REAL WORLD CAMERA APPLICATIONS

Microscopy for Diagnosing Cancer

Sub-pixel shifting digital camera provides artifact-free images.

In cases where cancer is suspected, an incisional biopsy may be collected and then examined by a pathologist to determine whether the lesion is benign or malignant and to characterize what type of cancer is present. Hematoxylin and eosin (H&E), one of the most widely used stains in medical diagnosis and most commonly employed to identify and characterize suspected cases of cancer, is a staining method that involves the application of the basic dyes hematoxylin and eosin. Hematoxylin colors basophilic structures with a blue-purple hue, and alcohol-based eosin Y colors eosinphilic structures bright pink. Basophilic structures include the cell nucleus and ribosome as well as RNA rich cytoplasmatic regions. Eosinphilic structures are intercellular and extracellular proteins.

Precise color reproduction, megapixel resolution, and high-speed preview are important factors in sample imaging. It is critical that the colors observed in a microscope match those found in the final image of the sample, and that the image retains its consistency upon enlargement. This ensures a proper diagnosis of the suspected cancer.

The INFINITYX-32, a 32 megapixel CCD microscopy camera can be used by pathologists in this clinical application.. Dedicated microscopy cameras allow users to view a live preview of their sample, capture and image and perform any post capture processing. The camera uses a native 2.0 megapixel sensor and offers selectable capture resolutions ranging from 2 to 32 megapixel via pixel-shifting technology.

High Color Fidelity

Traditional color cameras that use a Bayer filter and interpolation to define color, but without pixel-shifting technology, can introduce artifacts into the image and may have difficulty reproducing the exact color of the H&E stain. Often, the purple-blue hue is rendered as black, and the pinks appear bleached out. These types of cameras use a specific arrangement of filters to create an image where a raw Bayer pattern image is created, with each filter containing only one of three primary colors (red, green or blue). As a result, two thirds of the color data is missing from each pixel. A complete color image is then obtained through the use of an algorithm to interpolate the red, green and blue values for each specific point. Interpolation errors may occur, resulting in an image whose final color does not precisely match the sample as seen in the microscope eyepiece.

The sensor in the digital scientific camera undergoes a sub-pixel shift, moving the sensor across the sample. Each color filter in the Bayer array is exposed to a specific area of the sample. This ensures that all primary colors (red, green, blue) are represented in each pixel for precise sample reproduction. The net effect on an H&E stained sample is that the color in the final image precisely duplicates what is seen in the eyepiece of the microscope.

Variable Resolution

A second important feature needed to properly characterize cancer biopsies is the ability to enlarge images to view specific areas of interest. With traditional lower-resolution cameras, pixilation occurs when an image is displayed at a larger size because the individual pixels (the smallest piece of information in the image), become visible. It is possible to use anti-aliasing techniques in imaging software packages to smooth this effect; however, this can produce blurriness in the image and does not completely remove the pixilation. In a clinical setting this reduces the ability to see detail in enlarged images and produces extremely poor images for presentations.

Another advantage of pixel-shifting technology is the camera’s ability to shift the native 2.0 megapixel CCD sensor providing resolution options of 2, 8, 16 and 32 megapixel. The scientific camera shifts the sensor a fraction of a pixel during each step of the capture process. As a result, objects that are considerably smaller than a pixel may be resolved without artifacts, and enlarged images demonstrate clear edges without pixilation effects.

Speed

A smooth live video preview provides simple focusing and stage manipulation. Using lower resolutions and binning modes allow frame rates as high as 80 fps, which are easily capable of producing videos. The ability to preview video images with
precise color and high resolution is critical for pathologists examining biopsies when cancer is suspected or needs to be characterized.

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