title: The relationship between subjective and objective parameters in CT phantom image evaluation.
abstract: OBJECTIVE
  To evaluate whether there is a relationship between subjective parameters determined by a reviewer (spatial resolution, low contrast resolution, and artifacts) and objective parameters (the CT number of water, noise, and image uniformity) in CT phantom image evaluations.
  
  
  METHODS
  We reviewed the CT results of phantom image evaluations conducted by Korean Institute for Accreditation of Medical Image (KIAMI) from May 2007 to June 2007. We compared the objective parameters against the pass or fail groups for the subjective parameters. We also evaluated whether there is a relationship between the artifact types and the other subjective parameters.
  
  
  RESULTS
  The mean noise value was significantly higher in the fail groups for the subjective parameters compared to the pass groups (p = 0.006). Specifically, noise and low contrast resolution were found to have a statistically significant positive correlation (r = 0.183, p < 0.001). In the fail group for low contrast resolution, the failure due to artifacts was significantly higher than the pass group (p < 0.001). In contrast, no statistically significant differences were found for the mean CT number of water, noise, or image uniformity based on the types of artifacts.
  
  
  CONCLUSIONS
  Subjective CT image parameters evaluated by a reviewer correlate with objectively measured parameters, especially noise. Therefore, a stricter noise standard might be able to improve the subjective parameters results, such as low contrast resolution.
authors.affiliation: Department of Radiology, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Hye Jung
authors.initials: HJ
authors.lastname: Park
authors.forename: Seung Eun
authors.initials: SE
authors.lastname: Jung
authors.forename: Young Joon
authors.initials: YJ
authors.lastname: Lee
authors.forename: Woo Il
authors.initials: WI
authors.lastname: Cho
authors.forename: Kyung Hyun
authors.initials: KH
authors.lastname: Do
authors.forename: Seung Hyup
authors.initials: SH
authors.lastname: Kim
authors.forename: Ki Hwang
authors.initials: KH
authors.lastname: Kim
mesh_terms: D016477:Artifacts; D007723:Korea; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed