title: Quantitative analysis shows that contrast medium in positron emission tomography/computed tomography may cause significant artefacts.
abstract: OBJECTIVE
  Attenuation correction algorithms are required for accurate quantification of PET data and for mapping of radioactive tracers. Modern PET systems incorporate computed tomography (CT) systems to perform attenuation correction. However, high-density media, such as contrast agents, may introduce potentially clinically significant artefacts in PET images when CT-based attenuation correction algorithms are used. Although various groups have investigated this issue, no study has quantitatively assessed the clinical significance of these artefacts by comparing artefact and lesion standardized uptake values (SUVs) in controlled phantom experiments. Furthermore, previous studies have focussed on the effects of increasing the concentration of contrast medium, without investigating the effects of increasing its transaxial area. This study quantifies the clinical significance of increasing the concentration and transaxial area of contrast agents and evaluates a commercially available contrast agent correction algorithm.
  
  
  METHODS
  Images of a phantom containing background activity, a volume of contrast agent and varying sizes of hot lesions were acquired using clinical acquisition protocols. Quantitative analysis was performed on transaxial image slices of PET data.
  
  
  RESULTS
  The densest medium caused a 125% SUV(mean) increase in the area containing, and immediately adjacent to, contrast medium when compared with a reference water phantom. As the transaxial area of the contrast medium increased, artefacts appeared as a ring of activity around the periphery of the contrast medium. The contrast correction algorithm reduced these artefacts to within ± 39% of the reference results.
  
  
  CONCLUSIONS
  Oral and IV contrast agents can cause clinically significant artefacts in CT-based attenuation-corrected PET images and should be used with caution.
authors.affiliation: West of Scotland PET Centre, Gartnavel General Hospital, Glasgow, UK. clare.mckeown@nhs.net
authors.forename: Clare
authors.initials: C
authors.lastname: McKeown
authors.forename: Mary-Frances
authors.initials: MF
authors.lastname: Dempsey
authors.forename: Gerry
authors.initials: G
authors.lastname: Gillen
authors.forename: Carolyn
authors.initials: C
authors.lastname: Paterson
mesh_terms: D000465:Algorithms; D016477:Artifacts; D003287:Contrast Media / Q000009:adverse effects*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D064847:Multimodal Imaging / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media