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Journal of Biomedical Optics

Nanorod-based flow estimation using a high-frame-rate photoacoustic imaging system
Author(s): Chao-Kang Liao; Sheng-Wen Huang; Chen-Wei Wei; Pai-Chi Li
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Paper Abstract

A quantitative flow measurement method that utilizes a sequence of photoacoustic images is described. The method is based on the use of gold nanorods as a contrast agent for photoacoustic imaging. The peak optical absorption wavelength of a gold nanorod depends on its aspect ratio, which can be altered by laser irradiation (we establish a wash-in flow estimation method of this process). The concentration of nanorods with a particular aspect ratio inside a region of interest is affected by both laser-induced shape changes and replenishment of nanorods at a rate determined by the flow velocity. In this study, the concentration is monitored using a custom-designed, high-frame-rate photoacoustic imaging system. This imaging system consists of fiber bundles for wide area laser irradiation, a laser ultrasonic transducer array, and an ultrasound front-end subsystem that allows acoustic data to be acquired simultaneously from 64 transducer elements. Currently, the frame rate of this system is limited by the pulse-repetition frequency of the laser (i.e., 15 Hz). With this system, experimental results from a chicken breast tissue show that flow velocities from 0.125 to 2 mm/s can be measured with an average error of 31.3%.

Paper Details

Date Published: 1 November 2007
PDF: 9 pages
J. Biomed. Opt. 12(6) 064006 doi: 10.1117/1.2812704
Published in: Journal of Biomedical Optics Volume 12, Issue 6
Show Author Affiliations
Chao-Kang Liao, National Taiwan Univ. (Taiwan)
Sheng-Wen Huang, Univ. of Michigan (United States)
Chen-Wei Wei, National Taiwan Univ. (Taiwan)
Pai-Chi Li, National Taiwan Univ. (Taiwan)

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