title: Quantitative contrast enhanced ultrasound of the liver for time intensity curves-Reliability and potential sources of errors.
abstract: BACKGROUND
  Time intensity curves for real-time contrast enhanced low MI ultrasound is a promising technique since it adds objective data to the more subjective conventional contrast enhanced technique. Current developments showed that the amount of uptake in modern targeted therapy strategies correlates with therapy response. Nevertheless no basic research has been done concerning the reliability and validity of the method.
  
  
  METHODS
  Videos sequences of 31 consecutive patients for at least 60s were recorded. Parameters analysed: area under the curve, maximum intensity, mean transit time, perfusion index, time to peak, rise time. The influence of depth, lateral shift as well as size and shape of the region of interest was analysed.
  
  
  RESULTS
  The parameters time to peak and rise time showed a good stability in different depths. Overall there was a variation >50% for all other parameters. Mean transit time, time to peak and rise time were stable from 3 to 10cm depths, whereas all other parameters showed only satisfying results at 4-6cm. Time to peak and rise time were stable as well against lateral shifting whereas all other parameters had again variations over 50%. Size and shape of the region of interest did not influence the results.
  
  
  CONCLUSIONS
  (1) It is important to compare regions of interest, e.g. in a tumour vs. representative parenchyma in the same depths. (2) Time intensity curves should not be analysed in a depth of less than 4cm. (3) The parameters area under the curve, perfusion index and maximum intensity should not be analysed in a depth more than 6cm. (4) Size and shape of a region of interest in liver parenchyma do not affect time intensity curves.
authors.affiliation: Department of Internal Medicine and Diagnostic Imaging, Caritas Hospital, Uhlandstr. 7, 97990 Bad Mergentheim, Germany. andre.ignee@gmx.de
authors.forename: Andre
authors.initials: A
authors.lastname: Ignee
authors.forename: Maciej
authors.initials: M
authors.lastname: Jedrejczyk
authors.forename: Gudrun
authors.initials: G
authors.lastname: Schuessler
authors.forename: Wieslaw
authors.initials: W
authors.lastname: Jakubowski
authors.forename: Christoph F
authors.initials: CF
authors.lastname: Dietrich
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D003287:Contrast Media / Q000493:pharmacokinetics; D005260:Female; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008297:Male; D008657:Metabolic Clearance Rate; D008954:Models, Biological; D010743:Phospholipids / Q000493:pharmacokinetics*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D013459:Sulfur Hexafluoride / Q000493:pharmacokinetics*; D014463:Ultrasonography / Q000379:methods*
chemical_list: D003287:Contrast Media; D010743:Phospholipids; C420843:contrast agent BR1; D013459:Sulfur Hexafluoride