Patent Application
20110270070
1. Field of the Invention
The present invention relates to a living body observation apparatus which observes a tissue property of a living body by using light scattering information at a time of ultrasound irradiation.
2. Description of the Related Art
As a living body tomographic imaging technique, various techniques are proposed, such as optical CT and Optical Coherence Tomography (hereinafter, referred to as OCT). Optical CT using a near-infrared light (700 nm to 1200 nm) can obtain a tomographic image several centimeters under a biological mucosa.
Meanwhile, “ultrasound modulated optical tomography (hereinafter, referred to as UMOT)” has been proposed for obtaining a tomographic image at a mucosal deep portion (several centimeters) with a spatial resolution higher than optical CT by an order of magnitude by irradiating a living body with ultrasound and a light as in Japanese Patent Application Laid-Open Publication No. 2008-170363.
In Non-Patent Document (C. Kim, K. H. Song, L. V. Wang, “Sentinel lymph node detection ex vivo using ultrasound-modulated optical tomography,” J. Biomed. Opt., Vol. 13, 020507, 2008), Kim, et al. succeeded in visualization of a sentinel lymph node several centimeters under a mucosa by detecting an irradiation light modulated by ultrasound.
Meanwhile, Japanese Patent Application Laid-Open Publication No. 2000-197635 discloses a system and a method which irradiate an inside of breast tissue or the like with a visible/near-infrared light and converge ultrasound thereon to generate light scattering waves. This publication records and images the amplitude and the phase of the light scattering waves in the region irradiated with ultrasound.
Further, Japanese Patent Application Laid-Open Publication No. 2001-208729 discloses detecting means in which surface elastic waves are incident on an inspection object, and the inspection object is irradiated with a laser light, a reflected light is received by a laser transmitter/receiver, and a frequency difference of the irradiated laser light and the reflected light is detected by a signal processing device.
The detection means measures a vibration velocity of (surface elastic waves) of a surface of the inspection object from the difference between the frequency of the incident laser light and the frequency of the reflected light from the inspection object, and detects a defect of the inspection object.
The conventional apparatus of Japanese Patent Application Laid-Open Publication No. 2001-208729 detects a defect such as a microscopic crack on the surface of an inspection object by using a difference in frequency due to the Doppler effect corresponding to a distribution of vibration velocities of surface elastic waves which change in accordance with the presence or absence and the size of a defect with respect to the surface of the inspection object.
A living body observation apparatus according to the present invention has
an ultrasound irradiating unit which irradiates a predetermined region inside a living body with ultrasound,
a light irradiating unit which irradiates the predetermined region, which is irradiated with the ultrasound, with a light of a predetermined frequency,
a detection unit which detects a scattered light with a frequency shifted from the predetermined frequency in the irradiated light in an ultrasound vibration state, with a living body constituent substance included in the predetermined region as a light scattering substance,
a signal processing unit which performs signal processing of calculating velocity information of the living body constituent substance from a frequency shift amount in a detection signal of the scattered light detected by the detection unit,
a density information calculating unit which calculates density information of the living body constituent substance in the predetermined region from the velocity information,
a discriminating unit which performs discrimination of a state of the living body constituent substance by using a value of a density as the calculated density information, and
a density information storing unit which stores velocity information measured in advance in at least one organ composing a living body, or a specific site, for the density information calculating unit to calculate the density information from the velocity information, and density information corresponding to the measured velocity information, by linking the velocity information and the density information with each other.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in
The ultrasound transducer 2 is mounted to a scanning unit 3 as scanning means which scans a predetermined scanning range. The scanning unit 3 is configured by including two piezoelectric elements or the like which scan in two directions orthogonal to each other, for example. Further, the ultrasound transducer 2 is formed into a concave surface shape as shown in
The ultrasound which is generated by the ultrasound transducer 2 is irradiated to converge on a local region 18 as a predetermined region in a region of interest in an organ or the like whose tissue property (property or state of tissue) is to be discriminated inside a living body 17.
The ultrasound transducer 2 forms ultrasound irradiating means which irradiates the local region 18 as a predetermined region with ultrasound.
A living body constituent substance of the local region 18 is locally ultrasonically vibrated by irradiation of focused ultrasound. The scanning unit 3 is caused to scan, and thereby, the center position (also referred to as a position of interest) of the local region 18 moves within the scanning range of the region of interest.
Further, the living body observation apparatus 1 has a light source apparatus 4 configured by a laser diode or the like generating a light of a predetermined frequency f, and the light generated by the light source apparatus 4 is incident on one end portion of an optical fiber 5 as a light guide section.
The optical fiber 5 guides the incident light to emit the light from a distal end portion as the other end portion. The distal end portion is also disposed at a position adjacent to one side (left side in
The light emitted from the distal end portion of the optical fiber 5 is irradiated to the local region 18 as the predetermined region of the living body 17. The distal end portion of the optical fiber 5 forms light irradiating means which irradiates a predetermined region in the living body 17 with a light of a predetermined frequency.
The living body constituent substance which is ultrasonically vibrating (in the ultrasound vibration state) in the local region 18 functions as a light scattering substance which scatters an irradiated light, and in the scattered light by the light scattering substance, the frequency is shifted from the frequency f of the light before scattered, that is, frequency-shift takes place due to the Doppler effect by the velocity of ultrasound vibration.
Further, a distal end portion of an optical fiber 6 is disposed to be adjacent to the other side (right side in
In this case, when the frequency of the irradiated light is set as f as described above, and a velocity of the ultrasound vibration of the living body constituent substance (to be more specific, an average value velocity in a period of the ultrasound vibration when ultrasound vibration takes place, or the velocity at which an intensity of ultrasound vibration becomes the maximum when ultrasound vibration takes place) is set as v, a frequency shift amount Δf of a scattered light is approximately expressed as expression (1).
Δf=f·v/(c−v)≈f·v/c (1)
Here, c represents a light velocity, and approximation with c>>v is performed. Further, in expression (1), approximation is made with the angle formed by the propagating direction of ultrasound and the direction of an incident light (irradiated light) and a scattered light being sufficiently small. When the configuration of the arrangement as shown in
The optical fiber 6 guides the light incident on the distal end portion thereof to a photodetector 7 configured by a photodiode or the like. The photodetector 7 outputs an electric signal which is made by receiving (detecting) the scattered light with a frequency shift and photoelectrically converting the scattered light to a signal processing device 8 as a detection signal.
More specifically, the photodetector 7 forms detection means which detects a scattered light with the frequency shifted. A scattered light may be directly received (detected) without using the optical fiber 6. The signal processing device 8 performs signal processing of actually calculating the frequency shift amount from the scattered light with the frequency shifted.
The above described signal processing device 8 forms signal processing means which detects the frequency shift amount Δf of expression (1) by signal processing of Fourier transform, for example, from the detection signal of the scattered light, and calculates the velocity v of the ultrasound vibration as the velocity information of the living body constituent substance (light scattering substance) from the frequency shift amount Δf. Accordingly, the signal processing device 8 also includes the function of calculating means of a frequency shift amount.
The signal processing device 8 outputs the information of the calculated velocity v to a personal computer (abbreviated as a PC) 9. The PC 9 has a lookup table (abbreviated as LUT) 10 formed by, for example, a flash memory as information storing means inside the PC 9. The LUT 10 stores in advance the information of the above described velocities v measured in advance in a plurality of organs, specific sites and the like in the living body 17, and the information of densities ρ corresponding to the information of the velocities v as the linked velocity-density conversion information.
An operator designates which organ the local region 18 where ultrasound is actually irradiated and the scattered light is measured belongs to, and thereby, from the information of the velocity v corresponding to the case of the organ, the operator can read the information of the density ρ corresponding to the information of the velocity v from the LUT 10.
More specifically, when the velocity v of the ultrasound vibration is calculated from the frequency shift amount Δf by the Doppler effect, the information of which organ or living body site the living body constituent substance composing the local region 18 where the velocity v is calculated belongs to is used, and thereby, the information of the density ρ which is more closely (than the velocity v) related to the property of the living body constituent substance can be calculated.
A density calculating unit 9a of the PC 9 forms density information calculating means which calculates the information of the density ρ from the information of the velocity v by using the velocity-density conversion information stored in the LUT 10. Further, the LUT 10 forms velocity-density conversion information storing means as density information storing means for calculating density information from velocity information.
The PC 9 calculates density information from velocity information by using the information stored in the LUT 10, and stores the density information and the information of a position of interest as a center position in the local region 18 whose density information is calculated in a memory 11 inside the PC 9, for example, by linking them with each other. The PC 9 stores the value of the density ρ in a memory cell with an address corresponding to, for example, a position of interest in the memory 11.
It is known that when the cells of the living tissue as the living body constituent substance which compose the living body 17 change into lesion tissue as cancer tissue from the state of normal tissue, its cell nuclei (also simply referred to as nuclei) are enlarged.
Therefore, statistically, the value of the density ρ as the physical property value is considered to change between the case of normal tissue and the case of cancer tissue. More specifically, the density ρ of lesion tissue is considered to increase due to enlargement of the nuclei as compared with the case of normal tissue.
In the present embodiment, a threshold value ρth of the density ρ for discriminating the properties of both tissues from the distribution of the density ρ in the case of the normal tissue and in the case of cancer tissue as lesion tissue in each of a plurality of organs composing the living body 17 and a specific site is stored in a threshold value information storing unit 10a provided in the LUT 10, for example. The threshold value information storing unit 10a may be stored in another storing means without being limited to the case of being provided in the LUT 10.
The LUT 10 stores the data showing the relation of the velocity v and the density ρ in the positions respectively shown by white circles in
Further, in the present embodiment, the relation of the velocity v and the density ρ is measured in advance and checked not only in the case of normal tissue but also in the case of lesion tissue, and from the measurement result, the threshold value ρth of the density ρ for discriminating both the tissues is set. The set threshold value ρth is stored in, for example, the threshold value information storing unit 10a.
Statistically from the measurement result, in the case of the density ρ exceeding the threshold value ρth, the possibility of lesion tissue is high as shown by the black circles. Further, the threshold value ρth differs in accordance with an organ.
The PC 9 makes comparison with a comparator by using the information of the threshold value ρth of the density ρ stored in the threshold value information storing unit 10a of the LUT 10, and thereby, discriminates the tissue property as to whether the living body constituent substance at the position where the density information is calculated is of normal tissue or lesion tissue.
The PC 9 determines that the possibility of lesion tissue is high when the density is the threshold value ρth or more, and determines that the possibility of normal tissue is high when the density is less than the threshold value ρth.
More specifically, a discriminating unit 9b of the PC 9 has the function as discriminating means which performs (state discrimination of a living body constituent substance including the case of) discrimination of the tissue property as to whether the living body constituent substance is of normal tissue or lesion tissue by using the density information.
As above, in the present embodiment, the information of the velocity v by ultrasound vibration is converted into density information, whereby, a tissue property is more easily discriminated than in the case of use of the information of the velocity v, and an operator easily grasps the discrimination standard for performing the discrimination (more specifically, the discrimination standard that as the value shifts to a larger extent from the value of the density in the case of normal tissue, the possibility of lesion tissue is higher).
For this reason, when the operator obtains the discrimination result, the operator easily grasps the extent to which the discrimination result should be referred to from the discrimination standard, and can properly perform diagnosis and the like.
As shown in
The pulse generator 12 generates a high-frequency pulse for causing ultrasound in a pulse form to be generated from the ultrasound transducer 2, and the high-frequency pulse is amplified by a power amplifier 14 to be applied to the ultrasound transducer 2. The ultrasound transducer 2 emits ultrasound in a pulse form by an applied high-frequency pulse.
The high-frequency pulse is a pulse including a sine wave corresponding to several periods which ultrasonically vibrates the ultrasound transducer 2 at a predetermined frequency. The ultrasound transducer 2 ultrasonically vibrates at the frequency of the sine wave, and emits the ultrasound from an exit surface of the concave surface.
The frequency in this case is about several MHz to several tens MHz, for example. A spatial resolution can be enhanced more when the frequency is made higher. However, when the frequency is made high, attenuation in the living body 17 also becomes large.
Further, the pulse generator 12 delays a high-frequency pulse and outputs the high-frequency pulse to the signal processing device 8. A time by which the pulse is delayed, that is, a delay time is about a time in which the ultrasound reaches the local region 18 after ultrasound in a pulse form is emitted from the ultrasound transducer 2.
In other words, at the timing when a high-frequency pulse delayed by the delay time is inputted in the signal processing device 8, the detection signal of the scattered light which goes through Doppler shift in the local region 18 and is detected by the photodetector 7 is inputted in the signal processing device 8.
The signal processing device 8 calculates the velocity information from the detection signal and outputs the velocity information to the PC 9, and outputs a scanning control signal (signal for moving to the next position of interest) for causing the scanning driver 13 to scan to the scanning driver 13.
The scanning driver 13 receives the scanning control signal, and moves the scanning unit 3 formed by piezoelectric elements or the like by one step. The scanning unit 3 can scan to cover a two-dimensional scanning range along, for example, an XY plane, that is, a horizontal plane. The scanning unit 3 may be capable of scanning on an XZ plane or a YZ plane without being limited to the XY plane.
Accordingly, the signal processing device 8 receives a detection signal of a scattered light in the state in which the position (position of interest) of ultrasound irradiation and light irradiation in the local region 18 is moved (scanned) little by little.
The above described PC 9 converts the velocity information of the velocity v inputted from the signal processing device 8 into the density information of the density ρ, stores the density information in the memory 11 by associating the density information with a position of interest R (scanning position), and outputs the density information to a monitor 15 as display means, as an image.
Further, when the PC 9 stores the density information in the memory 11, the PC 9 also stores the information of the discrimination result of whether or not the density information is the threshold value ρth or larger. The PC 9 has the function of an image processing unit 9c as image processing means which performs processing of displaying the information of the memory 11 as an image by the monitor 15 as display means.
When performing image processing, the PC 9 performs processing of displaying the density information in a luminance value in monochrome, for example, in accordance with the value ρ of the density, and performs processing of displaying the density information which is the threshold value ρth or larger in a red color, for example. Display is not limited to that in a red color, but may be in another color. Namely, the PC 9 performs image processing of displaying the density information in each scanning position in a scanning range on the monitor 15 by adding discrimination information as the information of the discrimination result by the discriminating means to the density information.
An operator can know that the portion displayed in a color (red color in a specific example) differing from the display in monochrome is highly likely to be of lesion tissue in the information displayed on the monitor 15 as an image, and easily makes efficient diagnosis by carefully diagnosing the portion.
An input unit 16 made up of a keyboard, a mouse and the like is connected to the PC 9, and when the operator is to perform discrimination of the tissue property of an organ actually, the operator inputs information designating the organ or the site from the input unit 16.
As described above, in the present embodiment, when the velocity-density conversion information is owned, which is obtained by investigation of the relation of the velocity information and the density information in advance by measurement in organs of different kinds, specific sites and the like as living body constituent substances which compose the living body 17, and discrimination of the tissue property of a desired organ is to be performed by using the velocity-density conversion information, the density information is calculated and the discrimination can be made.
Next, an operation of living body observation including discrimination of the tissue property of the living body 17 by using the living body observation apparatus 1 according to the present embodiment will be described with reference to
In the first step S1, an operator designates an organ or a site which the operator is going to diagnose or inspect in the living body 17.
In this case, the operator may be allowed to perform diagnosis or inspection by selecting the corresponding object from the list of the organs and sites in the living body 17 which is prepared in advance in the living body observation apparatus 1.
By this processing, when the velocity v of the ultrasound vibration is calculated, and even when the acoustic characteristic to ultrasound differs in accordance with the kinds of organs, the velocity v can be properly converted into the corresponding density information. This processing is not limited to the case of being performed first.
In the next step S2, for example, the signal processing device 8 sets a parameter k expressing the scanning position to an initial value k=1. Here, the parameter k includes a parameter in the scanning range in an X-direction and a parameter in the scanning range in a Y-direction which are the scanning range on the horizontal plane, for example.
In the next step S3, the light by the light source apparatus 4 is irradiated to a position of interest Rk(=R1) as the scanning position of the initial setting in the local region 18 of the living body 17 through the optical fiber 5. The position of interest Rk simply expresses the three-dimensional coordinates in Rk(xk, yk, zk).
As shown in step S3, as the light generated by the light source apparatus 4, for example, a laser light can be used. The laser light may be a continuum or a pulsed light.
Further, as shown in step S4, based on a high-frequency pulse generated at, for example, a predetermined frequency from the pulse generator 12, the ultrasound transducer 2 emits ultrasound in a pulse form. The emitted ultrasound converges on (the local region 18 of) the position of interest Rk.
In the position of interest Rk, the living body tissue constituent substance ultrasonically vibrates, and the laser light is scattered by the living body tissue constituent substance ultrasonically vibrated.
When the frequency of the laser light irradiated to the living body tissue constituent substance is set as f, the scattered light (scattered laser light) with the frequency shifted by the frequency shift amount Δfk (=Δf1) is detected by the photodetector 7 through the optical fiber 6, and the detection signal by the photodetector 7 is outputted to the signal processing device 8.
The pulse generator 12 outputs a high-frequency pulse which is an instruction to capture the detection signal of the scattered light to the signal processing device 8 after the delay time corresponding to the time in which the ultrasound in a pulse form reaches the position Rk of interest from the time at which the pulse generator 12 outputs the high-frequency pulse to the ultrasound transducer 2 through the power amplifier 14.
As shown in step S5, the signal processing device 8 captures the detection signal from the photodetector 7 in synchronism with the high-frequency pulse, and measures the frequency shift amount Δfk.
In this case, the signal processing device 8 performs Fourier transform for the inputted detection signal by, for example, a fast Fourier transform circuit (FFT) provided inside the signal processing device 8 to transform time series data I(t) of the intensity of the detection signal into frequency series data I(f).
Further, from the frequency series data I(f) of the intensity of the detection signal, the signal processing device 8 calculates the frequency shift amount Δfk by which the intensity reaches its peak.
Further, as shown in step S6, the signal processing device 8 calculates the velocity vk(=v1) of the living body constituent substance in the position of interest Rk from the frequency shift amount Δfk by using expression (1). The signal processing device 8 outputs the information of the calculated velocity vk to the PC 9.
As shown in step S7, the PC 9 calculates the corresponding density ρk (=ρ1) from the information of the velocity vk by referring to the LUT 10. The PC 9 stores the information of the calculated density ρk in the memory 11 in the PC 9 with the information of the position Rk of interest (parameter k may be adopted).
Further, as shown in step S8, the PC 9 also stores the discrimination information Dk as the information of the result of discrimination of whether or not the density ρk is the threshold value ρth or more in the memory 11.
In the next step S9, the signal processing device 8 discriminates whether or not the scanning ends. The signal processing device 8 changes the parameter k to k+1 and sets the parameter k+1 as shown in step S10 when the scanning does not end.
By changing and setting the parameter k, the signal processing device 8 outputs a signal for moving in (the X-direction in), for example, the horizontal direction by one step to the scanning driver 13. As shown in step S11, the scanning driver 13 moves the scanning unit 3 in, for example, the horizontal direction (more specifically, in the X-direction in the horizontal direction) by one step.
After the processing, the flow returns to the processing of step S3. In step S3, the position of interest Rk is R2, and the same processing is performed for the position of interest Rk(=R2). In this manner, when scanning in the predetermined scanning range with respect to the X-direction is finished, for example, similar scanning is also performed with respect to the Y-direction.
When scanning in the X-direction and the Y-direction, that is, in the predetermined two-dimensional scanning range ends, the flow shifts to the processing of step S12 subsequently to step S9.
In the step S12, the PC 9 reads the information of the densities ρ1 to ρn (when the number of scanning steps is set as n−1) in the predetermined scanning range and the discrimination information D1 to Dn, which are stored in the memory 11, and displays the density information and its discrimination information in the predetermined scanning range on the display screen of the monitor 15 as an image.
In this case, when the density ρk is less than the threshold value ρth according to the discrimination information D1 to Dn, the luminance value of the density ρ at the position is displayed in monochrome, for example, but when the density ρk is the threshold value ρth or more, the density at the position is displayed in a red color.
The operator can know that the portions displayed in a red color are highly likely to be of lesion tissue from the information displayed as the image on the monitor 15, and can perform efficient diagnosis by carefully diagnosing the portions.
As above, according to the present embodiment, the tissue property of the living body can be discriminated by using the light scattering information at the time of irradiation of ultrasound.
In this case, from the light scattering information of the living body constituent substance in the local region irradiated with ultrasound, the vibration velocity of the living body constituent substance is detected, and the density information of the living body constituent substance corresponding to the vibration velocity is calculated.
In the present embodiment, discrimination of the tissue property as to whether the living body constituent substance is of normal tissue or lesion tissue is performed by using the threshold value ρth in the density information, and therefore, the operator easily grasps the discrimination standard (according to the value of the density information) of the tissue property, and therefore, can efficiently perform diagnosis properly using the discrimination result.
When discrimination of whether the living body tissue is normal tissue or lesion tissue is performed, discrimination may be performed by using, for example, a plurality of threshold values ρth1 and ρth2 (for example, ρth1<ρth2) instead of using one threshold value ρth, and when the density is the threshold value ρth2 or more, the portion may be displayed in a color different from that in the case of the density of the threshold ρth1 or more. In the case of the threshold value ρth2 or more, the operator easily determines that the living tissue is more highly likely to be lesion tissue.
In this manner, the reliability of the information of the discrimination result of whether the living body tissue is normal tissue or lesion tissue can be enhanced.
Further, when discrimination is performed by using a plurality of threshold values ρth1 and ρth2 as described above, the threshold value ρth2 may be set at a value corresponding to the extent to which the cell nuclei composing the living body tissue are enlarged as cancer tissue from the state of normal tissue.
Further, the density ρ of the cell nuclei composing the living tissue in the state of the normal tissue is set at the reference value (for example, 1), and the information of an enlargement rate Ep corresponding to the ratio of enlargement of the cell nuclei from the state of the reference value may be stored in advance in, for example, the LUT 10 as an enlargement information storing unit 10b. When the discriminating unit 9b performs discrimination, the discriminating unit 9b performs state discrimination of whether or not the density exceeds the threshold value ρth, and may further refer to the information of the enlargement rate Ep of the enlargement information storing unit 10b in addition to the information of the discrimination result, and the information of enlargement of the cell nuclei also may be displayed. In this case, only when the density exceeds the threshold value ρth, the information of the enlargement rate Ep may be displayed. In this manner, the operator can use the value of the enlargement rate Ep of the cell nuclei as the diagnosis standard in the case of diagnosis.
Next, a second embodiment of the present invention will be described with reference to
A light of a light source apparatus 4b is incident on one end of an optical fiber 5a, an optical coupler 21 is provided midway of the optical fiber 5a, and the light guided by the optical fiber 5a is branched in the optical coupler 21 into an optical fiber 5b extended to a side of the scanning unit 3, and an optical fiber 5c extended to a side of a reference mirror 22.
A distal end portion of the optical fiber 5b is attached to the scanning unit 3 similarly to the first embodiment. However, in the present embodiment of
The optical fiber 5b emits the light from the light source apparatus 4b toward the local region 18 from a distal end portion thereof, and a scattered light scattered in the local region 18 is incident on the distal end portion.
Accordingly, the optical fiber 5b performs the functions of both the optical fiber 5 and the optical fiber 6 in the first embodiment. The scattered light incident on the distal end portion of the optical fiber 5b is guided to an optical fiber 5b which guides the light to the photodetector 7 from the optical coupler 21.
Further, the light guided by the optical fiber 5a from the light source apparatus 4b is also guided to the optical fiber 5c through the optical coupler 21. The light guided into the optical fiber 5c is reflected by the reference mirror 22 disposed to be opposed to a distal end of the optical fiber 5c, and returns to the optical coupler 21 again.
In this case, an optical path length (reference light optical path length) in which the light guided to the side of the optical fiber 5c from the optical coupler 21 is reflected by the reference mirror 22 and returns to the optical coupler 21 as the reference light, and an optical path length (measurement light optical path length) in which the light guided to the side of the optical fiber 5b from the optical coupler 21 is scattered at the local region 18 and returns to the optical coupler 21 (as the measurement light of the measurement object) again through the optical fiber 5b are set to substantially correspond to each other.
Further, in this embodiment, the light source apparatus 4b is a low-coherence light source apparatus, and the light generated by the light source apparatus 4b is a light of low coherence, for example. The low-coherence light is a light with a short coherent length which does not interfere with a light when the difference in the above described optical path length is about several tens μm or more, for example.
Accordingly, the low-coherence light from the light source apparatus 4b branches into the optical fiber 5b and the optical fiber 5c through the optical fiber 5a, and as for the light which is scattered at the side of the local region 18 through the optical fiber 5b and is incident on the optical fiber 5b again, only the scattered light from the vicinity of the inside of the local region 18 corresponding to the case of the optical path length which becomes substantially equal to the reference light optical path length interferes with the reference light.
As described in the first embodiment, the scattered light shifts from the frequency f of the light (irradiated before being scattered) by the frequency shift amount Δf by the Doppler effect, and therefore, the coherent light is the light subjected to heterodyne detection with the frequency shift amount Δf.
The coherent light is received by the photodetector 7 through the optical fiber 5d, is photoelectrically converted to be a detection signal and is inputted in the signal processing device 8.
Further, in the present embodiment, the angle formed by the direction in which the local region 18 is irradiated with ultrasound from the ultrasound transducer 2 to ultrasonically vibrate the living body constituent substance in the local region 18, and the direction of irradiating and detecting the light when the living body constituent substance in the local region 18 is irradiated with the light and the scattered light is detected is substantially zero, that is, both the directions substantially correspond to each other.
Therefore, expression (1) becomes better approximation than in the case of the first embodiment. In the case of the first embodiment, both the directions also may be configured to substantially correspond to each other like this. For example, the configuration may be adopted, in which the distal end portion of the optical fiber 6 is disposed as shown by the two-dot chain line to be adjacent to the distal end portion of the optical fiber 5 in
The signal processing device 8 calculates the frequency to be the peak in the detection signal subjected to heterodyne detection as in, for example, the first embodiment, and calculates the velocity v from the frequency.
The other components are the same as those in the first embodiment, and the description thereof will be omitted.
Further, the operation of the present embodiment is the same as that of the first embodiment by changing detection of a scattered light in the first embodiment to detection of a coherent light subjected to heterodyne detection. Therefore, the description of the operation of the present embodiment will be omitted.
The present embodiment detects the coherent light in the signal band of about the frequency shift amount Δf by causing the scattered light to interfere with the reference light without occurrence of the frequent shift, and therefore, can easily calculate the highly precise frequency shift amount Δf.
Further, the signal band of the coherent light becomes a sufficiently low band as compared with the case of the first embodiment, and therefore, the signal processing device at a lower speed than that of the first embodiment can be used. As for the rest, the present embodiment has the same effect as that of the first embodiment.
Next, a living body observation apparatus 1C according to a modified example of the present embodiment will be described with reference to
Further, in the present modified example, a light source apparatus 4c is adopted instead of the light source apparatus 4b in the living body observation apparatus 1B shown in
The light source apparatus 4c generates a laser light by a laser diode (LD) or an LED light by a light emitting diode (LED), for example.
In the second embodiment in
In contrast with this, the present modified example uses a light source such as an LD which generates a light with a longer coherent length than a low-coherence light of a low-coherence light source, and detects a coherent light of the scattered light from the vicinity of the local region 18 and the scattered light from the peripheral portion of the local region 18.
That is to say, in the peripheral portion of the local region 18, which is off the focus position of the converged ultrasound, the scattered light scattered in the peripheral portion becomes a scattered light without the frequency shift amount Δf.
A coherent light which is the result of interference of the scattered light with the frequency shift from the local region 18 irradiated with the focused ultrasound and a scattered light without the frequency shift is also incident on the optical fiber 5b. The photodetector 7 detects the coherent light component as a detection signal.
The signal processing for the detection signal detected by the photodetector 7 is substantially the same as that in the case of
According to the present modified example, by the configuration simpler than the case of
The present invention may have the configuration in which the aforementioned embodiments are modified. For example, the signal processing device 8 in the first embodiment may be configured to include the function of the PC 9. Further, in this case, the configuration may be adopted, in which a control program storing unit storing a control program which operates the living body observation apparatus 1 in accordance with the processing procedure of the flowchart shown in
Further, the scanning unit 3 may be configured to be able to perform three-dimensional scanning. Further, an arbitrary plane in a three dimension may be selected and set, so that observation including discrimination of the tissue property of the living body 17 can be performed. In this case, with use of the configuration of
In contrast with this, by using the configuration of
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-137481 | Jun 2009 | JP | national |
This application is a continuation application of PCT/JP2010/059509 filed on Jun. 4, 2010 and claims benefit of Japanese Application No. 2009-137481 filed in Japan on Jun. 8, 2009, the entire contents of which are incorporated herein by this reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2010/059509 | Jun 2010 | US |
| Child | 12967483 | US |
