Device for measuring fluorescent radiation on biological substances with a semi-conductor sensor arrangement | Patent Publication Number 20100219354
US 20100219354 A1The invention relates to a device for measuring fluorescent radiation emitted by biological substances, comprising a light source, a capturing unit, an evaluation unit, at least one emission fibre, and at least one detection fibre. Said emission fibre guides excitation radiation to the biological substrate and the detection fibre receives fluorescent radiation and guides it to the evaluation unit. The capturing unit comprises a semiconductor sensor arrangement that detects fluorescent radiation emitted by the biological substance in wave length areas that are separate from each other, are arranged. Data sets of at least two different reference measurements on at least two different biological substances are stored and compared to the measured measurement values to the stored data sets and issues a result relating to the pathological attacks of the examined biological substances and/or relating to the type of examined, biological substances.
- 1. A device for measuring fluorescent radiation emitted by biological substances, said device comprising:na light source,a receiving unit,an evaluation unit that is coupled to the receiving unit,at least one emission fiber coupled to the light source, and at least one detection fiber coupled to the receiving unit, said emission fiber guiding excitation radiation to the biological substance, and the detection fiber receiving the fluorescent radiation excited on the biological substance and guiding said radiation to the evaluation unit,wherein the receiving unit further comprises a semiconductor sensor arrangement in which at least three sensors are arranged inside a surface for detecting fluorescent radiation emitted by the biological substance in wave length ranges that are separate from each other, the evaluation unit having stored therein data sets of at least two different reference measurements on at least two different biological substances, and the evaluation unit comparing the measured measurement values to the stored data sets and outputting a result relating to the pathological attacks of the examined biological substances and/or relating to the type of examined biological substances.
The invention relates to a device for measuring fluorescent radiation on biological substances as defined in the preamble of claim 1.
A device for measuring fluorescent radiation on biological substances is known e.g. from DE-A-42 00 741. Said document discloses a device for detection of caries on teeth, comprising an illumination means for emitting radiation in the wavelength range of 360 to 580 nm onto a tooth. A filter will allow the passage of fluorescent radiation in a wavelength range larger than 620 nm returned by the tooth. The radiation allowed to pass through will be evaluated for detection of caries.
Known from DE-A-195 41 686 is a further device for measurement of fluorescent radiation wherein a light source will emit excitation radiation in a wavelength range between 600 and 670 nm onto a tooth under examination. The fluorescent radiation excited on the tooth will be detected and evaluated in a wavelength range between 670 and 800 nm.
The devices known so far have the disadvantage that, in case of an examination in a range of different or changed biological substances, imprecise results may be obtained.
Thus, it is an object of the invention to provide a device of the initially described type which makes it possible to obtain more-exact measurement results with regard to changes or deviations in the structure of biological substances. Biological substances can be endogenous substances or prosthetic materials.
The above object is achieved by the features of claim 1.
The invention advantageously provides that, in a device of the initially described type, a receiving unit comprises a semiconductor sensor arrangement wherein at least three sensors are arranged within a surface. Said at least three sensors are operative to capture the fluorescent radiation emitted on the biological substance in wavelength ranges that are separated from each other. The evaluation unit can have stored therein different sets of data, preferably in the form of multidimensional measurement values and more preferably three-dimensional measurement values, wherein the evaluation unit will compare the measured measurement values to said sets of data and will output a result relating to the pathological attacks of the examined biological substances and/or relating to the type of examined biological substances. In the evaluation unit, there can have been stored sets of data from at least two different reference measurements on two different biological substances. In order to enable the evaluation unit to issue a result with regard to the type of the examined biological substances, at least three reference measurements must have been stored in the evaluation unit. The result will be displayed by the display unit. Preferably, however, there are provided three or more reference measurements on three or more different biological substances.
The emission and detection fibers can be flexible light conductors as well as rod lenses in an endoscope.
The at least one detection fiber can be arranged with its proximal end preferably centrically above the semiconductor sensor arrangement at a distance from the surface of the semiconductor sensor arrangement.
The invention has the advantage that the sensors used will capture the fluorescent radiation excited on the biological substance, particularly on a biological tissue, in three mutually separated wavelength ranges and that an evaluation unit will evaluate the radiation.
In the previous state of the art, use has been made of the ratios between the measurement signals between the individual sensors to thus be able to obtain a result with regard to the pathological attacks of the examined biological substances. Ratios between the measurement signals of the individual sensors, however, can represent only linear curve developments. Stored reference measurements can also describe non-linear curve developments and can thus yield exact results within a large dynamic range.
The use of more than two reference measurements makes it possible to include a larger spectrum of various possible substances. Thus, for instance, endogenous substances and prosthetic materials have different optical signatures, such as e.g. the fluorescence spectra of the substances, which, however, should be evaluated identically in certain diagnostic analyses.
The deposition of at least three sets of reference data allows for a differentiated diagnostic statement on the type of the substance under examination.
The device of the invention can be used for detection of bacterial attack on teeth. Due to the large number of types of tissue or of tooth materials with different filling materials, an analysis based on three spectral ranges will be significantly more precise and reliable.
The device of the invention can also be used for detection of tumors, particularly malignant tumors, by endoscopic examination. For this purpose, a photoactive substance, preferably 5-aminolevulinic acid (5-ALA) will be introduced into the biological tissue. When excited by an excitation radiation, the biological substance will fluoresce, and the malignant cells will be clearly distinguishable from the healthy tissue. Malignant cells are equivalent to cells of a malignant tumor. However, due to the inherent fluorescence of the skin (autofluorescence), one may happen to obtain wrong results. In an analysis based on three spectral ranges, this autofluorescence is detectable and can be discriminated. In an analysis based on three spectral ranges, a diagnosis possible even without prior introduction of photoactive substances.
In the device of the invention, it can be provided that the light cone exiting from the proximal end of the detection fiber will illuminate the sensor surface of the semiconductor sensor arrangement without interposition of optical lenses.
In comparison to the previous state of the art, this has the advantage that the returned radiation does not have to be guided via separate light conductors to different optical receivers and does not have to be distributed among the optical receivers via mirrors or other optical elements. The light cone exiting from the proximal end of the detection fiber can illuminate the sensor surface without interposition of optical lenses.
With the aid of a light-conductor support, the detection fiber is held centrically above the semiconductor sensor arrangement and at a predetermined distance from the surface of the semiconductor sensor arrangement, said light-conductor support being fastened to the casing of the semiconductor sensor arrangement.
Said three sensors can be sensors for radiations lying in the wavelength ranges of the basic colors red, green and blue, respectively. The three sensors can also be sensors for radiations lying in other wavelength ranges, i.e. in the wavelength radiations of mixed colors.
The sensors can be arranged within a circular surface, and the respective basic color can have assigned thereto a circular surface segment of 120°.
This embodiment has the advantage that the returned radiation will be equally distributed onto the sensors because the detection fiber is positioned centrically to the semiconductor sensor arrangement.
Said three sensors are not restricted to being arranged within a circle but can also be arranged in any desired configuration relative to each other.
The sensor for radiation in the wavelength range of the basic color red has the highest sensitivity and is responsive up to at least 750 nm.
This has the advantage that the red fluorescence, which is weak relative to the green fluorescence, will be intensified so that an electrical crosstalk will be prevented.
The sensors can consist of photoresistors, phototransistors, photodiodes and/or pyroelectric sensors. The sensors can have different spectral sensitivities. The sensors can also be color image sensors, e.g. CCD or CMOS.
An optical prefilter for suppression of excitation radiation can be arranged between the at least one detection fiber and the semiconductor sensor arrangement and be fixed on the semiconductor sensor arrangement with the aid of an optically transparent casting compound.
The thickness of the optical prefilter can be less than 2 mm. The prefilter can be a dielectric filter.
Further, the semiconductor sensor arrangement can be arranged on a conductor plate which is shielded against electromagnetic radiation with the aid of an electrically conductive layer preferably made of copper.
Use can be made of any desired layer which is effective for shielding against electromagnetic radiation.
Between the receiving unit and the evaluation unit, three separate amplifiers can be arranged for amplification of the respective signals of the sensors.
The light source used can be an LED chip.
In contrast to laser devices, LEDs radiate light in a wide opening angle. Normal LEDs mounted on a substrate will thus radiate in all directions.
The transmission of light in a light conductor is performed substantially without a change of the opening angle, which is to say that, when exiting from the light conductor, the light will have the same opening angle as upon entrance.
Thus, in order to be able to realize light with a wide opening angle on the exit end of the emission fibers, it is provided, according to a further embodiment that the incoupling is performed without using optical lenses and that a distance of less than 0.3 mm and preferably of 0 mm exists between the LED chip and the proximal end face of the emission fiber.
By the elimination of optical lenses, significantly larger opening angles can be realized.
Between the LED chip and the proximal end face of the at least one emission fiber, a medium can be arranged which has a refractive index between that of the emission fiber and that of the surface of the LED chip. In this manner, the reflection losses at the transitions will be minimized. Preferably, the medium introduced into the intermediate space is optically transparent.
According to a further embodiment, the proximal end face of the emission fibers adjacent to the light-emitting surface of the LED chip is smaller than the light-emitting surface of the LED chip and is completely covered by the light-emitting surface of the LED chip.
According to a further embodiment, the LED chip is operative to emit light in the UV range and/or the adjacent visible range, preferably violet light in the wavelength range from 390 to 420 nm. The radiation in this wavelength range can very efficiently detect the optical differences between healthy and infected teeth or between malign cells and healthy tissue.
The light source can emit periodically modulated light. The excitation radiation can be modulated in its amplitude, the frequency of the amplitude modulation being about 2 kHz.
Between the receiving unit and the evaluation unit, there can be arranged three separate preamplifiers and/or at least one lock-in amplifier and/or at least one subtractor.
Said subtractor can be a hardware subtractor. This means that the circuit elements of the subtractor consist of concrete component parts, such as e.g. ohmic resistors, capacitors or amplifiers. The advantage of a hardware subtractor resides in that the dynamic range of the measurement is fully available independently from an offset.
According to a further embodiment, the emission fibers as well as the detection fibers can have an acceptance angle larger than 35°. Alternatively, the acceptance angle of the emission and detection fibers can be larger than 40°, preferably larger than 45°.
In previously known devices, the substantially axial emission of the radiation from the respective light conductor has turned out to be disadvantageous because, due to the substantially axial emission of the radiation, a sufficient illumination of linear portions of narrow cavities, e.g. gingival pockets, is not possible. For this reason, previously known devices are provided with additional optical elements at the radiation-exit end of the light conductors, which elements cause a not inconsiderable expenditure in manufacture and will considerably enlarge the total diameters of the light conductors.
The invention has the advantage that, due to the large acceptance angles of the emission as well as the detection fibers, bacterially infected sites or malignant cells in narrow cavities, such as e.g. in gingival pockets, can be detected better even without using additional optical elements.
Said acceptance angle larger than 35° corresponds to an opening angle of at least 70°. The advantage of an acceptance angle larger than 35° resides in that the bundle of emission and detection fibers of the present invention will be capable to illuminate also linear cavities without the need to use additional optical elements. In the inventive emission and detection fibers having an acceptance angle larger than 35°, the maximal intensity which is obtained on a plane surface extending vertically to the light exit surface, is considerably higher than in usual quartz-glass light conductors which are no wide-angle light conductors.
The emission and detection fibers can be provide with a single or multiple coating.
The entire distal end face of the emission and detection fibers can be coupled to the proximal end face of at least one light-conducting element, wherein the light-conducting element can be made of sapphire or a mineral material or plastic and have an acceptance angle larger than 35°. The acceptance angle can also be larger than 40°, preferably larger than 45°. The whole distal end face of the emission and detection fibers and the proximal end face of the light-conducting element can be pressed onto each other by application of a spring force.
Further, the fluorescence signals of the light-conducting element can be detectable by the different sensors of the semiconductor sensor arrangement. By comparing the measuring signals generated by the sensors with the reference data sets of different materials as stored in the evaluation unit, also the material of the at least one light-conducting element is detectable. The evaluation unit can indicate which material the light-conducting element is made of.
This has the advantage that the information on the material that the light-conducting element is made of, can be supplied to software means. Said software means determines, inter alia, the sensitivity with which the measurement values are to be evaluated. The supply of the information to said software means has the advantage that the sensitivity of the measurement can be adapted to the material of the light-conducting element. This is to say that the sensitivity with which the measurement values are evaluated can be adapted to the purpose of the application.
The light-conducting element can be guided within an inspection probe comprising a shaft and a coupling portion. Said inspection probe can be connected to a handle portion, and the connection site between the entire distal end face of the emission and detection fibers and the proximal end face of the light-conducting element can be arranged within the handle portion.
The light-conducting element can be rigid or flexible.
The light-conducting element can be operative for conducting the excitation radiation emitted by the light source via the emission fibers to the biological substance, and also for conducting the fluorescent radiation emitted by the biological substance.
The light-conducting element can consist of a single light conductor or of a plurality of light conductors, i.e. of a light conductor bundle.
The total diameter of the single light conductor or the total diameter of the light conductor bundle can be larger than or equal to the total diameter of the emission and detection fibers.
By way of alternative to using the light-conducting element, the emission and detection fibers can be guided directly, i.e. without interposition of a light-conducting element, to the biological substance, e.g. within an endoscope. Also the emission and detection fibers can be guided at the distal end within an inspection probe comprising a shaft and a coupling portion. Said shaft can be rigid and flexible. It can a also be bendable or curved. The shaft can be designed as a protective hose.
The two above described embodiments with inspection probe will allow for easier handling because, due to the curved shaft, the bundle of emission and detection fibers and respectively the light-conducting element can be easily introduced e.g. into gingival pockets.
The emission and detection fibers can terminate with the distal end of the shaft or project relative to the shaft by maximally about 5 cm.
According to a further embodiment, it is provided that the proximal end of the inspection probe is connectable to a handle portion, wherein the emission and detection fibers can be guided within said handle portion.
This has the advantage that the device can be handled in a more convenient manner because said handle portion allows for a better guidance of the bundle of emission and detection fibers.
Said light source can be arranged within the handle portion.
According to a further embodiment, it is provided that the length of the emission fiber or the total length of the emission fiber and the light-conducting element is less than 60 cm, preferably less than 10 cm.
These embodiments have the advantage that the emitted light does not have to cover long distances from the light source to the biological substance, which is relevant since, in wide-angle light-conductors, the intensity of the radiation will decrease with increasing length of the light conductor.
Embodiments of the invention will be explained in greater detail hereunder with reference to the drawings.
The drawings show the following schematic representations:
In said receiving unit 20, the fluorescent radiation will be detected in three mutually separated wavelength ranges and be converted into three electric signals. These will be transmitted, via separate preamplifiers 22, to a lock-in amplifier 24. By means of a subtractor 26, connected downstream of said lock-in amplifier 24, background signals can be subtracted. Background signals are caused by reflection of the excitation radiation at the distal end 8 of the emission and detection fibers 14,16 as well as by a slight inherent fluorescence of the light-conducting fibers and the adhesives used. The amount of the signal is directly proportionate to the excitation radiation. If the excitation radiation is kept constant, a constant offset signal will be obtained. This background signal will be measured during the switch-on routine of the measurement device and will be eliminated in said subtractor 26 prior to evaluation. Within the evaluation unit 28, there is arranged a memory 27 having stored therein the three-dimensional measurement values of healthy tooth material, diseased tooth material and synthetic filling material. The term “three-dimensional†is to be understood in the sense that, for each measurement value, the radiation intensity will be measured in three spectral ranges, e.g. in the spectral ranges of the basic colors red, green, blue. The currently measured three-dimensional measurement value will be compared to the stored comparative measurement values, and the distances to the closest comparative measurement value of healthy tooth material and/or synthetic filling material and diseased tooth material will be determined. The ratio of the distance between the currently measured measurement value and the closest comparative measurement value of healthy tooth material and synthetic filling material and the distance between the currently measured measurement value and the closest comparative measurement value of diseased tooth material, will be indicated in the form of values on a display unit 29. The user will know that, if this value is smaller than a certain value, the examined tooth region is free of bacterial remnants.
The inventive device for detection of tumors, particularly malignant tumors, is of a design similar to that of the device described in connection with
Alternatively, the arrangement according to
To keep the radiation losses of the excitation radiation low, one embodiment, shown in
Said light-conducting element 9 is guided within a centering device 15 and projects from the proximal end of said centering device 15 from the latter. The centering device 15 and thus the light-conducting element 9, together with the bundle of emission and detection fibers 14,16, are pressed against each other within a plug and coupling element 11 by means of a spring. Such a plug and coupling element 11 can be a commercially available ST plug provided with a bayonet catch. Said plug and coupling element 11 is arranged internally of handle portion 10. The light-conducting element 9 is pressed back into the first coupling member 7 by the length projecting relative to the proximal end of the centering device 15. Since the light-conducting element 9 is fixed or bonded within the shaft 4 and/or the distal end of coupling member 6, the light-conducting element 9 which in this case is a flexible light-conducting fiber made of plastic, is bent within the coupling member 6. By said bending, the light-conducting element 9 is subjected to tension, with the effect that the light-conducting element 9 is permanently pressed against the bundle of emission and detection fibers 14,16. This will safeguard a good incoupling of the radiation from the bundle of emission and detection fibers 14,16 into the light-conducting element 9, and vice versa.
At the connection site, the excitation radiation from the emission fiber 14 will be coupled into the light-conducting element 9. The light-conducting element 9 is guided within an injection probe 2. Said injection probe 2 comprises a shaft 4 and a coupling member 6. The light-conducting element 9 can terminate at its distal end together with the distal end of said shaft 4 or distally project therefrom, extending from the first shaft 5 maximally by 30 mm. The light distally exiting from the light-conducting element 9 will illuminate the tooth portion under examination. The light returned by the tooth portion under examination will be received by the distal end of the light-conducting element 9 and be guided to a receiving unit 20 via the detection fibers 16.
Alternatively, the light-conducting element 9 can also be made of sapphire or other mineral materials. The connection between the light-conducting element 9 and the bundle of emission and detection fibers 14,16 can also be realized without bending the light-conducting element 9, especially if the light-conducting element 9 is rigid. The light-conducting element 9 and the bundle of emission and detection fibers 14,16 can have a spherical end face so as to achieve a better incoupling of the light.
Further, the light-conducting element can consist of a plurality of light conductors, i.e. the light-conducting element consists of light conductor bundle. These light conductors have each have a diameter of about 30 μm. Also these light conductors can be made of sapphire or other mineral materials or plastics.
Further, in addition to the fluorescence signals of the illuminated tooth portions, also the fluorescence signals of the light-conducting element 9 can be received by the receiving unit 20. Also these latter fluorescence signals will then be converted into electric signals. Via separate preamplifiers 22, a lock-in amplifier 24 and a subtractor 26, these signals will be supplied to evaluation unit 28. Within the memory 27 which is located internally of evaluation unit 28, there can additionally be deposited three-dimensional measurement values of the materials of various possible light-conducting elements 9. The measured fluorescence signals of the light-conducting element 9 can be compared to the stored measurement values. In this manner, it can be detected of which material the light-conducting element 9 is made. The sensitivity of the measurement can be adapted to the material of the light-conducting element.
An inventive device for detection of tumors, particularly malignant tumors, is of a design similar to that of the devices described in connection with
Preferably, the wide-angle light conductors used are glass light conductors having an acceptance angle larger than 35°, preferably larger than 40°. However, one can also use wide-angle light-conductive fibers made of plastic, preferably of polystyrene.
B=NA2*10−((a*L)/10)
B: illumination strength
NA: numerical aperture
a: damping of the light-conductor in dB/m
L: length of the light-conductor in m
The open circles relate to a wide-angle light conductor with an opening angle of 120°. In the range of 400 nm, this wide-angle light conductor has a damping of about 17 dB/m. The black dots relate to a quartz-glass light conductor with an opening angle of 25°. In the range of 400 nm, this quartz-glass light conductor has a damping of about 0.1 dB/m.
From