1. 
   PA projection
   The standard frontal chest film projection; radiographic skull projection with the petrous ridge superimposed on the orbits. ... Synonym: posteroanterior projection. ... (05 Mar 2000) ...
   Found op http://www.mondofacto.com/facts/dictionary?PA+projection
   
   
2. 
   PA projection
   Type: Term Definitions: 1. the standard frontal chest film projection; radiographic skull projection with the petrous ridge superimposed on the orbits. Synonyms: posteroanterior projection
   Found op http://www.medilexicon.com/medicaldictionary.php?t=72640
   
   
3. 
   Parallel projection
   Parallel projections have lines of projection that are parallel both in reality and in the projection plane.{Clarify|date=November 2009} Parallel projection corresponds to a perspective projection with an infinite focal length (the distance from the image plane to the projection point), or "zoom". ...
   Found op http://en.wikipedia.org/wiki/Parallel_projection
   
   

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