Patent Application
20140142391
1. Field of the Invention
The present invention relates to a measurement probe connected to a biological optical measurement apparatus that measures optical characteristics of a body tissue.
2. Description of the Related Art
In recent years, biological optical measurement apparatuses are known that apply illumination light to a body tissue and estimate properties of the body tissue on the basis of measured values of detected light that is reflected or scattered from the body tissue. A biological optical measurement apparatus is used in combination with an endoscope for observing internal organs, such as digestive organs. For use as such a biological optical measurement apparatus, a biological optical measurement apparatus has been proposed that uses LEBS (low-coherence enhanced backscattering) for detecting properties of a body tissue by applying, to the body tissue, low-coherent white light having a short space coherence length from the tip of an illuminating fiber of a measurement probe and then measuring the distribution of the intensity of scattering light of multiple angles by using light receiving fibers (see US Patent Application Publication No. 2010/0053632, US Patent Application Publication No. 2010/0262020, and Japanese National Publication of International Patent Application No. 2009-537014).
A measurement probe according to one aspect of the invention is detachably connected to a biological optical measurement apparatus for performing optical measurement on a body tissue. The measurement probe includes an illumination fiber configured to irradiate the body tissue with illumination light, and a plurality of light receiving fibers configured to receive return light of the illumination light that is reflected and/or scattered from the body tissue. The illumination fiber and the light receiving fibers satisfy the following condition expressions:
0.21<NA<0.30 (1)
15 μm<Dcore<45 μm (2)
0.40<Dcore/Dclad<0.80 (3)
where NA indicates a numerical aperture of each of the illumination fiber and the receiving fibers, Dcore indicates a core diameter of each of the illumination fiber and the light receiving fibers, and Dclad indicates a cladding diameter of each of the illumination fiber and the light receiving fibers.
The above and other features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
Preferred embodiments of a measurement probe according to the present invention will be described in detail below with reference to the drawings. The embodiments do not limit the invention. The drawings are described with like numbers indicating like parts. The drawings are schematic and thus it should be noted that the relationship between the thickness and width of each member and proportions of members may be different in actuality. Furthermore, the respective drawings also include different relationships and proportions between the dimensions of the parts.
The biological optical measurement apparatus 2 will be described first. The biological optical measurement apparatus 2 includes a power supply 21, a light source unit 22, a connector 23, a light receiving unit 24, an input unit 25, an output unit 26, a recording unit 27, and a controller 28. The power supply 21 supplies power to each component of the biological optical measurement apparatus 2.
The light source unit 22 is realized by using an incoherent light source, such as a white LED (light emitting diode), a xenon lamp, a tungsten lamp, or a halogen lamp or, if required, multiple lenses, such as condenser lenses or collimating lenses. The light source unit 22 outputs, to the measurement probe 3 via the connector 23, incoherent light to be applied to the measurement target which contains at least one spectral component.
The connector 23 detachably connects a connection part 31 of the measurement probe 3 to the biological optical measurement apparatus 2. The connector 23 outputs light that is emitted by the light source unit 22 to the measurement probe 3 and outputs, to the light receiving unit 24, return light of illumination light that is emitted from the measurement probe 3 and reflected and/or scattered from the measurement target. The connector 23 outputs, to the controller 28, information regarding whether the measurement probe 3 is connected.
The light receiving unit 24 receives and measures the return light of the illumination light, which is emitted from the measurement probe 3 and reflected and/or scattered from the measurement target. The light receiving unit 24 is realized by using multiple spectrometers and light receiving sensors. Specifically, in the light receiving unit 24, spectrometers are provided in accordance with the number of light receiving fibers of the measurement probe 3 described later. The light receiving unit 24 measures spectral components and intensity distribution of the incident scattered light from the measurement probe 3 and measures each wavelength. The light receiving unit 24 outputs the result of the measurement to the controller 28.
The input unit 25 is realized by using a push-type switch or a touch panel. The input unit 25 receives an input of an instruction signal instructing the starting of the biological optical measurement apparatus 2 or an instruction signal instructing various operations and outputs the input to the controller 28.
The output unit 26 is realized by using a liquid crystal display or an organic EL (electro luminescence) display, and a speaker, etc. The output unit 26 outputs information on various processes in the biological optical measurement apparatus 2.
The recording unit 27 is realized by using a volatile memory or a non-volatile memory. The recording unit 27 records various programs for operating the biological optical measurement apparatus 2 and various types of data and various parameters used for optical measurement processing. The recording unit 27 temporarily records information on the biological optical measurement apparatus 2 during processing. The recording unit 27 also records the result of measurement performed by the biological optical measurement apparatus 2. The recording unit 27 may be configured using a memory card, etc. that is attached from the outside of the biological optical measurement apparatus 2.
The controller 28 is configured using a CPU (central processing unit), etc. The controller 28 controls processing operations of each unit of the biological optical measurement apparatus 2. The controller 28 controls operations of the biological optical measurement apparatus 2 by transferring instruction information or data corresponding to each unit of the biological optical measurement apparatus 2. The controller 28 records the result of measurement performed by the light receiving unit 24. The controller 28 includes an calculation unit 28a.
The calculation unit 28a performs multiple arithmetic processes on the basis of the result of measurement, which is performed by the light receiving unit 24, to compute a characteristic value regarding the properties of the measurement target. The type of the characteristic value is set according to, for example, the instruction signal received by the input unit 25.
The measurement probe 3 will be described below. The measurement probe 3 is realized by internally arranging multiple optical fibers. Specifically, the measurement probe 3 is realized by using an illumination fiber that emits illumination light to a measurement target and by using light receiving fibers on which the return light of the illumination light, which is reflected and/or scattered from the measurement target, is incident at different angles. The measurement probe 3 includes the connection part 31 that is detachably connected to the connector 23 of the biological optical measurement apparatus 2; a flexible part 32 that is flexible; a distal end 33 that applies the illumination light supplied from the light source unit 22 and receives the return light from the measurement target; and an optical device 34 that is provided to the distal end 33.
A configuration of the distal end 33, including the optical device 34, of the measurement probe 3 will be described in detail here.
As shown in
The illumination fiber 311 is configured by using a single core step-index fiber. The illumination fiber 311 propagates the illumination light output from the light source unit 22 and applies the illumination light to the measurement target via the optical device 34. The number of fibers of the illumination fiber 311 can be changed appropriately according to the item to be tested or the type of measurement target, such as blood flow or the site.
Each of the first light receiving fiber 312, the second light receiving fiber 313, and the third light receiving fiber 314 is configured using a single core step-index fiber. The first light receiving fiber 312, the second light receiving fiber 313, and the third light receiving fiber 314 propagate the return light of the illumination light reflected and/or scattered from the measurement target, which is the return light incident on the receiving fibers from their tips via the optical device 34, and output the return light to the light receiving unit 24 of the biological optical measurement apparatus 2. The number of light receiving fibers can be changed appropriately according to the item to be tested or the type of measurement target, such as the blood flow or site.
The optical device 34 is cylindrical and is configured using permeable glass having a predetermined refractive index. The optical device 34 includes an inclined surface that is cut obliquely with respect to the longitudinal direction of the measurement probe 3. The optical device 34 is formed such that the distance between the illumination fiber 311 and the measurement target is fixed and light can be applied with a steadily constant space coherent. The optical device 34 is further formed such that each of the distance between the first light receiving fiber 312 and the measurement target, the distance between the second light receiving fiber 313 and the measurement target, and the distance between the third light receiving fiber 314 and the measurement target is fixed and the return light at a predetermined scattering angle can be received stably. Furthermore, because the surface of the measurement target is flattened at the edge face of the optical device 34, the measurement target can be measured without being affected by the irregular shapes of the surface of the measurement target.
In the biological optical measurement system 1 configured as described above, as shown in
Because LEBS performed by the above-described biological optical measurement system 1 is a diagnosing method using interfering light, the space coherent length of light applied to the measurement target has to be constant in order to reduce the diameter of the measurement probe 3 without changing the diagnosing method. For this reason, the illumination fiber 311, the first light receiving fiber 312, the second light receiving fiber 313, and the third light receiving fiber 314 satisfy the following condition expressions:
0.10<NA<0.30 (1)
15 μm<Dcore<45 μm (2)
0.40<Dcore/Dclad<0.80 (3),
where NA indicates the numerical aperture of each of the illumination fiber 311 and the first light receiving fiber 312 to the third light receiving fiber 314; Dcore indicates the core diameter of each of the illumination fiber 311 and the first light receiving fiber 312 to the third light receiving fiber 314; and Dclad indicates the cladding diameter of each of the illumination fiber 311 and the first light receiving fiber 312 to the third light receiving fiber 314 (see
Regarding the expression (1), preferably,
0.15<NA<0.25 (1)′
and more preferably,
0.21<NA<0.23. (1)″
Regarding expression (2), preferably,
20 μm<Dcore<30 μm (2)′
and more preferably,
25 μm<Dcore<27 μm. (2)″
Regarding expression (3), preferably,
0.50<Dcore/Dclad<0.75 (3)′
and more preferably,
0.70<Dcore/Dclad<0.73. (3)″
Regarding the measurement probe 3, the longitudinal length DR (see
1 mm<DR<10 mm (4)
preferably,
3 mm<DR<8 mm (4)′
and more preferably,
5 mm<DR<8 mm. (4)″
Regarding the measurement probe 3, the refractive index Nd with respect to the d-line (wavelength of 587.56 nm) of the optical device 34 satisfies the following condition expression:
1.5<Nd<1.6. (5)
The maximum outer diameter Dout (see
0.50 mm<Dout<2.80 mm (6)
1.50 mm<Dout<2.78 mm (6)′
2.50 mm<Dout<2.75 mm. (6)″
The LEBS method performed by the biological optical measurement system 1 satisfies the following expression:
LSC=((λ/Nd)/n Dcore)DR (7),
where LSC is a constant indicating the coherence of illumination light. In addition, λ denotes the wavelength of illumination light, ND indicates the refractive index with respect to the d-line of the optical device 34, and DR indicates the length from the center of the edge face on the base side of the optical device 34 to the center of the edge face on the tip side (see
Regarding the illumination fiber 311 of
Regarding the conventional optical fiber, Dcore=25 μm, Dclad=30 μm, NA=0.22, and Dout=2.7 mm. Accordingly, Dcore/Dclad=0.83.
The measurement of fiber transmittance in
(a) A 200-μm optical patch cord is connected to an Xe light source to measure a reference light, and light emitted from the 200-μm optical patch cord is measured using a spectrometer to obtain a measurement result A.
(b) A 200-μm optical patch cord and a 26-μm core optical fiber are connected in sequence to an Xe light source to measure a reference light, and the light emitted from the optical fiber is measured using a spectrometer to obtain a measurement result B.
(c) The transmittance is calculated according to the following equation:
Transmittance=(measurement result B/measurement result A)×(core area of 20-μm optical patch cord/core area of 26-μm core optical fiber) (8)
It is clear from the curved line L1 in
According to the above-described embodiment of the present invention, because the illumination fiber 311, the first light receiving fiber 312, the second light receiving fiber 313, and the third light receiving fiber 314 satisfy the above-described condition expressions (1) to (3), insertion into the instrument channel 111 of the endoscope device 110 can be done and accurate measurement can be performed.
According to the embodiment of the present invention, because the measurement probe 3 is detachable from the biological optical measurement apparatus 2, the measurement probe 3 is disposable and thus the measurement probe 3 does not have to be sterilized in medical facilities and furthermore, because relatively poor durability is acceptable, the cost of the measurement probe 3 can be reduced.
According to the embodiment of the present invention, because the numerical aperture (NA) of the illumination fiber 311 satisfies the condition expression (1), the angle of light emitted from the illumination fiber 311 is optimum and accordingly, a favorable density of light on the object, which is the measurement target, and a favorable irradiated area can be obtained and the dependency of fiber transmittance on wavelength can be reduced. Furthermore, measurement of an interference signal using the LEBS method can be easily performed.
According to the embodiment of the present invention, because the core diameter and core-cladding ratio of each of the illumination fiber 311, the first light receiving fiber 312, the second light receiving fiber 313, and the third light receiving fiber 314 satisfy the condition expressions (2) and (3), preferable transmittance can be obtained even if the core diameter is small. Particularly, transmittance is preferable in the long wavelength region of 600 nm or more. Furthermore, because the interval between the illumination fiber 311, the first light receiving fiber 312, the second light receiving fiber 313, and the third light receiving fiber 314 can be reduced without increasing the cladding thickness, favorable detection sensitivity can be maintained.
According to the embodiment of the present invention, because each of the illumination fiber 311, the first light receiving fiber 312, the second light receiving fiber 313, and the third light receiving fiber 314 is configured as a single core step-index fiber, availability can be assured and the cost-effective measurement probe 3 can be prepared. Furthermore, the diameter can be smaller than that of a multi-core fiber.
According to the embodiment of the present invention, because the optical device 34 satisfies the condition expression (4), the hard part (the optical device 34) of the measurement probe 3 can be small and thus smooth insertion can be done during insertion into the instrument channel 111 of the endoscope device 110. Furthermore, because the illumination light is not directly applied to the edge of the optical device 34, the occurrence of stray light can be prevented. Furthermore, appropriate space coherence length can be obtained.
According to the embodiment of the present invention, because the optical device 34 satisfies the condition expression (5), appropriate space coherence length can be obtained.
According to the embodiment of the present invention, because the measurement probe 3 satisfies the condition expression (6), smooth insertion into the instrument channel 111 of the endoscope device 110 can be done. Furthermore, the durability during insertion can be improved.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
This application is a continuation of International Application No. PCT/JP2013/060556, designating the United States and filed on Apr. 5, 2013 which claims the benefit of priority from U.S. provisional application No. 61/651,843 filed on May 25, 2012, and the entire contents of the International application and the United States provisional application are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61651843 | May 2012 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2013/060556 | Apr 2013 | US |
| Child | 14075473 | US |
