JP2000210246A - Fluorescence observation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce a high S/N fluorescent image by a fluorescence observation device. SOLUTION: This fluorescence observation device has an excitation light irradiation means 10 and a fluorescent image pickup means 14. The excitation light irradiation means 10 irradiates excitation light 3 in the excitation wavelength range of a light sensitive material to a part 1 of a patient's body including the light sensitive material which emits fluorescence 2. The fluorescent image pickup means 14 detects the fluorescence 2 and picks up a fluorescent image. The excitation light 3 is modulated in intensity by a modulation means 15 according to a prescribed periodic function, and a specific value corresponding to the amplitude of the periodic intensity variation of the fluorescence for each pixel is found by an analysis means 21 based on the image data in a time series outputted from the fluorescent image pickup means 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for irradiating a living body containing a substance that emits fluorescent light with excitation light, capturing an image of the fluorescent light emitted from the fluorescent substance at that time, and using the image for diagnosis of the living body. The present invention relates to an observation device.

[0002]

2. Description of the Related Art Conventionally, PDD (Photodynamic Diagn
Various studies have been made on fluorescence diagnosis called osis). This PDD is a photosensitizer (ATX-S10, 5) that has tumor affinity and emits fluorescence when excited by light.
-ALA, HAT-D01, etc.) is absorbed and bound in advance to the tumor part of the living body, and the part is irradiated with excitation light in the excitation wavelength region of the photosensitizer to generate fluorescence, and an image based on this fluorescence is generated. This is a technique for diagnosing the location and infiltration of a lesion by displaying the information, and preventing oversight thereof.

[0003] As another form of the fluorescence diagnosis, a technique of focusing on a fluorescent substance derived from a living body, irradiating the fluorescent substance with excitation light to generate fluorescence (so-called autofluorescence), and applying the same to a similar diagnosis is also known. Are known. In this case, detection of a tumor part is performed by utilizing the difference between the autofluorescence spectrum of the tumor tissue and the autofluorescence spectrum of the normal tissue.

For example, Japanese Patent Publication No. 63-9664,
No. 136630 and JP-A-7-59783 disclose a fluorescence observation apparatus for performing this fluorescence diagnosis. Basically, this kind of fluorescence observation apparatus basically irradiates the living body with excitation light in the excitation wavelength region of the fluorescent substance, and captures a fluorescent image of the living body by detecting the fluorescence emitted by the fluorescent substance. Means, and an image display means for receiving the output of the imaging means and displaying the fluorescence image,
In many cases, it is configured in a form incorporated in an endoscope inserted into the body cavity, a colposcope, an operation microscope, or the like.

[0005] In the above-mentioned fluorescence observation apparatus, an imaging device such as a CCD is widely used to capture a fluorescent image, that is, an image due to the fluorescence emitted from a fluorescent substance. Since the CCD can be cooled to reduce the dark current,
If this is used, an image based on weak fluorescence can be captured. In this CCD, the switching noise peculiar to the solid-state imaging device among the noises involved in the reading can be significantly reduced by the correlated double sampling method, so that the main noise involved in the reading is amplifier noise. Therefore, conventionally, by performing low-speed scanning to narrow the bandwidth, noise associated with reading has been reduced to improve the S / N of the image signal.

Further, use of an II (Image Intensifier) -CCD for imaging a fluorescent image has been considered. Since the II-CCD has a function of multiplying the number of photons incident on the CCD, it is possible to capture a fluorescent image in so-called real time by using this function.

[0007]

However, since the object to be imaged in the fluorescence diagnosis is an image with extremely weak fluorescence,
Regardless of whether the above-mentioned cooled CCD or II-CCD is used, the fluorescence image S
/ N is reduced.

The present invention has been made in view of the above circumstances, and provides a fluorescence observation apparatus capable of capturing a high S / N fluorescence image by eliminating the influence of disturbances such as background light and noise. With the goal.

[0009]

According to the present invention, there is provided a fluorescence observation apparatus comprising: an excitation light irradiating means for irradiating a part of a living body containing a fluorescent substance emitting fluorescence with excitation light in an excitation wavelength region of the fluorescent substance; A fluorescence observation apparatus comprising: a fluorescence image capturing unit that detects fluorescence emitted by the fluorescent substance to capture a fluorescence image of a living body; a modulation unit that modulates intensity of the fluorescence incident on the imaging unit according to a predetermined periodic function. And, from the time-series image data output by the fluorescence image imaging means,
Analysis means for obtaining a characteristic value corresponding to the amplitude of the periodic change in the fluorescence intensity is provided for each pixel.

The above-mentioned modulating means can be configured to modulate fluorescence by modulating excitation light, for example.

Alternatively, when the excitation light irradiating means is configured to emit excitation light of a constant intensity, the modulation means may be configured to modulate the fluorescence at a portion inserted in the optical path of the fluorescence. .

The characteristic value may be the amplitude of the periodic change in the fluorescence intensity.

More specifically, the above-mentioned analysis means includes:
Means is used in which the time-series image data for each pixel is Fourier-transformed, and a predetermined Fourier coefficient obtained thereby is obtained as the characteristic value.

Alternatively, as the analysis means, a means for obtaining a regression curve indicating a periodic change of the image data by, for example, the least squares method, and obtaining a value corresponding to the amplitude of the regression curve as the characteristic value can be applied. is there.

Obviously, in the present invention, finding the regression curve as described above does not only mean finding the specific shape of the curve, but also includes finding the coefficients of the equation representing the regression curve. It is a thing.

In the fluorescence observation apparatus according to the present invention, preferably, there are provided a plurality of frame memories for storing the image data at the same address for the data on the same position of the living body, respectively, However, based on the image data read from these frame memories, the characteristic value is obtained for each image data stored at a common address.

On the other hand, the modulation means may be one that continuously modulates the intensity of the fluorescence incident on the imaging means, or one that intermittently modulates the intensity. More specifically, as the modulating means, a modulating means which modulates the intensity of the fluorescence incident on the imaging means in a sinusoidal manner or a sawtooth modulating means is preferably used.

[0018]

In the fluorescence observation apparatus of the present invention, when the intensity of the excitation light is modulated according to a predetermined periodic function, the intensity of the fluorescence emitted from the fluorescent substance is regularly modulated according to the periodic function. Originally, when the living body is uniformly irradiated with excitation light having a constant intensity, a fluorescent image is formed based on the fluorescent intensity at each position of the living body. However, the intensity of the fluorescent light is modulated as described above. In such a case, the amplitude corresponds to the fluorescence intensity itself when the excitation light having a constant intensity is irradiated.

The image data output by the fluorescent image pickup means is:
Normally, the light is affected by disturbance such as the background light and noise. However, even if the image data is such, if a characteristic value corresponding to the amplitude of the periodic change in the fluorescence intensity is obtained therefrom, the amplitude of the fluorescence based on this characteristic value,
That is, the fluorescence intensity itself excluding the influence of the disturbance can be detected. As a result, according to the present invention, a high S / N fluorescent image can be reproduced.

On the other hand, also in the case where the intensity of the fluorescence is modulated at the portion inserted into the optical path of the fluorescence, the fluorescence amplitude corresponds to the fluorescence intensity itself, excluding the influence of random disturbance factors. Therefore, also in this case, a high S / N fluorescent image can be reproduced.

[0021]

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

FIG. 1 shows a schematic configuration of a fluorescence observation apparatus according to a first embodiment of the present invention. The apparatus of this embodiment includes an excitation light source 10 for emitting excitation light 3, an excitation light power supply 11 for driving the excitation light source 10, and a condenser lens 12 for condensing fluorescent light 2 emitted from the living tissue 1 as described later. , An excitation light cut filter 13 disposed in front of the filter, and a high-sensitivity image sensor 14 composed of, for example, a high-sensitivity CCD for receiving the collected fluorescence 2.

The fluorescence observation apparatus is connected to a computer 15
And an image sensor driver 16 for driving the high-sensitivity image sensor 14
And a low-pass filter receiving the output of the high-sensitivity image sensor 14
17, an A / D converter 18 receiving the output of the low-pass filter 17, a multiplexer 19 for distributing digital image data output from the A / D converter 18, and an image data distributed by the multiplexer 19 for one image. .., M6 and M7, each storing eight minutes, an arithmetic circuit 21 receiving image data output from each of the frame memories M0 to M7, and an arithmetic circuit 21. Has a frame memory 22 for receiving the image data output by the CPU, and a display 23 such as a CRT display device for displaying an image based on the image data output from the frame memory 22.

The excitation light power supply 11 and the image sensor driver
The operations of the A / D converter 18, multiplexer 19, frame memories M0 to M7, arithmetic circuit 21, and frame memory 22 are controlled by the computer 15.

The operation of the fluorescence observation device will be described below. The living tissue 1 is preliminarily absorbed with a photosensitizer having a tumor affinity and emitting fluorescence when excited by light. When the living tissue 1 is irradiated with the excitation light 3 emitted from the excitation light source 10, fluorescence 2 is emitted from the photosensitive substance excited by the excitation light 3. As will be described later in detail, a modulation signal Sm is input to the excitation light power supply 11 from a computer 15 constituting a modulation means, and the fluorescence 2 is intensity-modulated.

The condenser lens 12 forms a fluorescent image of the living tissue 1 due to the fluorescent light 2 on the imaging surface of the high-sensitivity image sensor 14, and the fluorescent image is captured by the high-sensitivity image sensor 14. The excitation light 3 reflected by the living tissue 1 and traveling toward the condenser lens 12 is cut by an excitation light cut filter 13.

The time-series image data output from the high-sensitivity image sensor 14 is digitized by an A / D converter 18 after unnecessary high-frequency components are cut by a low-pass filter 17. The digitized image data D is sorted by the multiplexer 19 for each data of one image, and each of the frame memories M0, M1, M2... M6, M7.
Are sequentially stored. Note that the frame memories M0, M1, M
2. The image data stored in M6 and M7 is
0, D1, D2,..., D6, D7.

Frame memories M0, M1, M2... M6, M
7, image data D0, D1, D2,.
.. D6 and D7 are input to an arithmetic circuit 21, where image data D 'for one image is formed from the image data. The image data D ′ is input to the display 23, where a fluorescent image of the living tissue 1 is reproduced and displayed based on the image data D ′.

Next, data processing up to the formation of the image data D 'will be described with reference to FIGS. FIG. 2A shows an intensity modulation state of the excitation light 3, and FIG. 2B shows an example of an intensity change of the fluorescence 2 at a certain point of the living tissue 1. In this example, the intensity Ie of the excitation light 3
Is a sine wave Ie (t) = Ao · sin (ω
t) + Ao. Ao is a constant and is set to a sine wave period T = 2π / ω = 160 ms (millisecond).

When the intensity of the excitation light 3 is modulated in this manner, the intensity of the fluorescent light 2 generated by the excitation is also shown in FIG.
It changes in a substantially sinusoidal manner as shown in (2). The high-sensitivity imaging device 14 captures a fluorescence image of the living tissue 1 by the fluorescence 2 at a constant interval τ = 20 ms, that is, eight times within the sine wave cycle T. T0, t1, t2... T6, t7 shown in FIG.
Indicates the time points of this imaging, and the dots at those time points indicate the measured fluorescence intensities.

The digital image data representing the fluorescent images picked up at the time points t0, t1, t2... T6 and t7 are stored in the frame memories M0 and M1 as D0, D1, D2. , M2... M6, M7.
The image data D0, D1, D2,..., D6, D7 do not indicate purely the fluorescence intensity alone, but include the above-described disturbance factors such as background light and noise superimposed on the fluorescence detection component.

Here, data on the same position of the living tissue 1 are mutually stored in the frame memories M0, M1, M2,.
6, stored in the same address of M7. FIG. 3 schematically illustrates this. That is, in the figure, it is assumed that the positions of the squares of the frame memories M0, M1, M2,... M6, M7 correspond to the addresses. Living tissue 1
Are stored for the same position.

Here, the image data D (fluorescence detection signal) is
Generally, it is represented by the following Fourier series Is (t).

[0034] _{Is (t) = a 0/} 2 + a 1 · cos (ωt) + a 2
・ Cos (2ωt) + …… + b ₁・ sin (ωt) + b ₂・ sin (2ω
t) + ...... Note a _0/2 represents the DC component of the fluorescence intensity, the contribution of the DC components such as background light noise. Also, a ₁ · cos (ωt) +
_{a 2 · cos (2ωt) +} ...... + b 2 · sin (2ωt) + a 1 · cos
(ωt) indicates a noise component mixed into the fluorescence detection signal.
B ₁ · sin (ωt) indicates the fluorescence intensity induced by the intensity-modulated excitation light 3. Therefore, b ₁ · sin
By obtaining (ωt), it is possible to obtain a state in which the fluorescence detection signal has been passed through a narrow band filter and remove various disturbance noise components.

In the arithmetic circuit 21, the image data D0, D1, D2,..., D6, D7 stored in the frame memories M0, M1, M2,. (That is, for each image data stored at the same address), a Fourier series b ₁ is obtained.

It is generally known that the Fourier series b ₁ can be obtained by b ₁ = 1 / T · １ ／ Is (t) · exp (−jωt) dt. For discrete data, the following equation b ₁ = (1 / Nτ) · ΣIs (k) · sin (−2πk / Nτ) is applied. Here, N indicates the total number of samples, k indicates the sampling point, and Σ will be executed in the range of k = 0 to 7.

As described above, the Fourier series b _1, which is the characteristic value corresponding to the amplitude of the periodic change in the fluorescence intensity, is obtained for each pixel, and these values are framed as image data D ′ representing a fluorescent image. The information is temporarily stored in the memory 22. Then, a fluorescent image of the living tissue 1 is reproduced and displayed on the display 23 based on the image data D ′ read from the frame memory 22 at a predetermined timing. The fluorescent image displayed in this manner has a high S / N ratio except for the influence of disturbance such as background light and noise as described above.

Next, a second embodiment of the present invention will be described with reference to FIG. The device of the second embodiment has the same basic configuration as that of the first embodiment, except that the driving method of the excitation light source 10 is different. FIG. 4A shows an intensity modulation state of the excitation light 3, and FIG. 4B shows an example of a change in the intensity of the fluorescence 2 at a certain point of the living tissue 1.

That is, in this embodiment, in order to set the DC bias of the modulated pump light 3 large, the pump light 3 is modulated so that its intensity Ie exhibits a sine wave Ie (t) = Ao · sin (ωt) + Bo. I do. Here, Ao <Bo.

By modulating the excitation light 3 in this manner, the intensity of the excitation light is higher as a whole than in the first embodiment, and therefore, it is more advantageous in detecting and imaging weak biological fluorescence. Become.

Next, a third embodiment of the present invention will be described with reference to FIG. The device according to the third embodiment also has the same basic device configuration as that of the first embodiment.
Ten driving methods are different. FIG. 5A shows an intensity modulation state of the excitation light 3, and FIG.
An example of a change in the intensity of the fluorescence 2 at a certain point is shown.

That is, in the present embodiment, the excitation light source 10 is intermittently driven so as to emit the excitation light 3 in a pulse shape, and the excitation light 3
The imaging operation of the high-sensitivity image sensor 14 is performed only when is issued.

When the excitation light source 10 is pulse-driven in this manner, the excitation light 3 is output so as to exhibit a cosine waveform. In this case, compared to the first embodiment, the high-sensitivity image sensor 14
Since the fluorescence intensity does not change during the exposure, the measurement accuracy is improved.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In FIG. 6, elements that are the same as the elements in FIG. 1 are given the same reference numerals, and descriptions thereof will be omitted unless otherwise necessary (the same applies hereinafter).

The device shown in FIG. 6 is configured as a fiberscope endoscope, and includes a relay lens 30 for condensing the excitation light 3 emitted from the excitation light source 10 and a condensing excitation light 3. And a light guide 31 composed of an optical fiber for guiding. The light guide 31 is housed in a flexible probe 32 inserted into a living body.

The probe 32 further includes a diffusion lens 33 for diffusing the excitation light 3 emitted from the tip of the light guide 31, and a fluorescent light emitted from a photosensitive substance in the living tissue 1 upon receiving the irradiation of the excitation light 3. A condenser lens 34 for condensing the fluorescent light 2 and an image fiber 35 for transmitting the collected fluorescent light 2
Is stored.

The fluorescent light 2 emitted from the image fiber 35 passes through the excitation light cut filter 13 and is condensed by the condenser lens 12. Thus, the fluorescence 2
Is formed on the imaging surface of the high-sensitivity imaging device 14, and the fluorescent image is captured by the high-sensitivity imaging device 14.

In the present embodiment, the modulation of the excitation light 3 and the processing of the image data output from the high-sensitivity image sensor 14 are performed in the same manner as in the first embodiment, whereby the high S / N ratio is achieved.
Can be reproduced.

Next, a fifth embodiment of the present invention will be described. FIG. 7 shows a schematic configuration of a fluorescence observation device according to a fifth embodiment of the present invention. Compared with the apparatus of FIG. 1, the apparatus of this embodiment has frame memories M0, M1, M2... M7, M8 each of which stores the image data D distributed by the multiplexer 19 for one image. The difference is that the number is provided. The manner of modulating the excitation light 3 and the arithmetic processing performed by the arithmetic circuit 21 under the control of the computer 15 are also different from those in the apparatus shown in FIG. Other configurations are basically the same as those in the apparatus of FIG.

The operation of the fluorescence observation device will be described below. The living tissue 1 is preliminarily absorbed with a photosensitizer having a tumor affinity and emitting fluorescence when excited by light. When the living tissue 1 is irradiated with the excitation light 3 emitted from the excitation light source 10, fluorescence 2 is emitted from the photosensitive substance excited by the excitation light 3. As will be described later in detail, a modulation signal Sm is input to the excitation light power supply 11 from a computer 15 constituting a modulation unit, and the fluorescence 2 is intensity-modulated.

The condenser lens 12 forms a fluorescent image of the living tissue 1 by the fluorescent light 2 on the imaging surface of the high-sensitivity image sensor 14, and the fluorescent image is picked up by the high-sensitivity image sensor 14. The excitation light 3 reflected by the living tissue 1 and traveling toward the condenser lens 12 is cut by an excitation light cut filter 13.

The time-series image data output from the high-sensitivity image sensor 14 is digitized by an A / D converter 18 after unnecessary high-frequency components are cut by a low-pass filter 17. The digitized image data D is distributed by the multiplexer 19 for each data of one image, and each of the frame memories M0, M1, M2... M7, M8.
Are sequentially stored. Note that the frame memories M0, M1, M
2. The image data stored in M7 and M8 is
0, D1, D2... D7, D8.

Frame memories M0, M1, M2... M7, M
8, image data D0, D1, D2,.
.., D7 and D8 are input to an arithmetic circuit 21, where image data D 'for one image is formed from the image data. The image data D ′ is input to the display 23, where a fluorescent image of the living tissue 1 is reproduced and displayed based on the image data D ′.

Next, data processing up to the formation of the image data D 'will be described with reference to FIGS. FIG. 8A illustrates an intensity modulation state of the excitation light 3, and FIG. 8B illustrates an example of a change in the intensity of the fluorescence 2 at a certain point of the living tissue 1. In this example, the intensity Ie of the excitation light 3
Is a sine wave Ie (t) = a · sin (t) with time t as a variable
+ B. Note that a and b are constants, and the sine wave cycle T is set to 160 ms (millisecond).

When the intensity of the excitation light 3 is modulated as described above, the intensity of the fluorescence 2 generated by the excitation is also changed as shown in FIG.
It changes in a substantially sinusoidal manner as shown in (2). The waveform of the fluorescence intensity I is theoretically I (t) = a ′ · sin (t) + b ′, where t is time and a ′ and b ′ are constants. The high-sensitivity image sensor 14 captures a fluorescent image of the living tissue 1 by the fluorescent light 2 at a constant interval τ = 20 ms. .., T8 and t8 shown in FIG. 8 (2) indicate the time points of this imaging, and the dots at those time points indicate the measured fluorescence intensities.

.., D7,..., D7, D8 and D8, respectively, as described above. , M2... M7, M8.
The image data D0, D1, D2,..., D7, D8 do not simply indicate only the fluorescence intensity, but include the above-described disturbance factors such as background light and noise superimposed on the fluorescence detection component. Hereinafter, the measured fluorescence intensity values corresponding to the time series ti (i = 0 to 8) indicated by these image data D0 to D8 are represented by Iti.
(I = 0 to 8).

Data about the same position of the living tissue 1 are stored in frame memories M0, M1, M2,.
It is stored at the same address of M8. FIG. 9 schematically illustrates this. That is, here, it is assumed that the positions of the squares of the frame memories M0, M1, M2... M7, M8 correspond to the addresses. The data for the same position is stored.

Since the measured fluorescence intensity Iti includes disturbance factors as described above, the theoretical curve I (t) = a '· sin
(T) + b ′ randomly. However, it is known that a regression curve can be accurately obtained from data including random noise by, for example, the least squares method. In the present embodiment, a regression curve is obtained by obtaining a and b that minimize the following expression e = {[Iti- {a · sin (ti) + b}] ² .

A and b are given by Σe / ∂a = 0, ∂e / ∂b = 0, and a = ΣIti / Σsin (ti) b = {1 / Σsin (ti)} Σ {Iti sin (ti )-{ΣIti /
sin (t)} · sin ² (t)].

Therefore, in the arithmetic circuit 21, the image data D0, D1, D2,..., D7, D8 stored in the frame memories M0, M1, M2,. (That is, for each image data stored at the same address)
Is required. Here, the coefficient a indicates a relative value of the fluorescence intensity for each observation position, that is, for each pixel, and the value is temporarily stored in the frame memory 22 as image data D ′ indicating a fluorescent image.

Then, a fluorescent image of the living tissue 1 is reproduced and displayed on the display 23 based on the image data D ′ read from the frame memory 22 at a predetermined timing.
The fluorescent image displayed in this manner has a high S / N ratio except for the influence of disturbance such as background light and noise as described above.

Even when the fluorescence intensity is obtained based on the regression curve as described above, the excitation light source 10 may be driven by a pulse as in the third embodiment described above. Since the fluorescence intensity does not change during exposure of the high-sensitivity image sensor 14, the measurement accuracy is improved.

Next, a sixth embodiment of the present invention will be described with reference to FIG. The apparatus of the sixth embodiment is different from the fifth embodiment of FIG. 7 in that only three frame memories M0, M1, and M2 are provided for storing image data D distributed by the multiplexer 19 for each image. Is different. Also, the manner of modulating the excitation light 3 and the arithmetic processing performed by the arithmetic circuit 21 under the control of the computer 15 are different from those in the apparatus of FIG. Other configurations are basically the same as those in the apparatus of FIG.

The operation of the fluorescence observation apparatus will be described below. In the present apparatus, the image data D digitized by the A / D converter 18 is distributed to data of one image by the multiplexer 19, and is sequentially stored in the frame memories M0, M1, and M2. Note that the image data stored in the frame memories M0, M1, and M2 are denoted as D0, D1, and D2, respectively.

The image data D0, D1, and D2 read from the frame memories M0, M1, and M2, respectively, are input to an arithmetic circuit 21. The arithmetic circuit 21 outputs the image data for one image from the image data. D ′ is formed. The image data D ′ is input to the display 23, where a fluorescent image of the living tissue 1 is reproduced and displayed based on the image data D ′.

Next, data processing up to the formation of the image data D 'will be described with reference to FIG. FIG. 11A shows an intensity modulation state of the excitation light 3, and FIG. 11B shows an example of a change in the intensity of the fluorescence 2 at a certain point of the living tissue 1. In this example, the intensity Ie of the excitation light 3
Is modulated so as to exhibit a sawtooth wave Ie (t) = at × t + b with time t as a variable. Note that a and b are constants, and are set to a sawtooth wave period T = 90 ms (millisecond).

When the intensity of the excitation light 3 is modulated as described above,
The intensity of the fluorescence 2 generated by the excitation is also shown in FIG.
It changes roughly like a sawtooth. The waveform of the fluorescence intensity I is theoretically I (t) = a'.t + b ', where t is time and a' and b 'are constants. High-sensitivity image sensor 14
Represents a fluorescence image of the living tissue 1 by the fluorescence 2 at a constant interval τ
= 30 ms. T0, t1, shown in FIG.
t2 indicates the time point of this imaging, and the dot at each of those time points indicates the measured fluorescence intensity.

The digital image data representing the fluorescent images taken at the time points t0, t1, and t2 are stored in the frame memories M0, M1, and M2 as D0, D1, and D2, respectively, as described above. Note that the image data D0, D1, and D2 do not simply indicate only the fluorescence intensity, but include the above-described disturbance factors such as background light and noise superimposed on the fluorescence detection component. Hereinafter, the measured fluorescence intensity values corresponding to the time series ti (i = 0 to 2) indicated by these image data D0 to D2 are represented by Iti.
(I = 0 to 2).

Data about the same position of the living tissue 1 is stored at the same address in the frame memories M0, M1, and M2.

Since the measured fluorescence intensity Iti includes disturbance factors as described above, the theoretical curve I (t) = a'.t +
It randomly varies with respect to b ′. But in this case too,
For example, a regression curve can be obtained with high accuracy by the least square method. In the present embodiment, a regression curve is obtained by obtaining a and b that minimize the following equation e = {Iti- (at · t + b)} ² .

A and b are obtained from ＝ e / ∂a = 0 and ∂e / ∂b = 0, so that a = {nΣ (ti ・ Iti) -ΣtiΣΣIti} / {nΣΣti ^{2-
(Σti) 2} b = {} ΣIti · Σti 2 -Σti · Σ (ti · Iti)} / {n · Σti 2
-(Σti) ² }.

Therefore, in the arithmetic circuit 21, the image data D0, D2 stored in the frame memories M0, M1, M2 are stored.
From D1, D2, the coefficients a and b are obtained for each data at the same position of the living tissue 1 (that is, for each image data stored at the same address). Here, the coefficient a indicates a relative value of the fluorescence intensity for each observation position, that is, for each pixel, and the value is temporarily stored in the frame memory 22 as image data D ′ indicating a fluorescent image.

Then, a fluorescent image of the living tissue 1 is reproduced and displayed on the display 23 based on the image data D ′ read from the frame memory 22 at a predetermined timing.
The fluorescent image displayed in this manner has a high S / N ratio except for the influence of disturbance such as background light and noise as described above.

Next, a seventh embodiment of the present invention will be described with reference to FIG. The device of the seventh embodiment has the same basic configuration as that of the sixth embodiment.
Are driven differently. FIG. 12A shows an intensity modulation state of the excitation light 3, and FIG.
An example of a change in the intensity of the fluorescence 2 at a certain point is shown.

That is, in the present embodiment, the excitation light source 10 is intermittently driven so as to emit the excitation light 3 in a pulse shape, and the excitation light 3
Only when is issued, the high-sensitivity image sensor 14 performs an imaging operation.

When the excitation light source 10 is pulse-driven in this manner, the intensity of the fluorescent light 2 also exhibits a sawtooth waveform. In this case, compared to the sixth embodiment, since the fluorescence intensity does not change during exposure of the high-sensitivity image sensor 14, the measurement accuracy is improved.

Next, an eighth embodiment of the present invention will be described with reference to FIG. The device of the eighth embodiment is configured as a fiberscope endoscope similarly to the device of the fourth embodiment shown in FIG. And in this case,
Excitation light 3 is modulated in the same manner as in the sixth embodiment of FIG. 10, and the fluorescence intensity of each pixel is obtained based on the regression curve.

Next, a ninth embodiment of the present invention will be described with reference to FIGS. FIG. 14 shows a schematic shape of the ninth embodiment device. As shown in the figure, this apparatus is different from the eighth embodiment shown in FIG. 13 in that a rotary filter 50 is provided between the condenser lens 12 and the high-sensitivity image sensor 14.

FIG. 15 shows the rotary filter 50 in detail. As shown there, the rotating filter 50
It is composed of a transparent plate 50a having a transmittance of 100%, an ND filter 50b having a transmittance of 80%, and an ND filter 50c having a transmittance of 60%. And this rotary filter 50 is a driving means
The transparent plate 50a and the ND filter 50 are intermittently rotated by the
b, one of the ND filters 50c is sequentially inserted. Further, the excitation light source 10 is driven so as to emit the excitation light 3 having a constant intensity in a pulse shape in synchronization with the intermittent rotation of the rotary filter 50.

When the rotary filter 50 is intermittently rotated as described above, the intensity of the fluorescence 2 incident on the high-sensitivity image sensor 14 is modulated. FIG. 16A shows the intensity of the excitation light 3, and FIG. 16B shows an example of the intensity change of the fluorescence 2. As shown, in this case also, the fluorescence intensity detected by the high-sensitivity image sensor 14 changes with characteristics similar to those of the sixth embodiment shown in FIG.

As can be seen from the above description, the sixth
In the case of the embodiment, the fluorescence 2 itself emitted from the living tissue 1 is modulated, whereas in the case of the eighth embodiment,
There is a difference that the fluorescence 2 itself emitted from the living tissue 1 is not modulated.

However, in the case of the eighth embodiment, similarly to the sixth embodiment, the coefficients a and b of the regression curve are obtained by, for example, the least squares method, and the coefficient a indicating the relative value of the fluorescence intensity for each pixel is obtained. By reproducing the image as the image data D ′, a high S / N fluorescent image is reproduced.

When the fluorescence 2 incident on the high-sensitivity image sensor 14 is modulated as described above, the influence of background light and the like which are continuously mixed into the fluorescence 2 and detected cannot be eliminated, but the influence of random disturbance factors cannot be eliminated. Can be removed.

It is to be noted that a so-called electronic endoscope in which an image pickup element is incorporated at the distal end of the endoscope has been known, but the present invention can of course be applied to such an electronic endoscope. It is.

The fluorescence observation apparatus according to the present invention can be used not only for fluorescence diagnosis using a photosensitive substance but also for fluorescence diagnosis focusing on a fluorescent substance endogenous in a living body.
Needless to say.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fluorescence observation device according to a first embodiment of the present invention.

FIG. 2 is a graph showing a change in intensity of excitation light and fluorescence in the fluorescence observation apparatus.

FIG. 3 is a schematic diagram illustrating a state of storing image data in a frame memory of the fluorescence observation apparatus.

FIG. 4 is a graph showing intensity changes of excitation light and fluorescence in a fluorescence observation device according to a second embodiment of the present invention.

FIG. 5 is a graph showing changes in excitation light and fluorescence intensity in a fluorescence observation device according to a third embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a fluorescence observation device according to a fourth embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a fluorescence observation device according to a fifth embodiment of the present invention.

8 is a graph showing changes in the intensity of excitation light and fluorescence in the fluorescence observation device of FIG. 7;

9 is a schematic diagram illustrating a state of storing image data in a frame memory of the fluorescence observation apparatus in FIG. 7;

FIG. 10 is a schematic configuration diagram of a fluorescence observation device according to a sixth embodiment of the present invention.

11 is a graph showing changes in the intensity of excitation light and fluorescence in the fluorescence observation device of FIG. 10;

FIG. 12 is a graph showing changes in the intensity of excitation light and fluorescence in a fluorescence observation device according to a seventh embodiment of the present invention.

FIG. 13 is a schematic configuration diagram of a fluorescence observation device according to an eighth embodiment of the present invention.

FIG. 14 is a schematic configuration diagram of a fluorescence observation device according to a ninth embodiment of the present invention.

FIG. 15 is a front view showing a rotary filter provided in the fluorescence observation apparatus of FIG. 14;

FIG. 16 is a graph showing changes in the intensity of excitation light and detected fluorescence in the fluorescence observation apparatus of FIG. 14;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Biological tissue 2 Fluorescence 3 Excitation light 10 Excitation light source 11 Excitation light power supply 12 Condensing lens 13 Excitation light cut filter 14 High sensitivity image sensor 15 Computer 16 Image sensor driver 17 Low pass filter 18 A / D converter 19 Multiplexer 21 Operation circuit 22 Frame memory 23 Display 25 Excitation light cut filter 30 Relay lens 31 Light guide 32 Probe 33 Diffusion lens 34 Condensing lens 35 Image fiber 50 Rotation filter 50a Transparent plate 50b, 50c ND filter D0-D8, D 'Image data M0-M8 Frame memory

Claims (12)

[Claims] An excitation light irradiating means for irradiating a part of a living body containing a fluorescent substance that emits fluorescence with excitation light in an excitation wavelength region of the fluorescent substance; A fluorescence observation apparatus comprising: a fluorescence image imaging unit that captures a fluorescence image of: a modulation unit that intensity-modulates fluorescence incident on the imaging unit according to a predetermined periodic function; and a time series output by the fluorescence image imaging unit. Analyzing means for obtaining, for each pixel, a characteristic value corresponding to the amplitude of the periodic change in the fluorescence intensity from the image data. 2. The fluorescence observation apparatus according to claim 1, wherein the modulation means modulates the fluorescence by modulating the excitation light. 3. The excitation light irradiating means is configured to emit excitation light having a constant intensity, and the modulation means is configured to modulate the fluorescence at a portion inserted into an optical path of the fluorescence. The fluorescence observation device according to claim 1, wherein: 4. The image processing apparatus according to claim 1, wherein said analyzing means performs a Fourier transform on the time-series image data for each pixel, and obtains a predetermined Fourier coefficient obtained as the characteristic value. 4. The fluorescence observation device according to any one of items 1 to 3. 5. The fluorescence observation apparatus according to claim 4, wherein said analysis means performs said Fourier transform based on characteristics determined based on said periodic function. 6. The apparatus according to claim 1, wherein said analysis means obtains a regression curve indicating a periodic change of said image data, and obtains a value corresponding to an amplitude of said regression curve as said characteristic value. 4. The fluorescence observation device according to any one of items 1 to 3. 7. The fluorescence observation apparatus according to claim 6, wherein said analysis means obtains a regression curve by a least square method. 8. A plurality of frame memories for storing the image data at the same address for the data of the same position of the living body at the same address are provided, and the analyzing means is read from these frame memories. 8. The fluorescence observation apparatus according to claim 1, wherein the characteristic value is obtained for each image data stored at a common address based on the image data. 9. The fluorescence observation apparatus according to claim 1, wherein said modulation means continuously modulates the intensity of fluorescence incident on said imaging means. 10. The fluorescence observation apparatus according to claim 1, wherein the modulation unit intermittently modulates the intensity of the fluorescence incident on the imaging unit. 11. The fluorescence observation apparatus according to claim 1, wherein said modulation means modulates the intensity of fluorescence incident on said imaging means in a sinusoidal manner. 12. The fluorescence observation apparatus according to claim 1, wherein said modulation means modulates the intensity of fluorescence incident on said image pickup means in a sawtooth shape.