You need to do edge linking, that is, if edge detection is even what you want to do, which it's not in at least half of the images beginners try to segment. I'd have to see your image to be sure. Anyway, you can try my edge-linking demo, attached.
I would recommend you to try out all and see which one works better in your case. I had to do it once and I applied edge enhancement algorithms before using edge detection. In the following paperhttp://staff.science.uva.nl/~rein/nldiffusionweb/ named nldiffusioncode.pdf you can read about three algorithms they developed. The code is free and the link is matlab.zip. I could not find the actual webpage.
I also usedadapthisteq function from matlab to enhance contrast before before edge enhancement and detection
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