title: Intravascular ultrasound catheter to enhance microbubble-based drug delivery via acoustic radiation force.
abstract: Previous research has demonstrated that acoustic radiation force enhances intravascular microbubble adhesion to blood vessels in the presence of flow for moleculartargeted ultrasound imaging and drug delivery. A prototype acoustic radiation force intravascular ultrasound (ARFIVUS) catheter was designed and fabricated to displace a microbubble contrast agent in flow representative of conditions encountered in the human carotid artery. The prototype ARFIVUS transducer was designed to match the resonance frequency of 1.4- to 2.6-μm-diameter microbubbles modeled by an experimentally verified 1-D microbubble acoustic radiation force translation model. The transducer element was an elongated Navy Type I (hard) lead zirconate titanate (PZT) ceramic designed to operate at 3 MHz. Fabricated devices operated with center frequencies of 3.3 and 3.6 MHz with -6-dB fractional bandwidths of 55% and 50%, respectively. Microbubble translation velocities as high as 0.86 m/s were measured using a high-speed streak camera when insonating with the ARFIVUS transducer. Finally, the prototype was used to displace microbubbles in a flow phantom while imaging with a commercial 45-MHz imaging IVUS transducer. A sustained increase of 31 dB in average video intensity was measured following insonation with the ARFIVUS, indicating microbubble accumulation resulting from the application of acoustic radiation force.
authors.affiliation: Department of Biomedical Engineering, University of Virginia, Charlottesville, VA, USA.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Kilroy
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Klibanov
authors.forename: Brian R
authors.initials: BR
authors.lastname: Wamhoff
authors.forename: John  A
authors.initials: J
authors.lastname: Hossack
mesh_terms: D002339:Carotid Arteries / Q000000981:diagnostic imaging; D057785:Catheters; D003287:Contrast Media / Q000737:chemistry / Q000493:pharmacokinetics; D016503:Drug Delivery Systems / Q000295:instrumentation* / Q000379:methods; D020342:Finite Element Analysis; D006801:Humans; D045423:Microbubbles; D008955:Models, Cardiovascular; D019047:Phantoms, Imaging; D014159:Transducers; D018084:Ultrasonography, Interventional / Q000295:instrumentation* / Q000379:methods
chemical_list: D003287:Contrast Media