title: Toward contrast-enhanced microwave-induced thermoacoustic imaging of breast cancer: an experimental study of the effects of microbubbles on simple thermoacoustic targets.
abstract: Microwave-induced thermoacoustic tomography (MI-TAT) is an imaging technique that exploits dielectric contrast at microwave frequencies while creating images with ultrasound resolution. We propose the use of microbubbles as a dielectric contrast agent for enhancing the sensitivity of MI-TAT for breast cancer detection. As an initial investigation of this concept, we experimentally studied the extent to which the microwave-induced thermoacoustic response of a dielectric target is modified by the presence of air-filled glass microbubbles. We created mixtures of ethylene glycol with varying weight percentages of microbubbles and characterized both their microwave properties (0.5-6 GHz) and thermoacoustic response when irradiated with microwave energy at 3 GHz. Our data show that the microbubbles considerably lowered the relative permittivity, electrical conductivity and thermoacoustic response of the ethylene glycol mixtures. We hypothesize that the interstitial infusion of microbubbles to a tumor site will similarly create a smaller thermoacoustic response compared to the pre-contrast-agent response, thereby enhancing sensitivity through the use of differential imaging techniques.
authors.affiliation: Department of Electrical and Computer Engineering, University of Wisconsin, Madison, WI, USA. amashal@wisc.edu
authors.forename: Alireza
authors.initials: A
authors.lastname: Mashal
authors.forename: John H
authors.initials: JH
authors.lastname: Booske
authors.forename: Susan C
authors.initials: SC
authors.lastname: Hagness
mesh_terms: D000162:Acoustics; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000503:physiopathology*; D003287:Contrast Media; D003952:Diagnostic Imaging / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D045423:Microbubbles; D008872:Microwaves; D019047:Phantoms, Imaging; D013817:Thermography / Q000295:instrumentation / Q000379:methods*
chemical_list: D003287:Contrast Media