ImageJ: Area measurement of kidney fibrosis in immunohistochemistry staining

[camal307]

Hi all, I have problem with quantifying light microscopy images from immunostaining IHC. The problem is that some of images have background which will interfere with quantification of positive brown-stained areas, i.e., 4% of positive stained area in an image featuring tissue completely covering the slide, vs. 4% of positive staining in an image which has slide background covering ~1/4, with the rest covered with region of interest. How to cut to region of interest? Thank you.