Example of SDF imaging (Patient N°4) depicting the importance of the quality of image acquisition to ensure reliable microcirculation parameters and avoid artifacts: A slight local subarachnoid hemorrhage (yellow asterisk) secondary to the craniotomy may alter the image contrast. In this case, wall vessel normally not visible in SDF imaging becomes visible (blue arrow). The presence of fluids between the lens and the cortical surface should also be avoided and may interfere with the visibility of small arterioles distorting the vessel density index (blue asterisks). Please note the sluggish flow pattern (MFI:2) resulting in very low columns of globular erythrocytes (yellow arrows).