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Proceedings Paper

Continuous wavelet-transform analysis of photoacoustic signal waveform to determine optical absorption coefficient
Author(s): T. Hirasawa; M. Ishihara; K. Tsujita; K. Hirota; K. Irisawa; M. Kitagaki; M. Fujita; M. Kikuchi
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Paper Abstract

In photo-acoustic (PA) imaging, valuable medical applications based on optical absorption spectrum such as contrast agent imaging and blood oxygen saturation measurement have been investigated. In these applications, there is an essential requirement to determine optical absorption coefficients accurately. In present, PA signal intensities have been commonly used to determine optical absorption coefficients. This method achieves practical accuracy by combining with radiative transfer analysis. However, time consumption of radiative transfer analysis and effects of signal generation efficiencies were problems of this method. In this research, we propose a new method to determine optical absorption coefficients using continuous wavelet transform (CWT). We used CWT to estimate instantaneous frequencies of PA signals which reflects optical absorption distribution. We validated the effectiveness of CWT in determination of optical absorption coefficients through an experiment. In the experiment, planar shaped samples were illuminated to generate PA signal. The PA signal was measured by our fabricated PA probe in which an optical fiber and a ring shaped P(VDFTrFE) ultrasound sensor were coaxially aligned. Optical properties of samples were adjusted by changing the concentration of dye solution. Tunable Ti:Sapphire laser (690 - 1000 nm) was used as illumination source. As a result, we confirmed strong correlation between optical absorption coefficients of samples and the instantaneous frequency of PA signal obtained by CWT. Advantages of this method were less interference of light transfer and signal generation efficiency.

Paper Details

Date Published: 23 February 2012
PDF: 7 pages
Proc. SPIE 8223, Photons Plus Ultrasound: Imaging and Sensing 2012, 822333 (23 February 2012); doi: 10.1117/12.908088
Show Author Affiliations
T. Hirasawa, National Defense Medical College (Japan)
M. Ishihara, National Defense Medical College (Japan)
K. Tsujita, FUJIFILM Corp. (Japan)
K. Hirota, FUJIFILM Corp. (Japan)
K. Irisawa, FUJIFILM Corp. (Japan)
M. Kitagaki, National Defense Medical College (Japan)
M. Fujita, National Defense Medical College (Japan)
M. Kikuchi, National Defense Medical College (Japan)

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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