As others will certainly suggest to you, I suggest that you supply an example of what you are asking about. As far as I can tell there is no function in Mathematica called ImageList. Do you mean a list of images? If so then you Map
the function EdgeDetect
onto the list of images. I.e. if the list of images is called listOfImages
then you would execute
Map[EdgeDetect[#, r, t] &, listOfImages]
with suitable chosen values of r
But perhaps you mean something else. If so please give a more detailed version of your question.