title: Reproducibility of phantom-based quality assurance parameters in real-time ultrasound imaging.
abstract: BACKGROUND
  In a large radiological center, the ultrasound (US) quality assurance (QA) program involves several professionals. Although the operator and the parameters utilized can contribute to the results, the selected QA parameters should still reflect the quality of the US scanner, not the measuring process.
  
  
  OBJECTIVE
  To evaluate the reproducibility of recommended phantom-based US QA parameters in a realistic environment.
  
  
  METHODS
  Six sonographers measured six high-end US scanners with 20 transducers using a general purpose phantom. Every transducer was measured altogether seven times, using one frequency per transducer. The QA parameters studied were homogeneity, visualization depth, vertical and horizontal distance measurements, axial and lateral resolution, and the correct visibility of anechoic and high-contrast masses. The evaluation of the homogeneity was based on visual observations. Inter-observer interquartile ranges were computed for the grading of the masses. For the other QA parameters, the mean inter- and intra-observer coefficients of variation (CoV) were calculated. In addition, the symmetry of the reverberations when imaging air with a clean transducer was checked.
  
  
  RESULTS
  The mean inter-observer CoVs were: visualization depth 11 ± 4%, vertical distance 1.7 ± 0.4%, horizontal distance 1.4 ± 0.6%, axial resolution 22 ± 7%, and lateral resolution 16 ± 8%. The mean intra-observer values were about half of these values with similar standard deviations. The visual evaluation of the homogeneity and the symmetry of the reverberations produced false-positive findings in 5% of the cases, but were found useful in detecting a defective transducer. The grading of the masses had mean interquartile ranges of 20-30% of the grading scale.
  
  
  CONCLUSIONS
  The inter-observer variability in measuring phantom-based QA parameters can be relatively high. This should be considered when implementing a phantom-based QA protocol and evaluating the results.
authors.affiliation: HUS Helsinki Medical Imaging Center, Meilahti Hospital, Helsinki University Central Hospital, Helsinki, Finland. outi.sipila@hus.fi
authors.forename: Outi
authors.initials: O
authors.lastname: Sipilä
authors.forename: Päivi
authors.initials: P
authors.lastname: Blomqvist
authors.forename: Mervi
authors.initials: M
authors.lastname: Jauhiainen
authors.forename: Tiina
authors.initials: T
authors.lastname: Kilpeläinen
authors.forename: Paula
authors.initials: P
authors.lastname: Malaska
authors.forename: Vilma
authors.initials: V
authors.lastname: Mannila
authors.forename: Tuula
authors.initials: T
authors.lastname: Vinnurva-Jussila
authors.forename: Sari
authors.initials: S
authors.lastname: Virsula
mesh_terms: D006801:Humans; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care; D015203:Reproducibility of Results; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation / Q000592:standards*