title: Optical and acoustical interrogation of submicron contrast agents.
abstract: Unlike conventional ultrasound contrast agents with a diameter of several microns, in this paper we explore the use of submicron contrast agents for the detection and localization of lymph nodes. The submicron agents are gas-filled, double-walled microspheres that rupture when exposed to ultrasound energy at megahertz frequencies. In this study, three experimental systems are combined with model predictions to assist in understanding the response of these unique agents to a range of signal transmission parameters. Optical experimental results for each agent delineate the relative expansion as a function of acoustical peak negative pressure, pulse length, and center frequency. The optical images demonstrate an order of magnitude expansion in radius during the pulse rarefaction, in which the expansion magnitude is dependent on the transmitted pressure and frequency. Simulations using a modified Rayleigh-Plesset model predict an increasing relative expansion for the microbubbles (initial bubble radius ranging from 0.3-1.3 microm) with increasing pressure and decreasing initial radius. Acoustically recorded frequency spectra reveal the presence of harmonics for a range of transmitted pulses. In addition, in-vivo results from a normal canine model demonstrate marked contrast enhancement of first order lymph nodes. We hope to offer an alternative to present intra-operative procedures for sentinel node detection.
authors.affiliation: Department of Biomedical Engineering, University of California, Davis, Davis, CA 95616, USA. divpatel@ucdavis.edu
authors.forename: Divia
authors.initials: D
authors.lastname: Patel
authors.forename: Paul
authors.initials: P
authors.lastname: Dayton
authors.forename: Jana
authors.initials: J
authors.lastname: Gut
authors.forename: Erik
authors.initials: E
authors.lastname: Wisner
authors.forename: Katherine W
authors.initials: KW
authors.lastname: Ferrara
mesh_terms: D000818:Animals; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis; D003198:Computer Simulation; D003287:Contrast Media / Q000138:chemical synthesis* / Q000493:pharmacokinetics; D004285:Dogs; D006614:Hindlimb / Q000166:cytology / Q000000981:diagnostic imaging; D006801:Humans; D007279:Injections, Subcutaneous; D008198:Lymph Nodes / Q000166:cytology* / Q000000981:diagnostic imaging* / Q000378:metabolism; D008422:Materials Testing / Q000379:methods; D008863:Microspheres; D008954:Models, Biological; D036103:Nanotechnology; D009584:Nitrogen; D011108:Polymers; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012709:Serum Albumin / Q000493:pharmacokinetics; D014463:Ultrasonography
chemical_list: D020099:Coated Materials, Biocompatible; D003287:Contrast Media; D011108:Polymers; D012709:Serum Albumin; D009584:Nitrogen