Chapter 12 - Digital Pathology and Tissue Image Analysis

Abstract

The age of digitalization has arrived in light microscopy. While the current practice of toxicologic pathology remains largely based on the light microscopic evaluation of stained tissue sections, it is no longer limited to it. Thanks to the availability of whole-slide imaging (WSI), histopathologic evaluation can now be accomplished via a computer screen. Substituting a computer monitor for a traditional microscope may at first seem to be a minor change. However, the digitization of glass slides has opened up a host of new options to interrogate tissue sections. These include geographically remote viewing of slides for more convenient and expedient pathology peer review, simplification of obtaining rapid and even real-time consultations with specific subject matter experts, formation of pathology working groups with global membership, building digital workflows that link WSI to associated metadata stored in laboratory information management systems, integrating other relevant data (e.g., in vivo data), enhancing teaching and training capabilities, and applying image analysis algorithms to whole-slide images to extract data previously not easily accessible or quantified. While WSI has been commercially available for over 20 years and is being rapidly adopted by the global pathology community, regulatory guidance on the use of digital pathology and related topics in toxicologic pathology is still evolving and currently incomplete. This chapter introduces digital pathology, including WSI and tissue image analysis, and explores potential future use in nonclinical toxicology. Additional related topics such as stereology and alternative imaging modalities are briefly introduced. General principles for consideration in use of WSI in regulated studies are included. A list of relevant references provides additional scope for the interested reader.