Ultrasonography has been widely used in the maxillofacial region because of the ability to demonstrate pathological conditions in real time without radiation exposure. However, echo patterns of mass lesions vary with the surrounding tissue conditions. To examine the effects of the various surrounding conditions on depiction of such lesions on echograms, we constructed a model, an echo phantom consisting of an agar object, with or without scattering (methylcellulose) or absorptive (barium sulfate) material, and a corresponding surrounding medium. The object's boundary clarity decreased with increasing concentration of either the surrounding scattering or absorptive media, whereas the internal echo intensity of the object also decreased only with increasing concentration of the surrounding absorptive medium. The object with absorptive material produced peripheral echoes at the border. These results suggest that care should be taken when boundary echoes are evaluated as echo signs of lesions.
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