Image analysis – Applications – Biomedical applications
Reexamination Certificate
2003-03-12
2004-01-13
Patel, Jayanti K. (Department: 3736)
Image analysis
Applications
Biomedical applications
C382S128000, C600S425000
Reexamination Certificate
active
06678398
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a device and process that provides, in a screening mode, real-time screening and remote imaging, and in an analysis mode, rapid full-area, selective-spectral remote imaging and analysis. More specifically, this invention relates to a device for allowing real-time detection and rapid remote analysis of surfaces with differentiating spectral properties, such as potentially cancerous regions in the cervix, intestine, lungs or other organs.
PRIOR ART
Cancers, especially cancers in the intestine, cervix, lungs, and other hollow organs, need to be detected early for effective treatment. For example, intestinal cancers typically start with polyps, either protruding (pedunculated tubular adenomas) or flat (sessile villous adenomas). These polyps sometimes convert into cancer. Therefore, the detection or removal of polyps by colonoscopy significantly reduces the risk of getting colon cancer. Traditionally, polyps are detected using devices that allow a physician to visually examine the interior of the intestine. However, because of the large interior surface area of the intestine, such examinations need to be carried out at a rapid rate so that the maximum area of the intestine can be examined in a minimum amount of time. Further, the amount of time for such examinations must be minimized in order to minimize the expenses and physical impact of such examinations. It is also more difficult to detect flat polyps (sessile villous adenomas) with such examinations.
Two major types of procedures for intestinal examination are sigmoidoscopy and colonoscopy. In these procedures, a device for viewing the interior of a hollow organ, usually an endoscope, is inserted into the intestine through the anus. The endoscope usually includes input from a light source and includes lenses at the end of a long flexible cable. An imaging bundle of coherently bundled optical fibers is usually provided inside the cable to transmit an image with a resolution determined by the number of fibers in the bundle. The field of view of an endoscope can be 45 to 140 degrees, depending on the lenses selected. Some endoscopes also have a biopsy channel in the cable that allows the examining physician to extract a tissue sample, such as a portion of a polyp, for later analysis, such as by a biopsy (or even to extract an entire polyp). In sigmoidoscopy, the patient is conscious during the examination, and therefore, the time for the examination must be minimized to minimize the patient's discomfort during the procedure. Further, sigmoidoscopy does not screen the entire length of the intestine because a sigmoidoscope does not pass beyond a 120-degree bend in the intestine called the left colic (splenic flexure). In a colonoscopy, the entire length of the intestine can be screened, but the patient must be fully anesthetized, which introduces all the attendant risks of anesthetization. Traditional visual analysis of polyps and other colonic lesions requires training and experience. Because polyps are small, and not all polyps are cancerous, it is helpful to somehow mark pre-cancerous polyps or other abnormal tissues to enhance viewing and detection while screening. It is desirable to reduce the overall number of biopsies because there is an increased risk of morbidity with each additional biopsy.
Fluorescence is a well-known phenomenon in which an excitation light of one wavelength causes a material to emit fluorescent light of a different wavelength. For example, household fluorescent lamps are glass tubes filled with mercury vapor and interiorly coated with phosphor, having electrodes at both ends. When the electrodes are energized with electricity, they emit electrons, which strike the atoms of mercury vapor to cause those atoms to emit ultraviolet light. The ultraviolet light (the excitation light) then strikes the phosphor, which causes the phosphor atoms to emit white light (the fluorescent light). For another example, so-called “black light” is actually ultraviolet light that causes certain materials to emit visible light.
Visible light is considered to have wavelengths of between approximately 400 and approximately 760 nanometers (billionths of a meter, or “nm”). Light having wavelengths shorter than approximately 400 nm is considered to be ultraviolet light by the United States Food and Drug Administration and other countries' regulatory agencies. More specifically, UVA radiation is considered to range from approximately 315 nm to approximately 400 nm, UVB radiation is considered to range from approximately 280 nm to approximately 315 nm, and UVC radiation is considered to range from approximately 100 nm to approximately 280 nm. UVA radiation is sometimes referred to as long wave ultraviolet or “tanning rays.” UVB radiation is considered to be more dangerous than UVA and causes damage to genes, and UVC radiation is considered to be even more dangerous than UVB because of its shorter wavelength and higher energy. Thus, the power and allowable time for exposing patients to light having wavelengths of less than 400 nm is restricted. However, there are no such restrictions on exposing patients to visible light.
Although the human eye cannot see light having wavelengths shorter than about 400 nm, some imaging devices, such as certain types of CCDs (charge coupled devices) can detect light down to approximately 360 nm or lower.
It has been discovered that when tissues are excited by a certain excitation light (such as ultraviolet or blue or violet light) the fluorescent light emitted by abnormal tissues has a spectrum (including in the visible range) that differs from the fluorescence spectrum of normal tissues at certain differentiating portions (or bands) of the color spectrum. This is because types and/or amounts of various substances (each having distinctive fluorescence spectra) differ in abnormal tissues from those in normal tissues. This phenomenon of fluorescence due to natural characteristics of the tissues is known as “autofluorescence”. The naturally occurring substances in tissues that fluoresce when excited are referred to as “endogenous fluorophores.”
Another type of fluorescence that may be utilized in cancer detection is induced fluorescence, that is, fluorescence induced by administration of an exogenous (that is, introduced from outside the patient) fluorescent marker (or exogenous fluorphore) that selectively localizes in abnormal precancerous and cancerous tissues. Thus, the abnormal tissues will fluoresce at a particular marker wavelength (or set of wavelengths) when those tissues are illuminated with an excitation light that causes the exogenous fluorescent marker to fluoresce. An example of an exogenous fluorescent marker is 5-aminolaevullinic acid (“ALA”). ALA induces precancerous and cancerous tissue to preferentially accumulate protoporphyrin IX (“PpIX”). PpIX is a photosensitizer, but clears rapidly from the body, limiting the period of enhanced tissue sensitivity to between 24 and 48 hours. When excited with a marker excitation light having a wavelength of around 400 nm, PpIX emits a marker fluorescent light having a characteristic fluorescence spectrum with peaks centered at approximately 635 and 700 nm. In addition, PpIX occurs naturally in humans and causes few side effects.
The intensity of autofluorescence is fairly weak, relative to induced fluorescence, and can be difficult to detect, requiring a longer time for exposure, much as a photograph in weak light requires a long time exposure. Accordingly, it is desirable to use relatively bright light in the visible range (such as blue or violet light) or in the portion of the UVA range near 400 nm to apply enough excitation light to make autofluorescent light bright enough for rapid acquisition of autofluorescence images. Rapid acquisition of images is desirable to avoid blurring due to patient movement, minimizing time for examination, and for other reasons. It is not practical to use high intensity, long duration ultraviolet light to increase the intensity of autofluorescence because
Deweert Michael James
Seiple, Jr. Robert Benton
Sweat Joseph Allen
Walton David George Shibasaki
Wolters Rolf Holger
Azarian Seyed
Hsia Martin E.
Patel Jayanti K.
STI Medical Systems, Inc.
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