Table 1 The Microcirculation image quality score
Category | Brief description | Optimal (0) | Acceptable (1) | Unacceptable (10) |
|---|---|---|---|---|
Illumination | 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. |
Duration | 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) |
Focus | 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. |
Content | 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. |
Stability | 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 |
Pressure | 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. |