How can I use matlab to process this image?

I have two image of mammograms (one is a benign tumor, the other is a cancerous tumor), both have different sizes, the pixel but the tumor was contoured. I want to process them so that they have the same criteria (the sizes, the pixel) before I calculate their fractal dimension. Can you give me some advice or documentation which can help me. Thank you so much.

[Image Analyst]

I don't understand what you are asking. What is "the pixel"? And if you somehow process them so that they are the same, then they are the same, so how will you find any differences when they're the same?