by: Jennifer Jakubowski, BA, CT(ASCP), Biomedical Sciences Graduate Student, Drexel University
Whole-slide imaging (WSI) has been incorporated into numerous different histological workflows, where flat layers of tissue can be scanned and visualized effectively in their digitized form. Over the last few years, several WSI platforms have gained FDA approval for primary diagnosis, greatly reducing the use of a microscope and allowing pathologists to work remotely. These advancements have prompted more widespread adoption of digital pathology systems, but its application into cytology has been a struggle. Due to the 3D-oriented nature of cellular clusters present on cytologic slides, each layer within every cluster needs to be captured for clear visualization of the entire sample. This would require a scanner to capture depth in z-stacks, resulting in an image the emulates the up and down focus of a microscope. Earlier scanners lacked effective z-stacking capabilities, which was the first hurdle that needed to be overcome. Now that modern day scanners have z-stacking functionality, some other obstacles have deterred cytology expansion.
Consider a 2 GB WSI file. If ten z-planes were to be captured, the file size would increase by tenfold. A 2 GB file now becomes a 20 GB file for a single cytology slide, warranting a data storage/archival strategy that should cater to each laboratory’s unique workload. Excess data storage is an additional cost that needs to be considered on top of the department’s whole-slide imaging platform purchase. To curtail this setback, more efficient compression algorithms could serve as a preventative measure to keep file size down so less storage space is needed. Codec, such as JPEG 2000, has shown to outperform standard JPEG compression, while maintaining image quality. However, file sizes still remain relatively large. Additionally, although modern day scanners have z-stacking capabilities, slides need to be scanned ten individual times for ten z-stacks. Longer scan times increase turnaround times and may not be practical for higher volume laboratories. At PathVisions 2019, attendees had the opportunity to see firsthand innovative methods and instrumentation to address these issues. New research has shown that there could be more effective ways to harness the redundancy between z-planes by using video compression algorithms. Results have yielded smaller file sizes than both standard JPEG and JPEG 2000 compression strategies with minimal impact on image quality. Moreover, scanners have been developed to drop z-stack scanning times down to just a few minutes per slide. As an added perk to technological advancements, artificial intelligence (AI) based software that is tailor-made for cytopathology was demonstrated and discussed at the conference. Software can now locate areas of interest or suspected abnormal cells with high accuracy, reducing screening times for cytotechnologists. Area of interest accessibility requires less bandwidth, granting users faster, seamless image viewing. After talking to many speakers, poster presenters, vendors, and DPA committee members at the conference, I am optimistic for the adoption of whole-slide imaging into cytology in the near future. PathVisions is a place where pathologists, fellows, residents, students, and researchers can express their concerns to aid in the advancement of digital pathology. The DPA encourages and counts on input from attendees during talks and workshops so challenges, such as what cytology is facing, can be addressed by vendors and regulatory agencies. I truly believe that it is the collaboration of people from all different backgrounds in both clinical and research tracks that have brought digital pathology to where it is today. Looking forward to PathVisions 2020.
Disclaimer: In seeking to foster discourse on a wide array of ideas, the Digital Pathology Association believes that it is important to share a range of prominent industry viewpoints. This article does not necessarily express the viewpoints of the DPA, however we view this as a valuable point with which to facilitate discussion.