How to display only a certain portion of an image?

Hi,

I got this image as shown in figure. Now, I want is to display only a certain portion (I only want to show the middle part, ignoring the remaining outside parts) of this image. How can we do this?

I just want the green and blue parts but ignoring the outside red and orange part. I tried to use data cursor with the following line of code.

I tried following lines:

imagesc(abs(b1p(254:320,166:320)))

but all i get is blank image.

What is wrong with this line? or is there any other better way of doing this?

Thanks in advance!