title: Characterizing the subharmonic response of phospholipid-coated microbubbles for carotid imaging.
abstract: The subharmonic vibration of BR14 (Bracco Research S.A., Geneva, Switzerland) contrast agent microbubbles is investigated within the preferable frequency range for carotid ultrasound imaging (8-12 MHz). The response of the bubbles was recorded optically with an ultra-fast recording camera (Brandaris 128) at three acoustic pressures (50, 100 and 120 kPa). The vibration of the microbubbles was measured as a function of the excitation frequency and its frequency content was determined. Among 390 recordings, 40% showed subharmonic oscillations. It was observed that for smaller microbubbles (diameter < 3 μm) the frequency of the maximum subharmonic response increases for increasing pressures (shell hardening) opposite to what has been reported for larger microbubbles (3 μm < diameter < 15 μm). These findings are well predicted by the model proposed by Marmottant et al. (2005) after including the dilatational shell viscosity of the microbubbles measured by Van der Meer et al. (2007), which indicates a marked shear-thinning behavior of the phospholipid shell.
authors.affiliation: Biomedical Engineering Thoraxcenter, Erasmus Medical Center, Rotterdam, The Netherlands. t.faez@erasmusmc.nl
authors.forename: Telli
authors.initials: T
authors.lastname: Faez
authors.forename: Marcia
authors.initials: M
authors.lastname: Emmer
authors.forename: Margreet
authors.initials: M
authors.lastname: Docter
authors.forename: Jeroen
authors.initials: J
authors.lastname: Sijl
authors.forename: Michel
authors.initials: M
authors.lastname: Versluis
authors.forename: Nico
authors.initials: N
authors.lastname: de Jong
mesh_terms: D000818:Animals; D002339:Carotid Arteries / Q000000981:diagnostic imaging*; D020099:Coated Materials, Biocompatible / Q000737:chemistry* / Q000528:radiation effects*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008422:Materials Testing; D045423:Microbubbles; D010743:Phospholipids / Q000737:chemistry* / Q000528:radiation effects*; D011829:Radiation Dosage; D013010:Sonication / Q000379:methods*; D014463:Ultrasonography
chemical_list: D020099:Coated Materials, Biocompatible; D010743:Phospholipids