I am currently with a medical imaging project. Just wondering how to measure the shape of a sphere. For example, how to give a measurement that an object is more like a sphere than the other?

I know some algorithm can give the 'roundness' in 2D, but a measure of 'sphereness' in 3D would be more helpful.

Also, I am very interested in other shape analysis. The shape of the object could be a very interesting feature for further pattern recognition.

Thanks very much!