title: Quantitative analysis of factors affecting cobalt alloy clip artifacts in computed tomography.
abstract: OBJECTIVE
  Clip artifacts limit the visualization of intracranial structures in CT scans from patients after aneurysmal clipping with cobalt alloy clips. This study is to analyze the parameters influencing the degree of clip artifacts.
  
  
  METHODS
  Postoperative CT scans of 60 patients with straight cobalt alloy-clipped aneurysms were analyzed for the maximal diameter of white artifacts and the angle and number of streak artifacts in axial images, and the maximal diameter of artifacts in three-dimensional (3-D) volume-rendered images. The correlation coefficient (CC) was determined between each clip artifact type and the clip blade length and clip orientation to the CT scan (angle a, lateral clip inclination in axial images; angle b, clip gradient to scan plane in lateral scout images).
  
  
  RESULTS
  Angle b correlated negatively with white artifacts (r=-0.589, p<0.001) and positively with the angle (r=0.636, p<0.001) and number (r=0.505, p<0.001) of streak artifacts. Artifacts in 3-D images correlated with clip blade length (r=0.454, p=0.004). Multiple linear regression analysis revealed that angle b was the major parameter influencing white artifacts and the angle and number of streak artifacts in axial images (p<0.001), whereas clip blade length was a major factor in 3-D images (p=0.034).
  
  
  CONCLUSIONS
  Use of a clip orientation perpendicular to the scan gantry angle decreased the amount of white artifacts and allowed better visualization of the clip site.
authors.affiliation: Department of Neurosurgery, Inje University Seoul Paik Hospital, Seoul, Korea.
authors.forename: Sook Young
authors.initials: SY
authors.lastname: Sim
authors.affiliation: Department of Radiology, National Medical Center, Seoul, Korea.
authors.forename: Chi Hoon
authors.initials: CH
authors.lastname: Choi
keywords: Artifacts; Clip; Intracranial aneurysm; Multidetector computed tomography