Clinical significance of partial volume averaging of the temporal bone

The effects of partial volume averaging on computed tomographic images of temporal bone structures were evaluated. The models chosen for study included a cadaver stapes, two metallic prosthetic stapes, and a formalin-fixed temporal bone. The studies measured the changes in apparent dimension and Hounsfield units with incremental filling of voxels with metallic densities, changes in the angle of tomographic section in relation to small bony structures, and the effects of soft-tissue silhouetting. The clinical significance of these changes is demonstrated by examples of this phenomenon seen in actual patient examinations. This study confirms that partial volume averaging is one of the primary limitations in resolution of small structures of the temporal bone.