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Proceedings Paper

Photoacoustic imaging of a near-infrared fluorescent marker based on dual wavelength pump-probe excitation
Author(s): Julia Märk; Christoph Theiss; Franz-Josef Schmitt; Jan Laufer
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Paper Abstract

Photoacoustic imaging has been used to determine the spatial distribution of fluorophores, such as exogenous dyes and genetically expressed proteins, from images acquired in phantoms and in vivo. Most methods involve the acquisition of multiwavelength images and rely on differences in the absorption spectra of the tissue chromophores to estimate the spatial distribution and abundance of the latter using spectral decomposition techniques, such as model based inversion schemes. However, the inversion of 3-D images can be computationally expensive. Experimental approaches to localising contrast agents may therefore be useful, especially if quantification is not essential. This work aims to develop a method for determining the spatial distribution of a near-infrared fluorescent cell marker from images acquired using dual wavelength excitation. The excitation wavelengths coincided with the absorption and emission spectrum of the fluorophore. The contrast mechanism relies on reducing the excited state lifetime of the fluorophore by inducing stimulated emission. This changes the amount of energy thermalized by the fluorophore, and hence the photoacoustic signal amplitude. Since this is not observed in endogenous chromophores, the background may be removed by subtracting two images acquired with and without pulse delay between the pump and probe pulses. To characterise the fluorophore, the signal amplitude is measured in a cuvette as a function of pulse delay, concentration, and fluence. The spatial distribution of the fluorophore is determined from images acquired in realistic tissue phantoms. This method may be suitable for in vivo applications, such as imaging of exogenous or genetically expressed fluorescent cell markers.

Paper Details

Date Published: 3 March 2014
PDF: 7 pages
Proc. SPIE 8943, Photons Plus Ultrasound: Imaging and Sensing 2014, 894333 (3 March 2014); doi: 10.1117/12.2039467
Show Author Affiliations
Julia Märk, Technische Univ. Berlin (Germany)
Christoph Theiss, Technische Univ. Berlin (Germany)
Franz-Josef Schmitt, Technische Univ. Berlin (Germany)
Jan Laufer, Technische Univ. Berlin (Germany)
Charité Universitätsmedizin Berlin (Germany)

Published in SPIE Proceedings Vol. 8943:
Photons Plus Ultrasound: Imaging and Sensing 2014
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)

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