title: Effect of color Doppler system on the twinkling sign associated with urinary tract calculi.
abstract: OBJECTIVE
  The aim of this study was to assess the effect of the color Doppler system on the artifact known as the "twinkling sign."
  
  
  METHODS
  Sixty-five patients with at least 1 urinary tract calculus seen on sonography were examined with color Doppler sonography. Two color Doppler systems of 2 different generations were used. Examinations included gray-scale, color Doppler, power Doppler, and spectral evaluations of the calculus with various settings of Doppler gain, velocity range, color filter, focal depth, and acoustic power.
  
  
  RESULTS
  A color artifact was present within and/or distal to 29 (39%) of 75 urinary tract calculi when the old generation system was used. Use of the new generation system produced this color artifact within and/or distal to 72 (96%) of the urinary tract calculi. The intensity of the artifact was affected by the acoustic output of the equipment.
  
  
  CONCLUSIONS
  The twinkling sign is an artifact that can not only lead to misdiagnosis of vascular flow within a structure but also help differentiate a very small stone from other small echogenic structures when later generation "all-digital" systems are used. The color sensitivity of the system and acoustic power used are important technical factors that affect the production of this artifact.
authors.affiliation: Department of Radiology, Ankara University Faculty of Medicine, Ibn-i Sina Hospital, 06100 Sihhiye, Ankara, Turkey.
authors.forename: S K
authors.initials: SK
authors.lastname: Aytaç
authors.forename: H
authors.initials: H
authors.lastname: Ozcan
mesh_terms: D016477:Artifacts; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D018615:Ultrasonography, Doppler, Color / Q000295:instrumentation / Q000379:methods; D014545:Urinary Calculi / Q000000981:diagnostic imaging*