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Proceedings Paper

Photoacoustic spectral characterization of perfluorocarbon droplets
Author(s): Eric Strohm; Ivan Gorelikov; Naomi Matsuura; Michael Kolios
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Paper Abstract

Perfluorocarbon droplets containing optical absorbing nanoparticles have been developed for use as theranostic agents (for both imaging and therapy) and as dual-mode contrast agents. Droplets can be used as photoacoustic contrast agents, vaporized via optical irradiation, then the resulting bubbles can be used as ultrasound imaging and therapeutic agents. The photoacoustic signals from micron-sized droplets containing silica coated gold nanospheres were measured using ultra-high frequencies (100-1000 MHz). The spectra of droplets embedded in a gelatin phantom were compared to a theoretical model which calculates the pressure wave from a spherical homogenous liquid undergoing thermoelastic expansion resulting from laser absorption. The location of the spectral features of the theoretical model and experimental spectra were in agreement after accounting for increases in the droplet sound speed with frequency. The agreement between experiment and model indicate that droplets (which have negligible optical absorption in the visible and infrared spectra by themselves) emitted pressure waves related to the droplet composition and size, and was independent of the physical characteristics of the optical absorbing nanoparticles. The diameter of individual droplets was calculated using three independent methods: the time domain photoacoustic signal, the time domain pulse echo ultrasound signal, and a fit to the photoacoustic model, then compared to the diameter as measured by optical microscopy. It was found the photoacoustic and ultrasound methods calculated diameters an average of 2.6% of each other, and 8.8% lower than that measured using optical microscopy. The discrepancy between the calculated diameters and the optical measurements may be due to the difficulty in resolving the droplet edges after being embedded in the translucent gelatin medium.

Paper Details

Date Published: 23 February 2012
PDF: 8 pages
Proc. SPIE 8223, Photons Plus Ultrasound: Imaging and Sensing 2012, 82232F (23 February 2012); doi: 10.1117/12.906042
Show Author Affiliations
Eric Strohm, Ryerson Univ. (Canada)
Ivan Gorelikov, Sunnybrook Health Sciences Ctr. (Canada)
Naomi Matsuura, Sunnybrook Health Sciences Ctr. (Canada)
Michael Kolios, Ryerson Univ. (Canada)

Published in SPIE Proceedings Vol. 8223:
Photons Plus Ultrasound: Imaging and Sensing 2012
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)

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