Computed Tomography Artefacts: An Experimental Investigation of Causative Factors

N Strumas, O Antonyshyn, MJ Yaffe, G Mawdsley, P Cooper. Computed tomography artefacts: An experimental investigation of causative factors. Can J Plast Surg 1998;6(1):23-29.The factors that produce computed tomography (CT) artefacts associated with craniofacial fixation devices were analyzed. The effects of attenuation, motion, partial volume and implant shape were evaluated. By using a CT phantom model with an engine to produce reproducible motion, a vitallium rod, fixation plate and blank were scanned sequentially. for each experimental condition, the degree of artefact produced was quantified by measuring the standard deviation of the CT number at standardized regions of interest, and a comparative analysis was performed. Motion produced the greatest degree of artefact. Both the frequency and direction of motion were important, with high frequency motion in the plane of the CT slice producing the greatest degree of CT artefact. Partial volume artefacts increased as the volume of material in the plane of section increased. The amount of artefact produced was dependent on the volume of material x-rays passed through the object rather than on the geometric configuration. Attenuation effects were evaluated. Results revealed that the amount of artefact was greatest between highly attenuating objects.