How to plot a graph of a circle of pixels of an image showing intensity across it.

I want to take a grayscale image and plot intensity of some particle Pixels ( those Pixels are in a circular form which i have already its centre and radii )

to explain more there is the same Task but for a the line number 200 in my image

if true
  figure; plot(image(200,:))
end

what i want to do is the same thing but for a circular form .

thank you