Hi,
The image which you shared looks like some kind of shock wave. From the first look of the image, I think hard thresholding should be able to give you rings, may be try thresholding between 75 and 80 gray values and observe. Then possibly try imfindcircle function and see whether you are able to detect circle or not. It's not easy to detect this rings you may need to perform some smoothing and gradient operation to get some initiative. Its hard task and I don't think we will be able to generalise it to all images you have in your plate.
I hope this helps or atleast give you enough resources to explore.
Cheers
