Whole Slide Imaging (WSI) and Region of Interest (ROI)

Most folks have used a conventional microscope at some point in their life to view specimens on a glass slide, prepared either in their native state or stained using a variety of methods to help identify different structures within the sample. Over the past several decades, there has been a shift in the way microscopy samples are viewed. Physical slides are now being transformed into digital images using whole slide imaging (WSI). The digitized format provides a resource that is easily shared for a wide range of uses, such as educational aids for scientists and physicians, research tools for academia and industry, and for diagnostic purposes in pathology and clinical medicine.

The specimens come from a wide spectrum of sources that are just as varied as the methods in which they are prepared on the slides. Physical slides can contain a single or several tissue sections, cell types, organisms or structures from both related and unrelated sources. Whole slide imaging is meant to capture the entirety of the slide so as not to miss any important samples that may be present. However, there is a cost to imaging such large areas, especially when higher magnification objectives are used for increased resolution. Of primary concern is the large amount of data that is generated, given that many samples require several images per field of view to capture all of the colors that may represent the true visual aspects of a sample.

Recent advances in imaging instrumentation can help to alleviate the need to image an entire slide at high magnification to capture the detail needed for analysis. The recent launch of the Cytation™ 7 by BioTek Instruments provides a method to rapidly image a whole slide or part of a slide to determine the region(s) of interest (ROIs).

Once the ROI selection(s) is made (as shown outlined in green above), subsequent imaging of those particular regions at a higher resolution and/or with more complex imaging methods, such as fluorescence imaging, high contrast brightfield, phase contrast or color brightfield, can be performed using automated methods as seen below.

The image below shows a ROI of cardiac tissue (tissue section on the left in the above image) imaged at 10x with one individual tile shown in an exploded view.

The combination of an upright microscope and inverted fluorescence microscope in a single instrument provides a unique opportunity for users to determine the most important areas to image, using more sophisticated, automated imaging techniques while saving valuable time and data storage resources.

By: BioTek Instruments, Peter J. Brescia Jr., MSc, MBA