Brightness and contrast of video
Even illumination across the entire field of view. Contrast sufficient to see small vessels against a background of tissue.
The video borders on being too dark or bright to distinguish vessels from tissue but the vessels are still identifiable.
The video is oversaturated/too bright or too dark to make out analysable features. Insufficient contrast to resolve flow rate.
Number of frames in the video clip and how it represents the actual pathology
Analysable video segment is ≥5 s long (>150 frames)
Analysable video segment is 3–5 s (between 90 and 150 frames)
Analysable video segment <3 s (90 frames)
Image sharpness in region of interest
Good focus for all vessels (small and large) in the entire field of view. Plasma gaps and red blood cells are visible.
<1/2 field of view is out of focus or edges of the vessels are slightly out of focus.
Video is completely out of focus such that no small vessel can be seen.
Determination of the types of vessels and/or presence of occluding artefacts in the image.
Video is free of occlusions. Good distribution of large and small vessels. Less than 30 % of the vessels are looped upon themselves
Video may have a few artefacts. Acceptable distribution of large and small vessels. About 30–50 % of the vessels are looped.
Most of the field of view has occluding artefacts such as saliva or bubbles. More that 50 % vessels are looped upon themselves.
Frame motion that can be adequately stabilised without motion blur
Movement is within ¼ of the field of view. No motion blur.
Movement is within ½ field of view. No motion blur.
Movement is greater than ½ of the field of view and/or motion blur in frame
Iatrogenic mechanical pressure causing misrepresentation of flow
Flow is constant throughout the entire movie. No obvious signs of artificially sluggish or stopped flow. Good flow in the largest vessels.
Signs of pressure (localised sluggish flow in a specific large vessel), but flow appears to be unimpeded based on good flow in most large vessels.
Obvious pressure artefacts associated with probe movement, and/or flow that starts and stops, reversal of flow. Poor or changing flow in larger venules.