MATLAB: How to outline the inside border of this ring? ie. highlight the inner circle

digital image processingimageimage analysisimage processingimage segmentationMATLAB

I am trying to highlight the inner border of this ring in the image attached. Is this possible?
Thank you for your help

Best Answer

Try this: 
I = imread('Love Matlab image.jpeg');
IBW = im2bw(I);
Bnd = bwboundaries(IBW);
figure
imshow(IBW)
hold on
plot(Bnd{4}(:,2), Bnd{4}(:,1), '-r', 'LineWidth',2)
hold off
producing:
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