title: Polyacrylamide gel as an acoustic coupling medium for focused ultrasound therapy.
abstract: A hydrogel acoustic coupling medium was investigated as a practical alternative to water for clinical applications of focused ultrasound (US) therapy. Material characterization and functional testing of polyacrylamide gel couplers were performed. Acoustic, bulk and thermal properties were measured. Conical couplers were designed and fabricated to fit a 3.5-MHz, spherically concave transducer for functional tests, including Schlieren imaging, power efficiency measurements and in vivo hemostasis experiments. Polyacrylamide was shown to have favorable acoustic properties that varied linearly with acrylamide concentration from 10% to 20% weight in volume. Attenuation coefficient, sound speed and impedance ranged from 0.08 to 0.14 dB/cm at 1 MHz, 1546 to 1595 m/s and 1.58 to 1.68 Mrayl, respectively. An intraoperative in vivo hemostasis experiment in a sheep model demonstrated that the gel-coupled transducer was capable of inducing hemostasis in actively bleeding splenic and hepatic incisions. The results of this study show that polyacrylamide may be a promising coupling material for focused US therapy.
authors.affiliation: Bioengineering, University of Washington, Seattle, WA 98105, USA.
authors.forename: Adrian F
authors.initials: AF
authors.lastname: Prokop
authors.forename: Shahram
authors.initials: S
authors.lastname: Vaezy
authors.forename: Misty L
authors.initials: ML
authors.lastname: Noble
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Kaczkowski
authors.forename: Roy W
authors.initials: RW
authors.lastname: Martin
authors.forename: Lawrence A
authors.initials: LA
authors.lastname: Crum
mesh_terms: D000162:Acoustics; D000180:Acrylic Resins / Q000737:chemistry; D000818:Animals; D006470:Hemorrhage / Q000628:therapy; D006489:Hemostatic Techniques; D006358:Hot Temperature; D008107:Liver Diseases / Q000628:therapy; D012756:Sheep; D013158:Splenic Diseases / Q000628:therapy; D013814:Thermal Conductivity; D014159:Transducers; D014464:Ultrasonic Therapy / Q000295:instrumentation / Q000379:methods*; D014867:Water
chemical_list: D000180:Acrylic Resins; C016680:polyacrylamide gels; D014867:Water