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Proceedings Paper

Real-time sono-photoacoustic imaging of gold nanoemulsions
Author(s): Bastien Arnal; Chen-Wei Wei; Camilo Perez; Michael Lombardo; Ivan M. Pelivanov; Danilo Pozzo; Matthew O'Donnell
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Paper Abstract

Phase transition contrast agents were first introduced in ultrasound (US) in the form of perfluorocarbon droplets. When their size is reduced to the nanoscale, surface tension dominates their stability and high pressure is required to vaporize them using long US emissions at high frequencies. Our group recently showed that nanoemulsion beads (100-300 nm) coated with gold nanopsheres could be used as non-linear contrast agents. Beads can be vaporized with light only, inducing stronger photoacoustic signals by increasing thermal expansion. A photoacoustic cavitation threshold study (US: 1.2 MHz, Laser 750 nm and 10-ns pulse) shows that the vaporization thresholds of NEB-GNS can be greatly reduced using simultaneous light and US excitations. The resulting signal is driven only by the pressure amplitude for a fluence higher than 2.4 mJ/cm2. At diagnostic exposures, it is possible to capture very high signals from the vaporized beads at concentrations reduced to 10 pM with optical absorption smaller than 0.01 cm-1. A real-time imaging mode selectively isolating vaporization signals was implemented on a Verasonics system. A linear US probe (L74, 3 MHz) launched short US bursts before light was emitted from the laser. Vaporization of NEB-GNS resulted in a persistent 30-dB signal enhancement compared to a dye with the same absorption. Specific vaporization signals were retrieved in phantom experiments with US scatterers. This technique, called sonophotoacoustics, has great potential for targeted molecular imaging and therapy using compact nanoprobes with potentially high-penetrability into tissue.

Paper Details

Date Published: 11 March 2015
PDF: 6 pages
Proc. SPIE 9323, Photons Plus Ultrasound: Imaging and Sensing 2015, 93230S (11 March 2015); doi: 10.1117/12.2084709
Show Author Affiliations
Bastien Arnal, Univ. of Washington (United States)
Chen-Wei Wei, Univ. of Washington (United States)
Camilo Perez, Univ. of Washington (United States)
Michael Lombardo, Univ. of Washington (United States)
Ivan M. Pelivanov, Univ. of Washington (United States)
Moscow State Univ. (Russian Federation)
Danilo Pozzo, Univ. of Washington (United States)
Matthew O'Donnell, Univ. of Washington (United States)

Published in SPIE Proceedings Vol. 9323:
Photons Plus Ultrasound: Imaging and Sensing 2015
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)

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