title: Power Doppler ultrasound of rheumatoid synovitis: quantification of vascular signal and analysis of interobserver variability.
abstract: OBJECTIVE
  The objective of this study was to assess interobserver uncertainties in power Doppler (PD) examination of the fingers of patients with rheumatoid arthritis (RA), by separating the source of the discrepancy into (1) acquisition of the images and (2) criteria for assessment of the images.
  
  
  METHODS
  Twenty patients who had been diagnosed with RA were enrolled in this study. Ultrasound examinations were performed by one inexperienced and two experienced sonographers. Interobserver variation was measured using a conventional semiquantitative image grading scale. Interobserver variation of the quantitative PD (QPD) index (the summation of the colored pixels in a region of interest) was also assessed.
  
  
  RESULTS
  The agreement was higher between the two experienced sonographers (kappa value of 0.8) than between experienced and inexperienced sonographers (kappa value, 0.6-0.7) in the semiquantitative image grading scale. Results suggest that the difference in the assessment on the image grading scale was due more to the difference in the acquisition of the images than to variations in the grading criteria between sonographers. An excellent relationship was noted between the image grading scale and the QPD index for Doppler signal with a Spearman's coefficient of rank correlation of 0.83 (P < 0.0001).
  
  
  CONCLUSIONS
  Interobserver discrepancies in the image grading and QPD index methods were due more to the difference in the acquisition of the image than to the grading criteria used. The QPD index seems to be as reliable as the image grading scale with reasonable interobserver agreement between experienced sonographers.
authors.affiliation: Department of Radiology, Hokkaido University Hospital, N15 W7, Kita-ku, Sapporo 0600815, Japan. ktamotamo2@yahoo.co.jp
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Kamishima
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Tanimura
authors.forename: Mihoko
authors.initials: M
authors.lastname: Henmi
authors.forename: Akihiro
authors.initials: A
authors.lastname: Narita
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Sakamoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Terae
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D013585:Synovitis / Q000000981:diagnostic imaging*; D018608:Ultrasonography, Doppler / Q000379:methods*