Image analysis – Applications – Biomedical applications
Reexamination Certificate
2000-01-14
2003-03-18
Patel, Jayanti K. (Department: 2625)
Image analysis
Applications
Biomedical applications
C378S043000
Reexamination Certificate
active
06535626
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to specimen or sample inspection systems and more particularly to systems in which human operators inspect a substantial number of individual specimens to locate a particular subset such as “suspicious” or irregular specimens. As used herein, the term “specimen” is not necessarily limited to a medical or biological specimen but may more generally extend to any sample item or portion of a group as a whole.
2. Description of Related Art
The present invention may find particular use in a variety of contexts such as, for example, examining histological specimens (i.e., tissue-based as in anatomic pathology), examining cytological specimens (i.e., cellular samples (such as those taken from body cavity fluids, voided urine, sputum, and gynecological tract) as analyzed by cytotechnologists and cytopathologists, cytogeneticists, hematologists, neuroscientists, etc.), examining silicon wafers in an integrated circuit manufacturing process, and other materials inspection processes. In a typical scenario, a human inspector must inspect and analyze a substantial number of specimens each day to determine whether the specimens deviate from some predetermined norm. Abnormal specimens are identified and are subject to further, more detailed review. The subsequent, more detailed review may require a reviewer with additional expertise, such as a pathologist in the case of the Pap test. In a usual case, most of the specimens are considered “normal,” or “within normal limits,” and therefore need not be subjected to additional scrutiny. Depending on the detail and scope of this inspection and analysis, this additional scrutiny can unfortunately be a very slow, painstaking and costly process.
For purposes of illustration, the present invention will be described in the context of cytological specimen analysis, such as cervical Pap smear analysis. Pap smears, which are routinely taken from women, facilitate the detection of pre-cancerous changes and/or the early stages of cancer, thus reducing the chances of any cancer or related abnormal condition from spreading or advancing with the resultant negative impact on the prognosis for the patient. A Pap smear is prepared by first collecting a vaginal, cervical and endocervical tissue sample from a patient. The sample is then fixed to a slide, for instance by alcohol fixation, and appropriately stained to enable microscopic analysis.
It will be understood, however, that the conventional Pap smear process is limited, because it produces large numbers of cells (50,000 to 300,000 cells per Pap smear, typically) that are often obscured by inflammatory or other materials that make accurate and sensitive diagnoses more difficult in some cases. The Pap smear process is also limited because it deposits the cells in a spatially non-uniform manner that is difficult and time-consuming to analyze visually, as shown, for instance, in FIG.
8
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As an alternative to a Pap smear, the specimen may take the form of a liquid-based or monolayer preparation, prepared with instruments manufactured, for instance, by AutoCyte or Cytyc. One method of preparing such a specimen depends upon centrifugation to separate cells before deposition onto a glass microscope slide, for example. Another method relies upon physical filtration of a specimen through a filter with a controlled pore-size distribution. An example of the latter approach is the Cytyc ThinPrep® instrument and process.
The Cytyc ThinPrep® sample preparation generally comprises straining a sample through a filter having pores smaller than the average sample cell diameter but sufficiently large to allow passage of cellular and other debris. In one embodiment, the pore diameter is about 40-50 micrometers. The filter preferably has no rough edges or other features that would rupture the sample cells. Upon filtration, sample cells remain on the filter surface while the debris passes through, resulting in a filter surface enriched in sample cells and depleted in debris. The filter surface is next pressed onto a microscope slide to transfer the sample cells from the filter surface to the slide. This results in the slide having a monolayer of cells and, by employing a filter having a smaller area than the slide, a higher concentration of sample cells, substantially free of cellular and other debris that could interfere with a cytotechnologist's analysis of a slide. The Cytyc ThinPrep® sample preparation thus provides a more spatially uniform distribution of cells within a cellular disk (CD), as shown, for instance, in FIG.
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In practice, after the specimen is prepared, the slide is screened by a highly skilled technician (“cytotechnologist”), in an effort to identify possible cellular abnormalities in the specimen and to determine the specimen adequacy. The cytotechnologist generates notes regarding each specimen deemed to have possible abnormalities. The cytotechnologist then provides the specimen slide, together with notes of his or her findings, to an expert pathologist (i.e., specialized physician) for further review and final specimen diagnosis.
To screen a Pap smear specimen, the cytotechnologist generally views the Pap smear slide containing the Pap smear through a microscope to detect the presence of cancer cells or cells exhibiting other abnormal conditions. Because a cancerous cell may appear in only one of thousands of locations in an otherwise normal-appearing specimen, however, the cytotechnologist must generally examine every area of the slide in order to make a valid (i.e., accurate) determination. Further, many portions of the specimen slide may contain no cells at all, but the cytotechnologist must examine even those areas to at least determine the absence of pertinent (i.e., diagnostically significant) material. Of course, this process of thoroughly screening a specimen for the presence of cancerous or abnormal cells is often laborious, error-prone and costly. Still, cytotechnologists have been known to examine more than 20,000 slides annually in an effort to classify specimens as within normal limits and to identify abnormalities and enable pathologists to diagnose Pap smear specimens. In many cases, this specimen review rate is driven in part by financial concerns such as competition based on the number of specimens analyzed.
Based on the cytotechnologist's primary review (i.e., screening) of the specimen, the cytotechnologist determines either that the specimen contains suspicious material such as precancerous or cancer cells, or that the specimen is apparently within normal limits. Typically, statistically speaking, “suspicious” and “abnormal” specimens may account for approximately 5% to 10% of Pap smears in the United States, in laboratories that are screening asymptomate women. The remaining statistical 95% to 90% of the cases in turn are classified as apparently normal.
If a specimen contains even a single well preserved and well-stained cancer cell out of tens or hundreds of thousands of cells, the cytotechnologist should find the specimen to be suspicious, or atypical or abnormal. Failure to properly identify a specimen as abnormal during this screening process may be disastrous, as it may leave a cancer undetected and untreated and may ultimately lead to the death of the patient.
The cytotechnologist forwards all “suspicious,” or “atypical” or “abnormal,” specimens to a pathologist for detailed review and final diagnosis and “sign-out” in light of the cytotechnologist's notes and findings. One of the pathologist's goals is to analyze the specimen at issue and determine based on medical expertise whether the specimen contains cancerous or pre-cancerous cells. In doing so, the pathologist must strive to minimize both false negative diagnoses and false positive diagnoses, as false negative diagnoses could leave cancer undetected, while false positive diagnoses could result in unnecessary or inappropriate, harmful and costly cancer treatment such as chemotherapy or the like.
Most of the specimens
Domanik Richard A.
Pressman Norman J.
AccuMed International, Inc.
Patel Jayanti K.
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