AUTOMATED DETECTION OF OBJECTS IN A BIOLOGICAL SAMPLE CLAIM OF PRIORITY This application claims the benefit of priority, under 35 USC §119 (e) (1), of U. S. provisional application 60/143,823, filed July 13,1999, and this application is a continuation of U. S. Patent Application Serial No. 08/758,436, filed November 27, 1996, which claims the benefit of U. S. Provisional Application No. 60/026,805, filed on November 30, 1995.

TECHNICAL FIELD The invention relates generally to light microscopy and, more particularly, to automated light microscopic methods and an apparatus for detection of proteins associated with cell proliferative disorders.

BACKGROUND OF THE INVENTION In the field of medical diagnostics including oncology, the detection, identification, quantitation and characterization of cells of interest, such as cancer cells, through testing of biological specimens is an important aspect of diagnosis. Typically, a biological specimen such as bone marrow, lymph nodes, peripheral blood, cerebrospinal fluid, urine, effusions, fine needle aspirates, peripheral blood scrapings or other materials are prepared by staining the specimen to identify cells of interest. One method of cell specimen preparation is to react a specimen with a specific probe which can be a monoclonal antibody, a polyclonal antiserum, or a nucleic acid which is reactive with a component of the cells of interest, such as tumor cells. The reaction may be detected using an enzymatic reaction, such as alkaline phosphatase or glucose oxidase or peroxidase to convert a soluble colorless substrate to a colored insoluble precipitate, or by directly conjugating a dye to the probe. Examination of

biological specimens in the past has been performed manually by either a lab technician or a pathologist.

In the manual method, a slide prepared with a biological specimen is viewed at a low magnification under a microscope to visually locate candidate cells of interest. Those areas of the slide where cells of interest are located are then viewed at a higher magnification to confirm those objects as cells of interest, such as tumor or cancer cells. The manual method is time consuming and prone to error including missing areas of the slide. Automated cell analysis systems have been developed to improve the speed and accuracy of the testing process. One known interactive system includes a single high power microscope objective for scanning a rack of slides, portions of which have been previously identified for assay by an operator. In that system, the operator first scans each slide at a low magnification similar to the manual method and notes the points of interest on the slide for later analysis. The operator then stores the address of the noted location and the

associated function in a data file. Once the points of interest have been located and stored by the operator, the slide is then positioned in an automated analysis apparatus which acquires images of the slide at the marked points and performs an image analysis.

A number of cellular proteins are related to cell proliferation and cell signaling. Many of these proteins are critical for normal cell growth. For example, HER2 (neu) is a growth factor receptor and when found within tumor cells amounts to an aggressively growing tumor. Studies have determined that a significantly decreased disease-free survival and overall survival of a patient with over- expression of HER2. Before an oncologist prescribes an anti-HER2/neu therapeutic, an immunohistochemistry (IHC) assessment for HER2/neu is desirable.

Therapeutic availability increases the need for a standard methodology for assessing the expression of HER2/neu.

Three general methods are currently available for the detection of HER2/neu: genetic detection, protein expression, and protein activity. In situ hybridization methods are typically used for HER2/neu genetic detection. Immunohistochemistry methods are used for the assessment of HER2/neu protein expression.

SUMMARY OF THE INVENTION A problem with the foregoing automated system is the continued need for operator input to initially locate cell objects for analysis. Such continued dependence on manual input can lead to errors including cells of interest being missed. Such errors can be critical especially in assays for so- called rare events, e. g., finding one tumor cell in a cell population of one million normal cells.

Additionally, manual methods can be extremely time consuming and can require a high decree of training to identify and/or quantify cells. This is not only true for tumor cell detection, but also for other

applications ranging from neutrophil alkaline phosphatase assays, reticulocyte counting and maturation assessment, and others. The associated manual labor leads to a high cost for these procedures in addition to the potential errors that can arise from long, tedious manual examinations. A need exists, therefore, for an improved automated cell analysis system which can quickly and accurately scan large amounts of biological material on a slide.

Accordingly, the present invention provides a method and apparatus for automated cell analysis which eliminates the need for operator input to locate cell objects for analysis.

In accordance with the present invention, a slide prepared with a biological specimen and reagent is placed in a slide carrier which preferably holds four slides. The slide carriers are loaded into an input hopper of the automated system. The operator may then enter data identifying the size, shape, and location of a scan area on each slide, or, preferably, the system automatically locates a scan

area for each slide during slide processing. The operator then activates the system for slide processing. At system activation, a slide carrier is positioned on an X-Y stage of an optical system. Any bar codes used to identify slides are then read and stored for each slide in a carrier. The entire slide is rapidly scanned at a low magnification, typically lOx. At each location of the scan, a low magnification image is acquired and processed to detect candidate objects of interest. Preferably, color, size, and shape are used to identify objects of interest. The location of each candidate object of interest is stored.

At the completion of the low level scan for each slide in the carrier on the stage, the optical system is adjusted to a high magnification such as 40x or 60x, and the X-Y stage is positioned to the stored locations for the candidate objects of interest on each slide in the carrier. A high magnification image is acquired for each candidate object of interest and a series of image processing steps are

performed to confirm the analysis which was performed at low magnification. A high magnification image is stored for each confirmed object of interest.

Additionally, control slides including positive and negative controls, may be used to determine background staining. For example, positive control slides for a particular staining technique can be run followed by a negative control in order to determine a delta for the controls. Subsequent scanning for objects of interest may then differentiate such objects based upon their color or intensity above the delta.

These images are then available for retrieval by a pathologist or cytotechnologist to review for final diagnostic evaluation. Having stored the location of each object of interest, a mosaic comprised of the candidate objects of interest for a slide may be generated and stored. The pathologist or cytotechnologist may view the mosaic or may also directly view the slide at the location of an object of interest in the mosaic for further evaluation.

The mosaic may be stored on magnetic media for future reference or may be transmitted to a remote site for review and/or storage. The entire process involved in examining a single slide takes on the order of 2- 15 minutes depending on scan area size and the number of detected candidate objects of interest.

The present invention has utility in the field of oncology for the early detection of minimal residual disease ("micrometastases"). Other useful applications include prenatal diagnosis of fetal cells in maternal blood and in the field of infectious diseases to identify pathogens and viral loads, alkaline phosphatase assessments, reticulocyte counting, and others. The processing of images acquired in the automated scanning of the present invention preferably includes the steps of transforming the image to a different color space; filtering the transformed image with a low pass filter; dynamically thresholding the pixels of the filtered image to suppress background material; performing a morphological function to remove

artifacts from the thresholded image; analyzing the thresholded image to determine the presence of one or more regions of connected pixels having the same color; and categorizing every region having a size greater than a minimum size as a candidate object of interest.

According to another aspect of the invention, the scan area is automatically determined by scanning the slide; acquiring an image at each slide position; analyzing texture information of each image to detect the edges of the specimen; and storing the locations corresponding to the detected edges to define the scan area. According to yet another aspect of the invention, automated focusing of the optical system is achieved by initially determining a focal plane from an array of points or locations in the scan area. The derived focal plane enables subsequent rapid automatic focusing in the low power scanning operation. The focal plane is determined by determining proper focal positions across an array of locations and performing an analysis such as a least

squares fit of the array of focal positions to yield a focal plane across the array. Preferably, a focal position at each location is determined by incrementing the position of a Z stage for a fixed number of coarse and fine iterations. At each iteration, an image is acquired and a pixel variance or other optical parameter about a pixel mean for the acquired image is calculated to form a set of variance data. A least squares fit is performed on the variance data according to a known function. The peak value of the least squares fit curve is selected as an estimate of the best focal position.

In another aspect of the present invention, another focal position method for high magnification locates a region of interest centered about a candidate object of interest within a slide which were located during an analysis of the low magnification images. The region of interest is preferably n columns wide, where n is a power of 2.

The pixels of this region are then processed using a Fast Fourier Transform to generate a spectra of

component frequencies and corresponding complex magnitude for each frequency component. Magnitudes of the frequency components which range from 25% to 75% of the maximum frequency component are squared and summed to obtain the total power for the region of interest. This process is repeated for other Z positions and the Z position corresponding to the maximum total power for the region of interest is selected as the best focal position.

According to still another aspect of the invention, a method and apparatus for automated slide handling is provided. A slide is mounted onto a slide carrier with a number of other slides side-by- side. The slide carrier is positioned in an input feeder with other slide carriers to facilitate automatic analysis of a batch of slides. The slide carrier is loaded onto the X-Y stage of the optical system for the analysis of the slides thereon.

Subsequently, the first slide carrier is unloaded into an output feeder after automatic image analysis and the next carrier is

automatically loaded.

In a specific embodiment the invention provides an automated system for the quantitation of proteins associated with cell proliferative disorders, such as HER2/neu expression in tissue. The invention is useful to determine the over-expression of HER2 in tissue, especially breast tissue.

DESCRIPTION OF THE DRAWINGS The above and other features of the invention including various novel details of construction and combinations of parts will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular apparatus embodying the invention is shown by way of illustration only and not as a limitation of the invention. The principles and features of this invention may be employed in varied and numerous embodiments without departing from the scope of the invention.

Fig. 1 is a perspective view of an apparatus for automated cell analysis embodying the present invention.

Fig. 2 is a block diagram of the apparatus shown in Fig. 1.

Fig. 3 is a block diagram of the microscope controller of Fig. 2.

Fig. 4 is a plan view of the apparatus of Fig. 1 having the housing removed.

Fig. 5 is a side view of a microscope subsystem of the apparatus of Fig. 1.

Fig. 6a is a top view of a slide carrier for use with the apparatus of Fig. 1.

Fig. 6b is a bottom view of the slide carrier of Fig. 6a.

Fig. 7a is a top view of an automated slide handling subsystem of the apparatus of Fig. 1.

Fig. 7b is a partial cross-sectional view of the automated slide handling subsystem of Fig. 7a taken on line A-A.

Fig. 8 is an end view of the input module of the automated slide handling subsystem. 8a-8d illustrate the input operation of the automatic slide handling subsystem.

Fig. 9a-9d illustrate the output operation of the automated slide handling subsystem.

Fig. 10 is a flow diagram of the procedure for automatically determining a scan area.

Fig. 11 shows the scan path on a prepared slide in the procedure of Fig. 10.

Fig. 12 illustrates an image of a field acquired in the procedure of Fig. 10.

Fig. 13A is a flow diagram of a preferred procedure of redetermining focal position.

Fig. 13B is a flow diagram of a preferred procedure for determining a focal position for neutrophils stained with Fast Red and counterstained with hemotoxylin.

Fig. 14 is a flow diagram of a procedure for automatically determining initial focus.

Fig. 15 shows an array of slide positions for use in the procedure of Fig. 14.

Fig. 16 is a flow diagram of a procedure for automatic focusing at a high magnification.

Fig. 17A is a flow diagram of an overview of the preferred process to locate and identify objects of interest in a stained biological specimen on a slide.

Fig. 17B is a flow diagram of a procedure for color space conversion.

Fig. 18 is a flow diagram of a procedure for background suppression via dynamic thresholding.

Fig. 19 is a flow diagram of a procedure for morphological processing.

Fig. 20 is a flow diagram of a procedure for blob analysis.

Fig. 21 is a flow diagram of a procedure for image processing at a high magnification.

Fig. 22 illustrates a mosaic of cell images produced by the apparatus.

Fig. 23 is a flow diagram of a procedure for estimating the number of nucleated cells in an objective field.

Fig. 24 illustrates the apparatus functions available in a user interface of the apparatus.

DETAILED DESCRIPTION Overview The invention provides an automated tissue image analysis method for the detection of a cell proliferative disorder, for example those associated with HER2/neu. Other automated tissue image analysis methods, such as immunohistochemical analyses of estrogen receptor and progesterone receptor are also provided. Other methods are within the scope of the invention, such as analyses for MM/MRD for tissue, MIB-I, Microvessel density analysis, the oncogene p53, immunophenotyping, hematoxylin/eosin (H/E) morphological analysis, undifferentiated tumor classification, antibody titering, prominence of nucleoli, HIV p24, human papiloma virus (HPV; for

cervical biopsy), and mitotic index; generally any diagnostic method utilizing staining techniques is within the scope of the present invention. The invention has utility in the field of oncology for the early detection of minimal residual disease ("micrometastases").

For the HER2/neu application, the Automated Cellular Imaging System (ACIS) analyzes at least two subsamples: the H/E prepared slide and the immunohistochemistry prepared slide. A histological reconstruction of subsamples is displayed and used for the appropriate reviewing. An instrument automatically selects an area of interest, using color space transformations (and morphological filtering, if necessary) to identify and quantify the expression of the HER2/neu in the area of tissue selected from the immunohistochemistry prepared slide. The quantitative result, as well as any selected areas of interest from either slide, is incorporated into the patient report.

The following acronyms and terminology are used throughout this document: A worklist is a group of specimens that is prepared with the same staining techniques and typically analyzed with the same automated application. A specimen group consists of one or more patient cases. A histological reconstruction is an image of the whole specimen that has been mounted on a slide. This image is created by piecing together more than one fields of view at any objective. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below.

All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case

of conflict, the present application, including definitions, will control. In addition, the materials and methods described herein are illustrative only and not intended to be limiting.

Other features and advantages of the invention will be apparent from the following detailed description, the drawings, and from the claims.

Preferred Workflow A preferred workflow is provided in the following outline: 1. Specimens arrive in the laboratory. The specimens are labeled in accordance with standard hospital procedures to insure the chain of custody.

2. Sample Preparation.

2.1. Two or three tissue sections per patient case are preferable for this test.

2.2. Mount one piece of the tissue to a slide, to be stained with H/E. The H/E

staining protocol is compatible with HER2/neu immunohistochemistry staining.

2.3. Mount the second piece of the tissue to a slide, to be stained with the anti- HER2 immunohistochemistry staining system.

2.4. If deemed necessary, mount a third piece of the tissue to a third slide, to be stained with a third antibody (i. e., patient negative control) and the anti-HER2 staining system.

2.5. To avoid ACIS mechanical limitations, the specimen placement specifications is followed. Considering the frosted end of the slide as the top, specimen must be below 30 mm and above 65 mm from the top edge. The specimen may reach to the far side edges of the slide.

2.6. Other patient samples? If yes, repeat section 2.

2.7. Include two stain control slides.

3. Sample Staining.

3.1. Stain all H/E prepared slides with the H/E staining protocol.

3.2. Stain all immunohistochemistry slides with anti-HER2 staining system.

3.3. If deemed necessary, stain all negative immunohistochemistry slides with a third antibody (i. e., patient negative control) and the anti-HER2 staining system.

3.4. Stain the positive and negative control slides with the anti-HER2 staining system and the appropriate antibodies.

4. Barcode all prepared slides and place within open slots in the slide carriers.

5. Manually study the positive and negative control slides and verify the staining is in control. Manually study the patient's positive and negative immunohistochemistry

slides and verify patient doesn't have an abnormality in background staining.

6. Work-list entry 6.1. Enter the information that is consistent per work-list.

6.1.1. Specify the work-list identification.

6.1.2. Specify the protocol/application (HER2/neu) 6.1.3. Specify the barcodes of the positive and negative control slides 6.2. Enter the information that is related to each patient case.

6.2.1. Accession number and Patient Identification (ID) 6.2.2. Specify the two/three barcodes of the samples for this case (H/E, immunohistochemistry, patient negative control)

6.2.3. Patient specific information: Age (integer), Sex (M/F), Race (character-predefined selections), Diagnosis (character -2S6), Date of diagnosis (Date Format), Date of last treatment (Date Format), and Description of last treatment (character-512).

7. If daily calibration of the instrument hasn't been completed, please do so before starting the work-list (5 min per calibration, necessary once per a day).

This calibration consists of radiometric, geometric, and color standard calibration.

8. Load the carriers containing the control slides and patient cases into the input hopper.

9. Start the automated analysis of the work- list.

9.1. Should the stain controls not have a large enough delta A, the instrument

skips the rest of the slides within the worklist.

10. After completion of the analysis, review the results of the work-list and construct the appropriate reports online. For each case, the low power H/E image appears automatically with the selection of the patient ID, accession number, or sample identification.

10.1. While viewing the low power H/E Histological Reconstruction (HR) the user has the following choices: 10.1.1. Select an area of the H/E HR to zoom on.

10.1.2. Choose to go to the low power immunohistochemistry HR.

10.1.3. Select an area to save within the pre-constructed report format.

10.2. While viewing the high power H/E HR the user has the following choices:

10.2.1. Choose to go back to the low power H/E HR.

10.3. While viewing the low power immunohistochemistry HR the user has the following choices: 10.3.1. Select an area of the immunohistochemistry HR to zoom on.

10.3.2. Select an area of the low power immunohistochemistry HR and query for the following quantitative results. The quantitative results are relative to the scoring of the positive stain control and the patient's negative immunohistochemistry slide.

10.3.2.1. Over-expression within selected area reported as 0,1+, 2+, or 3+.

10.3.2.2. Percentage of positive cells within the selected area.

10.4. While viewing the high power immunohistochemistry HR the user has the following choices: 10.4.1. Select an area of the high power immunohistochemistry HR and query for the following quantitative results. The quantitative results are relative to the scoring of the positive stain control and the patient's negative immunohistochemistry slide.

10.4.1.1. Over-expression within selected area reported as 0,1+, 2+, or 3+.

10.4.1.2. Percentage of positive cells within the selected area.

10.4.2. Choose to go back to the low power immunohistochemistry HR.

10.5. Other samples to review? 10.5.1. If yes, repeat section 8.

10.6. Should the analysis result in the tissue not being scanned, reload slide, open application, and adjust scan area to location of the tissue, if necessary. Should the scan area be adequate, but the focus points not fall on an area of tissue, resulting in failed focus, in the application change the focus inset to a number closer to one and confirm that the scan area is centered on an area of tissue. Execute the application. Repeat steps 10.1- 10.5.

10.7. Manually record results of analysis.

11. Quality Assurance checks within the instrument.

11.1. At the completion of analyzing both the positive and negative control slides, the A between the scores are calculated. If this A isn't large enough, the analysis of all slides in this work-list is flagged accordingly and the instrument warns the user with an audible alarm.

11.2. If the A between the patient's positive and negative immunohistochemistry slide isn't large enough, the patient is flagged accordingly.

11.3. A montage of tissue sections from both the positive and negative controls. Five tissue section images from each are adequate.

12. Preview the reports online and modify as necessary.

13. Send the reports to the printer or by the Internet to the requesting clinicians. The

output of the worklist is a stained positive control slide, a stained negative control slide, two stained slides per patient case (one H/E and another IHC), and a comprehensive electronic report. The report includes the selected image sections, quantitative results, reference material, and other pertinent data.

Sample Staining A cellular specimen (a"sample") is split to provide two or more subsamples. The term"sample" includes cellular material derived from a subject.

Such samples include but are not limited to hair, skin samples, tissue sample, cultured cells, cultured cell media, and biological fluids. The term "tissue"refers to a mass of connected cells (e. g., CNS tissue, neural tissue, or eye tissue) derived from a human or other animal and includes the connecting material and the liquid material in association with the cells. The term"biological

fluid''refers to liquid material derived from a human or other animal. Such biological fluids include, but are not limited to, blood, plasma, serum, serum derivatives, bile, phlegm, saliva, sweat, amniotic fluid, and cerebrospinal fluid (CSF), such as lumbar or ventricular CSF. The term "sample"also includes media containing isolated cells. The quantity of sample required to obtain a reaction may be determined by one skilled in the art by standard laboratory techniques. The optimal quantity of sample may be determined by serial dilution.

The HER2/neu method uses an anti-HER2/neu staining system, such as a commercially available kit, like that provided by DAKO (Carpinteria, CA).

The steps for the immunohistochemistry protocol are as follows: (1) Prepare wash buffer solution.

(2) Deparaffinize and rehydrate specimens. (3) Perform epitope retrieval. Incubate 40 min in a 95°C water bath. Cool slides for 20 min at room temperature. (4) Apply peroxidase blocking reagent.

Incubate 5 min. (5) Apply primary antibody or negative control reagent. Incubate 30 min +/-1 min at room temperature. Rinse in wash solution. Place in wash solution bath. (6) Apply peroxidase labeled polymer. Incubate 30 min +/-1 min at room temperature. Rinse in wash solution. Place in wash solution bath. (7) Prepare DAB substrate chromagen solution. (8) Apply substrate chromogen solution (DAB). Incubate 5-10 min. Rinse with distilled water; (9) Counterstain. (10) Mount coverslips. The slide includes a cover-slip medium to protect the sample and to introduce optical correction consistent with microscope objective requirements. The coverslip covers the entire prepared specimen.

Mounting the coverslip does not introduce air bubbles obscuring the stained specimen. This coverslip could potentially be a mounted 1-1/2 thickness coverslip with DAKO Ultramount medium. (11) A set of staining control slides are run with every worklist. The set includes a positive and negative control. The positive control is stained with the anti-HER2

antibody and the negative is stained with another antibody. Both slides are identified with a unique barcode. Upon reading the barcode, the instrument recognizes the slide as part of a control set, and runs the appropriate application. There may be one or two applications for the stain controls. (12) A set of instrument calibration slides includes the slides used for focus and color balance calibration.

(13) A dedicated carrier is used for one-touch calibration. Upon successful completion of this calibration procedure, the instrument reports itself to be calibrated. Upon successful completion of running the standard slides, the user is able to determine whether the instrument is within standards and whether the inter-instrument and intra-instrument repeatability of test results.

The hematoxylin/eosin (H/E) slides are prepared with a standard H/E protocol. Standard solutions include the following: (1) Gills hematoxylin (hematoxylin 6.0 g; aluminium sulphate 4.2 g; citric acid 1.4 g; sodium iodate 0.6 g; ethylene glycol 269

ml; distilled water 680 ml); (2) eosin (eosin yellowish 1.0 g; distilled water 100 ml); (3) lithium carbonate 1% (lithium carbonate 1 g; distilled water 100 g); (4) acid alcohol 1% 70% (alcohol 99 ml conc.; hydrochloric acid 1 ml); and (5) Scott's tap water.

In a beaker containing 1 L distilled water, add 20 g sodium bicarbonate and 3.5 g magnesium sulphate. Add a magnetic stirrer and mix thoroughly to dissolve the salts. Using a filter funnel, pour the solution into a labeled bottle.

The staining procedure is as follows: (1) Bring the sections to water; (2) place sections in hematoxylin for 5 min; (3) wash in tap water; (4) blue'the sections in lithium carbonate or Scott's tap water; (5) wash in tap water; (6) place sections in 1% acid alcohol for a few seconds; (7) wash in tap water; (8) place sections in eosin for 5 min; (9) wash in tap water; and (10) dehydrate, clear. Mount sections.

The results of the H/E staining provide cells with nuclei stained blue-black, cytoplasm stained

varying shades of pink; muscle fibers stained deep pinky red; fibrin stained deep pink; and red blood cells stained orange-red.

The invention also provides automated methods for analysis of estrogen receptor and progesterone receptor. The estrogen and progesterone receptors, like other steroid hormone receptors, plays a role in developmental processes and maintenance of hormone responsiveness in target cells. From the molecular viewpoint, estrogen and progesterone receptor interaction with target genes is of paramount importance in maintenance of normal cell function and is also involved in regulation of mammary tumor cell function. The expression of progesterone receptor and estrogen receptor in breast tumors is a useful indicator for subsequent hormone therapy. An anti- estrogen receptor antibody labels epithelial cells of breast carcinomas which express estrogen receptor.

An immunohistochemical assay of the estrogen receptor is performed using an anti-estrogen receptor antibody, for example the well-characterized 1D5

clone, and the methods of Pertchuk, et al. (Cancer 77: 2514-2519,1996) or a commercially available immunohistochemistry system such as that provided by DAKO (Carpenteria CA; DAKO LSAB2 Immunostaining System).

In breast carcinoma cells, immunohistochemistry immunostaining of progesterone receptor has been demonstrated in the nuclei of cells from various histologic subtypes. An anti-progesterone receptor antibody labels epithelial cells of breast carcinomas which express progesterone receptor. An immunohistochemical assay of the progesterone receptor is performed using an anti-estrogen receptor antibody, for example the well-characterized 1A6 clone, and the methods of Pertchuk, et al. (Cancer 77: 2514-2519,1996).

Still other automated analyses are within the scope of the invention, including the following: Micrometastases/Metastatic Recurring Disease (MM/MRD). Metastasis is the biological process whereby a cancer spreads to the distant part of the

body from its original site. A micrometastases is the presence of a small number of tumor cells, particularly in the lymph nodes and bone marrow. A metastatic recurring disease is similar to micrometastasis, but is detected after cancer therapy rather than before therapy. An immunohistochemical assay for MM/MRD is performed using a monoclonal antibody which reacts with an antigen (a metastatic- specific mucin) found in bladder, prostate and breast cancers.

MIB-1. MIB-1 is an antibody that can be used in immunohistochemical assays for the antigen Ki-67.

The clinical stage at first presentation is related to the proliferative index measured with Ki-67. High index values of Ki-67 are positively correlated with metastasis, death from neoplasia, low disease-free survival rates, and low overall survival rates.

Microvessel Density Analysis. Microvessel density analysis is a measure of new blood vessel formation (angiogenesis). Angiogenesis is characteristic of growing tumors. Intratumor

microvessel density can be assessed by anti-CD34 immunostaining.

The Oncogene p53. Overexpression of the p53 oncogene has been implicated as the most common genetic alteration in the development of human malignancies. Investigations of a variety of malignancies, including neoplasms of breast, colon, ovary, lung, liver, mesenchyme, bladder and myeloid, have suggested a contributing role of p53 mutation in the development of malignancy. The highest frequency of expression has been demonstrated in tumors of the breast, colon and ovary. A wide variety of normal cells do express a wildtype form of p53 but generally in restricted amounts. Overexpression and mutation of p53 have not been recognized in benign tumors or in normal tissue. An immunohistochemical assay of p53 is performed using an anti-p53 antibody, for example the well-characterized DO-7 clone.

Immunophenotyping.

Undifferentiated tumor classification.

Antibody titering.

Prominence of Nucleoli. A nucleoli is an organelle in a cell nucleus. Cervical dysplasia refers to the replacement of the normal or metaplastic epithelium with atypical epithelial cells that have cytologic features that are pre-malignant (nuclear hyperchromatism, nuclear enlargement and irregular outlines, increased nuclear-to-cytoplasmic ratio, increased prominence of nucleoli) and chromosomal abnormalities. The changes seen in dysplastic cells are of the same kind but of a lesser degree than those of frankly malignant cells. In addition, there are degrees of dysplasia (mild, moderate, severe).

HIV p24 Protein. Human immunodeficiency virus (HIV) p24 antigen levels are measured in an immunohistochemistry assay using anti-HIV p24 antigen. The HIV p24 protein test is used for the detection of HIV virus. The test can be used to

detect the virus, measure the amount of virus, and examine the virus'genetic composition.

Human Papiloma Virus (HPV). HPV is a sexually transmitted virus which causes warts. HPV is an important health concern because it may cause cancer of the cervix. An immunohistochemical assay of HPV is performed using an antibody associated with cervical cancer. Several serological responses are strongly associated with cervical cancer, notably the IgG response against the HPV 16 epitopes LI: 13, E2: 9, and E7: 5, and the IgA response against an HPV 18 E2-derived antigen.

Mitotic Index. When a viral genome is incorporated into the nuclear genetic material, uncontrolled malignant growth of the host cell may be promoted.

Operating the Instrument While operating the instrument, the user interacts with a few screens including, but not limited to, Patient Entry, Review Data, Construct

Report, Manual Control, and User Preferences. Rather than the information entry revolving around the patient cases, the patient data entry interface is organized as worklist information composed of multiple patient cases. For example, a worklist for HER2/neu is composed of tissue samples that are prepared in one of two methods, the HER2/neu immunohistochemistry staining technique or the H/E technique. The slides within a HER2/neu worklist consists of a positive control slide (prepared with the immunohistochemistry technique and the HER2 antibody), a negative control slide (prepared with the immunohistochemistry technique and another antibody), and two slides for the one or more patient cases. Per patient case there are two slides prepared. One slide is prepared with the HER2/neu immunohistochemistry technique and a second is prepared with the H/E technique for general tissue analysis.

The data that is relevant for a HER2/neu worklist is the: (1) worklist name or identifier of

protocol (e. g., HER2/neu); barcode of the positive control slide; and barcode of the negative control slide. The data that is relevant on a per Patient Case is the: (4) patient ID; (5) accession number; (6) social security number; (7) referring hospital, (8) referring physician; (9) barcode of the immunohistochemistry prepared slide; and (10) barcode of the H/E prepared slide.

The user starts analysis with the batch button and the slide carriers loaded into the input hopper.

The input hopper is composed of all the immunohistochemistry slides from the patient cases, all the H/E slides from the patient cases, the positive control slide, and the negative control slide. During analysis the instrument reads the barcode on the slide and determines one of three situations and starts one of the three appropriate computer applications: (1) Slide is the positive control slide and run the HER2-positive application.

(2) Slide is the negative control slide and run the HER2-negative application. (3) Slide is either the

immunohistochemistry or H/E patient slide and run the HER2 application.

The system reads industry standard barcodes.

The barcode relates the type of protocol the instrument uses to analyze the slide. The type of data stored for each slide is determined by the stain preparation and the protocol used to analyze it.

During the transport of the slide through the system, therefore, the chain of custody is preserved. When a barcode is unreadable or isn't found in one of the defined worklists, the action taken by the instrument is to ignore the slide altogether and send it to the output hopper.

The HER2-positive application (1) finds the specimen, (2) goes to five locations within the specimen, (3) stores the image from each location, (4) completes color space transformations to obtain the intensity of stain at all five locations, and (5) stores the average value of intensity in the database (DB). This value is used as the normalized expression value for the HER2 quantitative analysis.

This value is also used to determine the A between the positive and negative control slides and verify that the A is large enough.

The HER2-negative application (1) finds the specimen, (2) goes to five locations within the specimen, (3) stores the image from each location, (4) completes color space transformations to obtain the intensity of stain at all five locations, and (5) stores the average value of intensity in the database. This value is used to determine the A between the positive and negative control slides and verify that the A is large enough.

The HER2 application (1) finds the specimen, (2) scans the slide at 10x and constructs a histological reconstruction object, and (3) stores the object in the database. Before a slide is analyzed, the instrument checks to see if the hard drive space has met a certain capacity for archiving data. If so, the user is prompted to archive before continuing instrument analysis. Compression may need to take

place prior to the object being stored within the database.

After completion of running all the slides within the worklist, the histological reconstruction objects are analyzed by the pathologist or physician.

The Slide Display Interface displays the list of slides that were analyzed, or the list of patient cases. Within tissue analysis, there are always at least two slides per patient case that are analyzed by the instrument. The set of patient slides is a logical unit. Therefore, a pathologist or physician may choose the patient case by the patient ID or the accession number.

Within the User Interface that displays the list of patient cases to be reviewed/analyzed, once the pathologist chooses the patient case, H/E image is always displayed first. Using the H/E image, the pathologist determines whether or not the cancer is invasive and whether or not analysis of the IHC slide is necessary.

Upon patient case selection, the low power H/E image is displayed. This image can be reduced to enable the whole tissue cross-section to be displayed within the system's monitor (resolution at least 1024 x 760).

The pathologist can have the features available to choose more than one patient case to review and then traverse from one case to the next with the following features. For each patient case, the reduced low power H/E image always appears first.

While viewing the reduced low power H/E image the pathologist has the following capabilities: (1) to zoom into an area of the low power H/E image for higher magnification; (2) to choose to go to the reduced low power immunohistochemistry image for the current patient case; (3) to select an area to incorporate within the patient report (Marking an image section); (4) to choose to go to the next patient case (if selected in previous user interface); and (5) to choose to go to the previous patient case.

While viewing the zoomed H/E image the pathologist has the following capabilities: (1) to go back to the reduced low power H/E image; (2) to choose to go to the reduced low power immunohistochemistry image for the current patient case; (3) to select an area to incorporate within the patient report (Marking an image section); (4) to choose to go to the next patient case (if selected in previous user interface); and (5) to choose to go to the previous patient case.

While viewing the reduced low power immunohistochemistry image the pathologist has the following capabilities: (1) to zoom into an area of the low power immunohistochemistry image for higher magnification; (2) to choose to go back to the reduced H/E image for the current patient case; (3) to select an area of the reduced immunohistochemistry image and query for quantitative results; (4) to select an area to incorporate within the patient report (Marking an image section); (5) to select a quantitative result to incorporate within the patient

report (Save the quantitative result); (6) to choose to go to the next patient case (if selected in previous user interface); and (7) to choose to go to the previous patient case (if applicable).

While viewing the zoomed immunohistochemistry image the pathologist has the following capabilities: (1) to go back to the reduced low power IHC image; (2) to choose to go back to the reduced H/E image for the current patient case; (3) to select an area of the zoomed immunohistochemistry image and query for quantitative results; (4) to select an area to incorporate within the patient report (Marking an image section); (5) to select a quantitative result to incorporate within the patient report (Save the quantitative result); (6) to choose to go to the next patient case (if selected in previous user interface); and (7) to choose to go to the previous patient case (if applicable).

After completion of the pathologist analysis and review of all the patient cases, the reports can be generated. A User Interface lists all the patient

cases that have already been reviewed and analyzed by the pathologist. The pathologist can choose one or more of the listed patient cases to view the reports electronically. The HER2/neu report for a patient case can contain the following information: (1) Patient Information and Demographics as entered within the Worklist Information Entry; (2) Referring Physician and Hospital as entered within the Worklist Information Entry; (3) Pathologist and Laboratory Information; (4) Sections of the H/E image marked during the review/analysis for report inclusion; (5) sections of the immunohistochemistry image marked during the review/analysis for report inclusion; (5) quantitative analysis saved during the review/analysis for report inclusion; and (6) HER2/neu application and scoring analysis reference materials.

The interface that displays the patient reports online contains the following functionality: (1) Print; (2) Send To, allows for (linked to e-mail, when available, and prompting the user for the

address of where to send the report); (3) Next Patient Case Report (if more than one case was selected from the previous interface); (4) Previous Patient Case Report (if applicable); and (5) Save/Apply (if the additional comments area is modified). Network connectivity is site specific.

Site specificity is desired for sending reports via the Internet without having to transport the report over to another host to send it. Direct sending capabilities are preferred.

The instrument can have at least two user modes.

One user mode is a locked protocol consistent with FDA regulations. A second user mode is modifiable by the user. For the second user mode, access to the following parameters of the application include: (1) definition of the scan area, center, width, and height; (2) toggle switch for whether or not the Find phase is used; (3) Focus Type; (4) Focus Threshold; and (5) Focus Inset.

Automated System Referring now to the figures, an apparatus for automated cell analysis of biological specimens is generally indicated by reference numeral 10 as shown in perspective view in Fig. 1 and in block diagram form in Fig. 2. The apparatus 10 comprises a microscope subsystem 32 housed in a housing 12. The housing 12 includes a slide carrier input hopper 16 and a slide carrier output hopper 18. A door 14 in the housing 12 secures the microscope subsystem from the external environment. A computer subsystem comprises a computer 22 having a system processor 23, an image processor 25 and a communications modem 29.

The computer subsystem further includes a computer monitor 26 and an image monitor 27 and other external peripherals including storage device 21, pointing device 30, keyboard 28 and color printer 35. An external power supply 24 is also shown for powering the system. Viewing oculars 20 of the microscope subsystem project from the housing 12 for operator viewing. The apparatus 10 further includes a CCD

camera 42 for acquiring images through the microscope subsystem 32. A microscope controller 31 under the control of system processor 23 controls a number of microscope-subsystem functions described further in detail. An automatic slide feed mechanism in conjunction with X-Y stage 38 provide automatic slide handling in the apparatus 10. An illumination light source 48 projects light onto the X-Y stage 38 which is subsequently imaged through the microscope subsystem 32 and acquired through CCD camera 42 for processing in the image processor 25. A Z stage or focus stage 46 under control of the microscope controller 31 provides displacement of the microscope subsystem in the Z plane for focusing. The microscope subsystem 32 further includes a motorized objective turret 44 for selection of objectives.

The purpose of the apparatus 10 is for the unattended automatic scanning of prepared microscope slides for the detection and counting of candidate objects of interest such as normal and abnormal cells, e. g., tumor cells. The preferred embodiment

may be utilized for rare event detection in which there may be only one candidate object of interest per several hundred thousand normal cells, e. g., one to five candidate objects of interest per 2 square centimeter area of the slide. The apparatus 10 automatically locates and counts candidate objects of interest and estimates normal cells present in a biological specimen on the basis of color, size and shape characteristics. A number of stains are used to preferentially stain candidate objects of interest and normal cells different colors so that such cells can be distinguished from each other.

As noted in the background of the invention, a biological specimen may be prepared with a reagent to obtain a colored insoluble precipitate. The apparatus of the present invention is used to detect this precipitate as a candidate object of interest.

During operation of the apparatus 10, a pathologist or laboratory technician mounts prepared slides onto slide carriers. A slide carrier 60 is illustrated in Fig. 8 and will be described further below. Each

slide carrier holds up to 4 slides. Up to 25 slide carriers are then loaded into input hopper 16. The operator can specify the size, shape and location of the area to be scanned or alternatively, the system can automatically locate this area. The operator then commands the system to begin automated scanning of the slides through a graphical user 25 interface.

Unattended scanning begins with the automatic loading of the first carrier and slide onto the precision motorized X-Y stage 38. A bar code label affixed to the slide is read by a bar code reader 33 during this loading operation. Each slide is then scanned at a user selected low microscope magnification, for example, lOx, to identify candidate objects of interest based on their color, size, and shape characteristics. The X-Y locations of candidate cells are stored until scanning is completed.

After the low magnification scanning is completed, the apparatus automatically returns to each candidate object of interest, reimages and refocuses at a higher magnification such as 40x and

performs further analysis to confirm the object candidate. The apparatus stores an image of the object for later review by a pathologist. All results and images can be stored to a storage device 21 such as a removable hard drive or DAT tape or transmitted to a remote site for review or storage.

The stored images for each slide can be viewed in a mosaic of images for further review. In addition, the pathologist or operator can also directly view a detected object through the microscope using the included oculars 20 or on image monitor 27.

Having described the overall operation of the apparatus 10 from a high level, the further details of the apparatus will now be described. Referring to Fig. 3, the microscope controller 31 is shown in more detail. The microscope controller 31 includes a number of subsystems connected through a system bus.

A system processor 102 controls these subsystems and is controlled by the apparatus system processor 23 through an RS 232 controller 110. The system processor 102 controls a set of motor-control

subsystems 114 through 124 which control the input and output feeder, the motorized turret 44, the X-Y stage 38, and the Z stage 46 (Fig. 2). A histogram processor 108 receives input from CCD camera 42 for computing variance data during the focusing operation described further herein. The system processor 102 further controls an illumination controller 106 for control of substage illumination 48. The light output from the halogen light bulb which supplies illumination for the system can vary over time due to bulb aging, changes in optical alignment, and other factors. In addition, slides which have been"over stained''can reduce the camera exposure to an unacceptable level. In order to compensate for these effects, the illumination controller 106 is included.

This controller is used in conjunction with light control software to compensate for the variations in light level. The light control software samples the output from the camera at intervals (such as between loading of slide carriers), and commands the controller to adjust the light level to the desired

levels. In this way, light control is automatic and transparent to the user and adds no substantial additional time to system operation. The system processor 23 may be any processor capable of performing the operations of the system, for example dual parallel Intel Pentium 90 MHZ devices, a T. I.

C80 processor for computation and processors capable of 8 to 32 bit operation on an NT system. The image processor 25 is preferably a Matrox Imaging Series 640 model. The microscope controller system processor 102 is an Advanced Micro Devices AMD29K device.

Figs. 4 and 5 show further detail of the apparatus 10 is shown. Fig. 4 shows a plan view of the apparatus 10 with the housing 12 removed. A portion of the automatic slide feed mechanism 37 is shown to the left of the microscope subsystem 32 and includes slide carrier unloading assembly 34 and unloading platform 36 which in conjunction with slide carrier output hopper 18 function to receive slide carriers which have been analyzed. Vibration

isolation mounts 40, shown in further detail in Fig.

5, are provided to isolate the microscope subsystem 32 from mechanical shock and vibration that can occur in a typical laboratory environment. In addition to external sources of vibration, the high-speed operation of the X-Y stage 38 can induce vibration into the microscope subsystem 32. Such sources of vibration can be isolated from the electro-optical subsystems to avoid any undesirable effects on image quality. The isolation mounts 40 comprise a spring 40a and piston 40b submerged in a high viscosity silicon gel which is enclosed in an elastomer membrane bonded to a casing to achieve damping factors on the order of 17 to 20%.

The automatic slide-handling feature of the present invention will now be described. The automated slide handling subsystem operates on a single slide carrier at a time. A slide carrier 60 is shown in Figs. 6a and 6b which provide a top view and a bottom view respectively. The slide carrier 60 includes up to four slides 70 mounted with adhesive

tape 62. The carrier 60 includes ears 64 for hanging the carrier in the output hopper 18. An undercut 66 and pitch rack 68 are formed at the top edge of the slide carrier 60 for mechanical handling of the slide carrier. A keyway cutout 65 is formed in one side of the carrier 60 to facilitate carrier alignment. A prepared slide 72 mounted on the slide carrier 60 includes a sample area 72a and a bar code label area 72b. Fig. 7a provides a top view of the slide handling subsystem which comprises a slide input module 15, a slide output module 17 and X-Y stage drive belt 50. Fig. 7b provides a partial cross- sectional view taken along line A-A of Fig. 7a. The slide input module 15 comprises a slide carrier input hopper 16, loading platform 52 and slide carrier loading subassembly 54. The input hopper 16 receives a series of slide carriers 60 (Figs. 6a and 6b) in a stack on loading platform 52. A guide key 57 protrudes from a side of the input hopper 16 to which the keyway cutout 65 (Fig. 6a) of the carrier is fit to achieve proper 15 alignment. The input module 15

further includes a revolving indexing cam 56 and a switch 90 mounted in the loading platform 52, the operation of which is described further below. The carrier loading subassembly 54 comprises an infeed drive belt 59 driven by a motor 86. The infeed drive belt 59 includes a pusher tab 58 for pushing the slide carrier horizontally toward the 20 X-Y stage 38 when the belt is driven. A homing switch 95 senses the pusher tab 58 during a revolution of the belt 59.

Referring specifically to Fig. 7a, the X-Y stage 38 is shown with x position and y position motors 96 and 97 respectively which are controlled by the microscope controller 31 (Fig. 3) and are not considered part of the slide handling subsystem. The X-Y stage 38 further includes an aperture 55 for allowing illumination to reach the slide carrier. A switch 91 is mounted adjacent the aperture 55 for sensing contact with the carrier and thereupon activating a motor 87 to drive stage drive belt 50 (Fig. 7b). The drive belt 50 is a double-sided

timing belt having teeth for engaging pitch rack 68 of the carrier 60 (Fig. 6b).

The slide output module 17 includes slide carrier output hopper 18, unloading platform 36 and slide carrier unloading subassembly 34. The unloading subassembly 34 comprises a motor 89 for rotating the unloading platform 36 about shaft 98 during an unloading operation described further below. An outfeed gear 93 driven by motor 88 rotatably engages the pitch rack 68 of the carrier 60 (Fig. 6b) to transport the carrier to a rest position against switch 92. A springloaded hold-down mechanism holds the carrier in place on the unloading platform 36.

The slide handling operation will now be described. Referring to Fig. 8, a series of slide carriers 60 are shown stacked in input hopper 16 with the top edges 60a aligned. As the slide handling operation begins, the indexing cam 56 driven by motor 85 advances one revolution to allow only one slide

carrier to drop to the bottom of the hopper 16 and onto the loading platform 52.

Figs. 8a-8d show the cam action in more detail.

The cam 56 includes a hub 56a to which are mounted upper and lower leaves 56b and 56c respectively. The leaves 56b, 56c are semicircular projections oppositely positioned and spaced apart vertically.

In a first position shown in Fig. 8a, the upper leaf 56b supports the bottom carrier at the undercut portion 66. At a 20 position of the cam 56 rotated 180°, shown in Fig. 8b, the upper leaf 56b no longer supports the carrier and instead the carrier has dropped slightly and is supported by the lower leaf 56c. Fig. 8c shows the position of the cam 56 rotated 270° wherein the upper leaf 56b has rotated sufficiently to begin to engage the undercut 66 of the next slide carrier while the opposite facing lower leaf 56c still supports the bottom carrier.

After a full rotation of 360° as shown in Fig. 8d, the lower leaf 56c has rotated opposite the carrier stack and no longer supports the bottom carrier which now

rests on the loading platform 52. At the same position, the upper leaf 56b supports the next carrier for repeating the cycle.

Referring again to Figs. 7a and 7b, when the carrier drops to the loading platform 52, the contact closes switch 90 which activates motors 86 and 87.

Motor 86 drives the infeed drive belt 59 until the pusher tab 58 makes contact with the carrier and pushes the carrier onto the X-Y stage drive belt 50.

The stage drive belt 50 advances the carrier until contact is made with switch 91, the closing of which begins the slide scanning process described further herein. Upon completion of the scanning process, the X-Y stage 38 moves to an unload position and motors 87 and 88 are activated to transport the carrier to the unloading platform 36 using stage drive belt 50.

As noted, motor 88 drives outfeed gear 93 to engage the carrier pitch rack 68 of the carrier 60 (Fig. 6b) until switch 92 is contacted. Closing switch 92 activates motor 89 to rotate the unloading platform 36.

The unloading operation is shown in more detail in end views of the output module 17 (Figs. 9a-9d).

In Fig. 9a, the unloading platform 36 is shown in a horizontal position supporting a slide carrier 60.

The hold-down mechanism 94 secures the carrier 60 at one end. Fig. 9b shows the output module 17 after motor 89 has rotated the unloading platform 36 to a vertical position, at which point the spring loaded hold-down mechanism 94 releases the slide carrier 60 into the output hopper 18. The carrier 60 is supported in the output hopper 18 by means of ears 64 (Figs. 6a and 6b). Fig. 9c shows the unloading platform 36 being rotated back towards the 20 horizontal position. As the platform 36 rotates upward, it contacts the deposited carrier 60 and the upward movement pushes the carrier toward the front of the output hopper 18. Fig. 9d shows the unloading platform 36 at its original horizontal position after having output a series of slide carriers 60 to the output hopper 18.

Having described the overall system and the automated slide handling feature, the aspects of the apparatus 10 relating to scanning, focusing and image processing will now be described in further detail.

In some cases, an operator will know ahead of time where the scan area of interest is on the slide.

Conventional preparation of slides for examination provides repeatable and known placement of the sample on the slide. The operator can therefore instruct the system to always scan the same area at the same location of every slide which is prepared in this fashion. But there are other times in which the area of interest is not known, for example, where slides are prepared manually with a known smear technique.

One feature of the invention automatically determines the scan area using a texture analysis process. Fig.

10 is a flow diagram that describes the processing associated with the automatic location of a scan area. As shown in this figure, the basic method is to pre-scan the entire slide area to determine texture features that indicate the presence of a

smear and to discriminate these areas from dirt and other artifacts.

At each location of this raster scan, an image such as in Fig. 12 is acquired and analyzed for texture information at steps 204 and 206. Since it is desired to locate the edges of the smear sample within a given image, texture analyses are conducted over areas called windows 78, which are smaller than the entire image as shown in Fig. 12. The process iterates the scan across the slide at steps 208,210,212 and 214.

In the interest of speed, the texture analysis process is performed at a lower magnification, preferably at a 4x objective. One reason to operate at low magnification is to image the largest slide area at any one time. Since cells do not yet need to be resolved at this stage of the overall image analysis, the 4x magnification is preferred. On a typical slide, as shown in Fig. 11, a portion 72b of the end of the slide 72 is reserved for labeling with identification information. Excepting this label

area, the entire slide is scanned in a raster scan fashion 76 to yield a number of adjacent images.

Texture values for each window include the pixel variance over a window, the difference between the largest and smallest pixel value within a window, and other indicators. The presence of a smear raises the texture values compared with a blank area.

One problem with a smear from the standpoint of determining its location is its non-uniform thickness and texture. For example, the smear is likely to be relatively thin at the edges and thicker towards the middle due to the nature of the smearing process. To accommodate for the non-uniformity, texture analysis provides a texture value for each analyzed area. The texture value tends to gradually rise as the scan proceeds across a smear from a thin area to a thick area, reaches a peak, and then falls off again to a lower value as a thin area at the edge is reached.

The problem is then to decide from the series of texture values the beginning and ending, or the edges, of the smear. The texture values are fit to a

square wave waveform since the texture data does not have sharp beginnings and endings.

After conducting this scanning and texture evaluation operation, one must determine which areas of elevated texture values represent the desired smear 74, and which represent undesired artifacts.

This is accomplished by fitting a step function, on a line-by-line basis to the texture values in step 216.

This function, which resembles a single square wave across the smear with a beginning at one edge, and end at the other edge, and an amplitude provides the means for discrimination. The amplitude of the best- fit step function is utilized to determine whether smear or dirt is present since relatively high values indicate smear. If it is decided that smear is present, the beginning and ending coordinates of this pattern are noted until all lines have been processed, and the smear sample area defined at 218.

After an initial focusing operation described further herein, the scan area of interest is scanned to acquire images for image analysis. The preferred

method of operation is to initially perform a complete scan of the slide at low magnification to identify and locate candidate objects of interest, followed by further image analysis of the candidate objects of interest at high magnification in order to confirm the objects as cells. An alternate method of operation is to perform high magnification image analysis of each candidate object of interest immediately after the object has been identified at low magnification. The low magnification scanning then resumes, searching for additional candidate objects of interest. Since it takes on the order of a few seconds to change objectives, this alternate method of operation would take longer to complete.

The operator can pre-select a magnification level to be used for the scanning operation. A low magnification using a lOx objective is preferred for the scanning operation since a larger area can be initially analyzed for each acquired scan image. The overall detection process for a cell includes a combination of decisions made at both low (10x) and

high magnification (40x) levels. Decision making at the lOx magnification level is broader in scope, i. e., objects that loosely fit the relevant color, size and shape characteristics are identified at the lOx level.

Analysis at the 40x magnification level then proceeds to refine the decision-making and confirm objects as likely cells or candidate objects of interest. For example, at the 40x level it is not uncommon to find that some objects that were identified at lOx are artifacts which the analysis process will then reject. In addition, closely packed objects of interest appearing at lOx are separated at the 40x level.

In a situation where a cell straddles or overlaps adjacent image fields, image analysis of the individual adjacent image fields could result in the cell being rejected or undetected. To avoid missing such cells, the scanning operation compensates by overlapping adjacent image fields in both the x and y directions. An overlap amount greater than half the

diameter of an average cell is preferred. In the preferred embodiment, the overlap is specified as a percentage of the image field in the x and y directions.

The time to complete an image analysis can vary depending upon the size of the scan area and the number of candidate cells, or objects of interest identified. For one example, in the preferred embodiment, a complete image analysis of a scan area of two square centimeters in which 50 objects of interest are confirmed can be performed in about 12 to 15 minutes. This example includes not only focusing, scanning, and image analysis, but also the saving of 40x images as a mosaic on hard drive 21 (Fig. 2). Consider the utility of the present invention in a"rare event"application where there may be one, two or a very small number of cells of interest located somewhere on the slide. To illustrate the nature of the problem by analogy, if one were to scale a slide to the size of a football field, a tumor cell, for example, would be about the

size of a bottle cap. The problem is then to rapidly search the football field and find the very small number of bottle caps and have a high certainty that none have been missed.

However the scan area is defined, an initial focusing operation must be performed on each slide prior to scanning. This is required since slides differ, in general, in their placement in a carrier.

These differences include slight (but significant) variations of tilt of the slide in its carrier.

Since each slide must remain in focus during scanning, the degree of tilt of each slide must be determined. This is accomplished with an initial focusing operation that determines the exact degree of tilt, so that focus can be maintained automatically during scanning.

The initial focusing operation and other focusing operations to be described later utilize a focusing method based on processing of images acquired by the system. This method was chosen for its simplicity over other methods including use of IR

beams reflected from the slide surface and use of mechanical gauges. These other methods also would not function properly when the specimen is protected with a coverglass. The preferred method results in lower system cost and improved reliability since no additional parts need be included to perform focusing. Fig. 13A provides a flow diagram describing the"focus point''procedure. The basic method relies on the fact that the pixel value variance (or standard deviation) taken about the pixel value mean is maximum at best focus. A "brute-force"method could simply step through focus, using the computer controlled Z or focus stage, calculate the pixel variance at each step, and return to the focus position providing the maximum variance. Such a method would be too time consuming.

Therefore, additional features were added as shown in Fig. 13A.

These features include the determination of pixel variance at a relatively coarse number of focal positions, and then the fitting of a curve to the

data to provide a faster means of determining optimal focus. This basic process is applied in two steps, coarse and fine. During the coarse step at 220-230, the Z stage is stepped over a user-specified range of focus positions, with step sizes that are also user- specified. It has been found that for coarse focusing, these data are a close fit to a Gaussian function. Therefore, this initial set of variance versus focus position data are least-squares fit to a Gaussian function at 228. The location of the peak of this Gaussian curve determines the initial or coarse estimate of focus position for input to step 232.

Following this, a second stepping operation 232- 242 is performed utilizing smaller steps over a smaller focus range centered on the coarse focus position. Experience indicates that data taken over this smaller range are generally best fit by a second order polynomial. Once this least squares fit is performed at 240, the peak of the second order curve provides the fine focus position at 244.

Fig. 14 illustrates a procedure for how this focusing method is utilized to determine the orientation of a slide in its carrier. As shown, focus positions are determined, as described above, for a 3 x 3 grid of points centered on the scan area at 264. Should one or more of these points lie outside the scan area, the method senses at 266 this by virtue of low values of pixel variance. In this case, additional points are selected closer to the center of the scan area. Fig. 15 shows the initial array of points 80 and new point 82 selected closer to the center. Once this array of focus positions is determined at 268, a least squares plane is fit to this data at 270. Focus points lying too far above or below this best-fit plane are discarded at 272 (such as can occur from a dirty cover glass over the scan area), and the data is then refit. This plane at 274 then provides the desired Z position information for maintaining focus during scanning.

After determination of the best-fit focus plane, the scan area is scanned in an X raster scan over the

scan area as described earlier. During scanning, the X stage is positioned to the starting point of the scan area, the focus (Z) stage is positioned to the best fit focus plane, an image is acquired and processed as described herein, and this process is repeated for all points over the scan area. In this way, focus is maintained automatically without the need for time-consuming refocusing at points during scanning. Prior to confirmation of cell objects at a 40x or 60x level, a refocusing operation is conducted since the use of this higher magnification requires more precise focus than the best-fit plane provides.

Fig. 16 provides the flow diagram for this process.

As may be seen, this process is similar to the fine focus method described earlier in that the object is to maximize the image pixel variance. This is accomplished by stepping through a range of focus positions with the Z stage at 276,278, calculating the image variance at each position at 278, fitting a second order polynomial to these data at 282, and calculating the peak of this curve to yield an

estimate of the best focus position at 284,286.

This final focusing step differs from previous ones in that the focus range and focus step sizes are smaller since this magnification requires focus settings to within 0.5 micron or better. It should be noted that for some combinations of cell staining characteristics, improved focus can be obtained by numerically selecting the focus position that provides the largest variance, as opposed to selecting the peak of the polynomial. In such cases, the polynomial is used to provide an estimate of best focus, and a final step selects the actual Z position giving highest pixel variance. It should also be noted that if at any time during the focusing process at 40x or 60x the parameters indicate that the focus position is inadequate, the system automatically reverts to a coarse focusing process as described above with reference to Fig. 13A. This ensures that variations in specimen thickness can be accommodated in an expeditious manner. For some biological specimens and stains, the focusing methods discussed

above do not provide optimal focused results. For example, certain white blood cells known as neutrophils may be stained with Fast Red, a commonly known stain, to identify alkaline phosphatase in the cytoplasm of the cells. To further identify these cells and the material within them, the specimen may be counterstained with hemotoxylin to identify the nucleus of the cells. In cells so treated, the cytoplasm bearing alkaline phosphatase becomes a shade of red proportionate to the amount of alkaline phosphatase in the cytoplasm and the nucleus becomes blue. However, where the cytoplasm and nucleus overlap, the cell appears purple. These color combinations appear to preclude the finding of a focused Z position using the focus processes discussed above.

In an effort to find a best focal position at high magnification, a focus method, such as the one shown in Fig. 13B, may be used. That method begins by selecting a pixel near the center of a candidate object of interest (Block 248) and defining a region

of interest centered about the selected pixel (Block 250). Preferably, the width of the region of interest is a number of columns which is a power of 2. This width preference arises from subsequent processing of the region of interest preferably using a one dimensional Fast Fourier Transform (FFT) technique. As is well known within, the art, processing columns of pixel values using the FFT technique is facilitated by making the number of columns to be processed a power of two. While the height of the region of interest is also a power of two in the preferred embodiment, it need not be unless a two dimensional FFT technique is used to process the region of interest.

After the region of interest is selected, the columns of pixel values are processed using the preferred one-dimensional FFT to determine a spectra of frequency components for the region of interest (Block 252). The frequency spectra ranges from DC to some highest frequency component. For each frequency component, a complex magnitude is computed.

Preferably, the complex magnitudes for the frequency components which range from approximately 25% of the highest component to approximately 75% of the highest component are squared and summed to determine the total power for the region of interest (Block 254).

Alternatively, the region of interest may be processed with a smoothing window, such as a Hanning window, to reduce the spurious high frequency components generated by the FFT processing of the pixel values in the region of interest. Such preprocessing of the region of interest permits all complex magnitude over the complete frequency range to be squared and summed. After the power for a region has been computed and stored (Block 256), a new focal position is selected, focus adjusted (Blocks 258,260), and the process repeated. After each focal position has been evaluated, the one having the greatest power factor is selected as the one best in focus (Block 262).

The following describes the image processing methods which are utilized to decide whether a

candidate object of interest such as a stained tumor cell is present in a given image, or field, during the scanning process. Candidate objects of interest which are detected during scanning are reimaged at higher (40x or 60x) magnification, the decision confirmed, and a region of interest for this cell saved for later review by the pathologist. The image processing includes color space conversion, low pass filtering, background suppression, artifact suppression, morphological processing, and blob analysis. One or more of these steps can optionally be eliminated. The operator is provided with an option to configure the system to perform any or all of these steps and whether to perform certain steps more than once or several times in a row. It should also be noted that the sequence of steps may be varied and thereby optimized for specific reagents or reagent combinations; however, the sequence described herein is preferred. It should be noted that the image processing steps of low pass filtering, thresholding, morphological processing, and blob

analysis are generally known image processing building blocks.

An overview of the preferred process is shown in Fig. 17A. The preferred process for identifying and locating candidate objects of interest in a stained biological specimen on a slide begins with an acquisition of images obtained by scanning the slide at low magnification (Block 288). Each image is then converted from a first color space to a second color space (Block 290) and the color converted image is low pass filtered (Block 292). The pixels of the low pass filtered image are then compared to a threshold (Block 294) and, preferably, those pixels having a value equal to or greater than the threshold are identified as candidate object of interest pixels and those less than the threshold are determined to be artifact or background pixels. The candidate object of interest pixels are then morphologically processed to identify groups of candidate object of interest pixels as candidate objects of interest (Block 296).

These candidate objects of interest are then compared

to blob analysis parameters (Block 298) to further differentiate candidate objects of interest from objects which do not conform to the blob analysis parameters and, thus, do not warrant further processing. The location of the candidate objects of interest may be stored prior to confirmation at high magnification. The process continues by determining whether the candidate objects of interest have been confirmed (Block 300). If they have not been confirmed, the optical system is set to high magnification (Block 302) and images of the slide at the locations corresponding to the candidate objects of interest identified in the low magnification images are acquired (Block 288). These images are then color converted (Block 290), low pass filtered (Block 292), compared to a threshold (Block 294), morphologically processed (Block 296), and compared to blob analysis parameters (Block 298) to confirm which candidate objects of interest located from the low magnification images are objects of interest.

The coordinates of the objects of interest are then stored for future reference (Block 303).

In general, the candidate objects of interest, such as tumor cells, are detected based on a combination of characteristics, including size, shape, and color. The chain of decision-making based on these characteristics preferably begins with a color space conversion process. The CCD camera coupled to the microscope subsystem outputs a color image comprising a matrix of 640 x 480 pixels. Each pixel comprises red, green, and blue (ROB) signal values.

It is desirable to transform the matrix of RGB values to a different color space because the difference between candidate objects of interest and their background, such as tumor and normal cells, may be determined from their respective colors.

Specimens are generally stained with one or more industry standard stains (e. g., DAB, New Fuchsin, AEC) which are"reddish"in color. Candidate objects of interest retain more of the stain and thus

appear red while normal cells remain unstained. The specimens may also be counterstained with hematoxalin so the nuclei of normal cells or cells not containing an object of interest appear blue. In addition to these objects, dirt and debris can appear as black, gray, or can also be lightly stained red or blue depending on the staining procedures utilized. The residual plasma or other fluids also present on a smear may also possess some color.

In the color conversion operation, a ratio of two of the RGB signal values is formed to provide a means for discriminating color information. With three signal values for each pixel, nine different ratios can be formed: R1R, R/G, RUB, G/G, G/B, G/R, B/B, B/G, B/R. The optimal ratio to select depends upon the range of color information expected in the slide specimen. As noted above, typical stains used for detecting candidate objects of interest such as tumor cells are predominantly red, as opposed to predominantly green or blue. Thus, the pixels of a cell of interest which has been stained contain a red

component which is larger than either the green or blue components. A ratio of red divided by blue (R/B) provides a value which is greater than one for tumor cells but is approximately one for any clear or white areas on the slide. Since the remaining cells, i. e., normal cells, typically are stained blue, the R/B ratio for pixels of these latter cells yields values of less than one. The R/B ratio is preferred for clearly separating the color information typical in these applications.

Fig. 17B illustrates the flow diagram by which this conversion is performed. In the interest of processing speed, the conversion is implemented with a look up table. The use of a look up table for color conversion accomplishes three functions: (1) performing a division operation; (2) scaling the result for processing as an image having pixel values ranging from 0 to 255; and (3) defining objects which have low pixel values in each color band (R, G, B) as "black"to avoid infinite ratios (i. e., dividing by zero). These"black"objects are typically

staining artifacts or can be edges of bubbles caused by pasting a coverglass over the specimen.

Once the look up table is built at 304 for the specific color ratio (i. e., choices of tumor and nucleated cell stains), each pixel in the original RGB image is converted at 308 to produce the output.

Since it is of interest to separate the red stained tumor cells from blue stained normal ones, the ratio of color values is then scaled by a user specified factor. As an example, for a factor of 128 and the ratio of (red pixel value)/ (blue pixel value), clear areas on the slide would have a ratio of 1 scaled by 128 for a final X value of 128. Pixels which lie in red stained tumor cells would have X value greater than 128, while blue stained nuclei of normal cells would have value less than 128. In this way, the desired objects of interest can be numerically discriminated. The resulting 640 x 480 pixel matrix, referred to as the X-image, is a gray scale image having values ranging from 0 to 255.

Other methods exist for discriminating color information. One classical method converts the RGB color information into another color space, such as HSI (hue, saturation, intensity) space. In such a space, distinctly different hues such as red, blue, green, yellow, may be readily separated. In addition, relatively lightly stained objects may be distinguished from more intensely stained ones by virtue of differing saturations. However, converting from RGB space to HSI space requires more complex computation. Conversion to a color ratio is faster; for example, a full image can be converted by the ratio technique of the present invention in about 30 ms while an HSI conversion can take several seconds.

In yet another approach, one could obtain color information by taking a single color channel from the camera. As an example, consider a blue channel, in which objects that are red are relatively dark.

Objects which are blue, or white, are relatively light in the blue channel. In principle, one could take a single color channel, and simply set a

threshold wherein everything darker than some threshold is categorized as a candidate object of interest, for example, a tumor cell, because it is red and hence dark in the channel being reviewed.

However, one problem with the single channel approach occurs where illumination is not uniform. Non- uniformity of illumination results in non-uniformity across the pixel values in any color channel, for example, tending to peak in the middle of the image and dropping off at the edges where the illumination falls off. Performing thresholding on this non- uniform color information runs into problems, as the edges sometimes fall below the threshold, and therefore it becomes more difficult to pick the appropriate threshold level. However, with the ratio technique, if the values of the red channel fall off from center to edge, then the values of the blue channel also fall off center to edge, resulting in a uniform ratio. non-uniformities. Thus, the ratio technique is more immune to illumination.

As previously described, the color conversion scheme is relatively insensitive to changes in color balance, i. e., the relative outputs of the red, green, and blue channels. However, some control is necessary to avoid camera saturation, or inadequate exposures in any one of the color bands. This color balancing is performed automatically by utilizing a calibration slide consisting of a clear area, and a dark''area having a known optical transmission or density. The system obtains images from the clear <BR> <BR> and"dark"areas, calculates"white''and"black" adjustments for the image processor 25, and thereby provides correct color balance.

In addition to the color balance control, certain mechanical alignments are automated in this process. The center point in the field of view for the various microscope objectives as measured on the slide can vary by several (or several tens of) microns. This is the result of slight variations in position of the microscope objectives 44a as determined by the turret 44 (Fig. 4), small

variations in alignment of the objectives with respect to the system optical axis, and other factors. Since it is desired that each microscope objective be centered at the same point, these mechanical offsets must be measured and automatically compensated.

This is accomplished by imaging a test slide which contains a recognizable feature or mark. An image of this pattern is obtained by the system with a given objective, and the position of the mark determined. The system then rotates the turret to the next lens objective, obtains an image of the test object, and its position is redetermined. Apparent changes in position of the test mark are recorded for this objective. This process is continued for all objectives. Once these spatial offsets have been determined, they are automatically compensated for by moving the stage 38 by an equal (but opposite) amount of offset during changes in objective. In this way, as different lens objectives are selected, there is no apparent shift in center point or

area viewed. A low pass filtering process precedes thresholding. An objective of thresholding is to obtain a pixel image matrix having only candidate objects of interest, such as tumor cells above a threshold level and everything else below it.

However, an actual acquired image will contain noise.

The noise can take several forms, including white noise and artifacts. The microscope slide can have small fragments of debris that pick up color in the staining process and these are known as artifacts.

These artifacts are generally small and scattered areas, on the order of a few pixels, which are above the threshold. The purpose of low pass filtering is to essentially blur or smear the entire color converted image. The low pass filtering process will smear artifacts more than larger objects of interest.

Such as tumor cells and thereby eliminate or reduce the number of artifacts that pass the thresholding process. The result is a cleaner thresholded image downstream. In the low pass filter process, a 3 x 3 matrix of coefficients is applied to each pixel in

the 640 x 480 x-image. A preferred coefficient matrix is as follows: 1/9 1/9 1/9 1/9 1/9 1/9 1/9 1/9 1/9 At each pixel location, a 3 x 3 matrix comprising the pixel of interest and its neighbors is multiplied by the coefficient matrix and summed to yield a single value for the pixel of interest. The output of this spatial convolution process is again a 640 x 480 matrix. As an example, consider a case where the center pixel and only the center pixel, has a value of 255 and each of its other neighbors, top left, top, top right and so forth, have values of 0.

This singular white pixel case corresponds to a small object. The result of the matrix multiplication and addition using the coefficient matrix is a value of 1/9 (255) or 28 for the center pixel, a value which is below the nominal threshold of 128. Now consider another case in which all the pixels have a value of 255 corresponding to a large

object. Performing the low pass filtering operation on a 3 x 3 matrix for this case yields a value of 255 for the center pixel. Thus, large objects retain their values while small objects are reduced in amplitude or eliminated. In the preferred method of operation, the low pass filtering process is performed on the X image twice in succession.

In order to separate objects of interest, such as a tumor cell in the x image from other objects and background, a thresholding operation is performed designed to set pixels within cells of interest to a value of 255, and all other areas to 0. Thresholding ideally yields an image in which cells of interest are white and the remainder of the image is black. A problem one faces in thresholding is where to set the threshold level. One cannot simply assume that cells of interest are indicated by any pixel value above the nominal threshold of 128. A typical imaging system may use an incandescent halogen light bulb as a light source. As the bulb ages, the relative amounts of red and blue output can change. The

tendency as the bulb ages is for the blue to drop off more than the red and the green. To accommodate for this light source variation over time, a dynamic thresholding process is used whereby the threshold is adjusted dynamically for each acquired image. Thus, for each 640 x 480 image, a single threshold value is derived specific to that image.

As shown in Fig. 18, the basic method is to calculate, for each field, the mean X value, and the standard deviation about this mean at 312. The threshold is then set at 314 to the mean plus an amount defined by the product of a (user specified) factor and the standard deviation of the color converted pixel values. The standard deviation correlates to the structure and number of objects in the image. Preferably, the user specified factor is in the range of approximately 1.5 to 2.5. The factor is selected to be in the lower end of the range for slides in which the stain has primarily remained within cell boundaries and the factor is selected to be in the upper end of the range for slides in which

the stain is pervasively present throughout the slide. In this way, as areas are encountered on the slide with greater or lower background intensities, the threshold may be raised or lowered to help reduce background objects. With this method, the threshold changes in step with the aging of the light source such that the effects of the aging are canceled out.

The image matrix resulting at 316 from the thresholding step is a binary image of black (0) 5 and white (255) pixels.

As is often the case with thresholding operations such as that described above, some undesired areas will lie above the threshold value due to noise, small stained cell fragments, and other artifacts. It is desired and possible to eliminate these artifacts by virtue of their small size compared with legitimate cells of interest.

Morphological processes are utilized to perform this function.

Morphological processing is similar to the low pass filter convolution process described earlier

except that it is applied to a binary image. Similar to spatial convolution, the morphological process traverses an input image matrix, pixel by pixel, and places the processed pixels in an output matrix.

Rather than calculating a weighted sum of neighboring pixels as m the low pass convolution process, the morphological process uses set theory operations to combine neighboring pixels in a nonlinear fashion.

Erosion is a process whereby a single pixel layer is taken away from the edge of an object.

Dilation is the opposite process which adds a single pixel layer to the edges of an object. The power of morphological processing is that it provides for further discrimination to eliminate small objects that have survived the thresholding process and yet are not likely tumor cells. The erosion and dilation processes that make up a morphological"open" preferably make small objects disappear yet allows large objects to remain. Morphological processing of binary images is described in detail in"Digital

Image Processing'', pages 127-137, G. A. Baxes, John Wiley & Sons (1994).

Fig. 19 illustrates the flow diagram for this process. As shown here, a morphological"open" process performs this suppression. A single morphological open consists of a single morphological erosion 320 followed by a single morphological dilation 322. Multiple"opens"consist of multiple erosions followed by multiple dilations. In the preferred embodiment, one or two morphological opens are found to be suitable. At this point in the processing chain, the processed image contains thresholded objects of interest, such as tumor cells (if any were present in the original image), and possibly some residual artifacts that were too large to be eliminated by the processes above.

Fig. 20 provides a flow diagram illustrating a blob analysis performed to determine the number, size, and location of objects in the thresholded image. A blob is defined as a region of connected pixels having the same"color,"in this case, a

value of 255. Processing is performed over the entire image to determine the number of such regions at 324 and to determine the area and x, y coordinates for each detected blob at 326. Comparison of the size of each blob to a known minimum area at 328 for a tumor cell allows a refinement in decisions about which objects are objects of interest, such as tumor cells, and which are artifacts. The location (x, y coordinates) of objects identified as cells of interest in this stage are saved for the final 40x reimaging step described below. Objects not passing the size test are disregarded as artifacts.

The processing chain described above identifies objects at the scanning magnification as cells of interest candidates. As illustrated in Fig. 21, at the completion of scanning, the system switches to the 40x magnification objective at 330, and each candidate is reimaged to confirm the identification 332. Each 40x image is reprocessed at 334 using the same steps as described above but with test parameters suitably modified for the higher

magnification (e. g., area). At 336, a region of interest centered on each confirmed cell is saved to the hard drive for review by the pathologist.

As noted earlier, a mosaic of saved images is made available for viewing by the pathologist. As shown in Fig. 22, a series of images of cells which have been confirmed by the image analysis is presented in the mosaic 150. The pathologist can then visually inspect the images to make a determination whether to accept (152) or reject (153) each cell image. Such a 5 determination can be noted and saved with the mosaic of images for generating a printed report.

In addition to saving the image of the cell and its region, the cell coordinates are saved should the pathologist wish to directly view the cell through the oculars or on the image monitor. In this case, the pathologist reloads the slide carrier, selects the slide and cell for review from a mosaic of cell images, and the system automatically positions the cell under the microscope for viewing.

It has been found that normal cells whose nuclei have been stained with hematoxylin are often quite numerous, numbering in the thousands per lOx image.

Since these cells are so numerous, and since they tend to clump, counting each individual nucleated cell would add an excessive processing burden, at the expense of speed, and would not necessarily provide an accurate count due to clumping. The apparatus performs an estimation process in which the total area of each field that is stained hematoxylin blue is measured and this area is divided by the average size of a nucleated cell. Fig. 23 outlines this process. In this process, a single color band (the red channel provides the best contrast for blue stained nucleated cells) is processed by calculating the average pixel value for each field at 342, establishing two threshold values (high and low) as indicated at 344,346, and counting the number of pixels between these two values at 348. In the absence of dirt, or other opaque debris, this provides a count of the number of predominantly blue

pixels. By dividing this value by the average area for a nucleated cell at 350, and looping over all fields at 352, an approximate cell count is obtained.

Preliminary testing of this process indicates an accuracy with +/-15%. It should be noted that for some slide preparation techniques, the size of nucleated cells can be significantly larger than the typical size. The operator can select the appropriate nucleated cell size to compensate for these characteristics.

As with any imaging system, there is some loss of modulation transfer (i. e., contrast) due to the modulation transfer function (MTF) characteristics of the imaging optics, camera, electronics, and other components. Since it is desired to save"high quality''images of cells of interest both for pathologist review and for archival purposes, it is desired to compensate for these MTF losses. An MTF compensation, or MTFC, is performed as a digital process applied to the acquired digital images. A digital filter is utilized to restore the high

spatial frequency content of the images upon storage, while maintaining low noise levels. With this MTFC technology, image quality is enhanced, or restored, through the use of digital processing methods as opposed to conventional oil-immersion or other hardware based methods. MTFC is described further in "The Image Processing Handbook,''pages 225 and 337, J. C. Rues, CRC Press (1995).

Referring to Fig. 24, the functions available in a user interface of the apparatus 10 are shown. From the user interface, which is presented graphically on computer monitor 26, an operator can select among apparatus functions which include acquisition 402, analysts 404, and system configuration 406. At the acquisition level 402, the operator can select between manual 408 and automatic 410 modes of operation. In the manual mode, the operator is presented with manual operations 409. Patient information 414 regarding an assay can be entered at 412. In the analysis level 404, review 416 and report 418 functions are made available. At the

review level 416, the operator can select a montage function 420. At this montage level, a pathologist can perform diagnostic review functions including visiting an image 422, accept/reject of cells 424, nucleated cell counting 426, accept/reject of cell counts 428, and saving of pages at 430. The report level 418 allows an operator to generate patient reports 432. In the configuration level 406, the operator can select to configure preferences at 434, input operator information 437 at 436, create a system log at 438, and toggle a menu panel at 440.

The configuration preferences include scan area selection functions at 442,452; montage specifications at 444, bar code handling at 446, default cell counting at 448, stain selection at 450, and scan objective selection at 454.

Computer Implementation Aspects of the invention may be implemented in hardware or software, or a combination of both.

However, preferably, the algorithms and processes of the invention are implemented in one or more computer programs executing on programmable computers each comprising at least one processor, at least one data storage system (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. Program code is applied to input data to perform the functions described herein and generate output information.

The output information is applied to one or more output devices, in known fashion.

Each program may be implemented in any desired computer language (including machine, assembly, high level procedural, or object oriented programming languages) to communicate with a computer system. In any case, the language may be a compiled or interpreted language.

Each such computer program is preferably stored on a storage media or device (e. g., ROM, CD-ROM, tape, or magnetic diskette) readable by a general or special purpose programmable computer, for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. The inventive system may also be considered to be implemented as a computer-readable storage medium, configured with a computer program, where the storage medium so configured causes a computer to operate in a specific and predefined manner to perform the functions described herein.

A number of embodiments of the present invention have been described. Nevertheless, various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited by the specific illustrated embodiment, but only by the scope of the appended claims.