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Proceedings Paper

Time-intensity based optoacoustic flow measurements with gold nanoparticles
Author(s): Pai-Chi Li; Chen-Wei Wei; Chao-Kang Liao; Hsiao-Chien Tseng; Yen-Ping Lin; Chia-Chun Chen
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Paper Abstract

The indicator-dilution theory has been used for flow rate measurements in various imaging modalities, including magnetic resonance imaging, computed tomography and ultrasound. The experimental procedure generally involves the injection of a dose of indicator (i.e., the contrast agent), after which the concentration of the agent is monitored as a function of time; it is therefore also known as the time-intensity method. Although the time-intensity method has been widely applied to other imaging modalities, it has not been demonstrated with optoacoustic imaging. In this study, we experimentally test the hypothesis that quantitative blood flow measurements are feasible with the time-intensity based method in optoacoustic imaging. Gold nanospheres (broad band absorption spectrum peaks at 520 nm) were used as the optoacoustic contrast agent. The imaging system consisted of a frequency-doubled Nd:YAG laser operating at 532 nm for optical illumination, and an ultrasonic single crystal transducer with a center frequency of 3.5 MHz and a focal depth of 7 cm for detection. The volumetric flow rate ranged from 0.23 to 4.29 ml/sec, and the volume of the mixing chamber was from 30 to 80 ml. Results show good agreement between the measured mean transit times and the predicted time constants (correlation coefficient higher than 0.88), thus demonstrating the feasibility of the time-intensity based flow measurement technique. In addition to describing the method and experimental results, issues regarding the system sensitivity and estimation of the dilution transfer function are also discussed.

Paper Details

Date Published: 25 April 2005
PDF: 10 pages
Proc. SPIE 5697, Photons Plus Ultrasound: Imaging and Sensing 2005: The Sixth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics, (25 April 2005); doi: 10.1117/12.591106
Show Author Affiliations
Pai-Chi Li, National Taiwan Univ. (Taiwan)
Chen-Wei Wei, National Taiwan Univ. (Taiwan)
Chao-Kang Liao, National Taiwan Univ. (Taiwan)
Hsiao-Chien Tseng, National Taiwan Normal Univ. (Taiwan)
Yen-Ping Lin, National Taiwan Normal Univ. (Taiwan)
Chia-Chun Chen, National Taiwan Normal Univ. (Taiwan)

Published in SPIE Proceedings Vol. 5697:
Photons Plus Ultrasound: Imaging and Sensing 2005: The Sixth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)

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