Detecting rings/ contours in FIM image data or annulus histogram

In the attached image (an image of a FIM micrograph), there are concentric rings of various radii around different points These rings overlap and intersect each other and are made of 'bright spots'.

Some of these rings are not perfectly circular and some 'bright spots' are members of more than one ring and some rings are incomplete.

I'm not terribly familiar with signal processing, however I'm after a robust method of defining these rings, maybe through a convex hull or by an edge detection algorithm.