Digital Pathology – From Slides to Screen

INTRODUCTION

The history of Digital Pathology (DP) goes back to the 1960s, when the concept of telepathology, that is, transmitting microscope images between remote locations was experimented. Later, in the 1990s, concept of virtual microscopy^[1] appeared in several life science research areas. The term ‘Digital Pathology’ to denote digitisation efforts in pathology was introduced at the turn of the century and has been around for nearly 50 years. However, it is in the past decade that true digital transformation of moving away from analogue into an electronic media has been happening. Over the past 5 years, Whole Slide Imaging (WSI) has been a game changer with affordable scanner technology and mass/cloud storage technologies appearing in the market. The field of radiology has undergone the digital transformation many years ago; however, the same is not true for the haematoxylin and eosin stained routine histological slides. Although virtual microscopy is being used for external quality assurance, continuing medical education programs, teaching purposes, etc., but the replacement of traditional glass slides for routine diagnostics still looks far from being true in most departments of laboratory medicine and pathology.

DP-WHAT AND WHY

DP can clearly be defined as the digitalisation of gross and microscopic tissue specimens, as well as the management, analysis, distribution and storage of clinical data and pathological images. It is a revolutionary idea to make pathology more objective, the routine work of pathologists involves the identification of patterns in gross and microscopic tissue sections to reach a diagnosis that can be rendered to the clinician and to the patient for further investigation or for starting therapy. Pathology has always been a very subjective speciality; with the evidence-based medicine taking precedence, it becomes imperative that we make efforts to objectify pathology, as a subject, too. This can be done by DP to a certain extent. In case of DP, the intellectual process of analysing and interpreting pathology images to provide a final diagnosis is one of the central aspects of the pathologist’s work. Therefore, both image and report must always include the name of the consultant pathologist and department where that intellectual work has been performed.

As a teaching tool also DP can be very useful, currently, archival tissue collections and new teaching cases are scanned and converted to static digital images, these images of gross and microscopic pathology specimens are captured by digital cameras, tablets, iPads and smartphones and then downloaded into personal computers or university servers for storage ready for teaching or discussion in the multidisciplinary clinical meetings.

WSI

The introduction of WSI has created some wonderful opportunities for the pathologist by allowing capturing images of the entire pathology slide without the need to select only a few regions of interest.^[2,3] A WSI scanner may be considered a digital microscope also known as virtual microscopy, which is fitted with special high-resolution cameras which combined with optics and software serves to produce diagnostic quality images.^[4] These images are an accurate representation of the scanned glass slide, and in some applications, they may be more valuable than the actual glass slides in terms of image resolution and ease of identification of specific diagnostic features. Modern WSI scanners can scan from 1 to 400 slides at a time, typically using a microscope lens with magnification of ×20 or ×40. Due to the high-resolution digital slides, the pathologist can scan the slides rapidly and focus by zooming in and out on the monitor using the keyboard, mouse or his/her finger and gather information to make the diagnosis.^[5] Digital imaging can be subdivided into two classes according to the aim, the first being digital microscope and the other being diagnosis-aided systems. The digital microscopes aim to create a digital image from an analogic image detected with a light microscope. Conversely, diagnosis-aided systems can detect the region of interest and give a presumptive diagnosis. The robotic microscopic scanner mechanically scans histologic glass slides containing the tissue already processed and stained. A software combines individual scanned fields into a composite digital image. This new technology applied with the WSI can be used for primary diagnosis, for publication of scientific data in peer-reviewed journals, and to capture static images for reporting, archiving or computer-aided analysis and training purposes in the universities and hospitals. At present, multiplane images are feasible, but take very long to scan slides and produce large files. Some pathologist has resorted to video microscopy on cytology material.^[6]

ADVANTAGES OF DP

The principal benefits of using DP are as follows:

LIMITATIONS OF DP

FUTURE TRENDS IN DP

DP has started to expand and will be providing advanced diagnostic skills for pathologists. Few biopharmaceutical companies and top clinical research organisations have adopted the concept of DP to streamline their drug development processes. DP can be relevant with the advent of assays such as markers or multiplex, which are difficult to discern with the human eye. Well-established DP companies need to consider building the required business framework to support the development of precision medicine using DP.

Some of the companies, such as Inspirata Inc. and MD Biosciences, have adopted different approaches to increase their foothold in the DP domain. Inspirata offers ‘Digital Informatics Solution’ that streamlines case management and communication among the entire care team, whereas MD Biosciences offers cutting-edge DP imaging equipment for rapid, high-resolution digitalisation of whole slides for reviewing and assessing through their secure and cloud-based image management system.

Several algorithms are being developed (e.g., pattern recognition algorithms) that improve accuracy, reliability and productivity. Computer-assisted Image Analysis has been used to score certain immunohistochemical stains, this gives all pathologists the same yardstick for scoring immunohistochemistry findings in cancer.

With the increased use of exponential technologies such as AI and Machine Learning, enhanced translational research, computer-aided diagnosis and personalised medicine is expected to grow in the near future. [Table 1] lists some of the companies actively working in digitalising pathology.

CONCLUSION

A variety of digital solutions are already available in the market for migrating the entire workflow of pathologists from manual to digital; these solutions have helped overcome barriers and address associated challenges with the traditional pathology workflow. The requirement now is fundamental change in how tissue is processed, the workflow is standardised and most important is the mindset and the willingness to adapt to this new system. Challenges such as high bandwidth requirements, electronic platforms, the operating systems and data storage have been targeted and are improving enormously. The solution is accelerating data storage, simplifying data management and improving data protection for cloud infrastructure, data analytics, AI-rich content, high scientific computing and numerous other applications that may be considered unconceivable currently. Therefore, it is time that pathology is completely digitalised, and we adapt to these winds of change.