Surgery – Endoscope – Having imaging and illumination means
Reexamination Certificate
2001-06-01
2003-03-04
Bennett, Henry (Department: 3743)
Surgery
Endoscope
Having imaging and illumination means
C600S180000, C600S181000, C600S160000, C600S478000, C359S385000
Reexamination Certificate
active
06527709
ABSTRACT:
This invention claims benefit of Japanese Patent Application No. 2001-60556 filed on Mar. 5, 2001, the contents of which are incorporated by this reference.
FIELD OF THE INVENTION
The present invention relates to an endoscope system for observing fluorescent, and more particularly, to a light source device for irradiating an inspection object, or a subject, with an excitation light to induce fluorescence.
BACKGROUND OF THE INVENTION
Generally, by irradiating organic tissue with an excitation light, the organic tissue can be made to generate fluorescence having a longer wavelength than that of the excitation light. A fluorophor in the body includes collagen, NADH (nicotinamide adenine dinucleotide acid), FAD (flavin adenine dinucleotide), pilus zinc nucleotide, etc. The details are described in “Ultraviolet Laser-Induced Fluorescence of Colonic tissue” K. T. Schomacker et al., Lasers in Surgery and Medicine 12: 63-78 (1992).
In a combination of the phenomenon of generating fluorescence and fluorescence measuring techniques, tissue abnormality may be detected with high precision at a single cell level. Additionally, combining the fluorescence measuring techniques with endoscope techniques may provide a potential for diagnosing an early lesion which has been impossible to be detected by conventional endoscopes.
Connective tissue containing collagen resides substantially in the lower layer of mucosa, or submucosa. For example, when an endoscope transmits an excitation light from its lumen through the mucosa to excite the collagen, the fluorescence intensity to be induced is subject to the state, particularly the thickness, of the mucosa. Since cancer cells typically arise in the mucosa, the increased thickness of the mucosa caused by the grown cancer cells may attenuate the fluorescence. Thus, the position of the cancer cells may be identified to diagnose the lesion by measuring the attenuation of the fluorescence intensity. In this case, the collagen is typically excited by ultraviolet light or a blue component of visible light.
When the organic tissue is irradiated with ultraviolet light of 365 nm in wavelength, the organic tissue emits blue fluorescence having a peak at a wavelength of 460 nm due to NADH contained therein. The fluorescence intensity of NADH varies depending upon the oxidation-reduction state of NADH. In the tissue of low oxygen concentration, NAD (nicotinamide adenine dinucleotide) contained in the tissue is deoxidized and thereby the ratio of NADH is increased. Based on this, the fluorescence intensity of the tissue is increased.
Since the tissue of cancer cells, or cancerous tissue, is typically in an oxidation state, such tissue has a lower ratio of NADH and resultingly weaker fluorescence intensity. Thus, the cancerous tissue may be diagnosed by detecting this variance in the fluorescence intensity of NADH.
FIG. 13
shows a fluorescence spectrum of organic tissue irradiated with light of 365 nm in wavelength. As shown in
FIG. 13
, each fluorescence intensity of inflammatory tissue and cancerous tissue is lower than normal tissue. The same phenomenon will arise when organic tissue is irradiated with white light.
FIG. 14
shows a reflection spectrum. As shown in
FIG. 14
, in a wavelength range of 400 to 600 nm, each reflection factor of inflammatory tissue and cancerous tissue is lower than normal tissue because the inflammatory tissue and cancerous tissue contain a larger amount of blood than that in the normal tissue. Japanese Patent Laid-Open Publication No. Hei 8-252218 discloses an endoscope adapted to selectively carry out visible light observation with the use of white light and fluorescent observation with the use of ultraviolet light by applying the above phenomenon.
Since fluorescent light, or fluorescence, detected by a fluorescent observation endoscope is weaker than the reflected light caused by irradiating with visible light, such fluorescent cannot be detected with a sufficient S/N ratio (signal—noise ratio) in regular endoscope observation. Thus, it is necessary to enhance the intensity of fluorescence to be detected. In order to improve this problem, it is effective to apply ultraviolet light of about 350 nm in wavelength to an excitation light. The conversion factor of the fluorescence resulting from exciting with the ultraviolet light is about ten times greater than that resulting from exciting with a blue component of visible light.
Conventional light source devices for endoscopes comprise a light source for emitting at least visible light between blue light and red light, an infrared cutoff filter for blocking infrared light, and a condenser lens for condensing light emitted from the light source at an incident end-face of a lightguide. The light emitted from the light source typically includes components of wavelengths other than that of visible light. Particularly, a xenon lamp may emit infrared light of 750 nm or more in wavelength with high energy. The light emitted from the light source is condensed at the incident end-face of the lightguide through the condenser lens. Then, light energy concentrated at the incident end-face of the lightguide is converted into thermal energy. The resultingly generated heat causes an undesirable high temperature at the incident end-face of the lightguide. In order to prevent this heat generation, the infrared cutoff filter is provided between the light source and the incident end-face of the lightguide to block infrared light. The infrared cutoff filter includes an infrared-cutoff interference filter composed of a transparent glass plate coated with a multilayer interference film and an infrared-cutoff absorption filter formed of a material capable of absorbing infrared light.
Japanese Patent Laid-Open Publication No. Hei 8-106059 discloses a method for dividing infrared light to block off the light in a particular frequency range. In this method, an interference filter and an absorption filter are disposed between a light source and an incident end-face of a lightguide. Spectral transmission factor properties of the infrared interference filter and infrared absorption filter are shown in the curves A and B of
FIG. 15
, respectively. Conventional infrared cutoff filters do not practically block light of 400 nm or less in wavelength and allow it to be transmitted therethrough. However, any transmission factor of an ultraviolet light region in the infrared interference filter is not specifically described. Further, as shown in
FIG. 16
, since the infrared interference filter has a sharp gradient of the transmission factor property around 350 nm in wavelength, the transmission factor in 350 nm in wavelength can be undesirably lowered to a large extent due to dispersion in manufacturing. In the interference filter, as compared with the transmission factor in the visible light region, the transmission factor in the ultraviolet light region is drastically lowered by a reflect action of the multilayer interference film and an absorption action of the material forming the multilayer interference film.
Thus, Japanese Patent Laid-Open Publication No. Hei 8-106059 merely discloses a technique for a regular light source optical system for endoscopes in which light of 400 nm or less in wavelength is not used and it is unnecessary to emit ultraviolet light, and describes a phenomenon that conventional infrared cutoff filters cannot sufficiently block light of about 400 nm in wavelength and resultingly allow it to be transmitted therethrough. However, when it is intended to positively emit ultraviolet light of 400 nm or less in wavelength (particularly, 350 nm in wavelength) with employing the infrared cutoff filter in a light source optical device for endoscopes, insufficient transmission factor of the ultraviolet light will be undesirably provided.
As described above, in the conventional infrared cutoff filters, ultraviolet light has a lower transmission factor than that of visible light. Consequently, when such infrared cutoff filters are applied to a light source for fluorescent observation endoscopes, ult
Armstrong Westerman & Hattori, LLP
Bennett Henry
Ferko Kathryn
Olympus Optical Co,. Ltd.
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