Remote digital pathology
Making judgment in the absence of holding the physical slide
Asking the right questions to determine “whether the quality of the images from the remote digital pathology devices are sufficient for interpretation of the pathological images?” (FDA).
In April the FDA issued an Enforcement Policy for Remote Digital Pathology Devices During the Coronavirus Disease 2019 (COVID19) Public Health Emergency. The FDA believes that the policy will help address some of the arising health concerns “By helping to expand the availability of remote digital pathology devices during this public health emergency. Increased availability of these devices may help to facilitate continuity of patient care by preventing disruptions to critical pathology services rendered by clinical laboratories, hospitals, and other healthcare facilities, and by reducing healthcare personnel contact and risk of exposure to SARS-CoV-2″.
For pathologists looking to perform diagnosis using remote digital pathology devices FFEI have pulled together a checklist to help make judgment on the quality of the images being received. It directs attention into three key areas, the remote scanning device, the viewer used and the viewing conditions.
1. Scanner calibration:
This is the first step in the chain. Scanner calibration is critical in ensuring you receive accurate, high quality images. Whether you are receiving images from a remote lab or setting up the scanner, it is important to ask the following questions
Is the scanner on the approved FDA list?
You can check by running a search on the FDA medical devices 510k clearance list – or received temporary approval under the new policy for remote digital pathology devices?
Has the scanner been calibrated?
It is good practice to check that when the scanner is turned on that it is correctly calibrated. Calibration of a slide scanner insures the integrity of the data image. All systems will have a calibration process. However how this is achieved will differ between vendor – the scanner may auto-calibrate or need manual initiation. It is worth checking the process with your technology provider and checking it has been performed and trained with your lab technician.
When was the scanner last serviced?
Make sure a trained engineer has serviced the device and that it is within the recommended service period. Ensure service visits scheduled well in advance to prevent down-time when fully reliant on remote methods.
Is a colour calibration process included?
Colour calibration enables images produced by the scanner to match those viewed on a physical slide. As an example Sierra provides a means of colour calibration that supports the Technical Performance Assessment of Digital Pathology Whole Slide Imaging Devices FDA guidelines for ensuring colour reproducibility, page 15.
For further background information on colour calibration of medical devices please read the Consistency and Standardization of Color in Medical Imaging: a Consensus Report
2. Viewer software supporting colour management:
Most pathologists will wish to use a type of viewer software to aid viewing and annotating slides. However it is vital that following step one, which helps ensure accurate colour data is going into the viewer, steps also must be taken to then make sure the software can display the image properly. Points to check include:-
Has your viewer has been colour calibrated properly?
You need to make sure that the viewer you are using is compatible with the images being viewed. These may come with an ICC profile or an alternative colour profile.
If the Image contains an ICC profile, you need to check that the viewing software is using the ICC profile for the display. If it doesn’t and has a fixed type of display – you need to make sure that the viewer has been calibrated to receive standard sRGB display.
3. Calibrated display and viewing conditions:
Reliability of diagnosis is essential – so ensuring images are viewed under optimal, replicable viewing conditions is key. The objective is for images to look the same as when looking at the physical slide.
How can I ensure optimal viewing conditions?
Ensuring suitable viewing conditions is also important. As illustrated in Figure 1 the key three elements to consider are the display monitor, environment and practice.
Figure 1: Optimal viewing conditions
- The use of a high-quality (ideally calibrated) display monitor with a wide colour gamut and good uniformity
- A screen size that can allow you to see in detail and a good section of the slide
- Calibrated display – there is a range of display calibration tools commercially available.
- A free display tool is available from the University of Leeds that can provide a good indication if your set-up requires improvement.
- Additional guidance from Royal College of Pathologists provides some guidance about display viewing:
- View in low-light conditions – use thick curtains or blackout blind where possible
- Avoid reflections, especially of highly coloured objects
- Distractions (noise/radio)
- Vibrations affecting eye focus (traffic/desk stability)
- Temperature (affecting comfort/concentration)
Limit the time spent sat viewing images – to avoid eye-strain and fatigue as discussed by the American Optometric Association guidelines for avoiding Computer Vision Syndrome, also referred to as Digital Eye Strain. Key points relate to
- Time viewing screen
- Proximity to monitor and angle
- Correct angle