Detecting the Prescence of a "Tail" I have a set of objects, which may be spherical or elongated, which may or may not have a tail like structure attached to one or two ends. The tail may be long or short. It may also have a curve to it.

I'm currently looking over the information returned by regionprops and trying to see if anything jumps out at me which could be used to discriminate between normals and tails. I am also playing around with some morphological operations.  

An opening operation followed by a comparison to the original mask is my current thought, but I'm not certain that this will be reliable enough in the presence of elongated cells, and I haven't yet found the "perfect" structuring element.  

As I am not highly experienced in the IA field (more of an intermediate level), I am thinking that it may be a good idea to reach out and see if others have any ideas that I have not yet considered.

Test images are below.  The effective dynamic range is 12-bits, but I've normalized them so that they can be viewed more easily.

  

And here is a "normal" for comparison:
You could check how "circular" a blob is, by computing the ratio between area and the square of perimeter.
For a circle that would be:

$A = \pi r^2 , P = 2 \pi r$, 

which implies that

$ \frac{A}{P^2} = \frac {1}{4 \pi}  $

Probably those who have tail will have different ratio.
Both the area and the perimeter of the blob can be calculated in Matlab by using regionprops.



Another option [which could be interesting if you have a lot of data] would be computing many blob properties and training an SVM/Boosting/Other machine learning algorithm.