JP3220213B2 - Optical tomographic imaging system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical tomographic imaging apparatus for imaging the inside of a living body or the like with light.

[0002]

2. Description of the Related Art As a living body observation apparatus using light, for example, Japanese Patent Application Laid-Open No. 61-37227 is known.
In this technique, a continuous light beam is projected onto a living body, and the transmitted light is received in the opposite direction to obtain a tomographic image.

[0003] On the other hand, there has been proposed a method that combines the incidence of a picosecond light pulse and the time-resolved measurement of light intensity by utilizing the fact that a living body is a strong light scattering medium. This is because when a picosecond light pulse is sufficiently diffused in a scattering medium such as a living body,
It takes advantage of the fact that the temporally measured light intensity pattern decreases exponentially with time, and the degree of the decrease depends on the concentration of the light absorbing substance in the scattering medium.

[0004]

However, in the above prior art, even if the internal information of the living body can be estimated to some extent, the external shape information has to be separately measured. Further, even though the internal information can be estimated, for example, in the measurement method using the exponential spread of the optical picosecond pulse due to the scattering of a living body, the intensity pattern of the obtained light depends on the scattering state of the measurement target. It is greatly affected, does not necessarily show an exponential phenomenon, and is often observed as a complicated pattern, which causes a problem that accurate measurement cannot be performed stably.

An object of the present invention is to provide an optical tomographic imaging apparatus capable of overcoming such problems.

[0006]

An optical tomographic imaging apparatus according to the present invention comprises: a light projecting means for projecting pulsed light having different wavelengths λ ₁ and λ ₂ toward a subject which is a scattering medium containing a light absorbing substance. A transmitted light detecting means for selectively detecting pulse light transmitted through the subject and emitted from a predetermined position of the subject to the outside; and a light projecting optical axis of the projecting means for transmitting the pulse light reflected by the subject. Reflected light detecting means for detecting on substantially the same axis as
Based on the output of the transmitted light detection means, on the line connecting the incident position of the pulsed light to the subject and the predetermined position where the transmitted light is emitted, and internal information calculation means for determining the concentration of the light-absorbing substance inside the subject at and near the line. Based on the output of the reflected light detection means, an outer shape information calculation means for determining the spatial position where the pulse light is applied to the surface of the subject, and an internal information calculation means when the pulse light is incident on a plurality of positions of the subject and An imaging unit that accumulates a calculation output of the outer shape information calculation unit and performs optical tomographic imaging of the subject based on the stored data.

Here, as a first mode of the internal information calculation, the light projecting means impinges pulse light of different wavelengths λ ₁ and λ _{2 on} the subject, and the internal information calculation means operates the scattering medium based on the incident pulse light. light intensity at a wavelength lambda ₁ time t ₁ of the light, t ₂ in the time response function of the light from the _{f 1 (t 1), f} 1 (t 2), at time t _1, t ₂ of the wavelength lambda ₂ light Light intensity f ₂ (t ₁ ), f ₂ (t
₂ ) is measured, and K is the absorption constant of the light-absorbing material of wavelengths λ ₁ and λ ₂ , and C is the speed of light in the scattering medium.
The concentration V of the light absorbing substance is calculated by the following equation: V = 1 / KC · 1 / (t ₁ −t ₂ ) × [log × f ₁ (t ₁ ) / f ₂ (t ₁ )｝ − log｝ f ₁ (t ₂ ) / F ₂ (t ₂ )｝]. As a second mode of the internal information calculation, the light projecting means impinges pulsed light of different wavelengths λ ₁ and λ _{2 on} the subject, and the internal information calculation means sets the absorbance of the light absorbing substance in the λ ₁ and λ ₂ light. A process for determining A ₁ and A ₂ , a process for measuring the optical path length L of the light absorbing material, and a light absorbing material based on the absorption coefficients ε ₁ and ε ₂ at A ₁ , A ₂ , L and λ ₁ , λ ₂ . And calculating the density V of V = (A ₁ −A ₂ ) / {L (ε ₁ −ε ₂ )}.

Further, the light emitting unit of the light emitting unit, the light receiving unit of the transmitted light detecting unit, and the light receiving unit of the reflected light detecting unit are attached to a support rotating around the subject. A plurality of light-receiving portions of the transmitted light detecting means, each of which is attached to a support; or a plurality of light-emitting portions of the light projecting means are arranged so as to surround the subject, and The light receiving section of the detecting means and the reflected light detecting means may be provided near each of the light projecting sections of the light projecting means.

[0009]

According to the present invention, by projecting pulsed light from the light projecting means toward the subject, internal information and spatial position information of the subject can be obtained at the same time. That is, the internal information is obtained by the transmitted light of the subject, and the outer shape information is obtained by the reflected light, and these are obtained as a result of the same pulsed light irradiation, so that accurate optical tomographic imaging can be performed.

Here, when the internal information calculation means is in the first mode, the following points are used. That is, when an optical pulse is incident on a scattering medium containing a light absorbing substance, the light intensity is logarithmically plotted on the vertical axis, and the light intensity of the light pulse that has passed through the scattering medium when the horizontal axis is time is shown in FIG. The light intensity (scattering profile) when there is no light absorbing substance in the scattering medium as shown in FIG. 1 (A) and the light intensity (absorption profile) when there is a light absorbing substance as shown in FIG. 1 (B) )
As shown in FIG. 1 (C), the product represented by the following equation (1) is used as the product of.

[0011]

(Equation 1)

Here, in FIG. 1B, ε is the extinction coefficient (depending on the wavelength), V is the molar concentration of the light absorbing substance, and C is the speed of light in the scattering medium.

Further, in addition to the above, the fact that the scattering profile does not change with the wavelength of the light pulse and the absorption profile changes with the wavelength is used. That is,
Using the fact that the scattering profile does not change with wavelength when there is no light absorbing substance in the scattering medium,
In the case of a type, two types of pulsed light having different wavelengths are incident, and the scattering profile is removed from the simultaneous equation of the obtained temporal profile of the light intensity for each wavelength and the equation of the scattering profile to remove the concentration of the light absorbing substance. Is measured.

On the other hand, when the internal information calculation means is of the second mode, the scattering medium containing the light absorbing substance is irradiated with picosecond pulsed light having different wavelengths λ ₁ and λ ₂ , and the corresponding absorbance A ₁ and A ₂ , and their difference △ A = A ₁ −
A ₂ is obtained, and the actual optical path length L of the scattering medium is obtained by introducing a time measurement method. Further, the arithmetic circuit calculates V = △ A / L (ε ₁ −ε ₂ ) to obtain the molar concentration V. Is what you want.

In the internal information calculation means according to these embodiments, the concentration of the light absorbing substance can be accurately measured as an actually measured value.
Further, the amount of accumulated data is small, and the operation method and the configuration of the device are simple. Furthermore, even if the input light intensity is not constant, the concentration of the light absorbing substance can be measured. In addition, even if a plurality of types of light-absorbing substances are present in the scattering medium by increasing the wavelength, the concentration of each light-absorbing substance can be accurately measured. For this reason, accurate optical tomographic imaging can be performed by accumulating the internal information of the subject for a case where the irradiation position of the pulse light and the emission position of the detected transmitted light from the subject are changed.

It should be noted that it is appropriate to use a single (single beam) or multiple (multi-beam) light projecting section of the light projecting means, or a single or plural transmitted light or reflected light detecting means. Can be combined. That is, when the number of the light projecting units is single, the inside and the outer shape information are accumulated by being rotationally driven around the subject, and when the number of the light projecting units is plural, the subject is sequentially driven by the pulse lighting to be driven. , Which is equivalent to being rotationally driven around, thereby enabling accurate optical tomographic imaging.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First, the basic principle will be described. In FIG. 2, it is considered that the subject (living body) partially contains the light absorbing substance. At this time, when an optical pulse is incident from point A in FIG. 2A and time-resolved measurement is performed on the light emitted from point B, the average light absorbing substance on the optical axis between A and B is measured. The concentration or the absorbance difference between the average wavelengths can be measured.

On the other hand, when considering the use of optical CT (computer tomography), it is necessary to perform a line integration of the substance concentration or the absorbance difference between A and B when performing image reconstruction. Therefore, it becomes necessary to know (measure) the physical distance between A and B. Therefore, as shown in FIG. 2B, the light pulse is emitted from the light incident portion indicated by the symbol C in the figure toward the living body using the light pulse and time-resolved measurement, and is reflected from the living body surface (G). If a time delay in which the returned light returns to the light detection unit denoted by reference numeral D is detected, and the time delay is converted into a distance traveled by the light, a distance from the point E on the inner surface of the gantry to the surface G of the living body can be obtained. By performing this for the entire inner circumference of the gantry, the outer shape of the living body can be known, and the distance between G and H can be obtained. Therefore, by performing these two types of measurements, it is possible to obtain the concentration distribution of the light-absorbing substance in the living body (in the object to be measured) or the light-absorbance difference distribution between wavelengths, thereby enabling optical CT.

The present invention uses the principle of measuring the concentration of a light-absorbing substance in a scattering medium, which will be described in detail later, to obtain an absorbance difference between two wavelengths between two points on the surface of a living body by photopicosecond pulse and phototime-resolved measurement. 1 and the spatial position and outer shape of the living body (measurement target) in the gantry are similarly measured using the optical picosecond pulse and the optical time-resolved measurement, and the space between the two points in the first measurement is measured. And the second measurement for calculating the target distance. This is a device that accumulates these measurement results and obtains an optical cross section. These two measurements can be performed by a common light source unit, gantry unit, and optical time-resolved measurement unit.

First, the first measurement will be described.
As shown in FIG. 3, a living body is set as an object to be measured inside the gantry, but a beam-like light pulse is directed toward the living body from one point M on the inner periphery of the gantry toward the center R of the gantry. Incident. Here, the light incident portion is
Similarly, it is paired with a light receiving unit that is collimated toward the center of the gantry. The reason why the incident portion and the light receiving portion are collimated in this way is to enable the second measurement to be performed.

The light pulse incident from the point M enters the living body at the surface O of the living body between the center R of the gantry and the inner surface M, and diffuses into the living body. And the surface P of the living body in it
The light pulse that has exited further enters a light receiving portion (light detecting portion) at an intersection N between a line obtained by extending a straight line connecting the point P and the center R of the gantry and the inner surface of the gantry. The light detector is collimated in the direction of line NR, and light emitted from other than point P is not detected by the detector at point N. Then, light intensity time-resolved measurement is performed on the light pulse that has entered the light detection unit at point N. This is performed at two wavelengths or multiple wavelengths, and the absorbance difference Co-p between the OPs is determined. This measurement is performed between each two points on the surface of the living body in the gantry.

Next, the second measurement will be described. FIG.
As shown in (a), the first point I on the inner surface of the gantry
In the same manner as in the measurement, a light pulse in the form of a beam is incident on the center R of the gantry. The light pulse is incident on the living body at one point J on the surface of the living body between I and R, but part of the light pulse is diffusely reflected out of the living body. Of the diffusely reflected light pulses, those returning to the point I are subjected to time-resolved light intensity measurement as shown in FIG. That is, by measuring the delay from the time when the light pulse is incident from point I to the time when the light pulse is diffusely reflected on the surface J of the living body and returns to I, the spatial distance between I and J can be obtained. Can be Here, the light detection unit may be common to the case of the first measurement. If this is performed for the entire inner circumference of the gantry, the position and outer shape of the living body to be measured in the gantry can be known.

When the position and outer shape of the living body are determined as described above, it is natural that the incident point O and the emission point P of the pulse light are determined.
The spatial distance Lo-p between is known. Here, point O-
Since the average absorbance difference between wavelengths (or the average concentration of the light-absorbing substance) between P is known by the first measurement, the line integral element necessary for re-image reconstruction is as shown in FIG.

In this manner, a similar value can be calculated between any two points on the surface of a living body (when there is no unevenness on the surface of the living body), and a tomographic image of the difference in absorbance between wavelengths in the gantry can be obtained. If this series of measurements is performed at multiple wavelengths, a tomographic image of the concentration distribution of the light absorbing substance in the living body can be obtained.

In light CT, when light passes through a measurement target such as a living body, the light is scattered multiple times within the measurement target, so that the distance that the light actually travels within the measurement target and the surface of the measurement target are determined. The linear distance between the light incident position and the light emitting position is different. Therefore, in the method of performing the quantification measurement by obtaining the actual traveling distance of light using time-resolved measurement, unless the linear distance from the light incident position to the emission position on the measurement target is obtained,
Projection data for tomographic image reconstruction cannot be obtained.

Next, an embodiment of the optical CT having the function of measuring the outer shape (the shape around the tomographic plane) of the object to be measured according to the present invention will be described below.

FIG. 6 shows the structure of the first embodiment. This embodiment is characterized in that only one set of a light pulse incident portion and reflected light and transmitted light receiving portions is provided, and these are reciprocated and rotated. That is, one line of data is taken by a set of sensing systems, and data of many lines is taken and stored by being driven, thereby performing imaging.

The light pulse light source 1 generates a light pulse according to a trigger signal from the control unit 2. The optical fiber for incident light 3 guides the light pulse generated from the light pulse light source 1 to the gantry 4, 5, and makes the beam 7 narrower than the light incident portion 6 to be incident on the measuring object 7. The light receiving unit 8 is provided with a collimator for selecting light incident in a direction parallel to and opposite to the light pulse emitted from the incident unit 6 and entering the light. The light pulse is provided sufficiently close to the incident portion 6 so as to selectively receive a component in a substantially opposite direction (shifted in the 180 ° direction) from the diffusely reflected light pulse.

The light pulse received by the light receiving unit 8 with collimator is guided to one channel of the multi-channel light intensity time-resolved measuring device 10 by the light receiving optical fiber 9 and controlled by the multi-channel light intensity time-resolved measuring device 10. The light intensity time-resolved measurement is performed by the trigger signal from the unit 2. Based on the measurement data, a time delay from the time when the light pulse is emitted from the incidence unit 6 to the time when the light pulse enters the collimator-equipped light receiving unit 8 is determined in the outer shape calculation unit 13, and the distance between A and B is calculated based on the time delay. Ask.

The light receiving section 11 is installed so as to face the incident section 6 and receives the light pulse transmitted through the object 7 to be measured. The received light pulse is guided to another channel of the multi-channel light intensity time-resolved measuring device 10 by the light receiving optical fiber 12, and the light intensity is time-resolved and measured. By performing the light intensity time-resolved measurement with light pulses of several wavelengths, the average absorbance difference between the wavelengths B and C or the concentration of the light absorbing substance is obtained in the projection data calculation unit 14.

Here, the gantry 4 reciprocates the incident unit 6, the light receiving unit with collimator 8 and the light receiving unit 11 in pairs according to the control signal of the control unit 2, and the gantry 5 converts the signal from the control unit 2 into a signal. Therefore, the gantry 4 including the incident part 6, the light receiving part with collimator 8 and the light receiving part 11
Is changed by 360 °, and the above measurement is repeated, so that the outer shape calculation unit 13 obtains outer shape information of the measurement object 7. Based on this external data, the projection data calculation unit 1
In 4, projection data required for tomographic image reconstruction of the measurement object 7 is calculated, and in the tomographic image reconstruction unit 15, a tomographic image is obtained and the display unit 1 is obtained.
6 is displayed.

FIG. 7 shows the configuration of the second embodiment. In this case, one reflected light receiving unit and a plurality of transmitted light receiving units are provided for one light pulse incidence unit. The gantry 5 on which these are mounted can be driven to rotate. In addition, the point of repeating measurement and accumulating data, and reconstructing a tomographic image is the same.

In the system of this embodiment, the light pulse incident on the measuring object 7 in the form of a beam from the incident section 6 is diffusely reflected on the surface of the measuring object 7 and spreads inside to form a fan beam. utilizing, by the light-receiving unit 11 installed multiple gantry 5 and can be from between B-C ₁ at a time to obtain a time-resolved measurement data of the light pulses between B-C _n. In addition, the gantry 5 is the incident part 6,
Together with the collimator-equipped light-receiving units 8 and 11, it receives a signal from the control unit 2 and rotates.

FIG. 8 shows the configuration of the third embodiment. In this embodiment, there is no need to rotate the gantry. A large number of probes 17 each having a pair of the incident section 6 and the light receiving section 8 with a collimator are regularly arranged on the fixed gantry 18. The optical fiber for incident light for transmitting the optical pulse emitted from the optical pulse light source 1 is determined by the optical rotary switch 19 based on the signal of the control unit 2. This operation replaces the rotation of the gantry in the first and second embodiments,
The incident part 6 is determined.

The collimator-equipped light-receiving section 8 receives reflection from the surface of the measuring object 7 for calculating the outer shape when an optical pulse is incident on the measuring object 7 from the paired incident section 6. At other times, the light pulse transmitted through the measuring object 7 is received.

Next, the processing by the internal information calculation means in the first, second and third embodiments will be described. This processing is based on the premise that the living body, which is the subject, is a scattering medium containing a light-absorbing substance, and includes the above-described first mode and second mode.

First, a description will be given of a process of measuring the concentration of the light absorbing substance in the case where only one kind of light absorbing substance is contained in the scattering medium in the first embodiment.

Light scattering depends on the wavelength of incident light and the substance causing the scattering. In the case of measurement at two wavelengths, if two types of wavelength light enter the measurement target (living body) under the same conditions and are observed under the same conditions, it is considered that the influence of the scattering medium on the incident light is equal. Further, it is conceivable that the scattering medium itself is also a light absorbing material at the same time. Furthermore, if the wavelengths of the incident different wavelength light are sufficiently close, the scattering within the scattering medium can be considered to be approximately equal.

Therefore, light having wavelengths λ ₁ and λ _{2 having} the same scattering profile f ₀ (t) shown in FIG. 1A and different absorption coefficients ε ₁ and ε ₂ is selected, 1)
The following equation is obtained for each wavelength.

[0041]

(Equation 2)

[0042]

(Equation 3)

Here, f ₁ (t) and f ₂ (t) are the wavelengths λ
₁ , the observed temporal profile of the λ ₂ light,
₁ and I ₂ are incident light intensities, and ε ₁ and ε ₂ are wavelengths λ ₁ ,
The light absorption coefficient of the light absorbing substance at λ ₂ light, V is the concentration of the light absorbing substance, C is the speed of light, and t is the time. Note that f ₁ (t) and f ₂ (t) need to be corrected when there is a difference in the profile of the incident light pulse.

When the logarithms are calculated on both sides of the above equations (2) and (3), the following equation is obtained.

Log ｛f ₁ (t)｝ = log I ₁ + log ｛f ₀ (t)｝ + (− ε ₁ VCt) ( _{2 ′} ) log ｛f ₂ (t)｝ = log I ₂ + log ｛f ₀ ( t)｝ + (− ε ₂ VCt) (3 ′) The equation ( ₂ ′) − (3 ′) becomes the following equation (4).

Log {f ₁ (t) / f ₂ (t)} = log {I ₁ / I ₂ } + (ε ₂ −ε ₁ ) VCt (4) The above equation (4) is expressed in FIG. As shown, since it is satisfied for all t, at each of t = t _{1 to} t _n ,
(4) The following equation is obtained by formulating the equation.

Log {f ₁ (t ₁ ) / f ₂ (t ₁ )} = log {I ₁ / I ₂ } + (ε ₂ −ε ₁ ) VCt ₁ :: log ｛f ₁ (t _n ) / f ₂ (t _n )｝ = log {I ₁ / I ₂ } + (ε ₂ −ε ₁ ) VC · t _n (5) In the above formula (5), log (I ₁ / I ₂ ) The concentration V is unknown and therefore log (I ₁ / I ₂ )
Is determined by the simultaneous equations for eliminating.

For example, when the density V is obtained by using the equations for the times t ₁ and t ₂ , the following is obtained.

Log {f ₁ (t ₁ ) / f ₂ (t ₁ )} − log {f ₁ (t ₂ ) / f ₂ (t ₂ )} = (ε ₂ −ε ₁ ) VC (t ₁ −t ₂ )... (6) Therefore, V = [1 / {C (ε ₂ −ε ₁ ) (t ₁ −t ₂ )}] × [log {f ₁ (t ₁ ) / f ₂ (t ₁ )} − log {f ₁ (t ₂ ) / f ₂ (t ₂ )}] (7).

The above is the case of one kind of light absorbing substance,
The n kinds of light absorbing substances can be obtained by measuring at N + 1 kinds of wavelength lights, and if more kinds of wavelength lights are used, the concentration vector can be determined even by using the least square method.

In the above description, the extinction coefficient ε of the substance to be measured for each wavelength is assumed to be known. However, even when the extinction coefficient is not known in advance, for example, pulse light is applied to the substance to be measured. The light may be incident, the absorption constant K of the light-absorbing substance may be measured based on the transmitted light at that time, and this may be used. In this case, it can be replaced with C (ε ₂ −ε ₁ ) = K in the equation (7).

Next, a second mode for measuring the concentration of a light-absorbing substance from the light wavelength and the absorbance will be described.

First, the second aspect will be considered from a theoretical point of view. Generally, the absorbance A of an opaque substance is represented by the following equation.

A = log (I ₀ / I ₁ ) = εVL + B (15) I ₀ : incident light intensity I ₁ : emission light intensity ε: molar extinction coefficient of light absorbing substance V: molar concentration of light absorbing substance L: optical path length B: Scattering intensity Absorbance measurement of an opaque substance is λ to eliminate the effect B of scattered light.
Performing two-wavelength measurement at ₁ and lambda _2.

A ₁ = ε ₁ VL + B (16) A ₂ = ε ₂ VL + B (17) ε ₁ : molar extinction coefficient at λ ₁ ε ₂ : molar extinction coefficient at λ _{2 From} equations (16) and (17) The following equation is obtained.

ΔA = A ₁ −A ₂ = (ε ₁ −ε ₂ ) VL ΔV = ΔA / L (ε ₁ −ε ₂ ) (18) In the equation (18), the optical path length L is As shown in FIG. 12, since the length is longer than the geometrical optical path length L due to scattering, the absolute density V cannot be obtained unless the actual optical path length L is obtained.

Here, when time measurement is introduced to obtain the actual optical path length L, it can be obtained from the following equation.

L = C · t = C ₀ / n · t (19) C: speed of light in sample C ₀ : speed of light in vacuum n: refractive index of sample t: average running time in sample This equation (19) By calculating the actual optical path length L from, the absolute concentration V of the light absorbing substance can be measured.

[0059]

According to the present invention, by projecting the pulsed light from the light projecting means toward the subject, the internal information and the position information of the subject can be obtained at the same time. That is, the internal information is obtained by the transmitted light of the subject, and the outer shape information is obtained by the reflected light, and these are obtained as a result of the same pulsed light irradiation.
Accurate optical tomographic imaging can be performed.

Here, when the internal information calculation means is set to the first mode or the second mode, it can be accurately measured as the actual measured value of the concentration of the light absorbing substance. Further, the amount of accumulated data is small, and the calculation method and the configuration of the device are simple. Furthermore, even if the input light intensity is not constant, the concentration of the light absorbing substance can be measured.

For this reason, when there is a single light projecting unit, the light is driven to rotate around the object, and when there are a plurality of light projecting units, pulse lighting driving is sequentially performed, so that the internal information of the object is pulsed. Accumulation of the irradiation position and the changed position of the detected transmitted light from the subject allows accurate optical tomographic imaging.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle of a method for measuring the concentration of a light-absorbing substance in a scattering medium.

FIG. 2 is an explanatory diagram of the principle of the present invention.

FIG. 3 is a diagram illustrating the principle of internal information measurement according to the present invention.

FIG. 4 is a view for explaining the principle of external shape information measurement according to the present invention.

FIG. 5 is a diagram illustrating the principle of internal information measurement according to the present invention.

FIG. 6 is a configuration diagram of the first embodiment.

FIG. 7 is a configuration diagram of a second embodiment.

FIG. 8 is a configuration diagram of a third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light pulse light source, 2 ... Control part, 3 ... Optical fiber for incident light, 4 ... Gantry (for reciprocating motion), 5 ... Gantry (for rotary motion), 6 ... Incident part, 7 ... Object to be measured, 8 ... Light receiving unit with collimator, 9 ... Optical fiber for light receiving, 10 ... Multi-channel light intensity time-resolved measuring device, 11 ... Light receiving unit, 12
... Optical fiber for receiving light, 13... Calculating section, 14... Calculating section, 15... Tomographic image reconstructing section, 16.
7 ... prog, 18 ... fixed gantry, 19 ... optical rotary switch.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-54439 (JP, A) JP-A-63-304106 (JP, A) JP-A-63-115548 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) A61B 10/00 G01N 21/17 620 G01N 21/47

Claims (5)

(57) [Claims] 1. A light projecting means for projecting pulsed light having different wavelengths λ ₁ and λ ₂ toward a subject which is a scattering medium containing a light absorbing substance, and a predetermined position of the subject passing through the subject. Transmitted light detecting means for selectively detecting the pulsed light emitted to the outside, and reflection for detecting the pulsed light reflected by the subject on substantially the same axis as the light projecting optical axis of the light projecting means A light detecting unit, based on an output of the transmitted light detecting unit, the light absorption inside the subject on and near a line connecting an incident position of the pulse light to the subject and a predetermined position from which the transmitted light is emitted. Internal information calculating means for determining the concentration of a substance; outer shape information calculating means for determining a spatial position at which the pulse light is irradiated on the surface of the subject based on the output of the reflected light detecting means; Multiple positions of the specimen Imaging means for accumulating operation outputs of the internal information operation means and the outer shape information operation means when incident on the object, and performing optical tomographic imaging of the subject based on the accumulated data; The calculating means is a light intensity f at times t ₁ and t ₂ of the wavelength λ ₁ light in a time response function of light from the scattering medium based on the incident pulse light emitted from the light projecting means.
_{1 (t 1), f 1} (t 2), the light intensity f ₂ (t ₁₎ at time t _1, t ₂ of the wavelength lambda ₂ light, f ₂ (t ₂₎ was measured, the wavelength lambda _1, lambda _Two
Assuming that the constant of light absorption in the light absorbing substance is K and the speed of light in the scattering medium is C, the concentration V of the light absorbing substance is expressed by the following equation: V = 1 / KC · 1 / (t ₁ −t ₂ ) × An optical tomographic imaging apparatus characterized in that it is calculated by [log {f ₁ (t ₁ ) / f ₂ (t ₁ )} − log {f ₁ (t ₂ ) / f ₂ (t ₂ )}. _2. A light projecting means for projecting pulsed light having different wavelengths λ ₁ and λ ₂ toward a subject which is a scattering medium containing a light absorbing substance, and a predetermined position of the subject passing through the subject. Transmitted light detecting means for selectively detecting the pulsed light emitted to the outside, and reflection for detecting the pulsed light reflected by the subject on substantially the same axis as the light projecting optical axis of the light projecting means A light detecting unit, based on an output of the transmitted light detecting unit, the light absorption inside the subject on and near a line connecting an incident position of the pulse light to the subject and a predetermined position from which the transmitted light is emitted. Internal information calculating means for determining the concentration of a substance; outer shape information calculating means for determining a spatial position at which the pulse light is irradiated on the surface of the subject based on the output of the reflected light detecting means; Multiple positions of the specimen Imaging means for accumulating operation outputs of the internal information operation means and the outer shape information operation means when incident on the object, and performing optical tomographic imaging of the subject based on the accumulated data; The calculating means determines the absorbances A ₁ and A ₂ of the λ ₁ and λ ₂ light emitted from the light projecting means due to the light absorbing substance in the subject, and measures the optical path length L in the subject. Process, and these A ₁ , A ₂ , L and λ ₁ , λ ₂
Calculating the concentration V of the light absorbing substance from V = (A ₁ −A ₂ ) / {L (ε ₁ −ε ₂ )} based on the absorption coefficients ε ₁ and ε ₂ in Optical tomographic imaging system. 3. A light-emitting device according to claim 1, wherein the light-emitting unit of the light-emitting unit, the light-receiving unit of the transmitted-light detecting unit, and the light-receiving unit of the reflected-light detecting unit are attached to a support that rotates around the subject. The optical tomographic imaging apparatus according to claim 1 or 2, wherein: 4. The optical tomographic imaging apparatus according to claim 3, wherein a plurality of light receiving portions of said transmitted light detecting means are provided, each being attached to said support. 5. A light projecting unit of the light projecting means, wherein a plurality of light projecting units are arranged so as to surround the subject, and the light receiving units of the transmitted light detecting means and the reflected light detecting means are light projecting units of the light projecting means. The optical tomographic imaging apparatus according to claim 1, wherein the optical tomographic imaging apparatus is provided near each of the following.