For fluorescence image contrast analysis, the relative difference between the fluorescence intensity in the tumor and normal brain tissue was calculated according to the equation:\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \mathrm{Contrast}=\frac{\left({F}_{\mathrm{T}}-{F}_{\mathrm{N}}\right)}{\left({F}_{\mathrm{N}}-{F}_{\mathrm{B}}\right)} $$\end{document}Contrast=FT−FNFN−FB