Difference between revisions of "Digital Pathology"

Revision as of 22:25, 21 October 2018

Digital Pathology is a broad term defined as a dynamic image-based environment that enables the acquisition, management and interpretation of pathology information generated from a glass slide. [1]. Or simply it is digitization of pathology. Whole slide imaging is commonly equated to digital pathology but digital pathology more broadly includes the capture of pathology slides by a simple camera on a microscope, or robotic microscopy. However, some may argue that photographic images of gross specimens with integration into laboratory information systems can be considered digital pathology [2].

Background

Digital Pathology is a much talked about field in pathology informatics. In the late 90’s early 00’s as digital cameras became increasingly used, microscopy photography of pathology slides became increasingly popular. It was also around this time that whole slide scanners (WSI) were first introduced [3].

Challenges with Incorporation

Early slide scanners could not load many slides at a time and scanned at very slow speeds. Due to this reason, many argued in the beginning that WSI is too disruptive and costly to implement t[4]. A large Pathology laboratory may generate up to 2400 slides per day. In order to process those number of slides with one scanner, the scanning speed must take less than a minute a slide and early scanners were significantly slower. The new FDA approved Philips Intellisite Pathology Solution scans a 15 x 15 mm area at 40X in 60 seconds and hold 300 slides at a time [5].

Regulatory Issues

There also have been significant regulatory issues concerning digital pathology which has slowed incorporation into clinical workflows. Light microscopy, is registered as a class I medical device and therefore does not need FDA approval to be sold in the healthcare setting [6]. However, in 2009 the FDA held a meeting to discuss the replacement of light microscopy by WSI for primary diagnosis. They debated making WSI a class II device requiring a 510K approval or a class III device requiring premarket approval clinical trials, with the latter being the final conclusion after a few years of discussion [7]. The primary diagnosis verbiage is emphasized to distinguish it from WSI of immunohistochemical stains. Images of these types are used to quantify the expression of prognostically important molecules but do not have diagnostic implications. Given the perceived reduced risk these scanners utilized for this purpose are classified as Class II devices. It took the FDA another 5 years to provide draft recommendations in 2014 on how to perform an assessment of WSI devices which wasn’t finalized till 2016 [8]. Because of this uncertainty, it wasn’t until 2017 a WSI scanner received regulatory approval, which was the Philips IntelliSite Pathology Solution. After this, the FDA made WSI scanners a class II medical device since a predicate device was established. Therefore, in the future it should be easier for WSI scanners to get FDA approval, thereby alleviating the barrier to implementation somewhat.

Interoperability

Interoperability of digital pathology images is difficult because no true universal format exists for both user support or for archiving. Many modern slide scanner manufactures have their own proprietary file formats. Many argue for this reason whole slide images should be saved in the DICOM format. DICOM has a standard for Pathology images which was developed by working group 26 that was only approved in 2010. Slide scanner vendors have slowly been incorporating this format with their provided image software. Last October “Connectathon” shows were put on where vendors (Philips, Ventana, Leica) proved they had interoperability by scanning and importing the resulting images using the DICOM standard into an agreed upon PACS system ahead of conference [9].

Interface with LIS

Interfacing the LIS with pathology images is necessary for clinical workflows. However, full integration with the LIS is not entirely necessary for pathology images and may be difficult with the current state of laboratory information systems. A modular or integrative approach may be used. [10] In the modular approach, images are stored outside of the LIS and a middleware solution is used to connect the image repository to the LIS. This has an increased flexibility in the sharing and viewing of the images. | Vendor neutral archives (VNA) are getting increased traction in the medical field today and the modular approach may allow the incorporation into these archives easier.

Submitted by Thomas Schneider