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Virtual microscopy aids in diagnosis of cancer

BioPhotonics
Dec 2006
Gary Boas

Diagnosing prostate cancer can be problematic because of benign lesions that mimic the cancer. For this reason, pathologists often combine immunohistochemistry methods and standard hematoxylin and eosin staining techniques to distinguish one from the other, as these have been shown to provide complementary information. One way to do this is to destain a slide previously stained for hematoxylin and eosin and use it for immunohistochemistry analysis. This technique, however, doesn’t allow side-by-side comparisons of the slides unless the stained one is imaged prior to destaining.

Researchers with the University of Tampere, the University of Helsinki, Helsinki University Central Hospital and Seinäjoki Central Hospital, all in Finland, have now developed a virtual microscopy method that allows them to visualize simultaneously hematoxylin and eosin and immunohistochemistry stainings performed one after the other on the same slide. The method enables viewing in either a transparent overlay mode or a side-by-side mode — at any magnification.


Researchers have developed a virtual microscopy method that allows simultaneous visualization of hematoxylin and eosin and immunohistochemistry stainings performed sequentially on the same slide. Use of the system could aid in the diagnosis of prostate cancer, for example.


They use the Surveyor/Turboscan made by Objective Imaging Ltd. of Cambridge, UK, to create the slides. This technology, a PCI board that fits into computers for motion control of microscopes combined with image acquisition software, enables rapid, mosaic imaging, in which multiple high-resolution images are stitched together to create a navigable composite image of a sample. It was developed in response to a perceived need in this area.

“The existing motion control technology had half the puzzle solved,” the company’s Don Laferty said. “What it didn’t have was integration with the camera side to capture images and perhaps even analyze them.” Such automation simplifies the process and speeds it up considerably.

There are other “virtual slide systems” on the market, but many are closed systems, like black boxes. Because most of the work is done by the controller card, researchers can use the Surveyor/Turboscan technology with any number of microscopes and motorized stages. Thus, it allows greater flexibility and a wider variety of applications than the other systems.

This also is the source of the technology’s biggest disadvantage. “Open systems such as ours provide for a range of options, some of which perform better than others,” Laferty explained. “So there does need to be more care to ensure an appropriate set of components is used.” He added that this is simply one of the prices to be paid for the flexibility.

Jorma Isola, one of the Tampere researchers who developed the new virtual microscopy method, appreciates the flexibility and versatility of the technology. Using it, he said, they can freely combine any number of imaging parameters. He also noted that scanning at multiple focal planes (the z-stack option) is extremely fast and very effective.

The investigators demonstrated the method in a study reported in the February 2006 issue of Journal of Urology. They selected 23 biopsy samples from the archive of the pathology department at Seinäjoki Central Hospital, stained them with hematoxylin and eosin, and digitized them with the new virtual microscopy slide scanning system. Then they washed them, restained them for analysis by immunohistochemistry and digitized them a second time. Scanning takes only a few moments per slide, and routine laboratory protocols can be used.

Besides providing simultaneous visualization of the two slides, the method allows viewing at any magnification, thanks to the mosaic imaging. This can be especially important in evaluation of prostatic biopsies, where diagnosis is largely dependent on assessments of the architectural growth pattern of the glands. Here, the pathologist can begin at relatively low magnification for an overview of the slides and zoom in to examine the cellular details.

The researchers use the hematoxylin-eosin stained slides for several applications, including teaching in basic medical and biotechnology courses, continued medical education of pathologists, virtual slide seminars and various interlaboratory quality-assurance programs. They maintain a Web site (www.webmicroscope.net) that facilitates several of these.

The researchers also are planning to begin large-scale high-throughput microscope slide scanning of all newly diagnosed cancer specimens in their hospital region, serving 500,000 people. The project aims to create a virtual slide archive of all cancer cases in the region, which will be used for quality assurance in histopathologic assessment as well as for continued education and scientific research. The virtual microscopy system currently uses the jpeg2000-JPIP file standard, which is likely to become the standard format for virtual slides used in clinical diagnostic institutions, Isola said. Also, jpeg2000 is the only virtual slide format compatible with the universal Dicom image and data archiving system.

As for the underlying technology, the company plans to continue adding dimensions. Currently, Laferty noted, Surveyor/Turboscan enables scanning in three dimensions, in the X, Y and Z planes. One possible direction, he said, is to add multichannel fluorescence. In this way, the technology is following the standard progression in the microscope world: from 2-D to 3-D to multichannel fluorescence to the combination of all of these in a single view.

“The difference is being able to handle much larger data sets,” he said, in addition to the various hardware capabilities available to the user.

Contact: Don Laferty, Objective Imaging Ltd.; e-mail: don.laferty@objectiveimaging.com.


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