title: Hepatic pseudo-anisotropy: a specific artifact in hepatic diffusion-weighted images obtained with respiratory triggering.
abstract: OBJECTIVE
  Hepatic pseudo-anisotropy is an artifact observed in hepatic diffusion-weighted imaging under respiratory triggering (RT-DWI). To determine the clinical significance of this phenomenon, hepatic RT-DW images were reviewed.
  
  
  METHODS
  One hundred and five MR examinations, including RT-DWI, were assessed. The patient group included 62 non-cirrhotic and 43 cirrhotic individuals. All images were evaluated by mutual agreement of two radiologists from the viewpoints of incidence of pseudo-anisotropy and correlation between pseudo-anisotropy and the quality of trace images. The ADC of normal hepatic parenchyma of non-cirrhotic livers were measured in both areas with and without pseudo-anisotropy.
  
  
  RESULTS
  Pseudo-anisotropy was observed in 60% of non-cirrhotic (37/62) and 30% of cirrhotic (13/43) images. The difference between the two groups was statistically significant (P < 0.001). The quality of trace images showed a tendency to worsen as pseudo-anisotropy became significant. However, the quality of trace images was generally satisfactory, with only two patients whose trace images were difficult to interpret due to pseudo-anisotropy. The areas with pseudo-anisotropy showed higher ADC than those without pseudo-anisotropy (P < 0.001).
  
  
  CONCLUSIONS
  Pseudo-anisotropy is a type of artifact that originates from respiratory movement. Even though respiratory triggering is employed, ADC measurement of the liver is inaccurate because of pseudo-anisotropy, especially in non-cirrhotic patients.
authors.affiliation: Department of Diagnostic Radiology, Tsukuba University School of Medicine, Tsukuba, Ibaraki, Japan. kanasu-u3@md.tsukuba.ac.jp
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Nasu
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Kuroki
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Fujii
authors.forename: Manabu
authors.initials: M
authors.lastname: Minami
mesh_terms: D000005:Abdomen / Q000473:pathology; D000368:Aged; D016880:Anisotropy; D016477:Artifacts; D018281:Cholangiocarcinoma / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008099:Liver / Q000033:anatomy & histology* / Q000473:pathology; D008113:Liver Neoplasms / Q000473:pathology; D008297:Male; D015656:Respiratory Mechanics / Q000502:physiology*