The Polka-Dot Sign

The polka-dot sign is seen on transverse computed tomographic (CT) images of vertebral bodies. The medullary cavity of the vertebral body shows numerous high attenuation dots, simulating the polka-dot pattern on clothing.  



               

The polka-dot sign on CT images is produced by thickened trabeculae in a vertebral body hemangioma, seen in cross section as small punctate areas of high attenuation. The trabecular thickening occurs due to reinforcement of the osseous network adjacent to the vascular channels of the lesion that have caused bone resorption. This process occurs within the fatty marrow.                 

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