Fig. 1

Illustration of Femtosecond Pulsed Laser Microscopy detection of BC in a macrophage. a Illustration of an image captured for image analysis showing two airway macrophages (AMs) stained by Diff-Quik from a participant in the LMIC group. The black arrow points out carbon in AM. Image at × 100, bar = 10 μm. b Light microscope (× 100) image of a single AM stained by Diff-Quik. The surface of black inclusions is used to estimate the amount of engulfed BC. c Montage retrieved from the same AM as the one shown in Panel b, of successive images obtained by white light 3D z-stacks scanning with 0.2 μm interval (from left top to right bottom), showing engulfed BC in red. d Bland-Altman plot comparing the difference between the median areas of 30 AM BC obtained from 3D converted images and 2D images. The green line represents the mean of differences in individual values (expressed as natural logarithm) obtained by the two methods; solid lines represent 2 SDs