Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-11-16
2002-10-29
Nerbun, Peter (Department: 1743)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06473637
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for displaying a fluorescence image, wherein intrinsic fluorescence, which is produced from living body tissues when excitation light is irradiated to the living body tissues, is detected and displayed as an image representing information concerning the living body tissues.
2. Description of the Related Art
Research has heretofore been conducted with respect to techniques, wherein intrinsic fluorescence, which is produced by an intrinsic dye in living body tissues when excitation light is: irradiated to the living body tissues, is detected as an image, the image having been formed with the intrinsic fluorescence is analyzed, and a change in tissue condition of the living body tissues due to various kinds of diseases is discriminated in accordance with the results of the analysis.
At the beginning, research was conducted to determine a tissue condition of a living body by paying attention to a variation in intensity of intrinsic fluorescence produced from living body tissues. However, the intensity of the excitation light, which is received by the living body tissues, varies in accordance with a difference in an irradiation angle of the excitation light with respect to the living body tissues, a difference in a distance between an excitation light irradiating system and the living body tissues, and the like. Due to the difference in intensity of the excitation light, which is received by the living body tissues, the intensity of the intrinsic fluorescence produced from the living body tissues varies. Therefore, it has been found that, only with the information representing the intensity of the intrinsic fluorescence, sufficient capability of discriminating the tissue condition of the living body tissues cannot be obtained. Accordingly, there have been proposed, for example, techniques for discriminating a tissue condition of a measuring site by calculating a ratio of an intensity of intrinsic fluorescence, which is produced from a site of living body tissues when the site of the living body tissues is exposed to excitation light, to an intensity of the excitation light, which is received by the site of the living body tissues, i.e. by calculating a value reflecting a fluorescence yield, which value is not affected by the irradiation angle and the irradiation distance of the excitation light.
However, it is not always possible to directly detect the intensity of the excitation light, which is received by each site of the living body tissues. Also, if a distribution of the intensity of the excitation light, which has been reflected from the living body tissues exposed to the excitation light, accurately reflects the distribution of the intensity of the excitation light, which is received by the living body tissues, the distribution of the intensity of the excitation light, which is received by the living body tissues, can be determined by measuring the distribution of the intensity of the excitation light, which has been reflected from the living body tissues. However, of the excitation light irradiated to the living body tissues in order to cause the living body tissues to produce the intrinsic fluorescence, excitation light components having wavelengths on a short wavelength side within the wavelength region of visible light are not subject to uniform absorption by various living body tissues. Therefore, even if the distribution of the intensity of the excitation light, which has been reflected from the living body tissues exposed to the excitation light, is measured, the measured intensity distribution will not accurately reflect the distribution of the intensity of the excitation light, which is received by the living body tissues. Accordingly, as one of techniques for calculating the fluorescence yield, there has been proposed a technique, wherein near infrared light, which is subject to uniform absorption by various living body tissues, is employed as reference light and irradiated to the living body tissues, a distribution of an intensity of reflected reference light, which has been reflected from the living body tissues exposed to the reference light, is detected, and the detected distribution of the intensity of the reflected reference light is utilized in lieu of the distribution of the intensity of the excitation light, which is received by the living body tissues.
Also, a novel technique for discriminating a change in tissue condition of a living body has been proposed in, for example, PCT Japanese Publication No. 10(1998)-500588. With the proposed technique, a two-dimensional image signal, which has been obtained by detecting the intensity of reflected reference light having been reflected from living body tissues, is fed to a red-color channel of a color display device, and an image signal, which has been acquired by detecting the intensity of intrinsic fluorescence having been produced from the living body tissues, is fed to a green-color channel of the color display device. Further, the ratio of the intensity of the intrinsic fluorescence to the intensity of the reflected reference light (i.e., the fluorescence yield) is processed as display signals for altering the color and the luminance, and a change in tissue condition of the living body is displayed as an image.
However, the display luminance of the image formed by feeding the image signal, which has been obtained by detecting the intensity of the reflected reference light having been reflected from the living body tissues, to the red-color channel of the color display device, and feeding the image signal, which has been acquired by detecting the intensity of the intrinsic fluorescence having been produced from the living body tissues, to the green-color channel of the color display device is represented by complicated information comprising a mixture of luminance information, which reflects the shape, the distance, shadows, and the like, of the living body tissues to be seen, and luminance information, which reflects the tissue condition of the living body (i.e., the tissue condition concerning whether the living body tissues are cancerous tissues or normal tissues, and the like). Therefore, when the displayed image is visually seen, it is difficult to make a judgment as to whether a dark area in the image is the one due to a diseased part or the one due to a remote location, a concavity, or the like. As a result, the problems often occur in that the tissue condition of the living body, which is important information for diagnosis, cannot be discriminated correctly. Further, the problems often occur in that, since the intensity of the intrinsic fluorescence produced from a diseased part is low and the display luminance corresponding to the intrinsic fluorescence produced from the diseased part becomes low, a variation in color cannot be discriminated easily, and the presence of the diseased part cannot be found.
Furthermore, ordinarily, a dynamic range of an image displayed on a display device is narrower than the dynamic range of an image formed by a detecting device. Therefore, when the image formed by the detecting device is displayed on the display device, the problems described above are aggravated.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a method of displaying a fluorescence image, wherein a tissue condition of a living body and a shape of the living body, which are information concerning living body tissues, are capable of being displayed accurately.
Another object of the present invention is to provide an apparatus for carrying out the method of displaying a fluorescence image.
The present invention provides a first method of displaying a fluorescence image, comprising the steps of:
i) irradiating excitation light and reference light to living body tissues, the excitation light causing the living body tissues to produce intrinsic fluorescence,
ii) detecting the intrinsic fluorescence, which has been produced from the living body tissues when the excitation
Fuji Photo Film Co. , Ltd.
Nerbun Peter
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