Calcium Pyrophosphate Dihydrate Crystals
This image shows calcium pyrophosphate dihydrate (CPPD) crystals extracted from synovial fluid viewed under polarized light microscopy. (The red arrow in the upper right indicates the axis of a red compensator, a device used to determine the alignment of the crystals. The positively birefringent CPPD crystals appear blue when parallel to the optical axis of the compensator and yellow when perpendicular to it.)
Image courtesy of Brian Mandell, MD.
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