Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-11-20
2003-03-04
Paik, Sang (Department: 3742)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S310000
Reexamination Certificate
active
06529768
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for acquiring a fluorescence image, wherein intrinsic fluorescence, which is produced from living body tissues when the living body tissues are exposed to excitation light, is acquired as an image. This invention also relates to a fluorescence imaging apparatus for imaging fluorescence, which is produced from a measuring site when the measuring site is exposed to excitation light.
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.
The intrinsic fluorescence produced from the living body tissues is weak, and image sensors having a high sensitivity have heretofore been utilized for detecting the weak intrinsic fluorescence as an image. For example, in order for the intrinsic fluorescence to be imaged, there have heretofore been utilized high-sensitivity CCD (charge coupled device) image sensors, which are capable of performing pixel binning, i.e. processing for integrating signal charges of a plurality of pixels in each of CCD image sensor chips and reading the integrated signal charges. Also, electron multiplication types of image sensors, such as ICCD's, have heretofore been utilized to image the intrinsic fluorescence.
By way of example, the excitation light may be irradiated to living body tissues in the body cavity having a complicated shape, or the like, and a fluorescence image of the intrinsic fluorescence produced from the living body tissues may be acquired by utilizing an endoscope system. In such cases, it is desired that the intrinsic fluorescence produced from diseased tissues, such as cancerous tissues, which are located at a position (i.e., a remote point) spaced 50 mm apart from a leading end of a measuring probe of the endoscope system, be detected with a signal-to-noise ratio of at least 1.
However, in cases where the technique for performing the pixel binning is utilized, when the signal charges occurring in a plurality of pixels having received the intrinsic fluorescence are integrated in each of the CCD image sensor chips, electric charges occurring due to dark noise, which is contained in the signal charges accumulated in the pixels to be subjected to the pixel binning, are integrated together with the signal charges.
Therefore, since the intrinsic fluorescence produced from the cancerous tissues is weak, it often occurs that the number of electric charges occurring in each pixel due to the dark noise is larger than the number of electric charges occurring in each pixel due to the receiving of the intrinsic fluorescence. In such cases, even if the signal charges having been accumulated in the plurality of pixels are integrated with the pixel binning, the level of the signal representing the intrinsic fluorescence produced from the cancerous tissues will become lower than the level of the signal due to the dark noise. Therefore, the signal-to-noise ratio cannot be enhanced and will become lower than 1. Also, in cases where the electron multiplication types of image sensors are utilized, if the setting of the image sensor is not performed sufficiently accurately, it will often occur that the intrinsic fluorescence produced from the cancerous tissues located at the aforesaid remote point cannot be detected with a signal-to-noise ratio of at least 1 due to the occurrence of the dark noise and reading noise.
Further, it is desired that the intrinsic fluorescence produced from normal tissues, which are located at a position (i.e., a near point) spaced 5 mm apart from the leading end of the measuring probe of the endoscope system, be detected such that saturation may not be reached in a light receiving capacity of an imaging apparatus.
However, dynamic ranges of the electron multiplication types of image sensors, such as ICCD's, are narrower than the order of 10
1
. Therefore, if the setting of the image sensor is not performed sufficiently accurately, saturation will be reached in the light receiving capacity of the imaging apparatus. In cases where the technique for performing the pixel binning is utilized, as for the pixels in a region in which the intensity of received light is high, the number of pixels subjected to the pixel binning may be set at a small value. In this manner, the number of pixels subjected to the pixel binning may be set in accordance with the intensity of received light. However, in such cases, if the setting of the image sensor is not performed sufficiently accurately, the problems will occur in that saturation will be reached in the light receiving capacity of the imaging apparatus.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a method of acquiring a fluorescence image, wherein an image of intrinsic fluorescence produced from a measuring site of living body tissues located at a remote point is capable of being acquired with a high signal-to-noise ratio.
Another object of the present invention is to provide a method of acquiring a fluorescence image, wherein an image of intrinsic fluorescence produced from a measuring site of living body tissues located at a near point is capable of being acquired such that saturation is not reached in light receiving capacity of an imaging apparatus.
A further object of the present invention is to provide an apparatus for carrying out the method of acquiring a fluorescence image.
A still further object of the present invention is to provide a fluorescence imaging apparatus, wherein reading noise is capable of being suppressed and a signal-to-noise ratio of a detected image is capable of being enhanced, such that adverse effects do not occur on displaying of a fluorescence image as a dynamic image.
The present invention provides a first method of acquiring a fluorescence image, comprising the steps of:
i) detecting intrinsic fluorescence, which has been produced from living body tissues when excitation light is irradiated to the living body tissues, with an image sensor, the excitation light causing the living body tissues to produce the intrinsic fluorescence, and
ii) reading out the detected intrinsic fluorescence as an image,
wherein the image is acquired by setting the image sensor such that a reading frequency, an area of one pixel, a total number of pixels, a number of pixels subjected to pixel binning, a number of reading ports, an exposure time, a quantum efficiency, an electron multiplication factor, and a sensor temperature of the image sensor satisfy the following condition formula:
RN+DN<
0.22
×P×H×G
The present invention also provides a second method of acquiring a fluorescence image, comprising the steps of:
i) detecting intrinsic fluorescence, which has been produced from living body tissues when excitation light is irradiated to the living body tissues, with an image sensor, the excitation light causing the living body tissues to produce the intrinsic fluorescence, and
ii) reading out the detected intrinsic fluorescence as an image,
wherein the image is acquired by setting the image sensor such that a reading frequency, an area of one pixel, a total number of pixels, a number of pixels subjected to pixel binning, a number of reading ports, an exposure time, a quantum efficiency, an electron multiplication factor, a sensor temperature, a floating diffusion capacity, and a full well capacity of the image sensor satisfy the following condition formulas:
(
RN+DN
)×1000
×G<Fd
(
RN+DN
)×1000
×G<Fw
The present invention further provides a first apparatus for acquiring a fluorescence image, comprising:
i) an image sensor for de
Fuji Photo Film Co. , Ltd.
Paik Sang
Sughrue & Mion, PLLC
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