title: Mobile echoes in liver cysts: a form of range-ambiguity artifact.
abstract: OBJECTIVE
  Faint moving echoes are occasionally encountered in large hepatic cysts, as an example of range-ambiguity artifacts. The aim of this article is to describe the pattern of these intracystic mobile echoes, to analyze the mechanism of their formation, and to discuss options to clear them.
  
  
  METHODS
  We analyzed the size and location of the hepatic cysts, the movement of the artifactual echoes, and the relationship between pulse repetition frequency (PRF) and the depth of these intracystic mobile echoes in 10 cases. In three cases examination at a lower PRF was made to ascertain whether the artifactual echoes would disappear.
  
  
  RESULTS
  Intracystic range-ambiguity echoes appeared when the heart was located distal to the hepatic cyst and these echoes moved according to cardiac motion. The depth of the intracystic artifacts changed according to the PRF and they disappeared at a low PRF.
  
  
  CONCLUSIONS
  Intracystic range-ambiguity artifacts are caused by an erroneous display of the returning echoes from the heart. Knowledge of the mechanism and appearance of this artifact helps prevent misdiagnosis of internal echoes in large hepatic cysts. Observation at different PRFs is key to recognizing this artifact, and examination at lower PRFs should be done to confirm the artifactual nature of the echoes.
authors.affiliation: Internal Medicine, Yokote Municipal Hospital, Yokote-shi, Akita, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Naganuma
authors.forename: Hideaki
authors.initials: H
authors.lastname: Ishida
authors.forename: Masato
authors.initials: M
authors.lastname: Funaoka
authors.forename: Shusei
authors.initials: S
authors.lastname: Fujimori
authors.forename: Atushi
authors.initials: A
authors.lastname: Okuyama
authors.forename: Masaru
authors.initials: M
authors.lastname: Odashima
authors.forename: Satoko
authors.initials: S
authors.lastname: Takeuchi
authors.forename: Akihiko
authors.initials: A
authors.lastname: Hanaoka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D003560:Cysts / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008107:Liver Diseases / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D009068:Movement; D014463:Ultrasonography