MEASUREMENT PROBE

A measurement probe includes an illumination fiber configured to irradiate a 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:     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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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.

FIG. 1is a block diagram schematically showing a configuration of a biological optical measurement system according to an embodiment of the present invention. A biological optical measurement system1shown inFIG. 1includes a biological optical measurement apparatus2that performs optical measurement on a measurement target, such as a body tissue that is a scattering object, to detect properties (characteristics) of the measurement target; and a measurement probe3for measurement that is detachably attached to the biological optical measurement apparatus2and inserted into a subject.

The biological optical measurement apparatus2will be described first. The biological optical measurement apparatus2includes a power supply21, a light source unit22, a connector23, a light receiving unit24, an input unit25, an output unit26, a recording unit27, and a controller28. The power supply21supplies power to each component of the biological optical measurement apparatus2.

The light source unit22is 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 unit22outputs, to the measurement probe3via the connector23, incoherent light to be applied to the measurement target which contains at least one spectral component.

The connector23detachably connects a connection part31of the measurement probe3to the biological optical measurement apparatus2. The connector23outputs light that is emitted by the light source unit22to the measurement probe3and outputs, to the light receiving unit24, return light of illumination light that is emitted from the measurement probe3and reflected and/or scattered from the measurement target. The connector23outputs, to the controller28, information regarding whether the measurement probe3is connected.

The light receiving unit24receives and measures the return light of the illumination light, which is emitted from the measurement probe3and reflected and/or scattered from the measurement target. The light receiving unit24is realized by using multiple spectrometers and light receiving sensors. Specifically, in the light receiving unit24, spectrometers are provided in accordance with the number of light receiving fibers of the measurement probe3described later. The light receiving unit24measures spectral components and intensity distribution of the incident scattered light from the measurement probe3and measures each wavelength. The light receiving unit24outputs the result of the measurement to the controller28.

The input unit25is realized by using a push-type switch or a touch panel. The input unit25receives an input of an instruction signal instructing the starting of the biological optical measurement apparatus2or an instruction signal instructing various operations and outputs the input to the controller28.

The output unit26is realized by using a liquid crystal display or an organic EL (electro luminescence) display, and a speaker, etc. The output unit26outputs information on various processes in the biological optical measurement apparatus2.

The recording unit27is realized by using a volatile memory or a non-volatile memory. The recording unit27records various programs for operating the biological optical measurement apparatus2and various types of data and various parameters used for optical measurement processing. The recording unit27temporarily records information on the biological optical measurement apparatus2during processing. The recording unit27also records the result of measurement performed by the biological optical measurement apparatus2. The recording unit27may be configured using a memory card, etc. that is attached from the outside of the biological optical measurement apparatus2.

The controller28is configured using a CPU (central processing unit), etc. The controller28controls processing operations of each unit of the biological optical measurement apparatus2. The controller28controls operations of the biological optical measurement apparatus2by transferring instruction information or data corresponding to each unit of the biological optical measurement apparatus2. The controller28records the result of measurement performed by the light receiving unit24. The controller28includes an calculation unit28a.

The calculation unit28aperforms multiple arithmetic processes on the basis of the result of measurement, which is performed by the light receiving unit24, 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 unit25.

The measurement probe3will be described below. The measurement probe3is realized by internally arranging multiple optical fibers. Specifically, the measurement probe3is 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 probe3includes the connection part31that is detachably connected to the connector23of the biological optical measurement apparatus2; a flexible part32that is flexible; a distal end33that applies the illumination light supplied from the light source unit22and receives the return light from the measurement target; and an optical device34that is provided to the distal end33.

A configuration of the distal end33, including the optical device34, of the measurement probe3will be described in detail here.FIG. 2is a diagram schematically showing a cross section along the longitudinal direction of the distal end33, including the optical device34, of the measurement probe3.

As shown inFIG. 2, the measurement probe3includes an illumination fiber311that applies illumination light to a measurement target; a first light receiving fiber312(first light receiving channel), a second light receiving fiber313(second light receiving channel), and a third light receiving fiber314(third light receiving channel) on which return light of the illumination light reflected and/or scattered from the measurement target is incident; a coating member315made of, for example, glass or resin, for preventing damage to or for positioning the illumination fiber311, the first light receiving fiber312, the second light receiving fiber313, and the third light receiving fiber314; a protector316made of, for example, glass or brass for protecting the optical device34and the coating member315from external force; and a probe outer layer317made of, for example, SUS.

The illumination fiber311is configured by using a single core step-index fiber. The illumination fiber311propagates the illumination light output from the light source unit22and applies the illumination light to the measurement target via the optical device34. The number of fibers of the illumination fiber311can 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 fiber312, the second light receiving fiber313, and the third light receiving fiber314is configured using a single core step-index fiber. The first light receiving fiber312, the second light receiving fiber313, and the third light receiving fiber314propagate 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 device34, and output the return light to the light receiving unit24of the biological optical measurement apparatus2. 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 device34is cylindrical and is configured using permeable glass having a predetermined refractive index. The optical device34includes an inclined surface that is cut obliquely with respect to the longitudinal direction of the measurement probe3. The optical device34is formed such that the distance between the illumination fiber311and the measurement target is fixed and light can be applied with a steadily constant space coherent. The optical device34is further formed such that each of the distance between the first light receiving fiber312and the measurement target, the distance between the second light receiving fiber313and the measurement target, and the distance between the third light receiving fiber314and 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 device34, 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 system1configured as described above, as shown inFIG. 3, the measurement probe3is inserted into a subject via an instrument channel111provided to an endoscope device110(endoscope) of an endoscope system100, the illumination fiber311applies illumination light to the measurement target, and the first light receiving fiber312, the second light receiving fiber313, and the third light receiving fiber314receive the return light of the illumination light, which is reflected and/or scattered from the measurement target, at different scattering angles, respectively, and propagate the return light to the light receiving unit24of the biological optical measurement apparatus2. The calculation unit28acomputes a characteristic value of the properties of the measurement target on the basis of the result of measurement performed by the light receiving unit24.

Because LEBS performed by the above-described biological optical measurement system1is 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 probe3without changing the diagnosing method. For this reason, the illumination fiber311, the first light receiving fiber312, the second light receiving fiber313, and the third light receiving fiber314satisfy the following condition expressions:

where NA indicates the numerical aperture of each of the illumination fiber311and the first light receiving fiber312to the third light receiving fiber314; Dcore indicates the core diameter of each of the illumination fiber311and the first light receiving fiber312to the third light receiving fiber314; and Dclad indicates the cladding diameter of each of the illumination fiber311and the first light receiving fiber312to the third light receiving fiber314(seeFIG. 4).

Regarding the expression (1), preferably,

and more preferably,

and more preferably,

and more preferably,

Regarding the measurement probe3, the longitudinal length DR(seeFIG. 2) of the optical device34in the longitudinal direction of the measurement probe3satisfies the following condition expressions:

and more preferably,

Regarding the measurement probe3, the refractive index Nd with respect to the d-line (wavelength of 587.56 nm) of the optical device34satisfies the following condition expression:

The maximum outer diameter Dout (seeFIG. 2) of the distal end33of the measurement probe3satisfies the following condition expressions:

The LEBS method performed by the biological optical measurement system1satisfies the following expression:

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 device34, and DRindicates the length from the center of the edge face on the base side of the optical device34to the center of the edge face on the tip side (seeFIG. 2). Thus, when the above-described condition expressions (1) to (6) are satisfied and LSC is constant, if λ and ND are equal, the more core diameter Dcore of the illumination fiber311is reduced, the more the length DRof the optical device34that is a hard part of the measurement probe3can be reduced. As a result, the measurement probe3can be easily inserted into the instrument channel111of the endoscope device110.

FIG. 5is a graph showing the relationship between wavelength and transmittance of the illumination fiber311of the present application and, for comparison, the same relationship for a conventional optical fiber. InFIG. 5, the horizontal axis indicates wavelength and the vertical axis indicates transmittance. The curved line L1indicates the characteristics of the illumination fiber311of the present application and the curved line L2indicates the characteristics of a conventional optical fiber.

The measurement of fiber transmittance inFIG. 5is performed in the following manner.

(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:

It is clear from the curved line L1inFIG. 5that the transmittance of the illumination fiber311of the embodiment is less dependent on the wavelength. In contrast, it is clear from the curved line L2that the transmittance of the conventional illumination fiber311is highly dependent on the wavelength.

According to the above-described embodiment of the present invention, because the illumination fiber311, the first light receiving fiber312, the second light receiving fiber313, and the third light receiving fiber314satisfy the above-described condition expressions (1) to (3), insertion into the instrument channel111of the endoscope device110can be done and accurate measurement can be performed.

According to the embodiment of the present invention, because the measurement probe3is detachable from the biological optical measurement apparatus2, the measurement probe3is disposable and thus the measurement probe3does not have to be sterilized in medical facilities and furthermore, because relatively poor durability is acceptable, the cost of the measurement probe3can be reduced.

According to the embodiment of the present invention, because the numerical aperture (NA) of the illumination fiber311satisfies the condition expression (1), the angle of light emitted from the illumination fiber311is 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 fiber311, the first light receiving fiber312, the second light receiving fiber313, and the third light receiving fiber314satisfy 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 fiber311, the first light receiving fiber312, the second light receiving fiber313, and the third light receiving fiber314can 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 fiber311, the first light receiving fiber312, the second light receiving fiber313, and the third light receiving fiber314is configured as a single core step-index fiber, availability can be assured and the cost-effective measurement probe3can 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 device34satisfies the condition expression (4), the hard part (the optical device34) of the measurement probe3can be small and thus smooth insertion can be done during insertion into the instrument channel111of the endoscope device110. Furthermore, because the illumination light is not directly applied to the edge of the optical device34, 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 device34satisfies the condition expression (5), appropriate space coherence length can be obtained.

According to the embodiment of the present invention, because the measurement probe3satisfies the condition expression (6), smooth insertion into the instrument channel111of the endoscope device110can be done. Furthermore, the durability during insertion can be improved.