title: Volume quantification by contrast-enhanced ultrasound: an in-vitro comparison with true volumes and thermodilution.
abstract: BACKGROUND
  Contrast-enhanced ultrasound (CEUS) has recently been proposed as a minimally- invasive, alternative method for blood volume measurement. This study aims at comparing the accuracy of CEUS and the classical thermodilution techniques for volume assessment in an in-vitro set-up.
  
  
  METHODS
  The in-vitro set-up consisted of a variable network between an inflow and outflow tube and a roller pump. The inflow and outflow tubes were insonified with an ultrasound array transducer and a thermistor was placed in each tube. Indicator dilution curves were made by injecting indicator which consisted of an ultrasound-contrast-agent diluted in ice-cold saline. Both acoustic intensity- and thermo-dilution curves were used to calculate the indicator mean transit time between the inflow and outflow tube. The volumes were derived by multiplying the estimated mean transit time by the flow rate. We compared the volumes measured by CEUS with the true volumes of the variable network and those measured by thermodilution by Bland-Altman and intraclass-correlation analysis.
  
  
  RESULTS
  The measurements by CEUS and thermodilution showed a very strong correlation (rs = 0.94) with a modest volume underestimation by CEUS of -40 ± 28 mL and an overestimation of 84 ± 62 mL by thermodilution compared with the true volumes. Both CEUS and thermodilution showed a high statistically significant correlation with the true volume (rs = 0.97 (95% CI, 0.95 - 0.98; P<0.0001) and rs = 0.96 (95% CI, 0.94 - 0.98; P<0.0001, respectively).
  
  
  CONCLUSIONS
  CEUS volume estimation provides a strong correlation with both the true volumes in-vitro and volume estimation by thermodilution. It may therefore represent an interesting alternative to the standard, invasive thermodilution technique.
authors.affiliation: Department of Anesthesia and Intensive Care, Catharina hospital Eindhoven, Michelangelolaan 2, Eindhoven 5623 EJ, The Netherlands. Ingeborg.Herold@cze.nl.
authors.forename: Ingeborg H F
authors.initials: IH
authors.lastname: Herold
authors.forename: Gianna
authors.initials: G
authors.lastname: Russo
authors.forename: Massimo
authors.initials: M
authors.lastname: Mischi
authors.forename: Patrick
authors.initials: P
authors.lastname: Houthuizen
authors.forename: Tamerlan
authors.initials: T
authors.lastname: Saidov
authors.forename: Marcel
authors.initials: M
authors.lastname: van het Veer
authors.forename: Hans C
authors.initials: HC
authors.lastname: van Assen
authors.forename: Hendrikus H M
authors.initials: HH
authors.lastname: Korsten
mesh_terms: D001810:Blood Volume / Q000502:physiology; D001811:Blood Volume Determination / Q000379:methods*; D003287:Contrast Media / Q000008:administration & dosage; D017548:Echocardiography, Transesophageal / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods; D019047:Phantoms, Imaging; D010743:Phospholipids / Q000008:administration & dosage; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013459:Sulfur Hexafluoride / Q000008:administration & dosage; D013815:Thermodilution
chemical_list: D003287:Contrast Media; D010743:Phospholipids; C420843:contrast agent BR1; D013459:Sulfur Hexafluoride