Anatomy of an Esrog

The above radiology image demonstrates the four characteristic features that distinguish a proper esrog from an esrog murkav (grafted). [Magen Avraham, Orach Chaim 648:23]

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   Bumpy rather than a smooth surface
  
  
  
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  An embedded or inward oketz.  The oketz of an esrog murkav protrudes outward.
  
  
  
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  A thick peel with a narrow center.  An esrog murkav has a thin peel and a thick juicy pulp.
  
  
  
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  Orientation of the seeds along the longitudinal axis of the esrog--except where it is "constrained by its neighbors".  In the above esrog notice how the seeds at the top and bottom of the pulp lay vertically.  The seeds toward the center are packed more tightly together and maintain a more oblique orientation.  The seeds of an esrog murkav are positioned horizontally even when there is sufficient space.
  
  
  

For extra credit:

Can you guess what radiology technique was used to produce this image?

(esrog image courtesy of Judah Burns, MD)