Fig. 2
Illustration of FSHG, BSHG, and FSHG/BSHG imaging as seen in Fig. 1. SHG imaging was performed on healthy, COP, and UIP formalin fixed paraffin embedded human lung tissue, and FSHG, BSHG, and FSHG/BSHG ratio images obtained, as described for Fig. 1. Panels a–c, showing look-up-table (LUT) “heatmaps” applied to the FSHG/BSHG ratio pixel values for representative FSHG/BSHG images, illustrate that Healthy lung tissues have the lowest collagen content (as expected) but higher FSHG/BSHG ratios compared to COP and UIP which evidence fibrosis and lower average FSHG/BSHG ratios as quantified in Fig. 1. Panels d–f and g–i respectively show the corresponding FSHG and BSHG images for each condition, with Healthy tissue again showing the lowest collagen content and highest FSHG signal intensity relative to BSHG signal intensity (i.e. the highest FSHG/BSHG ratio), whereas COP has high fibrosis and slightly higher BSHG relative to FSHG signals (intermediate FSHG/BSHG ratio), and UIP also has evident fibrosis and the least differential between the FSHG and BSHG signal intensities (i.e. the lowest FSHG/BSHG ratio). Levels (screen stretch) are linear and set the same for images a–c and d–i