COMPUTED-TOMOGRAPHY ARTIFACTS ASSOCIATED WITH CRANIOFACIAL FIXATION DEVICES - AN EXPERIMENTAL-STUDY

This study compares the artifacts caused by eight different craniofaci al fixation devices in computed tomography (CT) images. Using a Teflon CT phantom model, part I of this study involved the quantitative eval uation of the X-ray absorption properties of each fixation device. Par t II utilized a human cadaveric model to determine the degree to which the artifact interfered with the visualization of anatomic structures . In part I, each fixation device was secured to the surface of the ph antom and then scanned. All artifacts were compared on the basis of st andard deviation in CT number. The severity of the artifact was relate d to the physical size of the fixation device and its composition. Vit allium devices generated a greater degree of CT artifacts than titaniu m devices of comparable size. In part II, fixation devices were secure d to the orbital rims of human cadaveric heads and then scanned. Visua lization of specified anatomic structures was graded independently. Th e results revealed that titanium fixation devices did not cause signif icant bone or soft-tissue image degradation, whereas all vitallium fix ation devices, except micro mesh and micro (1.0 mm) straight plates, g enerated an artifact that resulted in some image degradation. The exte nt of image degradation was related to the fixation device size. Only the thickest vitallium fixation device, mini fragmentation (2.0 mm), r esulted in bony image degradation. The degree of soft-tissue image deg radation decreased as the size of vitallium fixation devices decreased such that micro fragmentation (0.8 mm) and pan fixation (1.3 mm) devi ces interfered with soft-tissue visualization only in the immediate vi cinity of the plate. The results of this study confirm the previous wo rk of Sullivan and colleagues and Fiala and associates. The data indic ate that when postoperative imaging is an important clinical considera tion: (1) the fewest number of internal fixation devices should be use d to achieve rigid bony fixation, (2) the proximity of fixation device s to the regions of interest should be considered at the time of fixat ion, (3) titanium implants produce less artifacts than vitallium impla nts of comparable size, and (4) vitallium micro mesh and micro (1.0 mm ) straight fixation devices do not produce artifacts resulting in sign ificant image degradation.