tooth
`
`demineralization leading to an increase in the porosity of the enamel surface. Leaving these lesions
`
`untreated may potentially lead to cavities reaching the dentine and pulp and perhaps eventually
`
`causing tooth loss. Occlusal surfaces (bite surfaces) and approximal surfaces (between the teeth) are
`
`among the most susceptible sites of demineralization due to acid attack from bacterial by-products in
`
`the biofilm. Therefore, there is a need for detection of lesions at an early stage, so that preventive
`
`agents may be used to inhibit or reverse the demineralization.
`
`[0007]
`
`Traditional methods for caries detection include visual examination and tactile
`
`probing with a sharp dental exploration tool, often assisted by radiographic (x-ray) imaging.
`
`However, detection using these methods may be somewhat subjective; and, by the time that caries
`
`are evident under visual and tactile examination, the disease may have already progressed to an
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`advanced stage. Also, because of the ionizing nature of x-rays, they are dangerous to use (limited
`
`use with adults, and even less used with children). Although x-ray methods are suitable for
`
`approximal surface lesion detection, they offer reduced utility for screening early caries in occlusal
`
`surfaces due to their lack of sensitivity at very early stages of the disease.
`
`[0008]
`
`Some of the current imaging methods are based on the observation of the changes of
`
`the light transport within the tooth, namely absorption, scattering, transmission, reflection and/or
`
`fluorescence of light. Porous media may scatter light more than uniform media. Taking advantage
`
`of this effect, the Fiber-optic trans-illumination is a qualitative method used to highlight the lesions
`
`within teeth by observing the patterns formed when white light, pumped from one side of the tooth,
`
`is scattered away and/or absorbed by the lesion. This technique may be difficult to quantify due to
`
`an uneven light distribution inside the tooth.
`
`[0009]
`
`Another method called quantitative light-induced fluorescence - QLF - relies on
`
`different fluorescence from solid teeth and caries regions when excited with bright light in the
`
`visible. For example, when excited by relatively high intensity blue light, healthy tooth enamel
`
`yields a higher intensity of fluorescence than does demineralized enamel that has been damaged by
`
`caries infection or any other cause. On the other hand, for excitation by relatively high intensity of
`
`red light, the opposite magnitude change occurs, since this is the region of the spectrum for which
`
`bacteria and bacterial by-products in carious regions absorb and fluoresce more pronouncedly than
`
`do healthy areas. However, the image provided by QLF may be difficult to assess due to relatively
`
`poor contrast between healthy and infected areas. Moreover, QLF may have difficulty
`
`discriminating between white spots and stains because both produce similar effects. Stains on teeth
`
`are commonly observed in the occlusal sites of teeth, and this obscures the detection of caries using
`
`visible light.
`
`[0010]
`
`As described in this disclosure, the near-infrared region of the spectrum offers a novel
`
`approach to imaging carious regions because scattering is reduced and absorption by stains is low.
`
`For example, it has been demonstrated that the scattering by enamel tissues reduces in the form of
`
`1/(wavelength) , e.g., inversely as the cube of wavelength. By using a broadband light source in the
`
`short-wave infrared (SWIR) part of the spectrum, which corresponds approximately to 1400nm to
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`2500nm, lesions in the enamel and dentine may be observed.
`
`In one embodiment, intact teeth have
`
`low reflection over the SWIR wavelength range.
`
`In the presence of caries, the scattering increases,
`
`and the scattering is a function of wavelength; hence, the reflected signal decreases with increasing
`
`wavelength. Moreover, particularly when caries exist in the dentine region, water build up may
`
`occur, and dips in the SWIR spectrum corresponding to the water absorption lines may be observed.
`
`The scattering and water absorption as a function of wavelength may thus be used for early detection
`
`of caries and for quantifying the degree of demineralization.
`
`[0011]
`
`SWIR light may be generated by light sources such as lamps, light emitting diodes,
`
`one or more laser diodes, super-luminescent laser diodes, and fiber-based super-continuum sources.
`
`The SWIR super-continuum light sources advantageously may produce high intensity and power, as
`
`well as being a nearly transform-limited beam that may also be modulated. Also, apparatuses for
`
`caries detection may include C-clamps over teeth, a handheld device with light input and light
`
`detection, which may also be attached to other dental equipment such as drills. Alternatively, a
`
`mouth-guard type apparatus may be used to simultaneously illuminate one or more teeth. Fiber
`
`optics may be conveniently used to guide the light to the patient as well as to transport the signal
`
`back to one or more detectors and receivers.
`
`[0012]
`
`In one embodiment, a diagnostic system includes a light source configured to
`
`generate an output optical beam comprising one or more semiconductor sources configured to
`
`generate an input beam, one or more optical amplifiers configured to receive at least a portion of the
`
`input beam and to deliver an intermediate beam to an output end of the one or more optical
`
`amplifiers, and one or more optical fibers configured to receive at least a portion of the intermediate
`
`beam and to deliver at least the portion of the intermediate beam to a distal end of the one or more
`
`optical fibers to form a first optical beam. A nonlinear element is configured to receive at least a
`
`portion of the first optical beam and to broaden a spectrum associated with the at least a portion of
`
`the first optical beam to at least 10 nanometers through a nonlinear effect in the nonlinear element to
`
`form the output optical beam with an output beam broadened spectrum, wherein at least a portion of
`
`the output beam broadened spectrum comprises a short-wave infrared wavelength between
`
`approximately 1400 nanometers and approximately 2500 nanometers, and wherein at least a portion
`
`of the one of more fibers is a fused silica fiber with a core diameter less than approximately 400
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`microns. An interface device is configured to receive a received portion of the output optical beam
`
`and to deliver a delivered portion of the output optical beam to a sample comprising enamel and
`
`dentine, wherein the delivered portion of the output optical beam is configured to generate a
`
`spectroscopy output beam from the sample. A receiver is configured to receive at least a portion of
`
`the spectroscopy output beam having a bandwidth of at least 10 nanometers and to process the
`
`portion of the spectroscopy output beam to generate an output signal based on a wavelength
`
`dependence of the spectroscopy output beam over the bandwidth of at least 10 nanometers.
`
`[0013]
`
`In another embodiment, a measurement system includes a light source configured to
`
`generate an output optical beam comprising a plurality of semiconductor sources configured to
`
`generate an input optical beam, a multiplexer configured to receive at least a portion of the input
`
`optical beam and to form an intermediate optical beam, and one or more fibers configured to receive
`
`at least a portion of the intermediate optical beam and to form the output optical beam, wherein the
`
`output optical beam comprises one or more optical wavelengths. An interface device is configured
`
`to receive a received portion of the output optical beam and to deliver a delivered portion of the
`
`output optical beam to a sample comprising enamel and dentine, wherein the delivered portion of the
`
`output optical beam is configured to generate a spectroscopy output beam from the sample. A
`
`receiver is configured to receive at least a portion of the spectroscopy output beam having a
`
`bandwidth of at least 10 nanometers and to process the portion of the spectroscopy output beam to
`
`generate an output signal based on a wavelength dependence of the spectroscopy output beam over
`
`the bandwidth of at least 10 nanometers.
`
`[0014]
`
`In yet another embodiment, a method of measuring includes generating an output
`
`optical beam comprising generating an input optical beam from a plurality of semiconductor sources,
`
`multiplexing at least a portion of the input optical beam and forming an intermediate optical beam,
`
`and guiding at least a portion of the intermediate optical beam and forming the output optical beam,
`
`wherein the output optical beam comprises one or more optical wavelengths. The method may also
`
`include receiving a received portion of the output optical beam and delivering a delivered portion of
`
`the output optical beam to a sample, wherein the sample comprises enamel and dentine. The method
`
`may further include generating a spectroscopy output beam having a bandwidth of at least 10
`
`nanometers from the sample, receiving at least a portion of the spectroscopy output beam, and
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`processing the portion of the spectroscopy output beam and generating an output signal based on a
`
`wavelength dependence of the spectroscopy output beam over the bandwidth of at
`
`least 10
`
`nanometers.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0015]
`
`For a more complete understanding of the present disclosure, and for further features
`
`and advantages thereof, reference is now made to the following description taken in conjunction
`
`with the accompanying drawings, in which:
`
`[0016]
`
`FIGURE 1 illustrates the structure of a tooth.
`
`[0017]
`
`FIGURE 2A shows the attenuation coefficient for dental enamel and water versus
`
`wavelength from approximately 600nm to 2600nm.
`
`[0018]
`
`FIGURE 2B illustrates the absorption spectrum of intact enamel and dentine in the
`
`wavelength range of approximately 1.2 to 2.4 microns.
`
`[0019]
`
`FIGURE 3 shows the near infrared spectral reflectance over the wavelength range of
`
`approximately 800nm to 2500nm from an occlusal tooth surface. The black diamonds correspond to
`
`the reflectance from a sound, intact tooth section. The asterisks correspond to a tooth section with
`
`an enamel lesion. The circles correspond to a tooth section with a dentine lesion.
`
`[0020]
`
`FIGURE 4 illustrates a hand-held dental tool design of a human interface that may
`
`also be coupled with other dental tools.
`
`[0021]
`
`FIGURE 5 illustrates a clamp design of a human interface to cap over one or more
`
`teeth and perform a non-invasive measurement for dental caries.
`
`[0022]
`
`FIGURE 6 shows a mouth guard design of a human interface to perform a non
`
`invasive measurement for dental caries.
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`[0023]
`
`FIGURE 7 illustrates a block diagram or building blocks for constructing high power
`
`laser diode assemblies.
`
`[0024]
`
`FIGURE 8 shows a platform architecture for different wavelength ranges for an all-
`
`fiber-integrated, high powered, super-continuum light source.
`
`[0025]
`
`FIGURE 9 illustrates one embodiment
`
`for a short-wave infrared super-continuum
`
`light source.
`
`[0026]
`
`FIGURE 10 shows the output spectrum from the SWIR SC laser of FIGURE 9 when
`
`about 10m length of fiber for SC generation is used. This fiber is a single -mode, non-dispersion
`
`shifted fiber that is optimized for operation near 1550nm.
`
`[0027]
`
`FIGURE 11A illustrates a schematic of the experimental set-up for measuring the
`
`diffuse reflectance spectroscopy using the SWIR-SC light source of FIGURES 9 and 10.
`
`[0028]
`
`FIGURE 11B shows exemplary reflectance from a sound enamel region, an enamel
`
`lesion region, and a dentine lesion region. The spectra are normalized to have equal value near
`
`205 Onm.
`
`[0029]
`
`FIGURE 12 illustrates high power SWIR-SC lasers that may generate light between
`
`approximately 1.4-1.8 microns (top) or approximately 2-2.5 microns (bottom).
`
`[0030]
`
`FIGURE 13 schematically shows that the medical measurement device can be part of
`
`a personal or body area network that communicates with another device (e.g., smart phone or tablet)
`
`that communicates with the cloud. The cloud may in turn communicate information with the user,
`
`dental or healthcare providers, or other designated recipients.
`
`DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
`
`[0031]
`
`As required, detailed embodiments of the present disclosure are disclosed herein;
`
`however,
`
`it
`
`is to be understood that
`
`the disclosed embodiments are merely exemplary of the
`
`disclosure that may be embodied in various and alternative forms. The figures are not necessarily to
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`scale; some features may be exaggerated or minimized to show details of particular components.
`
`Therefore, specific structural and functional details disclosed herein are not to be interpreted as
`
`limiting, but merely as a representative basis for teaching one skilled in the art to variously employ
`
`the present disclosure.
`
`[0032]
`
`Near-infrared (NIR) and SWIR light may be preferred for caries detection compared
`
`to visible light imaging because the NIR/SWIR wavelengths generally have lower absorption by
`
`stains and deeper penetration into teeth. Hence, NIR/SWIR light may provide a caries detection
`
`method that can be non-invasive, non-contact and relatively stain insensitive. Broadband light may
`
`provide further advantages because carious regions may demonstrate spectral signatures from water
`
`absorption and the wavelength dependence of porosity in the scattering of light.
`
`[0033]
`
`In general, the near-infrared region of the electromagnetic spectrum covers between
`
`approximately 0.7 microns (700nm) to about 2.5 microns (2500nm). However,
`
`it may also be
`
`advantageous to use just the short-wave infrared between approximately 1.4 microns (1400nm) and
`
`about 2.5 microns (2500nm). One reason for preferring the SWIR over the entire NIR may be to
`
`operate in the so-called "eye safe" window, which corresponds to wavelengths longer than about
`
`1400nm. Therefore, for the remainder of the disclosure the SWIR will be used for illustrative
`
`purposes. However, it should be clear that the discussion that follows could also apply to using the
`
`NIR wavelength range, or other wavelength bands.
`
`[0034]
`
`In particular, wavelengths in the eye safe window may not transmit down to the retina
`
`of the eye, and therefore, these wavelengths may be less likely to create permanent eye damage from
`
`inadvertent exposure. The near-infrared wavelengths have the potential to be dangerous, because the
`
`eye cannot see the wavelengths (as it can in the visible), yet they can penetrate and cause damage to
`
`the eye. Even if a practitioner is not looking directly at the laser beam, the practitioner's eyes may
`
`receive stray light from a reflection or scattering from some surface. Hence, it can always be a good
`
`practice to use eye protection when working around lasers. Since wavelengths longer than about
`
`1400nm are substantially not transmitted to the retina or substantially absorbed in the retina, this
`
`wavelength range is known as the eye safe window. For wavelengths longer than 1400nm, in
`
`general only the cornea of the eye may receive or absorb the light radiation.
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`[0035]
`
`FIGURE 1 illustrates the structure of an exemplary cross-section of a tooth 100. The
`
`tooth 100 has a top layer called the crown 101 and below that a root 102 that reaches well into the
`
`gum 106 and bone 108 of the mouth. The exterior of the crown 101 is an enamel layer 103, and
`
`below the enamel is a layer of dentine 104 that sits atop a layer of cementum 107. Below the dentine
`
`104 is a pulp region 105, which comprises within it blood vessels 109 and nerves 110.
`
`If the light
`
`can penetrate the enamel 103 and dentine 104, then the blood flow and blood constituents may be
`
`measured through the blood vessels in the dental pulp 105. While the amount of blood flow in the
`
`capillaries of the dental pulp 105 may be less than an artery or vein, the smaller blood flow could
`
`still be advantageous for detecting or measuring blood constituents as compared to detection through
`
`the skin if there is less interfering spectral features from the tooth. Although the structure of a molar
`
`tooth is illustrated in FIGURE 1, other types of teeth also have similar structure. For example,
`
`different types of teeth include molars, pre-molars, canine and incisor teeth.
`
`[0036]
`
`As used throughout this document, the term "couple" and or "coupled" refers to any
`
`direct or indirect communication between two or more elements, whether or not those elements are
`
`physically connected to one another. As used throughout this disclosure, the term "spectroscopy"
`
`means that a tissue or sample is inspected by comparing different features, such as wavelength (or
`
`frequency), spatial
`
`location,
`
`transmission, absorption, reflectivity, scattering, refractive index, or
`
`opacity.
`
`In one embodiment, "spectroscopy" may mean that the wavelength of the light source is
`
`varied, and the transmission, absorption, or reflectivity of the tissue or sample is measured as a
`
`function of wavelength.
`
`In another embodiment, "spectroscopy" may mean that the wavelength
`
`dependence of the transmission, absorption or reflectivity is compared between different spatial
`
`locations on a tissue or sample. As an illustration, the "spectroscopy" may be performed by varying
`
`the wavelength of the light source, or by using a broadband light source and analyzing the signal
`
`using a spectrometer, wavemeter, or optical spectrum analyzer.
`
`[0037]
`
`As used throughout this disclosure, the term "fiber laser" refers to a laser or oscillator
`
`that has as an output light or an optical beam, wherein at least a part of the laser comprises an optical
`
`fiber. For instance, the fiber in the "fiber laser" may comprise one of or a combination of a single
`
`mode fiber, a multi-mode fiber, a mid-infrared fiber, a photonic crystal fiber, a doped fiber, a gain
`
`fiber, or, more generally, an approximately cylindrically shaped waveguide or light-pipe.
`
`In one
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`

`embodiment, the gain fiber may be doped with rare earth material, such as ytterbium, erbium, and/or
`
`thulium, for example.
`
`In another embodiment,
`
`the mid-infrared fiber may comprise one or a
`
`combination of fluoride fiber, ZBLAN fiber, chalcogenide fiber, tellurite fiber, or germanium doped
`
`fiber.
`
`In yet another embodiment, the single mode fiber may include standard single-mode fiber,
`
`dispersion shifted fiber, non-zero dispersion shifted fiber, high-nonlinearity fiber, and small core size
`
`fibers.
`
`[0038]
`
`As used throughout
`
`this disclosure,
`
`the term "pump laser" refers to a laser or
`
`oscillator that has as an output light or an optical beam, wherein the output light or optical beam is
`
`coupled to a gain medium to excite the gain medium, which in turn may amplify another input
`
`optical signal or beam.
`
`In one particular example, the gain medium may be a doped fiber, such as a
`
`fiber doped with ytterbium, erbium, and/or thulium.
`
`In one embodiment, the "pump laser" may be a
`
`fiber laser, a solid state laser, a laser involving a nonlinear crystal, an optical parametric oscillator, a
`
`semiconductor laser, or a plurality of semiconductor lasers that may be multiplexed together.
`
`In
`
`another embodiment, the "pump laser" may be coupled to the gain medium by using a fiber coupler,
`
`a dichroic mirror, a multiplexer, a wavelength division multiplexer, a grating, or a fused fiber
`
`coupler.
`
`[0039]
`
`As used
`
`throughout
`
`this
`
`document,
`
`the
`
`term "super-continuum"
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`and or
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`"supercontinuum" and or "SC" refers to a broadband light beam or output that comprises a plurality
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`of wavelengths.
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`In a particular example, the plurality of wavelengths may be adjacent to one-
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`another, so that the spectrum of the light beam or output appears as a continuous band when
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`measured with a spectrometer. In one embodiment, the broadband light beam may have a bandwidth
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`or at
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`least
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`lOnm.
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`In another embodiment,
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`the "super-continuum" may be generated through
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`nonlinear optical
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`interactions in a medium, such as an optical fiber or nonlinear crystal. For
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`example,
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`the "super-continuum" may be generated through one or a combination of nonlinear
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`activities such as four-wave mixing,
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`the Raman effect, modulational
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`instability, and self-phase
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`modulation.
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`[0040]
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`As used throughout this disclosure, the terms "optical light" and or "optical beam"
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`and or "light beam" refer to photons or light transmitted to a particular location in space. The
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`"optical light" and or "optical beam" and or "light beam" may be modulated or unmodulated, which
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`also means that they may or may not contain information.
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`In one embodiment, the "optical light"
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`and or "optical beam" and or "light beam" may originate from a fiber, a fiber laser, a laser, a light
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`emitting diode, a lamp, a pump laser, or a light source.
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`TRANSMISSION OR REFLECTION THROUGH TEETH
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`[0041]
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`The transmission, absorption and reflection from teeth has been studied in the near
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`infrared, and, although there are some features,
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`the enamel and dentine appear to be fairly
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`transparent in the near infrared (particularly SWIR wavelengths between about 1400 and 2500nm).
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`For example, the absorption or extinction ratio for light transmission has been studied. FIGURE 2A
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`illustrates the attenuation coefficient 200 for dental enamel 201 (filled circles) and the absorption
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`coefficient of water 202 (open circles) versus wavelength. Near-infrared light may penetrate much
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`further without scattering through all the tooth enamel, due to the reduced scattering coefficient in
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`normal enamel.
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`Scattering in enamel may be fairly strong in the visible, but decreases as
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`approximately 1/(wavelength)
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`[i.e.,
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`inverse of the cube of the wavelength] with increasing
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`wavelength to a value of only 2-3 cm-1 at 1310nm and 1550nm in the near infrared. Therefore,
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`enamel may be virtually transparent
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`in the near infrared with optical attenuation 1-2 orders of
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`magnitude less than in the visible range.
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`[0042]
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`As another example, FIGURE 2B illustrates the absorption spectrum 250 of intact
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`enamel 25 1 (dashed line) and dentine 252 (solid line) in the wavelength range of approximately 1.2
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`to 2.4 microns.
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`In the near infrared there are two absorption bands in the areas of about 1.5 and 2
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`microns. The band with a peak around 1.57 microns may be attributed to the overtone of valent
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`vibration of water present in both enamel and dentine.
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`In this band, the absorption is greater for
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`dentine than for enamel, which may be related to the large water content in this tissue. In the region
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`of 2 microns, dentine may have two absorption bands, and enamel one. The band with a maximum
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`near 2.1 microns may belong to the overtone of vibration of PO hydroxyapatite groups, which is the
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`main substance of both enamel and dentine. Moreover, the band with a peak near 1.96 microns in
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`dentine may correspond to water absorption (dentine may contain substantially higher water than
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`enamel).
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`[0043]
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`In addition to the absorption coefficient, the reflectance from intact teeth and teeth
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`with dental caries (e.g., cavities) has been studied.
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`In one embodiment, FIGURE 3 shows the near
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`infrared spectral reflectance 300 over the wavelength range of approximately 800nm to 2500nm
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`from an occlusal (e.g., top) tooth surface 304. The curve with black diamonds 301 corresponds to
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`the reflectance from a sound, intact tooth section. The curve with asterisks (*) 302 corresponds to a
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`tooth section with an enamel lesion. The curve with circles 303 corresponds to a tooth section with a
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`dentine lesion. Thus, when there is a lesion, more scattering occurs and there may be an increase in
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`the reflected light.
`
`[0044]
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`For wavelengths shorter than approximately 1400nm, the shapes of the spectra remain
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`similar, but the amplitude of the reflection changes with lesions. Between approximately 1400nm
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`and 2500nm, an intact tooth 301 has low reflectance (e.g., high transmission), and the reflectance
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`appears to be more or less independent of wavelength. On the other hand, in the presence of lesions
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`302 and 303, there is increased scattering, and the scattering loss may be wavelength dependent. For
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`example, the scattering loss may decrease as the inverse of some power of wavelength, such as
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`1/(wavelength) — so, the scattering loss decreases with longer wavelengths. When there is a lesion
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`in the dentine 303, more water can accumulate in the area, so there is also increased water
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`absorption. For example, the dips near 1450nm and 1900nm may correspond to water absorption,
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`and the reflectance dips are particularly pronounced in the dentine lesion 303.
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`[0045]
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`FIGURE 3 may point
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`to several novel
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`techniques
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`for early detection and
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`quantification of carious regions. One method may be to use a relatively narrow wavelength range
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`(for example, from a laser diode or super-luminescent laser diode) in the wavelength window below
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`1400nm.
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`In one embodiment, wavelengths in the vicinity of 1310nm may be used, which is a
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`standard telecommunications wavelength where appropriate light sources are available. Also, it may
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`be advantageous to use a super-luminescent laser diode rather than a laser diode, because the broader
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`bandwidth may avoid the production of laser speckle that can produce interference patterns due to
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`light's scattering after striking irregular surfaces. As FIGURE 3 shows, the amplitude of the
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`reflected light (which may also be proportional to the inverse of the transmission) may increase with
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`dental caries. Hence, comparing the reflected light from a known intact region with a suspect region
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`may help identify carious regions. However, one difficulty with using a relatively narrow
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`wavelength range and