Get the particle percentages of inside the part only not of the whole image


I am a beginner to Imagej.

I want to do a porosity analysis on a X-CT scanned part. I want to know the percentage of pores inside the part.

I have tresholded the CT images using Otsu method and then used Analysed Particles.

While I do get the area % of the pores, it seems that this percentage is not of only the inside of the part but relating to the whole image. I only want the pore/particle percentage inside the part.

The way I found out that the percentage is of the whole image not only inside is by cropping the image and re-doing the analyses. The particles percentage was bigger since the image was cropped.

Thank you,

Try using the wand selection tool to select the part. Then get the histogram. I think that should get you what you want. That is assuming all you want is porosity (area fraction); as stated in your post.