Pixelation is Great For Art - But Bad for Diagnosis

Notre-Dame-de-la-Garde (La Bonne Mere), Marseilles by Paul Signac 1905-06.  The Metropolitian Museum of Art, NYC, personal photo

Written by Dr. David Hoak

Paul Signac was an impressionist who along with George Seurat developed the pointillists style of painting.  Signac applied paint in colorful “tiles” or mosaics to create his beautiful and evocative paintings.  Notre Dame de la Garde was the church that sailors would see as they sailed into Marseilles.

Whole slide images are made up of individual photos or tiles that are “stitched together. ”The files are stored in “pyramid” fashion to simulate the process of a microscope going from one objective magnification to the next. Think of it like Google Maps where one can zoom in close to a building or zoom out to see an entire city or country.

Figure 2. The Pyramid Image Rendering schema of pathology whole slide images.

However, sometimes when panning across a virtual slide or zooming in on a higher magnification, the image becomes “tiled” like Signac’s painting.  While the blurred image may be aesthetically pleasing it can be very fatiguing on the pathologist to wait for the image to be sharp and clear.  It can effect satisfaction and productivity. See the example below.  The usual cause of tiling is the bandwidth connectivity between the image storage location and the pathologist’s viewer.  But other causes include the WSI scanner’s proprietary image file format, the tile storage format within the pyramid, and what method the viewer determines to retrieve the next file.  Since these features differ among vendors it is important when looking to implement a WSI solution for pathologists to demo the scanner, viewer, archival system in as real a situation as possible.

Figure 3. Example of slow tiling of a WSI.

Image attribution: 1.      VirtualMicroscopy: ultra-fast interactive microscopy of gigapixel/terapixel images over internet, Ching-Wei Wang et. al, Scientific Reports volume5, Article number: 14069 (2015)

CAP and NSH Announce a Histology and WSI Scanning QC Program

blog jan 21 image.png

Blog Post by Dr. David Hoak

In the December 2018 issue of CAP Today, the College of American Pathologists and the National Society for Histology announced the 2019 release of a new quality improvement program called Whole Slide Image Quality Improvement Program. The program evaluates the quality of H&E sections cut and stained in a lab and the WSI scanned from that slide. The H&E slides are sent to CAP and the whole slide images are uploaded to CAP. Experts will then evaluate both the H&E and the WSI together.  By having both the glass and the WSI, the reviewing experts will be able to determine if an identified quality issue is due to microtomy, staining or scanning and will suggest improvements. There are two challenges a year with four slides and WSI to prepare for each challenge. The program is available at the CAP.org in the 2019 Surveys Catalog.          

When I was a Lab Medical Director, our lab participated in the CAP/NSH HistoQIP, a similar program but for histology only. I found the program very helpful and I would expect that the new program, for whole slide imaging, will be just as helpful. I would imagine that CAP/NSH will expand the program to include comparing special stains and IHC to the WSI. I would recommend that any laboratory that is currently, or is considering performing, primary diagnosis by whole slide imaging for H&E should participate in this program.

Image attribution: https://www.cap.org/laboratory-improvement/catalogs-ordering-and-shipping