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Proceedings Paper

Ultrahigh resolution photoacoustic microscopy via transient absorption
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Paper Abstract

We have developed a novel, hybrid imaging modality, Transient Absorption Ultrasonic Microscopy (TAUM), which fuses photoacoustic microscopy with non-linear microscopy. Photoacoustic microscopy is well known for its ability to image chromophores deep (> 1 mm) in scattering media with spatial resolutions in the 10s of microns. Non-linear microscopy is well known for its exquisite spatial resolution in three dimensions. This superior spatial resolution is attributed to the fact that the collected signal has a non-linear dependence on the light intensity. This dependence confines the signal to a very small focal volume, producing optically resolved voxels. Transient absorption is a non-linear process often used to map the excited state lifetimes of molecules exhibiting low fluorescence quantum efficiency. This sensitivity to non-radiative transitions makes transient absorption an attractive process to combine with photoacoustic imaging. We have built a prototype transient absorption ultrasonic microscope, implementing off-axis photoacoustic detection to allow the use of a high-quality, high numerical aperture objective. This high-quality, commercial lens is required to provide the tight focusing needed to optimize non-linear effects. We have demonstrated the increased spatial resolution of TAUM by imaging Rhodamine 6G in a capillary tube. The capillary cross-section is fully resolved, suggesting an axial resolution of < 10 microns. A 6 MHz transducer was used in this experiment, which results in an axial resolution of ~ 400 microns when used in a traditional photoacoustic microscope. Boasting the superior penetration depth and absorption contrast offered by photoacoustic emission and complemented by spatial resolutions comparable to confocal microscopy, we believe that Transient Absorption Ultrasonic Microscopy has excellent potential for producing volumetric images with cellular/subcellular resolution in three dimensions deep inside living tissue.

Paper Details

Date Published: 17 February 2011
PDF: 5 pages
Proc. SPIE 7899, Photons Plus Ultrasound: Imaging and Sensing 2011, 78990S (17 February 2011); doi: 10.1117/12.875578
Show Author Affiliations
Ryan Shelton, Texas A&M Univ. (United States)
Brian E. Applegate, Texas A&M Univ. (United States)

Published in SPIE Proceedings Vol. 7899:
Photons Plus Ultrasound: Imaging and Sensing 2011
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)

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