how to extract the diameter of the region between the contour lines?

I am trying to find the diameter of this artery in the retinal image. I have contoured the artery and want to find the width of the region in the between the blue lines. After that when i have sufficient vales for the width i will take an average and further continue.

I have used the following:

imcontour(Z,3)

Please help me find the diameter.

Answer 1

[Image Analyst]

It doesn't look like your algorithm is any good, so no sense even starting with that image you produced. It looks like you just did an edge detection (like most beginners mistakenly do) and then got contours on that.

There are tons of papers on how to properly segment retinal images. Just see section 20.5 of Vision Bibliography