How distinguish comma from ellipsoid shapes?

Hi!

Any ideas on how to distinguish these structures from each other?

I have already achieved to differentiate the structures of the first column from the rest by ieans of regional maxima (they use to have more than 1, one by ball).

But I find serious difficulties in differentiating the structures from the second (comma shape) and the third columns (spheres or ellipse). I have tried with sphereicity, major/minos axis ratio, feret's diameter... but nothing works fine...

Is there any function describing the shape of a 'comma'?

I am working with 3D images.

Thanks in advanced!!!!!!

Maria

[Guillaume]

It seems to me that the main difference between 2nd and 3rd column is not the shape but the intensity distribution. In your 2nd column, the object is brighter at one end, whereas in your 3rd colum, it's more or less uniform. Perhaps you can use that property to distinguish the two.

[MARIA RODRIGUEZ SANZ]

I've also been trying with mean and sd but it didn't work! :(