title: Feasibility of the flash-replenishment concept in renal tissue: which parameters affect the assessment of the contrast replenishment?
abstract: The purpose of the study was to evaluate whether power pulse inversion (PPI) and pulse inversion (PI) techniques allow the measurement of indices of microcirculatory flow in real-time at low emission power using contrast microbubbles. PPI and PI imaging were performed in a kidney perfusion model during continuous infusion of Definity (0.12 mL/min). At steady state of tissue enhancement, contrast was destroyed by emission of echo bursts at high emission power (MI = 1.3). Consecutively, contrast replenishment was assessed at low emission power (MI = 0.09) in real-time imaging modes (PPI: 12 Hz; PI: 25 Hz). Regions-of-interest (ROI) of variable sizes were placed in the renal cortex and bigger arteries to compare replenishment of macro- and microcirculation. Nonlinear curve fitting was performed using the mathematical model y=s+A(1-e(-betat)), with A as the parameter describing blood volume and beta as a parameter describing the speed of microbubble contrast replenishment. Replenishment curves could be visually appreciated and quantitatively analyzed in all renal segments. A was significantly higher in bigger arteries compared to renal cortex (p < 0.001). beta was found to be significantly higher in the arteries as compared to the cortex (p < 0.001). The SD of beta diminishes with increasing size of the ROI. The acquisition of replenishment curves following ultrasound (US)-induced destruction of contrast microbubbles is feasible at low power using PPI and PI. Assessment of replenishment kinetics allows the differentiation between macro- and microcirculation. Size and position of the ROI have an important impact on the generation of replenishment curves in both imaging modalities, which has to be taken into account.
authors.affiliation: Department of Cardiology, University of Bonn, Bonn, Germany
authors.forename: T
authors.initials: T
authors.lastname: Schlosser
authors.forename: C
authors.initials: C
authors.lastname: Pohl
authors.forename: C
authors.initials: C
authors.lastname: Veltmann
authors.forename: S
authors.initials: S
authors.lastname: Lohmaier
authors.forename: J
authors.initials: J
authors.lastname: Goenechea
authors.forename: A
authors.initials: A
authors.lastname: Ehlgen
authors.forename: J
authors.initials: J
authors.lastname: Köster
authors.forename: D
authors.initials: D
authors.lastname: Bimmel
authors.forename: S
authors.initials: S
authors.lastname: Kuntz-Hehner
authors.forename: H
authors.initials: H
authors.lastname: Becher
authors.forename: K
authors.initials: K
authors.lastname: Tiemann
mesh_terms: D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage; D005240:Feasibility Studies; D005466:Fluorocarbons / Q000008:administration & dosage; D066298:In Vitro Techniques; D007262:Infusions, Intravenous; D007668:Kidney / Q000000981:diagnostic imaging*; D008833:Microcirculation; D008863:Microspheres; D008962:Models, Theoretical; D012079:Renal Circulation; D013552:Swine; D014463:Ultrasonography
chemical_list: D003287:Contrast Media; D005466:Fluorocarbons; C042852:perflutren