title: Image alterations in the teaching microscope. A source of error in synovial fluid crystal identification.
abstract: An erroneous identification of sodium urate and calcium pyrophosphate crystals in synovial fluid may occur when utilizing compensated polarized microscopy with a dual-viewing-head teaching microscope. This is due to alteration of the observed image orientation with respect to the actual orientation of the crystal in space. By viewing a simple geometric figure through each microscope head, two basic types of image alterations are identified: a 180-degree rotation and a mirror-image transformation. Combinations of these two may also occur. This problem is clarified and illustrated and suggestions are offered to avoid erroneous crystal identification.
mesh_terms: D002131:Calcium Pyrophosphate / Q000032:analysis*; D002805:Chondrocalcinosis / Q000175:diagnosis; D003460:Crystallization; D003937:Diagnosis, Differential; D011756:Diphosphates / Q000032:analysis*; D006073:Gout / Q000175:diagnosis; D006801:Humans; D008859:Microscopy, Polarization / Q000379:methods*; D013582:Synovial Fluid / Q000032:analysis*; D014527:Uric Acid / Q000032:analysis*
chemical_list: D011756:Diphosphates; D014527:Uric Acid; D002131:Calcium Pyrophosphate