EP1392158A1 - Method and device for the acquisition and treatment of dental images - Google Patents
Method and device for the acquisition and treatment of dental imagesInfo
- Publication number
- EP1392158A1 EP1392158A1 EP02740822A EP02740822A EP1392158A1 EP 1392158 A1 EP1392158 A1 EP 1392158A1 EP 02740822 A EP02740822 A EP 02740822A EP 02740822 A EP02740822 A EP 02740822A EP 1392158 A1 EP1392158 A1 EP 1392158A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- tooth
- images
- wavelength
- fluorescence
- area
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
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- 238000012545 processing Methods 0.000 claims abstract description 13
- 238000000295 emission spectrum Methods 0.000 claims abstract description 10
- 230000005284 excitation Effects 0.000 claims abstract description 10
- 238000001914 filtration Methods 0.000 claims description 20
- 238000002073 fluorescence micrograph Methods 0.000 claims description 12
- 230000010365 information processing Effects 0.000 claims description 8
- 238000005259 measurement Methods 0.000 claims description 8
- 230000005540 biological transmission Effects 0.000 claims description 7
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 7
- 239000011707 mineral Substances 0.000 claims description 7
- 230000003287 optical effect Effects 0.000 claims description 7
- 238000005286 illumination Methods 0.000 claims description 5
- 108091008695 photoreceptors Proteins 0.000 claims description 5
- 239000011521 glass Substances 0.000 claims description 4
- 239000004973 liquid crystal related substance Substances 0.000 claims description 4
- 238000004020 luminiscence type Methods 0.000 claims description 4
- 239000000835 fiber Substances 0.000 claims description 2
- 238000001228 spectrum Methods 0.000 claims 1
- 208000002925 dental caries Diseases 0.000 abstract description 13
- 238000001514 detection method Methods 0.000 description 10
- 238000011161 development Methods 0.000 description 6
- 239000013307 optical fiber Substances 0.000 description 6
- 238000009825 accumulation Methods 0.000 description 4
- 230000004298 light response Effects 0.000 description 4
- 239000013078 crystal Substances 0.000 description 3
- 210000003298 dental enamel Anatomy 0.000 description 3
- 210000004268 dentin Anatomy 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 238000005115 demineralization Methods 0.000 description 2
- 230000002328 demineralizing effect Effects 0.000 description 2
- 229910052588 hydroxylapatite Inorganic materials 0.000 description 2
- 208000015181 infectious disease Diseases 0.000 description 2
- 230000003902 lesion Effects 0.000 description 2
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- 238000012986 modification Methods 0.000 description 2
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- XYJRXVWERLGGKC-UHFFFAOYSA-D pentacalcium;hydroxide;triphosphate Chemical compound [OH-].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O XYJRXVWERLGGKC-UHFFFAOYSA-D 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
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- 238000001429 visible spectrum Methods 0.000 description 2
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- 241000894006 Bacteria Species 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- 208000035473 Communicable disease Diseases 0.000 description 1
- 208000037273 Pathologic Processes Diseases 0.000 description 1
- 208000003251 Pruritus Diseases 0.000 description 1
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- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
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Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
- A61B5/0082—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence adapted for particular medical purposes
- A61B5/0088—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence adapted for particular medical purposes for oral or dental tissue
Definitions
- the present invention relates to a method and a device for acquiring and processing images of a tooth, for the detection of dental caries.
- a disadvantage of this known technique is that by using a monochromatic lighting light whose wavelength is between 350 and 600 nm approximately, it is not known by which component of the tooth the light response to the illumination of the tooth is produced, which is a factor of uncertainty in the results since, in particular, the light response of the organic part of the tooth varies as a function of a certain number of factors such as the quality of tooth brushing, the patient's eating habits, etc.
- Another drawback of this known technique relates to the measurement on two wavelengths only of the integrated light response of the illuminated area of the tooth, this punctual measurement not providing sufficient information on the state of the examined area of the tooth, this which is another factor of uncertainty about the quality of the results.
- Another disadvantage is that, if the examined area of the tooth is illuminated by monochromatic light whose wavelength is less than about 400 nm and is therefore outside the visible spectrum, the practitioner does not know exactly which area the tooth is lit and is likely to have a cavity. This leads in practice to limit the use of this technique to visible light lighting, which is the cause of imprecise or erroneous results on the measurements, for reasons which will be explained in more detail below.
- the invention particularly relates to a method and a device of the aforementioned type, which do not have the aforementioned drawbacks of the known technique.
- It also relates to a method and a device of this type, which allow reliable and precise detection of dental caries, even at a stage early in their development, and which also allow precise visualization and localization of the examined area of the tooth.
- the invention provides a method of acquiring and processing images of a tooth, consisting in illuminating an area of a tooth in monochromatic light and in capturing the luminescence emitted by the illuminated area of the tooth, characterized in that it also consists of: - to be used to illuminate said zone of the tooth with monochromatic light whose wavelength is chosen to excite a fluorescence emission by the mineral part of the tooth,
- the detection of possible caries is based on the detection of the fluorescence emitted in two wavelength bands by the mineral component of a tooth, which is formed of hydroxylapatite single crystals.
- Dental caries is a progressive and localized demineralization of the hard tissues of the tooth surface, caused by the acids produced by bacteria and resulting in a reduction in size of the hydroxylapatite crystals and in a modification of the photo-physical properties of the dental surface.
- the mineral component of the tooth In response to light excitation at an appropriate wavelength, the mineral component of the tooth emits fluorescence which is shifted towards red in the case of tooth decay.
- the point-by-point image of the report of the spectral intensity measurements makes it possible to eliminate the influence of the shape of the surface of the illuminated area of the tooth and therefore to overcome variations due to the presence of grooves or wells in the dental surface, the inclination of this surface relative to the optical axis of the detection device, and the non-uniformity of the lighting of the examined area of the tooth.
- the method according to the invention thus allows reliable and precise detection of dental caries, even at an early stage of their development. It also makes it possible to precisely control the effectiveness of a surgical intervention to remove demineralized dental material, so as to achieve the complete elimination of the decayed parts without altering the healthy parts of the tooth.
- the wavelength of the lighting light is between approximately 300 and 370 nm and the spectral intensity of the fluorescence emitted is measured in a band of wavelengths which s extends between the excitation wavelength and a wavelength between 450 and 600 nm approximately and in a wavelength band which extends from 550-600 to 750-800 nm approximately.
- the method consists in illuminating said area of the tooth with alternating light pulses at the aforementioned wavelength and at a wavelength of the visible spectrum, to be taken with the video means images of said area illuminated successively at these two wavelengths and to transmit them to image processing and display means.
- this method also consists in accumulating images taken at these two wavelengths before processing them and displaying an image of the fluorescence emitted by the illuminated area of the tooth and an image of this area illuminated in visible light.
- This dual display allows the practitioner to accurately view and locate the examined area of the tooth.
- the same laser generator can be used to produce fluorescence excitation pulses and visible light illumination pulses, these pulses having a duration of between several microseconds and a nanosecond or less for example, the laser generator can also be used to produce synchronization pulses, for example in infrared.
- a laser generator of the Nd: YAG-Qs itch type which produces pulses of very short duration at wavelengths of 1064 nm for synchronization, of 532 ' nm (second harmonic) for lighting visible and 355 nm (third harmonic) for excitation of fluorescence.
- the invention also provides a device for carrying out the method described above, this device comprising a monochromatic light source, optical means for lighting an area of the tooth with the light emitted by said source and for taking up light from the tooth, means for transmitting the light taken up to spectral filtering means, photoreceptors capturing the light leaving the spectral filtering means and processing means receiving the output signals from the photoreceptors, this device being characterized in that the source emits on a wavelength chosen to excite a fluorescence emission by the mineral part of the tooth, in that it comprises video means for taking images of the illuminated area of the tooth , associated with shutter or time gate means for alternately taking pictures of fluorescence of the tooth in bands of wavelengths in the parts high energy and low energy respectively of the emission spectrum and images of the tooth illuminated in visible light, and in that the information processing means are provided for reporting, at each point of the image, the intensities measured in said wavelength bands of the emission spectrum.
- the spectral filtering means used include, for example, interchangeable color filters,
- the transmission means comprise a fiber optic image guide or a glass rod horoscope having a transverse gradient of refractive index.
- FIG. 1 schematically represents the essential components of the device according to the invention
- FIG. 3 schematically represents the fluorescence spectra of different parts of a tooth and the wavelength bands used for measuring the spectral intensity of the fluorescence
- Figure 4 is a graph showing 'the variations in the ratios of the measured fluorescence intensities in both wavelength bands wave for different parts of a tooth.
- the method and the device according to the invention are based on the illumination of an area 12 of a tooth 10 by a beam 14 of monochromatic ultraviolet light exciting a fluorescence emission by the mineral part of the tooth and on the detection of fluorescence images of tooth zone 12 in two bands of different wavelengths, in the ' high energy part and in the low energy part of the emission spectrum, the point-to-point ratio of spectral intensity measurements fluorescence in these two bands making it possible to determine whether or not the zone 12 examined of the tooth has a cavity.
- caries is an infectious disease the lesions of which are signs and symptoms which appear long after the primary infection and the initiation of the pathological process, when prevention has not been made or has failed, the lesions being due to physicochemical phenomena according to which the acids produced by the metabolism of the bacterial plaque cause a demineralization of the surface of the calcified tissues of the tooth.
- the detection of dental pathologies is essentially based on direct and tactile visual evaluations of a practitioner or on X-ray radiographs. The ionizing nature of X-ray radiographs does not allow them to be used repeatedly and routinely for cavity prevention and care control.
- the visual assessment or tactile by a practitioner does not allow to detect caries at an early stage of their development where a remineralization of the attacked areas by the precipitation in situ of calcium and phosphate ions would be possible and would avoid a curative surgical intervention.
- the device according to the invention precisely allows this early detection, in a reliable and independent manner from individuals.
- the device according to the invention shown diagrammatically in FIG. 1, comprises a laser generator 16, for example of the Nd: YAG "Q-switch" type which produces pulses at different wavelengths, for example 1064 nm, 532 nm and 355 nm with a repetition frequency of 12 kHz and which is associated with means 18 of spectral filtering and a lens 20 for focusing on the input of an optical fiber 22 for transmitting pulses 14 which, at the output of the optical fiber 22, pass through an objective 24 and are reflected by a mirror 26 towards the examined area 12 of the tooth 10.
- a laser generator 16 for example of the Nd: YAG "Q-switch" type which produces pulses at different wavelengths, for example 1064 nm, 532 nm and 355 nm with a repetition frequency of 12 kHz and which is associated with means 18 of spectral filtering and a lens 20 for focusing on the
- the spectral filtering means 18 comprise for example two interchangeable color filters, one of which transmits the wavelengths of 355 n and stops the wavelengths of 532 nm and the other of which, conversely, transmits the lengths of 532 nm wave and stops the wavelengths of 355 nm.
- These two filters are mounted on a support of the electromechanical type for example, which makes it possible to place them in turn on the output of the laser generator 16.
- the means 24, 26 for lighting the zone 12 of the tooth also form means for resuming the emitted fluorescence 28 which is focused on the input of optical transmission means 30 such as for example an image guide formed by a bundle of optical fibers.
- the means 22, 24, 26, 30 are advantageously combined into a single-piece assembly which the practitioner can hold with one hand and the end of which he can introduce into the mouth of a patient for examining the patient's teeth.
- the light beam 28 leaving the transmission means 30 is directed towards video acquisition means 32, through a lens 34, means 36 for spectral filtering and means 38 forming a shutter or time gate.
- the spectral filtering means 36 comprise two color filters of the bandpass type, one of which transmits the wavelengths between the excitation wavelength and approximately 450-600 nm and the other of which transmits those between 550-600 and 750-800 nm approximately.
- the means 38 forming a shutter or time gate are controlled to allow the video acquisition means 32 to pass either the wavelengths of the high energy band, or those of the low energy band, or even those corresponding to the pulses at the wavelength of 532 nm which are reflected and scattered by the examined area 12 of the tooth.
- the colored filters of the means 36 are mounted on the same support of the electromechanical type which interposes them in turn on the optical axis of the light leaving the transmission means 30 and which places none on this axis during the transmission of the light corresponding to the reflection and diffusion of the pulses at the wavelength of 532 nm.
- the means 38 forming a shutter or time gate are formed for example by an image intensifier with voltage modulation on the acceleration grid, this shutter remaining open only for the passage of fluorescence and visible light pulses coming from tooth 10 When this shutter is closed, it blocks all light that does not carry information on the properties of the tooth surface.
- the image acquisition means 32 are preferably formed by a black and white matrix camera with photoreceptors of the CCD type, the output of which is connected to the input of information processing means 40, such as a microphone. - PC or similar type computer.
- Synchronization means 42 are associated with the information processing means 40, the generator 16, the filtering means 18 and 36, the shutter means 38 and the video acquisition means 32. These synchronization means 42 receive the synchronization pulses produced at the wavelength of 1064 nm by the laser generator 16.
- the means 22, 24, 26, 30 form a probe which the practitioner can hold and orient towards the zone 12 to be examined on the tooth 10.
- the pulses emitted by the laser generator at the lengths of waves of 532 and 355 nm are transmitted alternately by the means of spectral filtering 18 and the optical fiber 22, towards the zone 12 of the tooth.
- the pulses at 355 nm are absorbed by the components of the tissues of the dental surface, which de-excite by emitting fluorescence for a very short time, typically a few nanoseconds.
- the pulses of visible light at the wavelength of 532 nm are reflected and diffused by the tooth surface.
- the light pulses from the tooth are picked up by the optical means 24, 26, and transmitted by the means 30 to the spectral filtering means 36 associated with the video acquisition means 32 by the means 38 forming a shutter or time gate.
- the video images acquired by the means 32 are transmitted to the information processing means 40 and are displayed on appropriate means, in particular on a display screen.
- the processing carried out by the means 40 comprises at 78 a storage of fluorescence images in high energy band 80 and a storage of fluorescence images in low energy band 82, as well as a processing 84 of fluorescence images and a storage 86 of the images in visible light, then in 88 a display 90 of the resulting images of fluorescence and of the resulting images 92 in visible light.
- the device operating steps can be swapped.
- the processing of the fluorescence images which is carried out at 84 consists in measuring the spectral intensity of the fluorescence emitted in the aforementioned high and low energy bands, making their report and comparing it with predetermined values.
- the processing carried out on the fluorescence images in the passbands E and F consists in measuring the intensity of the energy of the fluorescence in these two bands and in reporting them.
- Three examples of variations of this ratio are shown diagrammatically in FIG. 4, as a function of a dimension of space represented on the abscissa and measured on the tooth.
- the ratio of fluorescence energy in the high energy band / fluorescence energy in the low energy band of the emission spectrum can vary between values which are between 2 and 3 approximately for the enamel, which are substantially equal. to 4 for dentin and which are between 0.5 and 1 for the decayed parts.
- the ratio of these intensities to the fluorescence images makes it possible to overcome the shape of the examined surface of the tooth, that is to say the presence of grooves or wells, as well as the inclination of this. surface relative to the axis lighting optics and non-uniformity of lighting.
- the display of fluorescence images and visible light images on a display screen allows the practitioner to precisely locate the decayed area of a tooth. It is also possible to represent the variations in the ratios of the fluorescence energies in false colors, so that, for example ', the decayed areas appear in red and are clearly visible to the practitioner.
- the image transmission means 30 which, in a preferred embodiment of the invention, comprise a flexible image guide having for example a millimeter in diameter and a length of about one meter and which may include thirty thousand individual optical fibers can be replaced by a system of mirrors and lenses or by a horoscope based on the use of a glass rod with a transverse gradient of refractive index.
- the spectral filtering means can consist of an acousto-optical filter, a set of dichroic mirrors, a liquid crystal filter, etc.
- the video acquisition means 32 which are formed by a matrix of CCD sensors in the preferred embodiment of the invention, can be replaced by arrays of photodiodes, vidicon, CMOS sensors, with an analog video output or digital, monochrome or color.
- the means 22 for transmitting the lighting light may comprise several optical fibers, which are arranged at their ends for an effective uniform injection of the intensity of the laser beam produced by the generator 16 and at the other end for uniform illumination of area 12 of the tooth.
- optical lighting and recovery means 24, 26 can also use optical lighting and recovery means 24, 26 different from those which have been described and shown.
Abstract
A method and device for the acquisition and treatment of dental images, comprising means for the excitation of a region (12) of a tooth using monochromatic ultraviolet light pulses alternating with visible light pulses, video means (32, 34, 36, 38) for taking images of the fluorescence emitted by the tooth in two high and low energy wavelength bands of the emission spectrum and means (40) for processing the information in order to compare the spectral intensities of the fluorescence in said two wavelength bands and to ascertain the presence or absence of caries in the examined region (12) of the tooth.
Description
Procédé et dispositif d'acquisition et de traitement d'images d'une dent. Method and device for acquiring and processing images of a tooth.
La présente invention concerne un procédé et un dispositif d'acquisition et de traitement d'images d'une dent, en vue de la détection de caries dentaires.The present invention relates to a method and a device for acquiring and processing images of a tooth, for the detection of dental caries.
On a déjà proposé, notamment dans les documents US- A-4 290 443 et 4 479 499, un procédé de détection des caries dentaires dans la bouche d'un patient, qui consiste à éclairer une zone d'une dent par une lumière monochromatique, à mesurer l'intensité de la luminescence émise par la dent sur deux longueurs d'onde prédéterminées, l'une pour laquelle les zones cariées et les zones non cariées de la dent ont sensiblement la même réponse lumineuse à l'excitation par la lumière d'éclairage, et -l'autre pour laquelle 1 ' intensité de la luminescence émise est supérieure dans le cas d'une zone cariée, ce procédé consistant finalement à comparer les mesures faites à ces deux longueurs d'onde pour une zone que l'on sait non cariée et pour la zone examinée de la dent.We have already proposed, in particular in documents US-A-4 290 443 and 4 479 499, a method of detecting dental caries in the mouth of a patient, which consists in illuminating an area of a tooth with monochromatic light , to measure the intensity of the luminescence emitted by the tooth over two predetermined wavelengths, one for which the decayed areas and the non-decayed areas of the tooth have substantially the same light response to excitation by light lighting, and the other for which the intensity of the emitted luminescence is greater in the case of a decayed area, this method finally consisting in comparing the measurements made at these two wavelengths for an area that the 'we know not decayed and for the examined area of the tooth.
Il a été proposé notamment d'éclairer la dent par une lumière monochromatique dont la longueur d'onde est comprise entre 350 et 600 nm environ, et de mesurer l'intensité de la lumière émise par la dent à une première longueur d'onde comprise entre 440 et 470 nm et à une seconde longueur d'onde comprise entre 560 et 640 nm.It has been proposed in particular to illuminate the tooth with monochromatic light whose wavelength is between 350 and 600 nm approximately, and to measure the intensity of the light emitted by the tooth at a first wavelength included between 440 and 470 nm and at a second wavelength between 560 and 640 nm.
Un inconvénient de cette technique connue est qu ' en utilisant une lumière monochromatique d'éclairage dont la longueur d'onde est comprise entre 350 et 600 nm environ, on ne sait pas par quel composant de la dent
est produite la réponse lumineuse à l'éclairage de la dent, ce qui est un facteur d'incertitude sur les résultats puisque, notamment, la réponse lumineuse de la partie organique de la dent varie en fonction d'un certain nombre de facteurs tels que la qualité du brossage des dents, les habitudes alimentaires du patient, etc.A disadvantage of this known technique is that by using a monochromatic lighting light whose wavelength is between 350 and 600 nm approximately, it is not known by which component of the tooth the light response to the illumination of the tooth is produced, which is a factor of uncertainty in the results since, in particular, the light response of the organic part of the tooth varies as a function of a certain number of factors such as the quality of tooth brushing, the patient's eating habits, etc.
Un autre inconvénient de cette technique connue concerne la mesure sur deux longueurs d'onde uniquement de la réponse lumineuse intégrée de la zone éclairée de la dent, cette mesure ponctuelle ne renseignant pas suffisamment sur l'état de la zone examinée de la dent, ce qui est un autre facteur d'incertitude sur la qualité des résultats. Un autre inconvénient est que, si la zone examinée de la dent est éclairée par une lumière monochromatique dont la longueur d'onde est inférieure à 400 nm environ et se trouve donc en dehors du spectre visible, le praticien ne sait pas exactement quelle zone de la dent est éclairée et est susceptible de présenter une carie. Cela conduit en pratique à limiter l'utilisation de cette technique à un éclairage en lumière visible, ce qui est la cause de résultats imprécis ou erronés sur les mesures, pour des raisons qui seront expliquées plus en détail ci-dessous.Another drawback of this known technique relates to the measurement on two wavelengths only of the integrated light response of the illuminated area of the tooth, this punctual measurement not providing sufficient information on the state of the examined area of the tooth, this which is another factor of uncertainty about the quality of the results. Another disadvantage is that, if the examined area of the tooth is illuminated by monochromatic light whose wavelength is less than about 400 nm and is therefore outside the visible spectrum, the practitioner does not know exactly which area the tooth is lit and is likely to have a cavity. This leads in practice to limit the use of this technique to visible light lighting, which is the cause of imprecise or erroneous results on the measurements, for reasons which will be explained in more detail below.
L'invention a notamment pour objet un procédé et un dispositif du type précité, qui ne présentent pas les inconvénients précités de la technique connue.The invention particularly relates to a method and a device of the aforementioned type, which do not have the aforementioned drawbacks of the known technique.
Elle a également pour objet un procédé et un dispositif de ce type, qui permettent une détection fiable et précise des caries dentaires, même à un stade
précoce de leur développement, et qui permettent également une visualisation et une localisation précise de la zone examinée de la dent .It also relates to a method and a device of this type, which allow reliable and precise detection of dental caries, even at a stage early in their development, and which also allow precise visualization and localization of the examined area of the tooth.
L'invention propose à cet effet un procédé d'acquisition et de traitement d'images d'une dent, consistant à éclairer une zone d'une dent en lumière monochromatique et à capter la luminescence émise par la zone éclairée de la dent, caractérisé en ce qu'il consiste également: - à utiliser pour éclairer ladite zone de la dent une lumière monochromatique dont la longueur d'onde est choisie pour exciter une émission de fluorescence par la partie minérale de la dent,To this end, the invention provides a method of acquiring and processing images of a tooth, consisting in illuminating an area of a tooth in monochromatic light and in capturing the luminescence emitted by the illuminated area of the tooth, characterized in that it also consists of: - to be used to illuminate said zone of the tooth with monochromatic light whose wavelength is chosen to excite a fluorescence emission by the mineral part of the tooth,
- à prendre avec des moyens vidéo des images de la zone éclairée de la dent dans deux bandes de longueurs d'onde dont l'une est dans la partie haute énergie et 1 ' autre dans la partie basse énergie du spectre d' émission,- to take with video means images of the illuminated area of the tooth in two wavelength bands, one of which is in the high energy part and the other in the low energy part of the emission spectrum,
- à mesurer l'intensité spectrale en chaque point de l'image de la fluorescence émise dans ces deux bandes de longueurs d'onde,to measure the spectral intensity at each point of the image of the fluorescence emitted in these two wavelength bands,
- à faire le rapport des intensités mesurées en chaque point dans les deux bandes précitées de longueurs d'onde et à comparer ce rapport à des valeurs prédéterminées.- making the ratio of the intensities measured at each point in the two aforementioned bands of wavelengths and comparing this ratio with predetermined values.
La détection de caries éventuelles est basée sur la détection de la fluorescence émise dans deux bandes de longueurs d'onde par le composant minéral d'une dent, qui est formé de monocristaux de hydroxylapatite . Les caries dentaires sont des déminéralisations progressives et localisées des tissus durs de la surface dentaire, provoquées par les acides produits
par des bactéries et se traduisant par une réduction de taille des cristaux de hydroxylapatite et par une modification des propriétés photo-physiques de la surface dentaire. En réponse à une excitation lumineuse à une longueur d'onde appropriée, le composant minéral de la dent émet une fluorescence qui est décalée vers le rouge dans le cas d'une carie dentaire. En mesurant 1 ' intensité spectrale de la fluorescence' émise dans deux bandes de longueur d'onde, dont l'une est dans la partie haute énergie et l'autre dans la partie basse énergie du spectre d'émission, et en faisant le rapport de ces deux mesures, on obtient des valeurs qui sont égales à 2-3 environ pour l'émail, à 4 environ pour la dentine et 0,5-1 environ pour une carie, ces valeurs étant indépendantes du stade de développement de la carie et de la présence de matière organique coagulée.The detection of possible caries is based on the detection of the fluorescence emitted in two wavelength bands by the mineral component of a tooth, which is formed of hydroxylapatite single crystals. Dental caries is a progressive and localized demineralization of the hard tissues of the tooth surface, caused by the acids produced by bacteria and resulting in a reduction in size of the hydroxylapatite crystals and in a modification of the photo-physical properties of the dental surface. In response to light excitation at an appropriate wavelength, the mineral component of the tooth emits fluorescence which is shifted towards red in the case of tooth decay. By measuring the spectral intensity of the fluorescence emitted in two wavelength bands, one of which is in the high energy part and the other in the low energy part of the emission spectrum, and making the report from these two measurements, values are obtained which are equal to approximately 2-3 for the enamel, to approximately 4 for dentin and approximately 0.5-1 for caries, these values being independent of the stage of caries development and the presence of coagulated organic matter.
De plus, l'image point par point du rapport des mesures d'intensité spectrale permet d'éliminer l'influence de la forme de la surface de la zone éclairée de la dent et donc de s'affranchir des variations dues à la présence de sillons ou de puits dans la surface dentaire, de l'inclinaison de cette surface par rapport à l'axe optique du dispositif de détection, et de la non-uniformité de l'éclairage de la zone examinée de la dent.In addition, the point-by-point image of the report of the spectral intensity measurements makes it possible to eliminate the influence of the shape of the surface of the illuminated area of the tooth and therefore to overcome variations due to the presence of grooves or wells in the dental surface, the inclination of this surface relative to the optical axis of the detection device, and the non-uniformity of the lighting of the examined area of the tooth.
De façon globale, le procédé selon l'invention permet ainsi une détection fiable et précise des caries dentaires, même à un stade précoce de leur développement. Il permet également de contrôler avec précision l'efficacité d'une intervention chirurgicale d'enlèvement de matière dentaire déminéralisée, de
façon à parvenir à l'élimination complète des parties cariées sans altérer les parties saines de la dent.Overall, the method according to the invention thus allows reliable and precise detection of dental caries, even at an early stage of their development. It also makes it possible to precisely control the effectiveness of a surgical intervention to remove demineralized dental material, so as to achieve the complete elimination of the decayed parts without altering the healthy parts of the tooth.
Selon d'autres caractéristiques de l'invention, la longueur d'onde de la lumière d'éclairage est comprise entre 300 et 370 nm environ et l'intensité spectrale de la fluorescence émise est mesurée dans une bande de longueurs d'onde qui s'étend entre la longueur d'onde d'excitation et une longueur d'onde comprise entre 450 et 600 nm environ et dans une bande de longueurs d'onde qui s'étend de 550-600 à 750-800 nm environ.According to other characteristics of the invention, the wavelength of the lighting light is between approximately 300 and 370 nm and the spectral intensity of the fluorescence emitted is measured in a band of wavelengths which s extends between the excitation wavelength and a wavelength between 450 and 600 nm approximately and in a wavelength band which extends from 550-600 to 750-800 nm approximately.
La sensibilité et la précision de la détection des caries dentaires sont alors maximales.The sensitivity and precision of the detection of dental caries are then maximum.
Selon une autre caractéristique de l'invention, le procédé consiste à éclairer ladite zone de la dent avec une alternance d'impulsions lumineuses à la longueur d'onde précitée et à une longueur d'onde du spectre visible, à prendre avec les moyens vidéo des images de ladite zone éclairée successivement à ces deux longueurs d'onde et à les transmettre à des moyens de traitement d'image et d'affichage.According to another characteristic of the invention, the method consists in illuminating said area of the tooth with alternating light pulses at the aforementioned wavelength and at a wavelength of the visible spectrum, to be taken with the video means images of said area illuminated successively at these two wavelengths and to transmit them to image processing and display means.
Avantageusement, ce procédé consiste également à accumuler des images prises à ces deux longueurs d'onde avant de les traiter et d'afficher une image de la fluorescence émise par la zone éclairée de la dent et une image de cette zone éclairée en lumière visible.Advantageously, this method also consists in accumulating images taken at these two wavelengths before processing them and displaying an image of the fluorescence emitted by the illuminated area of the tooth and an image of this area illuminated in visible light.
Ce double affichage permet au praticien de visualiser et de localiser avec précision la zone examinée de la dent .This dual display allows the practitioner to accurately view and locate the examined area of the tooth.
Avantageusement, on peut utiliser un même générateur laser pour produire des impulsions d'excitation de la fluorescence et des impulsions d'éclairage en lumière visible, ces impulsions ayant
une durée comprise entre plusieurs microsecondes et une nanoseconde ou moins par exemple, le générateur laser pouvant également être utilisé pour produire des impulsions de synchronisation, par exemple en infrarouge. On peut notamment utiliser un générateur laser du type Nd : YAG-Q-s itch qui produit des impulsions de durée très courte à des longueurs d'onde de 1064 nm pour la synchronisation, de 532 'nm (deuxième harmonique) pour 1 ' éclairage en lumière visible et de 355 nm (troisième harmonique) pour l'excitation de fluorescence .Advantageously, the same laser generator can be used to produce fluorescence excitation pulses and visible light illumination pulses, these pulses having a duration of between several microseconds and a nanosecond or less for example, the laser generator can also be used to produce synchronization pulses, for example in infrared. One can in particular use a laser generator of the Nd: YAG-Qs itch type which produces pulses of very short duration at wavelengths of 1064 nm for synchronization, of 532 ' nm (second harmonic) for lighting visible and 355 nm (third harmonic) for excitation of fluorescence.
L'invention propose également un dispositif pour l'exécution du procédé décrit ci-dessus, ce dispositif comprenant une source de lumière monochromatique, des moyens optiques d'éclairage d'une zone de la dent par la lumière émise par ladite source et de reprise de la lumière en provenance de la dent, des moyens de transmission de la lumière reprise à des moyens de filtrage spectral, des photorécepteurs captant la lumière sortant des moyens de filtrage spectral et des moyens de traitement recevant les signaux de sortie des photorécepteurs, ce dispositif étant caractérisé en ce que la source émet sur une longueur d'onde choisie pour exciter une émission de fluorescence par la partie minérale de la dent, en ce qu'il comprend des moyens vidéo de prise d'images de la zone éclairée de la dent, associés à des moyens d'obturation ou de porte temporelle pour prendre en alternance des images de fluorescence de la dent dans des bandes de longueurs d'onde dans les parties haute énergie et basse énergie respectivement du spectre d'émission et des images de la dent éclairée en lumière visible, et en ce que les
moyens de traitement de l'information sont prévus pour effectuer le rapport, en chaque point de l'image, des intensités mesurées dans lesdites bandes de longueurs d'onde du spectre d'émission. Les moyens de filtrage spectral utilisés comprennent par exemple des filtres colorés interchangeables, ou un filtre acousto-optique ou à cristaux liquides, ou un jeu de miroirs dichroïques .The invention also provides a device for carrying out the method described above, this device comprising a monochromatic light source, optical means for lighting an area of the tooth with the light emitted by said source and for taking up light from the tooth, means for transmitting the light taken up to spectral filtering means, photoreceptors capturing the light leaving the spectral filtering means and processing means receiving the output signals from the photoreceptors, this device being characterized in that the source emits on a wavelength chosen to excite a fluorescence emission by the mineral part of the tooth, in that it comprises video means for taking images of the illuminated area of the tooth , associated with shutter or time gate means for alternately taking pictures of fluorescence of the tooth in bands of wavelengths in the parts high energy and low energy respectively of the emission spectrum and images of the tooth illuminated in visible light, and in that the information processing means are provided for reporting, at each point of the image, the intensities measured in said wavelength bands of the emission spectrum. The spectral filtering means used include, for example, interchangeable color filters, or an acousto-optical or liquid crystal filter, or a set of dichroic mirrors.
Avantageusement, les moyens de transmission comprennent un guide d'images à fibres optiques ou un horoscope à barreau de verre ayant un gradient transversal d'indice de réfraction.Advantageously, the transmission means comprise a fiber optic image guide or a glass rod horoscope having a transverse gradient of refractive index.
L'invention sera mieux comprise et d'autres caractéristiques, détails et avantages de celle-ci apparaîtront plus clairement à la lecture de la description qui suit, faite à titre d'exemple en référence aux dessins annexés dans lesquels : la figure 1 représente schématiquement les composants essentiels du dispositif selon l'inventionThe invention will be better understood and other characteristics, details and advantages thereof will appear more clearly on reading the description which follows, given by way of example with reference to the accompanying drawings in which: FIG. 1 schematically represents the essential components of the device according to the invention
- la figure 2 illustre le fonctionnement dans le temps de ce dispositif ; la figure 3 représente schématiquement les spectres de fluorescence de différentes parties d'une dent et les bandes de longueur d'onde utilisées pour la mesure de 1 ' intensité spectrale de la fluorescence ; et la figure 4 est un graphe représentant ' les variations des rapports des intensités mesurées de fluorescence dans les deux bandes de longueur d'onde pour différentes parties d'une dent.
Le procédé et le dispositif selon l'invention sont basés sur l'éclairage d'une zone 12 d'une dent 10 par un faisceau 14 de lumière monochromatique ultraviolette excitant une émission de fluorescence par la partie minérale de la dent et sur la détection d'images de fluorescence de la zone 12 de la dent dans deux bandes de longueurs d'onde différentes, dans la 'partie haute énergie et dans la partie basse énergie du spectre d'émission, le rapport point par point des mesures d'intensité spectrale de la fluorescence dans ces deux bandes permettant de déterminer si la zone 12 examinée de la dent présente ou non une carie.- Figure 2 illustrates the operation over time of this device; FIG. 3 schematically represents the fluorescence spectra of different parts of a tooth and the wavelength bands used for measuring the spectral intensity of the fluorescence; and Figure 4 is a graph showing 'the variations in the ratios of the measured fluorescence intensities in both wavelength bands wave for different parts of a tooth. The method and the device according to the invention are based on the illumination of an area 12 of a tooth 10 by a beam 14 of monochromatic ultraviolet light exciting a fluorescence emission by the mineral part of the tooth and on the detection of fluorescence images of tooth zone 12 in two bands of different wavelengths, in the ' high energy part and in the low energy part of the emission spectrum, the point-to-point ratio of spectral intensity measurements fluorescence in these two bands making it possible to determine whether or not the zone 12 examined of the tooth has a cavity.
Pour bien faire comprendre la nature du problème résolu par l'invention, on rappellera que la carie est une maladie infectieuse dont les lésions sont des signes et des symptômes qui apparaissent longtemps après la primo-infection et l'initiation du processus pathologique, lorsqu'une prévention n'a pas été faite ou a échoué, les lésions étant dues à des phénomènes physico-chimiques selon lesquels les acides produits par le métabolisme de la plaque bactérienne provoquent une déminéralisation de surface des tissus calcifiés de la dent . Dans la technique actuelle, la détection des pathologies dentaires repose essentiellement sur des évaluations visuelles directes et tactiles d'un praticien ou sur des radiographies aux rayons X. La nature ionisante des radiographies aux rayons X ne permet pas de les utiliser de façon répétitive et routinière pour la prévention des caries et le contrôle des soins. Par ailleurs, l'évaluation visuelle ou
tactile par un praticien ne permet pas de détecter les caries à un stade précoce de leur développement où une reminéralisation des zones attaquées par la précipitation in situ d'ions calcium et phosphate serait possible et éviterait une intervention chirurgicale curative .To clearly understand the nature of the problem solved by the invention, it will be recalled that caries is an infectious disease the lesions of which are signs and symptoms which appear long after the primary infection and the initiation of the pathological process, when prevention has not been made or has failed, the lesions being due to physicochemical phenomena according to which the acids produced by the metabolism of the bacterial plaque cause a demineralization of the surface of the calcified tissues of the tooth. In the current technique, the detection of dental pathologies is essentially based on direct and tactile visual evaluations of a practitioner or on X-ray radiographs. The ionizing nature of X-ray radiographs does not allow them to be used repeatedly and routinely for cavity prevention and care control. In addition, the visual assessment or tactile by a practitioner does not allow to detect caries at an early stage of their development where a remineralization of the attacked areas by the precipitation in situ of calcium and phosphate ions would be possible and would avoid a curative surgical intervention.
Le dispositif selon l'invention permet précisément cette détection précoce, d'une façon ' fiable et indépendante des individus . Le dispositif selon l'invention, représenté schématiquement en figure 1, comprend un générateur laser 16, par exemple du type Nd:YAG"Q-switch" qui produit des impulsions à des longueurs d'onde différentes, par exemple de 1064 nm, 532 nm et 355 nm avec une fréquence de répétition de 12 kHz et qui est associé à des moyens 18 de filtrage spectral et à un objectif 20 de focalisation sur l'entrée d'une fibre optique 22 de transmission des impulsions 14 qui, à la sortie de la fibre optique 22, traversent un objectif 24 et sont réfléchies par un miroir 26 vers la zone examinée 12 de la dent 10.The device according to the invention precisely allows this early detection, in a reliable and independent manner from individuals. The device according to the invention, shown diagrammatically in FIG. 1, comprises a laser generator 16, for example of the Nd: YAG "Q-switch" type which produces pulses at different wavelengths, for example 1064 nm, 532 nm and 355 nm with a repetition frequency of 12 kHz and which is associated with means 18 of spectral filtering and a lens 20 for focusing on the input of an optical fiber 22 for transmitting pulses 14 which, at the output of the optical fiber 22, pass through an objective 24 and are reflected by a mirror 26 towards the examined area 12 of the tooth 10.
Les moyens de filtrage spectral 18 comprennent par exemple deux filtres colorés interchangeables, dont l'un transmet les longueurs d'onde de 355 n et arrête les longueurs d'onde de 532 nm et dont l'autre, inversement, transmet les longueurs d'onde de 532 nm et arrête les longueurs d'onde de 355 nm. Ces deux filtres sont montés sur un support du type électromécanique par exemple, qui permet de les placer tour à tour sur la sortie du générateur laser 16.The spectral filtering means 18 comprise for example two interchangeable color filters, one of which transmits the wavelengths of 355 n and stops the wavelengths of 532 nm and the other of which, conversely, transmits the lengths of 532 nm wave and stops the wavelengths of 355 nm. These two filters are mounted on a support of the electromechanical type for example, which makes it possible to place them in turn on the output of the laser generator 16.
Les moyens 24, 26 d'éclairage de la zone 12 de la dent forment également des moyens de reprise de la
fluorescence émise 28 qui est focalisée sur l'entrée de moyens de transmission optique 30 tels par exemple qu'un guide d'images formé d'un faisceau de fibres optiques . Les moyens 22, 24, 26, 30 sont avantageusement rassemblés en un ensemble monobloc que le praticien peut tenir d'une main et dont il peut introduire l'extrémité dans la bouche d'un patient pour l'examen des dents du patient. Le faisceau lumineux 28 sortant des moyens de transmission 30 est dirigé vers des moyens 32 d'acquisition vidéo, à travers un objectif 34, des moyens 36 de filtrage spectral et des moyens 38 formant obturateur ou porte temporelle. Les moyens 36 de filtrage spectral comprennent deux filtres colorés du type passe-bande dont l'un transmet les longueurs d'onde comprises entre la longueur d'onde d'excitation et 450-600 nm environ et dont l'autre transmet celles comprises entre 550-600 et 750-800 nm environ.The means 24, 26 for lighting the zone 12 of the tooth also form means for resuming the emitted fluorescence 28 which is focused on the input of optical transmission means 30 such as for example an image guide formed by a bundle of optical fibers. The means 22, 24, 26, 30 are advantageously combined into a single-piece assembly which the practitioner can hold with one hand and the end of which he can introduce into the mouth of a patient for examining the patient's teeth. The light beam 28 leaving the transmission means 30 is directed towards video acquisition means 32, through a lens 34, means 36 for spectral filtering and means 38 forming a shutter or time gate. The spectral filtering means 36 comprise two color filters of the bandpass type, one of which transmits the wavelengths between the excitation wavelength and approximately 450-600 nm and the other of which transmits those between 550-600 and 750-800 nm approximately.
Les moyens 38 formant obturateur ou porte temporelle sont commandés pour laisser passer vers les moyens 32 d'acquisition vidéo soit les longueurs d'onde de la bande haute d'énergie, soit celles de la bande basse énergie, soit encore celles correspondant aux impulsions à la longueur d'onde de 532 nm qui sont réfléchies et diffusées par la zone examinée 12 de la dent. Les filtres colorés des moyens 36 sont montés sur un même support du type électromécanique qui les interpose tour à tour sur l'axe optique de la lumière sortant des moyens de transmission 30 et qui n'en place aucun sur cet axe lors de la transmission de la lumière
correspondant à la réflexion et la diffusion des impulsions à la longueur d'onde de 532 nm.The means 38 forming a shutter or time gate are controlled to allow the video acquisition means 32 to pass either the wavelengths of the high energy band, or those of the low energy band, or even those corresponding to the pulses at the wavelength of 532 nm which are reflected and scattered by the examined area 12 of the tooth. The colored filters of the means 36 are mounted on the same support of the electromechanical type which interposes them in turn on the optical axis of the light leaving the transmission means 30 and which places none on this axis during the transmission of the light corresponding to the reflection and diffusion of the pulses at the wavelength of 532 nm.
Les moyens 38 formant obturateur ou porte temporelle sont formés par exemple par un intensificateur d'images avec modulation de tension sur la grille d'accélération, cet obturateur restant ouvert uniquement pour le passage des impulsions de fluorescence et de lumière visible provenant de la dent 10. Quand cet obturateur est fermé, il bloque toute la lumière non porteuse d'informations sur les propriétés de la surface dentaire. En variante, on peut également utiliser un obturateur mécanique ou à cristaux liquides, un déflecteur acousto-optique, une caméra à très faible durée d'accumulation, etc. Les moyens 32 d'acquisition d'images sont de préférence formés par une caméra matricielle noir et blanc à photorécepteurs du type CCD, dont la sortie est reliée à l'entrée de moyens 40 de traitement de l'information, tels qu'un micro-ordinateur du type PC ou analogue. Des moyens 42 de synchronisation sont associés aux moyens 40 de traitement de l'information, au générateur 16, aux moyens de filtrage 18 et 36, aux moyens obturateurs 38 et aux moyens 32 d'acquisition vidéo. Ces moyens de synchronisation 42 reçoivent les impulsions de synchronisation produites à la longueur d'onde de 1064 nm par le générateur laser 16.The means 38 forming a shutter or time gate are formed for example by an image intensifier with voltage modulation on the acceleration grid, this shutter remaining open only for the passage of fluorescence and visible light pulses coming from tooth 10 When this shutter is closed, it blocks all light that does not carry information on the properties of the tooth surface. As a variant, it is also possible to use a mechanical or liquid crystal shutter, an acousto-optical deflector, a camera with a very short accumulation time, etc. The image acquisition means 32 are preferably formed by a black and white matrix camera with photoreceptors of the CCD type, the output of which is connected to the input of information processing means 40, such as a microphone. - PC or similar type computer. Synchronization means 42 are associated with the information processing means 40, the generator 16, the filtering means 18 and 36, the shutter means 38 and the video acquisition means 32. These synchronization means 42 receive the synchronization pulses produced at the wavelength of 1064 nm by the laser generator 16.
Ce dispositif est utilisé de la façon suivante : les moyens 22, 24, 26 , 30 forment une sonde que le praticien peut tenir et orienter vers la zone 12 à examiner sur la dent 10. Les impulsions émises par le générateur laser aux longueurs d'onde de 532 et de 355 nm sont transmises en alternance par les moyens de
filtrage spectral 18 et la fibre optique 22, vers la zone 12 de la dent. Les impulsions à 355 nm sont absorbées par les composants des tissus de la surface dentaire, qui se désexcitent en émettant une fluorescence pendant une durée très brève, typiquement de quelques nanosecondes. De même, les impulsions de lumière visible à la longueur d'onde de 532 nm sont réfléchies et diffusées par la surface dentaire. Les impulsions lumineuses en provenance de la dent sont reprises par les moyens optiques 24, 26, et transmises par les moyens 30 jusqu'aux moyens de filtrage spectral 36 associés aux moyens 32 d'acquisition vidéo par les moyens 38 formant obturateur ou porte temporelle. Les images vidéo acquises par les moyens 32 sont transmises aux moyens 40 de traitement de l'information et sont affichées sur des moyens appropriés, notamment sur un écran de visualisation.This device is used in the following way: the means 22, 24, 26, 30 form a probe which the practitioner can hold and orient towards the zone 12 to be examined on the tooth 10. The pulses emitted by the laser generator at the lengths of waves of 532 and 355 nm are transmitted alternately by the means of spectral filtering 18 and the optical fiber 22, towards the zone 12 of the tooth. The pulses at 355 nm are absorbed by the components of the tissues of the dental surface, which de-excite by emitting fluorescence for a very short time, typically a few nanoseconds. Likewise, the pulses of visible light at the wavelength of 532 nm are reflected and diffused by the tooth surface. The light pulses from the tooth are picked up by the optical means 24, 26, and transmitted by the means 30 to the spectral filtering means 36 associated with the video acquisition means 32 by the means 38 forming a shutter or time gate. The video images acquired by the means 32 are transmitted to the information processing means 40 and are displayed on appropriate means, in particular on a display screen.
On a représenté schématiquement les principales étapes de ce procédé en figure 2, où l'on retrouve en 44 l'émission des impulsions lumineuses par le générateur 16, en 46 le filtrage spectral de ces impulsions par les moyens 18, qui permettent de transmettre des impulsions d'excitation de fluorescence pendant une première période 48 puis des impulsions de lumière visible pendant une deuxième période 50, et ainsi de suite, en 48 l'émission d'impulsions de fluorescence 52 par la zone examinée 12 de la dent, suivies par des impulsions 54 de lumière visible qui sont réfléchies et/ou diffusées par la surface de cette zone, et en 56 le filtrage spectral des impulsions lumineuses transmises par les moyens 30, ce filtrage spectral étant réalisé successivement dans une bande
haute énergie 58, dans une bande basse énergie 60 et laissant passer finalement en 62 les impulsions de lumière visible réfléchies et/ou diffusées par la surface de la dent. On trouve ensuite en 64 l'acquisition d'images de fluorescence dans les bandes haute et basse énergie du spectre d'émission et d'images en lumière visible pendant les intervalles 66 d'ouverture dés moyens 38 d'obturation ou de porte temporelle. Cela conduit en 70 à une accumulation 72 d'images de fluorescence en bande haute énergie, à une accumulation 74 d'images de fluorescence en bande basse énergie et à une accumulation 76 d'images en lumière visible . Ensuite, le traitement réalisé par les moyens 40 comprend en 78 un stockage d'images de fluorescence en bande haute énergie 80 et un stockage d'images de fluorescence en bande basse énergie 82, ainsi qu'un traitement 84 des images de fluorescence et un stockage 86 des images en lumière visible, puis en 88 un affichage 90 des images résultantes de fluorescence et des images résultantes 92 en lumière visible. Les étapes de fonctionnement du dispositif peuvent être permutées . De façon plus détaillée, le traitement des images de fluorescence qui est réalisé en 84 consiste à mesurer l'intensité spectrale de la fluorescence émise dans les bandes haute et basse énergie précitées, à faire leur rapport et à le comparer à des valeurs prédéterminées.The main stages of this process have been represented diagrammatically in FIG. 2, in which we find at 44 the emission of light pulses by the generator 16, at 46 the spectral filtering of these pulses by the means 18, which make it possible to transmit fluorescence excitation pulses during a first period 48 then visible light pulses during a second period 50, and so on, at 48 the emission of fluorescence pulses 52 by the examined area 12 of the tooth, followed by pulses 54 of visible light which are reflected and / or scattered by the surface of this zone, and at 56 the spectral filtering of the light pulses transmitted by the means 30, this spectral filtering being carried out successively in a band high energy 58, in a low energy band 60 and finally passing at 62 the pulses of visible light reflected and / or scattered by the surface of the tooth. Then there is at 64 the acquisition of fluorescence images in the high and low energy bands of the emission spectrum and of images in visible light during the intervals 66 of opening of the means 38 of shutter or time gate. This leads in 70 to an accumulation 72 of fluorescence images in high energy band, to an accumulation 74 of fluorescence images in low energy band and to an accumulation 76 of visible light images. Next, the processing carried out by the means 40 comprises at 78 a storage of fluorescence images in high energy band 80 and a storage of fluorescence images in low energy band 82, as well as a processing 84 of fluorescence images and a storage 86 of the images in visible light, then in 88 a display 90 of the resulting images of fluorescence and of the resulting images 92 in visible light. The device operating steps can be swapped. In more detail, the processing of the fluorescence images which is carried out at 84 consists in measuring the spectral intensity of the fluorescence emitted in the aforementioned high and low energy bands, making their report and comparing it with predetermined values.
On a représenté schématiquement en figure 3, les courbes de variation de la fluorescence émise en
fonction de la longueur d'onde par la dentine (courbe A), par l'émail (courbe B) , par une carie à un stade précoce de développement (courbe C) et par une carie à un stade avancé de développement (courbe D) . Les courbes E et F représentent les bandes passantes des filtres haute énergie et basse énergie des moyens de filtrage spectral 36.Schematically shown in Figure 3, the variation curves of the fluorescence emitted in wavelength function by dentin (curve A), by enamel (curve B), by decay at an early stage of development (curve C) and by decay at an advanced stage of development (curve D ). The curves E and F represent the passbands of the high energy and low energy filters of the spectral filtering means 36.
On voit que les courbes de fluorescence sont décalées vers le rouge dans le cas d'une carie et que 1 ' intensité de la fluorescence émise est plus faible dans le cas d'une carie avancée, en raison de la présence de matière organique coagulée.It can be seen that the fluorescence curves are shifted towards the red in the case of decay and that the intensity of the fluorescence emitted is lower in the case of advanced decay, due to the presence of coagulated organic matter.
Le traitement réalisé sur les images de fluorescence dans les bandes passantes E et F consiste à mesurer l'intensité de l'énergie de la fluorescence dans ces deux bandes et à en faire le rapport. Trois exemples de variations de ce rapport sont représentés schématiquement en figure 4, en fonction d'une dimension d'espace représentée en abscisse et mesurée sur la dent. On voit notamment que le rapport énergie de fluorescence dans la bande haute énergie/énergie de fluorescence dans la bande basse énergie du spectre d'émission peut varier entre des valeurs qui sont comprises entre 2 et 3 environ pour l'émail, qui sont sensiblement égales à 4 pour la dentine et qui sont comprises entre 0,5 et 1 pour les parties cariées.The processing carried out on the fluorescence images in the passbands E and F consists in measuring the intensity of the energy of the fluorescence in these two bands and in reporting them. Three examples of variations of this ratio are shown diagrammatically in FIG. 4, as a function of a dimension of space represented on the abscissa and measured on the tooth. We see in particular that the ratio of fluorescence energy in the high energy band / fluorescence energy in the low energy band of the emission spectrum can vary between values which are between 2 and 3 approximately for the enamel, which are substantially equal. to 4 for dentin and which are between 0.5 and 1 for the decayed parts.
Le rapport de ces intensités sur les images de fluorescence permet de s'affranchir de la forme de la surface examinée de la dent, c'est-à-dire de la présence de sillons ou de puits, ainsi que de l'inclinaison de cette surface par rapport à l'axe
optique d'éclairage et de la non-uniformité de 1 ' éclairage.The ratio of these intensities to the fluorescence images makes it possible to overcome the shape of the examined surface of the tooth, that is to say the presence of grooves or wells, as well as the inclination of this. surface relative to the axis lighting optics and non-uniformity of lighting.
L'affichage des images de fluorescence et des images en lumière visible sur un écran de visualisation permet au praticien de localiser précisément la zone cariée d'une dent. On peut par ailleurs représenter les variations des rapports des énergies de fluorescence en fausses couleurs, pour que, par exemple', les zones cariées apparaissent en rouge et soient bien visibles par le praticien.The display of fluorescence images and visible light images on a display screen allows the practitioner to precisely locate the decayed area of a tooth. It is also possible to represent the variations in the ratios of the fluorescence energies in false colors, so that, for example ', the decayed areas appear in red and are clearly visible to the practitioner.
Bien entendu, diverses modifications peuvent être apportées aux moyens décrits et représentés : par exemple, on peut utiliser d'autres générateurs laser, par exemple à cristaux ou à verres dopés au Nd , Yb, etc., avec génération d'harmoniques, ou des lasers à azote fonctionnant à 337 nm, à excimer fonctionnant à 308 ou à 351 nm, des lasers à semi-conducteurs , des lampes ultra-violettes à décharge électrique, etc. Par ailleurs, les moyens 30 de transmission d'images qui, dans un mode de réalisation préféré de l'invention, comprennent un guide d'images flexible ayant par exemple un millimètre de diamètre et une longueur d'environ un mètre et pouvant comprendre trente milles fibres optiques individuelles, peuvent être remplacés par un système de miroirs et de lentilles ou bien par un horoscope basé sur l'utilisation d'un barreau de verre avec un gradient transversal d'indice de réfraction.Of course, various modifications can be made to the means described and shown: for example, it is possible to use other laser generators, for example crystals or glasses doped with Nd, Yb, etc., with generation of harmonics, or nitrogen lasers operating at 337 nm, excimer operating at 308 or 351 nm, semiconductor lasers, ultra-violet electric discharge lamps, etc. Furthermore, the image transmission means 30 which, in a preferred embodiment of the invention, comprise a flexible image guide having for example a millimeter in diameter and a length of about one meter and which may include thirty thousand individual optical fibers can be replaced by a system of mirrors and lenses or by a horoscope based on the use of a glass rod with a transverse gradient of refractive index.
Les moyens de filtrage spectral peuvent être constitués d'un filtre acousto-optique, d'un jeu de miroirs dichroïques, d'un filtre à cristaux liquides, etc.
Les moyens 32 d'acquisition vidéo, qui sont formés d'une matrice de capteurs CCD dans le mode de réalisation préféré de l'invention, peuvent être remplacés par des matrices de photodiodes, de vidicons, de capteurs CMOS, avec une sortie vidéo analogique ou numérique, monochrome ou couleur.The spectral filtering means can consist of an acousto-optical filter, a set of dichroic mirrors, a liquid crystal filter, etc. The video acquisition means 32, which are formed by a matrix of CCD sensors in the preferred embodiment of the invention, can be replaced by arrays of photodiodes, vidicon, CMOS sensors, with an analog video output or digital, monochrome or color.
Bien évidemment, les moyens 22 de transmission de la lumière d'éclairage peuvent comprendre plusieurs fibres optiques, qui sont agencées à leurs extrémités pour une injection efficace uniforme de l'intensité du faisceau laser produit par le générateur 16 et à 1 ' autre extrémité pour un éclairage uniforme de la zone 12 de la dent.Obviously, the means 22 for transmitting the lighting light may comprise several optical fibers, which are arranged at their ends for an effective uniform injection of the intensity of the laser beam produced by the generator 16 and at the other end for uniform illumination of area 12 of the tooth.
On peut également utiliser des moyens optiques d'éclairage et de reprise 24, 26 différents de ceux qui ont été décrits et représentés.
One can also use optical lighting and recovery means 24, 26 different from those which have been described and shown.
Claims
REVENDICATIONS
1 - Procédé d'acquisition et de traitement d'images d'une dent, consistant à éclairer une zone (12) d'une dent en lumière monochromatique et à capter la luminescence émise par la zone éclairée de la dent, caractérisé en ce qu'il consiste également :'1 - Method for acquiring and processing images of a tooth, consisting in illuminating an area (12) of a tooth in monochromatic light and in capturing the luminescence emitted by the illuminated area of the tooth, characterized in that 'it also consists of:'
- à utiliser pour éclairer ladite zone (12) de la dent une lumière monochromatique dont la longueur d'onde est choisie pour exciter une émission de fluorescence par la partie minérale de la dent,- to be used to illuminate said area (12) of the tooth with monochromatic light whose wavelength is chosen to excite a fluorescence emission by the mineral part of the tooth,
- à prendre avec des moyens vidéo (32) des images de la zone éclairée de la dent dans deux bandes de longueurs d'onde dont l'une est dans la partie haute énergie et l'autre dans la partie basse énergie du spectre d'émission, à mesurer l'intensité spectrale de la fluorescence émise dans ces deux bandes de longueurs d'onde en chaque point desdites images,- to take with video means (32) images of the illuminated area of the tooth in two wavelength bands one of which is in the high energy part and the other in the low energy part of the spectrum emission, to measure the spectral intensity of the fluorescence emitted in these two wavelength bands at each point of said images,
- à faire le rapport des mesures en chaque point dans les deux bandes de longueurs d'onde précitées et à comparer ce rapport à des valeurs prédéterminées.- report the measurements at each point in the two aforementioned wavelength bands and compare this report with predetermined values.
2 - Procédé selon la revendication 1, caractérisé en ce que la longueur d'onde d'éclairage est comprise entre 300 et 370 nm environ.2 - Method according to claim 1, characterized in that the lighting wavelength is between 300 and 370 nm approximately.
3 - Procédé selon la revendication 1 ou 2, caractérisé en ce que les longueurs d'onde des bandes précitées sont comprises entre la longueur d'onde
d'excitation et 450-600 nm environ et entre 550-600 et 750-800 nm environ respectivement.3 - Method according to claim 1 or 2, characterized in that the wavelengths of the aforementioned bands are between the wavelength excitation and approximately 450-600 nm and between approximately 550-600 and 750-800 nm respectively.
4 - Procédé selon l'une des revendications précédentes, caractérisé en ce -qu'il consiste à éclairer ladite zone (12) de la dent par une alternance d'impulsions à deux longueurs d'onde différentes, l'une ultraviolette et l'autre visible, à prendre avec les moyens vidéo (32) des images de fluorescence dans lesdites bandes haute et basse énergie de la zone éclairée par les impulsions de longueur d'onde ultraviolette et des images de ladite zone (12) éclairée par les impulsions de longueur d'onde visible et à transmettre ces images à des moyens (40) de traitement d'information et d'affichage.4 - Method according to one of the preceding claims, characterized in that it consists in illuminating said area (12) of the tooth by alternating pulses at two different wavelengths, one ultraviolet and the other visible, to be taken with the video means (32) of images of fluorescence in said high and low energy bands of the zone illuminated by the pulses of ultraviolet wavelength and images of said zone (12) illuminated by the pulses of visible wavelength and transmitting these images to information processing and display means (40).
5 - Procédé selon la revendication 4, caractérisé en ce qu'il consiste à accumuler des images de fluorescence dans les bandes haute et basse énergie précitées et des images à la longueur d'onde visible avant de les traiter et d'afficher une image du rapport des intensités spectrales de fluorescence et une image de ladite zone (12) de la dent éclairée en lumière visible .5 - Method according to claim 4, characterized in that it consists in accumulating fluorescence images in the aforementioned high and low energy bands and images at the visible wavelength before processing them and displaying an image of the ratio of the spectral intensities of fluorescence and an image of said area (12) of the tooth illuminated in visible light.
6 - Procédé selon l'une des revendications précédentes, caractérisé en ce qu'il consiste à utiliser un même générateur laser (16) pour produire des impulsions (14) d'excitation de la fluorescence et d'éclairage à une longueur d'onde visible, ces impulsions ayant une durée comprise entre quelques microsecondes et une nanoseconde ou moins.
7 - Procédé selon la revendication 6, caractérisé en ce qu'il consiste à utiliser le même générateur laser (16) pour produire des impulsions de synchronisation, par exemple en infrarouge.6 - Method according to one of the preceding claims, characterized in that it consists in using the same laser generator (16) to produce pulses (14) excitation of fluorescence and lighting at a wavelength visible, these pulses having a duration of between a few microseconds and a nanosecond or less. 7 - Method according to claim 6, characterized in that it consists in using the same laser generator (16) to produce synchronization pulses, for example in infrared.
8 - Dispositif pour l'exécution du procédé décrit dans l'une des revendications précédentes ', comprenant une source (16) de lumière monochromatique, des moyens optiques (22, 24, 26) d'éclairage d'une zone (12) de la dent et de reprise d'une lumière en provenance de la dent, des moyens (30) de transmission de la lumière reprise à des moyens (36) de filtrage spectral, des photorécepteurs captant la lumière sortant des moyens (36) de filtrage spectral, et des moyens (40) de traitement de l'information recevant des signaux de sortie des photorécepteurs, caractérisé en ce que la source (16) émet une longueur d'onde choisie pour exciter une émission de fluorescence par la partie minérale de la dent, en ce qu'il comprend des moyens vidéo (32) de prise d'images de la zone (12) éclairée de la dent, associés à des moyens (38) d'obturation ou de porte temporelle pour prendre en alternance des images de fluorescence de la zone (12) de la dent dans des bandes de longueurs d'onde haute et basse énergie respectivement du spectre d'émission et des images de cette zone (12) éclairée en lumière visible, et en ce que les moyens (40) de traitement de l'information sont prévus pour effectuer le rapport, en chaque point de l'image, des intensités mesurées dans lesdites bandes de longueurs d'onde du spectre d'émission.
9 - Dispositif selon la revendication 8, caractérisé en ce que les moyens (36) de filtrage spectral comprennent des filtres colorés interchangeables ou un filtre acousto-optique ou à cristaux liquides, ou un jeu de miroirs dichroïques .8 - Device for carrying out the method described in one of the preceding claims ' , comprising a source (16) of monochromatic light, optical means (22, 24, 26) for lighting an area (12) of the tooth and for picking up light from the tooth, means (30) for transmitting the picked up light to means (36) for spectral filtering, photoreceptors capturing the light leaving the means (36) for spectral filtering , and information processing means (40) receiving output signals from the photoreceptors, characterized in that the source (16) emits a wavelength chosen to excite a fluorescence emission by the mineral part of the tooth , in that it comprises video means (32) for taking images of the illuminated area (12) of the tooth, associated with means (38) of shutter or time gate for alternately taking images of fluorescence of the tooth area (12) in length bands high and low energy wave respectively of the emission spectrum and images of this area (12) illuminated in visible light, and in that the information processing means (40) are provided for carrying out the report, in each point of the image, intensities measured in said wavelength bands of the emission spectrum. 9 - Device according to claim 8, characterized in that the means (36) of spectral filtering include interchangeable colored filters or an acousto-optical or liquid crystal filter, or a set of dichroic mirrors.
10 - Dispositif selon la revendication 8 ou 9, caractérisé en ce que les moyens (30) de 'transmission comprennent un guide d'images à fibres optiques ou un horoscope à barreau de verre ayant un gradient d'indice transversal de réfraction.10 - Device according to claim 8 or 9, characterized in that the means (30) of 'transmission comprise a fiber optic image guide or a glass rod horoscope having a gradient of transverse index of refraction.
11 - Dispositif selon l'une des revendications 8 à 10, caractérisé en ce que les moyens d'éclairage comprennent un générateur laser (16) associé à des moyens (18) de filtrage spectral et commandé pour produire des impulsions à des longueurs d'onde différentes pour l'éclairage de la dent en lumière ultraviolette et en lumière visible.11 - Device according to one of claims 8 to 10, characterized in that the lighting means comprise a laser generator (16) associated with means (18) of spectral filtering and controlled to produce pulses at lengths of different wave for the illumination of the tooth in ultraviolet light and in visible light.
12 - Dispositif selon la revendication 11, caractérisé en ce que le générateur laser (16) est commandé pour produire également des impulsions de synchronisation, par exemple en infrarouge.12 - Device according to claim 11, characterized in that the laser generator (16) is controlled to also produce synchronization pulses, for example in infrared.
13 - Dispositif selon l'une des revendications 8 à13 - Device according to one of claims 8 to
12, caractérisé en ce qu'il comprend également des moyens de synchronisation (42) reliés à la source de lumière (16), aux moyens vidéo (32) de prise d'images, aux moyens (18, 36) de filtrage spectral, aux moyens12, characterized in that it also comprises synchronization means (42) connected to the light source (16), to the video means (32) for taking images, to the spectral filtering means (18, 36), to the means
(36) d'obturation ou de porte temporelle et aux moyens(36) shutter or time gate and means
(40) de traitement de l'information.
(40) information processing.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR0107274 | 2001-06-01 | ||
| FR0107274A FR2825260B1 (en) | 2001-06-01 | 2001-06-01 | METHOD AND DEVICE FOR DETECTION OF DENTAL CARIES |
| PCT/FR2002/001776 WO2002096281A1 (en) | 2001-06-01 | 2002-05-27 | Method and device for the acquisition and treatment of dental images |
Publications (1)
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| EP1392158A1 true EP1392158A1 (en) | 2004-03-03 |
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| EP02740822A Withdrawn EP1392158A1 (en) | 2001-06-01 | 2002-05-27 | Method and device for the acquisition and treatment of dental images |
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| US (1) | US20040236232A1 (en) |
| EP (1) | EP1392158A1 (en) |
| JP (1) | JP2004526550A (en) |
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| FR2856546B1 (en) | 2003-06-17 | 2005-11-04 | Centre Nat Rech Scient | METHOD AND DEVICE FOR ACQUIRING AND PROCESSING IMAGES OF AN OBJECT SUCH AS A TOOTH |
| FR2858205B1 (en) * | 2003-07-28 | 2005-09-16 | Sopro Soc | APPARATUS FOR DETECTING AND CHARACTERIZING BIOLOGICAL TISSUES |
| JP2005204869A (en) * | 2004-01-22 | 2005-08-04 | Matsushita Electric Ind Co Ltd | Gums observing apparatus |
| US8616967B2 (en) | 2004-02-25 | 2013-12-31 | Cfph, Llc | System and method for convenience gaming |
| US7324661B2 (en) * | 2004-04-30 | 2008-01-29 | Colgate-Palmolive Company | Computer-implemented system and method for automated and highly accurate plaque analysis, reporting, and visualization |
| US7270543B2 (en) * | 2004-06-29 | 2007-09-18 | Therametric Technologies, Inc. | Handpiece for caries detection |
| JP4496135B2 (en) * | 2005-06-13 | 2010-07-07 | 株式会社モリタ製作所 | Dental lighting device and dental medical device |
| CA2517252A1 (en) * | 2005-08-29 | 2007-02-28 | Neks Technologies Inc. | Detection of interproximal caries aided by optical sensor examining the occlusal surface of teeth |
| US7596253B2 (en) | 2005-10-31 | 2009-09-29 | Carestream Health, Inc. | Method and apparatus for detection of caries |
| US7577284B2 (en) * | 2006-04-21 | 2009-08-18 | Carestream Health, Inc. | Optical detection of dental caries |
| CN101889902B (en) * | 2006-07-25 | 2013-10-16 | 宝洁公司 | Methods and products for analyzing gingival tissues |
| US7668355B2 (en) * | 2006-08-31 | 2010-02-23 | Carestream Health, Inc. | Method for detection of caries |
| US8360771B2 (en) * | 2006-12-28 | 2013-01-29 | Therametric Technologies, Inc. | Handpiece for detection of dental demineralization |
| FR2924808B1 (en) * | 2007-12-11 | 2010-09-03 | Commissariat Energie Atomique | SYSTEM FOR FLUORESCENCE ANALYSIS OF A FIELD IN A LIGHT AREA |
| US8866894B2 (en) * | 2008-01-22 | 2014-10-21 | Carestream Health, Inc. | Method for real-time visualization of caries condition |
| GB0807611D0 (en) * | 2008-04-25 | 2008-06-04 | Univ Manchester | Dental imaging and apparatus thereof |
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- 2002-05-27 EP EP02740822A patent/EP1392158A1/en not_active Withdrawn
- 2002-05-27 WO PCT/FR2002/001776 patent/WO2002096281A1/en not_active Application Discontinuation
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Also Published As
| Publication number | Publication date |
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| FR2825260A1 (en) | 2002-12-06 |
| JP2004526550A (en) | 2004-09-02 |
| CA2448936A1 (en) | 2002-12-05 |
| FR2825260B1 (en) | 2004-08-20 |
| US20040236232A1 (en) | 2004-11-25 |
| WO2002096281A1 (en) | 2002-12-05 |
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