title: Acoustic detection of controlled laser-induced microbubble creation in gelatin.
abstract: A high-frequency (85 MHz) acoustic technique is used to identify system parameters for controlled laser-induced microbubble creation inside tissue-mimicking, gelatin phantoms. Microbubbles are generated at the focus of an ultrafast 793-nm laser source and simultaneously monitored through ultrasonic pulse-echo recordings. Displayed in wavefield form, these recordings illustrate microbubble creation, and integrated backscatter plots provide specifics about microbubble characteristics and dissolution behavior. By varying laser parameters, including pulse fluence (or pulse energy flux, J/cm2), total number of pulses delivered, and the period between pulses, the size, lifetime, and dissolution dynamics of laser-induced microbubbles may be independently controlled. Pulse fluence is the main size-controlling parameter, whereas both increases in pulse fluence and pulse number can lengthen microbubble lifetime from tens to hundreds of milliseconds. In short, a microbubble of particular lifetime does not necessarily have to be of a particular size. Microbubble behavior, furthermore, is independent of pulse periods below a fluence-dependent threshold value, but it exhibits stochastic behavior if pulse repetition is too slow. These results demonstrate that laser pulse fluence, number, and period may be varied to deposit energy in a specific temporal manner, creating and stabilizing microbubbles with particular characteristics and, therefore, potential uses in sensitive acoustic detection and manipulation schemes.
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2125, USA. ctse@umich.edu
authors.forename: Christine
authors.initials: C
authors.lastname: Tse
authors.forename: Marwa J
authors.initials: MJ
authors.lastname: Zohdy
authors.forename: Jing Yong
authors.initials: JY
authors.lastname: Ye
authors.forename: Theodore B
authors.initials: TB
authors.lastname: Norris
authors.forename: Lajos P
authors.initials: LP
authors.lastname: Balogh
authors.forename: Kyle W
authors.initials: KW
authors.lastname: Hollman
authors.forename: Matthew
authors.initials: M
authors.lastname: O'Donnell
mesh_terms: D000162:Acoustics; D003238:Connective Tissue / Q000737:chemistry / Q000000981:diagnostic imaging*; D003287:Contrast Media / Q000032:analysis / Q000737:chemistry; D005780:Gelatin / Q000737:chemistry* / Q000528:radiation effects*; D007834:Lasers; D045423:Microbubbles; D010316:Particle Size; D019047:Phantoms, Imaging; D014463:Ultrasonography / Q000295:instrumentation / Q000379:methods*
chemical_list: D003287:Contrast Media; D005780:Gelatin