JP4643253B2 - Fluorescence observation system - Google Patents

Description

  The present invention relates to a fluorescence observation system that obtains information on fluorescence emitted from a subject by irradiating a subject containing a fluorescent substance with excitation light.

  2. Description of the Related Art In recent years, various studies on photodynamic diagnosis generally referred to as PDD (Photodynamics Diagnostics) have been made. In this photodynamic diagnosis, a fluorescent agent that tends to accumulate in tumor tissue is administered to the subject, irradiated with excitation light, and a fluorescence image emitted from the fluorescent agent accumulated in the tumor tissue is observed. It is a technique for diagnosing a tumor part by observing the presence or absence and the shape.

In order to increase the contrast between the fluorescence of the fluorescent agent accumulated in the tumor tissue and the reflected light when the normal tissue is irradiated with excitation light, light in the fluorescence excitation wavelength range is transmitted and light in the high wavelength range is blocked. A fluorescence observation system has been proposed in which a filter is provided on the light source side, and a filter that transmits only a part of reflected light and blocks light in a low wavelength region is provided on the imaging means side (see, for example, Patent Document 1). .
Japanese National Patent Publication No. 11-511369 (FIG. 1)

  However, in this proposal, an overlapping portion between the transmission characteristic of the filter on the light source side and the filter and transmission characteristic on the imaging means side is detected as reflected light from normal tissue. There is a problem that the brightness and hue of the reflected light change, and a desired contrast cannot be obtained.

  Therefore, in the present invention, there is provided a fluorescence observation system that can always detect reflected light having a stable brightness and hue regardless of variations in the transmission characteristics of the filter, and can improve the contrast between fluorescence and reflected light. The purpose is to provide.

A fluorescence observation system according to the present invention is a fluorescence observation system that displays a fluorescence image obtained by irradiating a subject containing a fluorescent material with excitation light, a light source that generates illumination light including excitation light, and a light source The illumination light, which is disposed between the subject and the subject and is emitted from the light source, is obtained by the excitation light and the filter means that alternately transmits the excitation light and the background light in the discrete wavelength band. An image pickup means for picking up a fluorescent image of the subject and a background light image of the subject obtained by background light, and synchronizes the fluorescent image and the background light image, and processes the image to display it as a fluorescent image on the image display means. and an image processing means for outputting, in order to, the image processing means, said background image for performing tone adjusted to opposite color to the fluorescent image And having a color tone adjusting means.

  It is possible to realize a fluorescence observation system that can always detect reflected light having a stable brightness and hue and can improve the contrast between fluorescence and reflected light.

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

(First embodiment)
First, based on FIG. 1, the whole structure of the fluorescence observation system 1 concerning the 1st Embodiment of this invention is demonstrated. FIG. 1 is a block diagram illustrating the overall configuration of a fluorescence observation system 1 according to the present embodiment. As shown in FIG. 1, a fluorescence observation system 1 according to the present embodiment includes an electronic endoscope 2 provided with an imaging unit, a light source device 3 that supplies illumination light to the electronic endoscope 2, and an electronic endoscope. A video processor 4 serving as an image processing unit that processes an image pickup signal output from 2 to generate an image signal, and an observation monitor 5 serving as an image display unit that displays an image signal output from the video processor 4. The image filing device 6 encodes an image signal output from the video processor 4 and stores it as a compressed image.

  The electronic endoscope 2 includes a rigid endoscope 7 that is inserted into a body cavity, and a camera head unit 8 that is detachably connected to a proximal end side of the rigid endoscope 7. The camera head unit 8 is provided with a CCD 9 as an imaging unit that generates an imaging signal by imaging light from a subject received by an objective lens (not shown) of the rigid mirror 7. A light guide cable 10 is extended from the side end surface of the rigid endoscope 7, and one end thereof is connected to the light source device 3. The electronic endoscope 2 is provided with a light guide 11 that is a glass fiber bundle that transmits illumination light to the tip of the rigid endoscope 7. The light guide 11 is inserted through the rigid mirror 7 and the light guide cable 10 and connected to the light source device 3, and guides the illumination light emitted from the light source device 3 to the tip of the rigid mirror 7.

  The light source device 3 includes a xenon lamp 12 that generates white light as illumination light. The white light emitted from the xenon lamp 12 is transmitted through a heat ray cut filter 13 disposed in the optical path, the heat ray is cut off, and after passing through a diaphragm device 14 for limiting the amount of light, a disc as a filter means The light enters the rotary filter 15 having a shape. The illumination light that has been converted into the surface sequential light by passing through the rotary filter 15 is condensed by the condenser lens 16 and is incident on the incident end of the light guide 11.

  Here, the structure and characteristics of the rotary filter 15 will be described with reference to FIGS. 2 is a schematic diagram illustrating the structure of the rotary filter 15, FIG. 3 is a diagram illustrating an example of the transmission characteristics of the first filter set 17, and FIG. 4 is the transmission of the second filter set 18 and the excitation light cut filter 24. It is a figure explaining an example of a characteristic. As shown in FIG. 2, the rotary filter 15 has a first observation filter set 17 for concentric circular outer periphery and a second filter set 18 for fluorescence observation on a concentric inner peripheral side. One of the filters is selected according to the observation mode, and is inserted into the optical path of the illumination light. The first filter set 17 for normal observation includes an R1 filter 17r1, a G1 filter 17g1, and a B1 filter 17b1, and each filter has a transmission characteristic as shown in FIG. 3, for example. That is, the R1 filter 17r1 is set to transmit the red wavelength band of 580 nm to 720 nm, the G1 filter 17g1 is set to transmit the green wavelength band of 480 nm to 620 nm, and the B1 filter 17b1 is set to transmit the blue wavelength band of 380 nm to 520 nm. Yes. By passing through the first filter set 17, the illumination light becomes frame sequential light suitable for color reproduction.

  On the other hand, the second filter group 18 for fluorescence observation is composed of two excitation filters 18e1 and 18e2 that generate excitation light and a background filter 18b2 that generates background light. The transmission characteristics as shown in FIG. That is, the excitation filters 18e1 and 18e2 are set to transmit a wavelength band of 385 nm to 435 nm centered at 410 nm, and the background filter 18b2 is set to transmit a wavelength band of 475 nm to 525 nm. By passing through the second filter set 18 having discrete spectral characteristics in this way, the illumination light is made into two-band narrow-band frame sequential light.

  The rotary filter 15 having the above-described configuration and characteristics includes a rotary filter motor 19 that rotates the rotary filter 15 around the optical axis of the illumination light and a direction orthogonal to the optical path of the illumination light by the mode switching motor 20 (FIG. 1). The first filter set 17 and the second filter set 18 arranged in the rotary filter 15 are selectively inserted on the optical path. Further, the light source device 3 includes a power source 21 that supplies power for driving the xenon lamp 12, the diaphragm device 14, the rotary filter motor 19, and the mode switching motor 20, and a control circuit 22 that controls the operation of the rotary filter motor 19. And.

  The illumination light incident on the light guide 11 passes through an illumination window (not shown) on the distal end surface of the rigid endoscope 7 and is irradiated on the subject. In normal observation mode, red (R), green (G), and blue (B) surface-sequential illumination light is irradiated to the subject, and in fluorescence observation mode, surface-sequential illumination of excitation light and background light is performed. The subject is irradiated with light.

  On the other hand, the camera head unit 8 is provided with an objective optical system 23 that condenses light from the subject, and a CCD 9 is disposed at the imaging position of the objective optical system 23. An excitation light cut filter 24 is inserted between the front end side of the CCD 9 and the objective optical system 23, and the fluorescence light is extracted by blocking the excitation light of 385 nm to 435 nm from the reflected light from the subject. As shown in FIG. 4, the excitation light cut filter 24 is set so as to transmit a wavelength band of 470 nm or more and is set so as not to overlap with the transmission characteristics of the excitation filters 18e1 and 18e2. That is, the light transmitted through the background filter 18b2 can also be transmitted through the excitation light cut filter 24, but the light transmitted through the excitation filters 18e1 and 18e2 is blocked by the excitation light cut filter 24. Imaging signals corresponding to the irradiation light that has passed through the filters of the rotary filter 15 are sequentially output from the CCD 9 to the video processor 4 in time series. The imaging signals output in time series are R, B, and G color signals in the normal observation mode, and in the fluorescence observation mode, the imaging signals are captured under the fluorescence signal and background light captured under the excitation light. Background signal.

  A time-series imaging signal that is photoelectrically converted and output from the CCD 9 is input to the video processor 4 and input to an amplifier 31 for amplifying it into an electric signal (for example, 0 to 1 volt) within a predetermined range. The output signal of the amplifier 31 is input to the process circuit 32 where processing such as correlated double sampling and noise removal is performed. The imaging signal output from the process circuit 32 is input to the A / D converter 33 and converted into a digitized image signal. The digital image signal output from the A / D converter 33 is input to a white balance circuit (indicated as WB in FIG. 1) 34, and white balance adjustment, that is, transmission characteristics of the optical system, etc. In order to correct variations in color tone caused by variations in equipment (including differences between models and individual differences), the levels of the R, G, and B color signals are equal when a reference white subject is imaged. The gain is adjusted for each color signal. The image signal output from the white balance circuit 34 is input to a 1-input 3-output selector 35. The image signals sent in time series are R, G, B color signals by the selector 35, the fluorescence signal by the excitation light transmitted through the excitation filter 18e1, the fluorescence signal by the excitation light transmitted through the excitation filter 18e2, and the background. The signals are separated into optical signals and sequentially input to the synchronization memories 36, 37, and 38, and are synchronized when read out. The signals output from the synchronization memories 36, 37, and 38 are input to the image processing circuit 39, where gamma correction processing, contour enhancement processing, color tone adjustment processing, and the like are performed. Each signal output from the image processing circuit 39 is input to the D / A conversion circuits 40, 41, and 42, converted into an analog signal, and output to the observation monitor 5 and the encoding circuit 43. The observation monitor 5 displays an endoscopic image illuminated and imaged with normal white light, or a fluorescent image illuminated and imaged with excitation light and background light. The analog signals converted by the D / A conversion circuits 40, 41, 42 are output to the encoding circuit 43 in addition to the observation monitor 5, and are encoded. The encoded signal is output to the digital filing device 6 for filing an image and stored as a compressed image.

  The video processor 4 is also provided with a CCD driver 44 for driving the CCD 9. Furthermore, the video processor 4 receives a synchronization signal synchronized with the rotation of the rotary filter 15 from the control circuit 22 of the light source device 3 and outputs a timing signal for controlling the operation timing to each circuit in the video processor 4. A generator 45 (shown as TG in FIG. 1) is also provided.

  In the present embodiment, the subject can be observed in two types of modes, the normal observation mode and the fluorescence observation mode, and the observation mode can be set by the mode switch 46 provided in the camera head unit 8. . The set observation mode is output from the mode changeover switch 46 to the mode changeover circuit 47 provided in the video processor 4. The mode switching circuit 47 outputs a control signal corresponding to the set observation mode to the dimming control parameter circuit 48, the dimming circuit 49, and the mode switching motor 20. The dimming control parameter circuit 48 outputs a dimming control parameter corresponding to the rotary filter 15 used in the set observation mode to the dimming circuit 49. That is, in the normal observation mode, a dimming control parameter corresponding to the first filter set 17 is output, and in the fluorescent observation mode, a dimming control parameter corresponding to the second filter set 18 is output. Based on the control signal received from the mode switching circuit 47 and the dimming control parameter received from the dimming control parameter circuit 48, the dimming circuit 49 is configured to irradiate the subject with illumination light with appropriate brightness. The diaphragm device 14 is controlled. The mode switching motor 20 moves the rotary filter 15 in a direction orthogonal to the optical path of the illumination light so that a filter corresponding to the set observation mode is inserted on the optical path of the illumination light. That is, in the normal observation mode, the rotary filter 15 is moved so that the first filter set 17 is inserted in the optical path, and in the fluorescence observation mode, the second filter set 18 is inserted in the optical path. The rotary filter 15 is moved to. In addition to the above-described various controls, the mode switching circuit 47 can also perform gain control (not shown), image field number control, and the like.

  The operation of the fluorescence observation system 1 configured as described above will be described. First, the operation when the normal observation mode is selected will be described. When the rigid mirror 7 is disposed at a position facing the subject and a power source (not shown) of the fluorescence observation system 1 is turned on, white light as illumination light is emitted from the xenon lamp 12 of the light source device 3. The illumination light is transmitted through the heat ray cut filter 13 to block the heat ray, is adjusted to an appropriate light amount by the aperture device 14, and is incident on the rotary filter 15.

  When the normal observation mode is selected, the first filter set 17 is inserted on the optical path of the illumination light. Therefore, the incident illumination light passes through the R1 filter 17r1, the G1 filter 17g1, and the B1 filter 17b1, and only red (R), green (G), and blue (B) light is filtered. The light is emitted sequentially from the light source device 3 to the light guide 11. The R, G, and B plane-sequential illumination light incident on the light guide 11 passes through an illumination window (not shown) on the distal end surface of the rigid endoscope 7 and is irradiated to the subject. By irradiating frame-sequential illumination light, scattered light, reflected light, and radiated light are generated from the subject. These lights are collected by the objective optical system 23 provided in the camera head unit 8, pass through the excitation light cut filter 24, and light in a wavelength region of less than 470 nm is cut off, and then the photoelectric conversion surface of the CCD 9. It is imaged and photoelectrically converted. A time-series imaging signal that is photoelectrically converted and output from the CCD 9 is input to the video processor 4 and input to an amplifier 31 for amplifying it into an electric signal (for example, 0 to 1 volt) within a predetermined range. The output signal of the amplifier 31 is input to the process circuit 32 where processing such as correlated double sampling and noise removal is performed. The imaging signal output from the process circuit 32 is input to the A / D converter 33 and converted into a digitized image signal. The digital image signal output from the A / D converter 33 is input to the white balance circuit 34, and white balance adjustment is performed. The image signal output from the white balance circuit 34 is input to a 1-input 3-output selector 35. The image signals sent in time series are separated into R, G, and B color signals by the selector 35, are sequentially input to the synchronization memories 36, 37, and 38, and are synchronized when read out. The signals output from the synchronization memories 36, 37, and 38 are input to the image processing circuit 39, where gamma correction processing, contour enhancement processing, color tone adjustment processing, and the like are performed. Each signal output from the image processing circuit 39 is input to the D / A conversion circuits 40, 41, and 42, converted into an analog signal, and then output to the observation monitor 5. The observation monitor 5 displays an endoscopic image illuminated and imaged with normal white light. The analog signals converted by the D / A conversion circuits 40, 41, 42 are output to the encoding circuit 43 in addition to the observation monitor 5, and are encoded. The encoded signal is output to the image filing device 6 and stored as a compressed image.

  As shown in FIG. 3, the wavelength band of the light transmitted by the R1 filter 17r1 and the wavelength band of the light transmitted by the G1 filter 17g1 overlap each other, and the wavelength band of the light transmitted by the G1 filter 17g1 and the B1 filter The transmission characteristics of the first filter set 17 are set so as to overlap a part of the wavelength band of light transmitted by 17b1. By setting the transmission characteristics of the first filter set 17 in this way, it is possible to obtain an endoscope image having a color tone desired by the observer and an endoscope image having a natural hue.

  Next, the operation in the fluorescence observation mode will be described. Examples of the observation in the fluorescence observation mode include a case in which a cancer tissue of bladder cancer is examined and treated. Prior to the examination, when 5-ALA (5-Aminolevulinic.acid) is administered to a subject, which is a site to be examined, only a tumor part, which is a cancer tissue, undergoes a chemical change and Protoporphyrin IX is generated. Protoporphyrin IX has the property of exciting fluorescence of 630 nm wavelength when irradiated with excitation light of 417 nm wavelength. Fluorescence observation is performed using this property.

  First, when the observation mode is switched from the normal observation mode to the fluorescence observation mode by operating the mode changeover switch 46 provided in the camera head unit 8, the mode changeover motor 20 is operated and the second filter set 18 is operated. Is moved in a direction orthogonal to the optical path of the illumination light (the direction indicated by the arrow P in FIG. 1). In addition, the diaphragm device 14 is also operated and adjusted so that illumination light with appropriate brightness is irradiated onto the subject. Then, the white light emitted from the xenon lamp 12 of the light source device 3 and incident on the rotary filter 15 through the heat ray cut filter 13 and the diaphragm device 14 passes through the excitation filters 18e1 and 18e2 and the background filter 18b2. Thus, only excitation light having a wavelength of 385 nm to 435 nm and background light having a wavelength of 475 nm to 525 nm are filtered and sequentially emitted from the light source device 3 to the light guide 11. The surface-sequential illumination light incident on the light guide 11 passes through an illumination window (not shown) on the distal end surface of the rigid endoscope 7 and is irradiated to the subject. By irradiating the excitation light, fluorescence having a wavelength of 630 nm is generated from a tumor portion which is a cancer tissue in the subject. Further, when the background light is irradiated, scattered light, reflected light, and radiated light are generated from a portion of the subject other than the tumor portion. These lights are collected by the objective optical system 23 provided in the camera head unit 8, pass through the excitation light cut filter 24, and light in a wavelength region of less than 470 nm is cut off, and then the photoelectric conversion surface of the CCD 9. It is imaged and photoelectrically converted. A time-series imaging signal that is photoelectrically converted from the CCD 9 and output is input to the video processor 4, subjected to signal processing similar to that in the normal observation mode, and output to the observation monitor 5. The observation monitor 5 displays a fluorescent image illuminated and imaged with background light that is excitation light and white light. The observer can perform treatment such as excision of cancer tissue while observing the displayed fluorescent image. The analog signals converted by the D / A conversion circuits 40, 41, 42 are output to the encoding circuit 43 in addition to the observation monitor 5, and are encoded. The encoded signal is output to the digital filing device 6 and stored as a compressed image.

  Thus, in the fluorescence observation system 1 according to the present embodiment, the second filter set 18 has discrete spectral characteristics and is set to transmit two-band narrow-band surface-sequential light. Therefore, variation in optical brightness (transmittance) of fluorescence intensity and background light intensity is suppressed, and reflected light with stable brightness and hue can be detected at all times, and the contrast between fluorescence and reflected light can be increased. Can be improved.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. Since the fluorescence observation system in the present embodiment has the same configuration as that of the fluorescence observation system in the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted. Here, only the characteristic operation in the fluorescence observation mode will be described.

  White light emitted from the xenon lamp 12 of the light source device 3 and incident on the rotary filter 15 through the heat ray cut filter 13 and the diaphragm device 14 is excited light having a wavelength of 385 nm to 435 nm and a background having a wavelength of 475 nm to 525 nm. Only light is filtered and sequentially emitted from the light source device 3 to the light guide 11. The surface-sequential illumination light incident on the light guide 11 passes through an illumination window (not shown) on the distal end surface of the rigid endoscope 7 and is irradiated to the subject. By irradiating the excitation light, fluorescence having a wavelength of 630 nm is generated from a tumor portion which is a cancer tissue in the subject. Further, when the background light is irradiated, scattered light, reflected light, and radiated light are generated from a portion of the subject other than the tumor portion. These lights are collected by the objective optical system 23 provided in the camera head unit 8, pass through the excitation light cut filter 24, and light in a wavelength region of less than 470 nm is cut off, and then the photoelectric conversion surface of the CCD 9. It is imaged and photoelectrically converted. A time-series imaging signal output by photoelectric conversion from the CCD 9 is input to the video processor 4.

  The imaging signal input to the video processor 4 is sequentially subjected to predetermined signal processing in an amplifier 31, a process circuit 32, an A / D converter 33, and a white balance circuit 34, and then input to a selector 35 having one input and three outputs. Is done. The image signal sent in time series is separated by the selector 35 into a fluorescence signal by the excitation light transmitted through the excitation filter 18e1, a fluorescence signal by the excitation light transmitted through the excitation filter 18e2, and a background light signal. Are sequentially input to the synchronization memories 36, 37, 38 and are synchronized when read. The signals output from the synchronization memories 36, 37, and 38 are input to the image processing circuit 39, where gamma correction processing, contour enhancement processing, color tone adjustment processing, and the like are performed. In particular, in the color tone adjustment processing, processing is performed so that fluorescence and background light always have opposite colors. Each signal output from the image processing circuit 39 is input to the D / A conversion circuits 40, 41, and 42, converted into an analog signal, and then output to the observation monitor 5. The observation monitor 5 displays a fluorescence image illuminated and imaged with excitation light and background light. The analog signals converted by the D / A conversion circuits 40, 41, 42 are output to the encoding circuit 43 in addition to the observation monitor 5, and are encoded. The encoded signal is output to the digital filing device 6 and stored as a compressed image.

  As described above, in the fluorescence observation system 1 according to the present embodiment, the image processing circuit 39 performs the color tone adjustment processing so that the fluorescence and the background light always have opposite colors. Correction of variation in hue of detection light (fluorescence and reflected light of background light) caused by variation in the wavelength of light transmitted through the background filter 18b2, and further improving the contrast between fluorescence and reflected light Can do.

  From the above embodiment, there is a feature in the points described in the following additional items.

(Additional Item 1) The light source device includes a rotating plate including a plurality of excitation filters that excite fluorescence in the light source device and a background filter that generates background light.
A fluorescence observation system that emits light of a plurality of wavelengths by rotating the rotating plate.

  (Additional Item 2) The fluorescence observation system according to Additional Item 1, further comprising an image processing circuit in which the background light and the fluorescence have opposite colors.

It is a block diagram explaining the whole structure of the fluorescence observation system 1 concerning this Embodiment. FIG. 2 is a schematic diagram for explaining the structure of the rotary filter 15. FIG. 6 is a diagram for explaining an example of transmission characteristics of a first filter set 17. It is a figure explaining an example of the transmission characteristic of the 2nd filter group and the excitation light cut filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluorescence observation system, 2 Electronic endoscope, 3 Light source device 3 Video processor, 5 Observation monitor 5, 6 Image filing device, 7 Rigid mirror, 8 Camera head part, 9 CCD, 10 Light guide cable, 11 Light guide, 12 Xenon lamp, 13 Heat ray cut filter, 14 Aperture device, 15 Rotation filter, 16 Condensing lens, 17 First filter set, 17r1 R1 filter, 17g1 G1 filter, 17b1 B1 filter, 18 Second filter set, 18e1, 18e2 Excitation filter, 18b2 background filter, 19 rotary filter motor, 20 mode switching motor, 21 power supply, 22 control circuit, 23 objective optical system, 24 excitation light cut filter, 31 amplifier, 32 process circuit, 33 A / D converter, 34 White balance circuit, 35 Selector, 36, 37, 38 Synchronization memory, 39 Image processing circuit, 40, 41, 42 D / A conversion circuit, 43 Encoding circuit, 44 CCD driver, 45 Timing generator, 46 Mode change switch, 47 Mode change circuit, 48 dimming control parameter circuit, 49 dimming circuit,
Agent Patent Attorney Susumu Ito

Claims (2)

In a fluorescence observation system that displays a fluorescent image obtained by irradiating excitation light to a subject containing a fluorescent substance,
A light source for generating illumination light including the excitation light;
Filter means that is disposed between the light source and the subject and that alternately transmits the excitation light and background light in a discrete wavelength band to the illumination light emitted from the light source. When,
Imaging means for capturing the fluorescent image of the subject obtained by the excitation light and the background light image of the subject obtained by the background light;
Image processing means for synchronizing the fluorescent image and the background light image, outputting the processed image to display on the image display means as a fluorescent image;
Bei to give a,
The image processing unit includes a color tone adjusting unit for performing color tone adjustment so that the background image has an opposite color to the fluorescent image.
A fluorescence observation system characterized by that . 2. The apparatus according to claim 1, further comprising a second filter unit that blocks the excitation light and transmits the background light image and the fluorescent image between the subject and the imaging unit. The fluorescence observation system described .

Images