CT and MR appearance of otolaryngologic packing materials

PURPOSE: To examine the CT and MR appearances of four packing materials commonly used in otolaryngologic surgery.

METHODS: The CT and MR appearances of bismuth and iodoform paraffin paste, aqueous betadine gauze, calcium sodium alginate, and triadocortyl cream were examined. CT attenuation values were measured using phantoms containing packing materials. MR characteristics were examined by packing the external auditory meati of volunteers. Two illustrative case reports also are presented.

RESULTS: Bismuth and iodoform paraffin paste has a high CT attenuation (> 3000 Hounsfield units) resulting in severe image degradation attributable to streak artifact. Aqueous betadine gauze was of high attenuation (258 Hounsfield units; SD, 16.5) but did not cause image degradation. The attenuation values of calcium sodium alginate and triadocortyl creme coincided with those of muscle and fat, respectively. On MR, calcium sodium alginate and bismuth and iodoform paraffin paste had imaging characteristics similar to muscle and aqueous betadine gauze had appearances similar to bone marrow. Triadocortyl cream had a high signal equal to that of fat on T1-weighted images but a lower signal similar to bone marrow on T2-weighted images.

CONCLUSIONS: The presence of bismuth and iodoform paraffin paste can give rise to clinically important image degradation on CT. More seriously, residual packing material may be misinterpreted as infection or tissue necrosis.