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System and method for finding regions of interest for microscopic digital montage imaging

System and method for finding regions of interest for microscopic digital montage imaging description/claims

This application is a continuation of U.S. patent application Ser. No. 11/221,331 filed Sep. 6, 2005, which is a continuation of U.S. patent application Ser. No. 09/758,037, filed Jan. 11, 2001, now U.S. Pat. No. 6,993,169, both of which are incorporated herein by reference.

Laboratories in many biomedical specialties, such as anatomic pathology, hematology, and microbiology, examine tissue under a microscope for the presence and the nature of disease. In recent years, these laboratories have shown a growing interest in microscopic digital imaging as an adjunct to direct visual examination. Digital imaging has a number of advantages including the ability to document disease, share findings, collaborate (as in telemedicine), and analyze morphologic findings by computer. Though numerous studies have shown that digital image quality is acceptable for most clinical and research use, some aspects of microscopic digital imaging are limited in application.

Perhaps the most important limitation to microscopic digital imaging is a “subsampling” problem encountered in all single frame images. The sub-sampling problem has two components: a field of view problem and a resolution-based problem. The field of view problem occurs when an investigator looking at a single frame cannot determine what lies outside the view of an image on a slide. The resolution-based problem occurs when the investigator looking at an image is limited to the resolution of the image. The investigator cannot “zoom in” for a closer examination or “zoom out” for a bird's eye view. Significantly, the field of view and resolution-based problems are inversely related. Thus, as one increases magnification to improve resolution, one decreases the field of view. For example, as a general rule, increasing magnification by a factor of two decreases the field of view by a factor of four.

To get around the limitations of single frame imaging, developers have looked at two general options. The first option takes the general form of “dynamic-robotic” imaging, in which a video camera on the microscope transmits close to real time images to the investigator looking at a monitor, while the investigator operates the microscope by remote control. Though such systems have been used successfully for telepathology, they do not lend themselves to documentation, collaboration, or computer based analysis.

The second option being investigated to overcome the limitations inherit in single frame imaging is a montage (or “virtual slide”) approach. In this method, a robotic microscope systematically scans the entire slide, taking an image at every field. The individual images are then “knitted” together in a software application to form a very large data set with very appealing properties. The robotic microscope can span the entire slide area at a resolution limited only by the power of the optical system and camera. Software exists to display this data set at any resolution on a computer screen, allowing the user to zoom in, zoom out, and pan around the data set as if using a physical microscope. The data set can be stored for documentation, shared over the Internet, or analyzed by computer programs.

The “virtual slide” option has some limitations, however. One of the limitations is file size. For an average tissue section, the data generated at 0.33 um/pixel can be between two and five gigabytes uncompressed. In an extreme case, the data generated from one slide can be up to thirty-six gigabytes.

A much more difficult limitation with the prior systems is an image capture time problem. Given an optical primary magnification of twenty and a two-third inch CCD, the system field of view is approximately (8.8 mm.times.6.6 mm)/20=0.44.times.0.33 mm. A standard microscope slide typically has a specimen area of 25 mm.times.50 mm or 12.5 square centimeters. This requires over eighty-six hundred fields to image this entire specimen region. However, the average tissue section for anatomic pathology is approximately 2.25 square centimeters. This only requires approximately fifteen hundred fields to cover the tissue alone, approximately 80 percent less fields.

Traditionally, field rate in montage systems is limited by three factors—camera frame rate, image processing speed, and the rate of slide motion between fields. Given today's technology, the limiting factor can be reduced to only the camera frame rate. Using a 10 frame per second camera for the example above, imaging the entire slide would require 860 seconds or 14.33 minutes. If only the region of interest was imaged, this average time could be reduced to 150 seconds or 2.5 minutes; substantially increasing the slide throughput of an imaging system.

Thus, a system is needed to automatically find the region of interest on a microscope slide and image only this region.

The present invention relates to microscopic digital imaging of tissue sections for medical and research use. In particular it describes a method to find regions of interest for high throughput montage imaging of microscope slides using a standard microscope and camera.

An embodiment of a tissue finding method disclosed herein includes differentiating tissue containing regions of a microscope slide from non-tissue containing regions of the microscope slide. An embodiment of a tissue finding apparatus disclosed herein includes a device to differentiate tissue containing regions of a microscope slide from non-tissue containing regions of the microscope slide.

The present invention relates to a method and system for processing a thumbnail image from a microscope slide to determine tissue locations on the slide. An embodiment of the system comprises an image cropping component, a tissue finding component, and a scan control component. The image cropping component crops the thumbnail image and removes portions of the image that fall outside of determined slide boundaries. The cropped image from the image cropping component is inputted into the tissue finding component. The tissue finding component identifies tissue regions by applying a sequence of filters that incorporate knowledge of typical appearance and location of tissue and non-tissue slide regions. The tissue finding component outputs a tiling matrix whose values indicate which tiles should be imaged. The scan control component interprets the tiling matrix and transposes positions of the tiling matrix into actual stage coordinate for a microscopic imaging.

Accordingly, it is an object of an embodiment of the invention to provide a microscopic imaging system for whole slide montage in which standard microscope optics, off the shelf cameras and a simple motorized stage can be used to select the region of interest, image only this section and produce aligned image tiles.

An embodiment of the present invention uses a pre-scan process applied to a macroscopic image of the slide, to guide a high-resolution slide scanning process and ensure high-quality images of the entire specimen are acquired. The pre-scan process includes an image cropping component, a tissue-finding component, and a scan control component. The image cropping and tissue finding components identify interesting regions on the slide to be scanned. The scan control component generates the control parameters for a motorized microscopic imaging system.

It is another object of an embodiment of the invention to use a high-resolution slide scanning process to control the operation of the motorized stage and camera. This process utilizes information gathered by the pre-scan process, namely the imaging regions, to control the positioning of the stage to image only the regions of interest and to ensure the individual images are well aligned.

Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and advantages of the invention to be realized and attained by the microscopic image capture system will be pointed out in the written description and claims hereof as well as the appended drawings.

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