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Application of CT in diagnosing carcinoma of the maxillary sinuses. Part 2: An experimental study of pitfalls encountered when diagnosing carcinoma of the maxillary sinuses with CT.

A phantom simulating the transverse section of the maxillary sinuses was constructed for experimentation with various CTscanners to study the following: (I) the occasional inability to image the very thin posterior-lateral walls which have no real bone defects, and (2) to verify whether or not the bony walls surrounding the maxillary sinuses are actually as thick as they appear on CT. The phantom was made of an acrylic cylinder containing three cavities simulating the maxillary sinuses and the nasal cavity and filled with water. The walls, made of thin aluminum and acrylic plates and placed between water and air, disappeared in some CT images. The thickness of the walls calculated from CT values was greater than the true thickness imaged by each CT scanner. The author stresses that in CT images, either experimentally or c!inically, thin bony walls placed between water and air or fat tend to disappear, and that bony walls tend to appear thicker than their true thickenss.