Real-time sono-photoacoustic imaging of gold nanoemulsions

Bastien Arnal; Chen-Wei Wei; Camilo Perez; Michael Lombardo; Ivan M. Pelivanov; Danilo Pozzo; Matthew O'Donnell

doi:10.1117/12.2084709

11 March 2015 Real-time sono-photoacoustic imaging of gold nanoemulsions

Bastien Arnal, Chen-Wei Wei, Camilo Perez, Michael Lombardo, Ivan M. Pelivanov, Danilo Pozzo, Matthew O'Donnell

Proceedings Volume 9323, Photons Plus Ultrasound: Imaging and Sensing 2015; 93230S (2015) https://doi.org/10.1117/12.2084709
Event: SPIE BiOS, 2015, San Francisco, California, United States

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.

Citation Download Citation

Bastien Arnal, Chen-Wei Wei, Camilo Perez, Michael Lombardo, Ivan M. Pelivanov, Danilo Pozzo, and Matthew O'Donnell "Real-time sono-photoacoustic imaging of gold nanoemulsions", Proc. SPIE 9323, Photons Plus Ultrasound: Imaging and Sensing 2015, 93230S (11 March 2015); https://doi.org/10.1117/12.2084709

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