title: Modeling of the acoustic response from contrast agent microbubbles near a rigid wall.
abstract: In ultrasonic targeted imaging, specially designed encapsulated microbubbles are used, which are capable of selectively adhering to the target site in the body. A challenging problem is to distinguish the echoes from such adherent agents from echoes produced by freely circulating agents. In the present paper, an equation of radial oscillation for an encapsulated bubble near a plane rigid wall is derived. The equation is then used to simulate the echo from a layer of contrast agents localized on a wall. The echo spectrum of adherent microbubbles is compared to that of free, randomly distributed microbubbles inside a vessel, in order to examine differences between the acoustic responses of free and adherent agents. It is shown that the fundamental spectral component of adherent bubbles is perceptibly stronger than that of free bubbles. This increase is accounted for by a more coherent summation of echoes from adherent agents and the acoustic interaction between the agents and the wall. For cases tested, the increase of the fundamental component caused by the above two effects is on the order of 8-9 dB. Bubble aggregates, which are observed experimentally to form near a wall due to secondary Bjerknes forces, increase the intensity of the fundamental component only if they are formed by bubbles whose radii are well below the resonant radius. If the formation of aggregates contributes to the growth of the fundamental component, the increase can exceed 17 dB. Statistical analysis for the comparison between adhering and free bubbles, performed over random space bubble distributions, gives p-values much smaller than 0.05.
authors.affiliation: Institute of Nuclear Problems, Belarus State University, Minsk, Belarus. doinikov@bsu.by
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Doinikov
authors.forename: Shukui
authors.initials: S
authors.lastname: Zhao
authors.forename: Paul A
authors.initials: PA
authors.lastname: Dayton
mesh_terms: D000162:Acoustics; D001808:Blood Vessels / Q000000981:diagnostic imaging*; D003287:Contrast Media; D005583:Fourier Analysis; D006801:Humans; D045423:Microbubbles; D014465:Ultrasonics; D014463:Ultrasonography
chemical_list: D003287:Contrast Media
references.citation: J Acoust Soc Am. 2005 Jul;118(1):539-50
references.pmid: 16119373
references.citation: Mol Imaging. 2004 Jul;3(3):135-48
references.pmid: 15530249
references.citation: J Acoust Soc Am. 2006 Aug;120(2):661-669
references.pmid: 21442034
references.citation: Ultrasound Med Biol. 2003 Dec;29(12):1749-57
references.pmid: 14698342
references.citation: Invest Radiol. 2006 Mar;41(3):354-62
references.pmid: 16481920
references.citation: Ultrasound Med Biol. 1998 May;24(4):523-33
references.pmid: 9651962
references.citation: IEEE Trans Ultrason Ferroelectr Freq Control. 2005 Mar;52(3):421-33
references.pmid: 15857050
references.citation: Ultrasound Med Biol. 2002 Jun;28(6):805-16
references.pmid: 12113793
references.citation: IEEE Eng Med Biol Mag. 2004 Sep-Oct;23(5):18-29
references.pmid: 15565796
references.citation: J Magn Reson Imaging. 2002 Oct;16(4):362-77
references.pmid: 12353252
references.citation: Mol Imaging. 2007 Nov-Dec;6(6):384-92
references.pmid: 18053409
references.citation: J Acoust Soc Am. 2000 Apr;107(4):2272-80
references.pmid: 10790053
references.citation: Ultrasonics. 1993;31(3):175-81
references.pmid: 8484195
references.citation: IEEE Trans Ultrason Ferroelectr Freq Control. 2000;47(6):1494-509
references.pmid: 18238696
references.citation: J Acoust Soc Am. 2007 Jan;121(1):648-56
references.pmid: 17297818
references.citation: J Acoust Soc Am. 2002 Nov;112(5 Pt 1):2183-92
references.pmid: 12430830
references.citation: Ultrasonics. 1992 Mar;30(2):95-103
references.pmid: 1557838
references.citation: J Acoust Soc Am. 2007 Jun;121(6):3331-40
references.pmid: 17552685
references.citation: J Acoust Soc Am. 2006 Dec;120(6):EL63-9
references.pmid: 17225437
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2001 Aug;64(2 Pt 2):026301
references.pmid: 11497693
references.citation: J Acoust Soc Am. 2003 Sep;114(3):1678-90
references.pmid: 14514221
references.citation: Appl Phys Lett. 2005 Sep 26;87(13):1341031-1341033
references.pmid: 16755307
references.citation: Invest Radiol. 2000 Nov;35(11):661-71
references.pmid: 11110302