Single-energy wash-in photoacoustic blood flow measurements using shape transitions of gold nanorods

Chen-Wei Wei; Sheng-Wen Huang; Ya-Chin Chiou; Cheng-Dah Chen; Churng-Ren Chris Wang; Pai-Chi Li

doi:10.1117/12.645272

6 March 2006 Single-energy wash-in photoacoustic blood flow measurements using shape transitions of gold nanorods

Chen-Wei Wei, Sheng-Wen Huang, Ya-Chin Chiou, Cheng-Dah Chen, Churng-Ren Chris Wang, Pai-Chi Li

Proceedings Volume 6086, Photons Plus Ultrasound: Imaging and Sensing 2006: The Seventh Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics; 60860L (2006) https://doi.org/10.1117/12.645272
Event: SPIE BiOS, 2006, San Jose, California, United States

Abstract

A time-intensity based method for photoacoustic blood flow measurements was proposed in last year's meeting. The method made use of the strong photoacoustic response of gold nanospheres and the "wash-out" characteristics of the nanospheres were analyzed. In this paper, we develop a new quantitative technique for measuring blood flows based on the "wash-in" characteristics of the nanoparticles. In particular, the technique makes use of the shape dependence of the optical absorption of gold nanorods (i.e., cylindrical nanoparticles) and the transitions in their shape induced by pulsed laser irradiation. The photon-induced shape transition of gold nanorods involves mainly a rod-to-sphere conversion and a shift in the peak optical absorption wavelength. The application of a series of laser pulses with the same laser energy will induce shape changes in gold nanorods as they flow through a region of interest, with quantitative flow information being derived from the photoacoustic signals from the irradiated gold nanorods measured as a function of time. To demonstrate the feasibility of the technique, an Nd:YAG laser operating at 1064 nm was used for irradiation and a ultrasonic transducer with a center frequency of 1 MHz was used for acoustic detection. Excellent agreement between the measured velocities and the actual velocities was demonstrated, with a linear regression correlation coefficient higher than 0.9. Compared to the wash-out analysis, the wash-in analysis is more suitable for measuring flows in microcirculation.

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Chen-Wei Wei, Sheng-Wen Huang, Ya-Chin Chiou, Cheng-Dah Chen, Churng-Ren Chris Wang, and Pai-Chi Li "Single-energy wash-in photoacoustic blood flow measurements using shape transitions of gold nanorods", Proc. SPIE 6086, Photons Plus Ultrasound: Imaging and Sensing 2006: The Seventh Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics, 60860L (6 March 2006); https://doi.org/10.1117/12.645272

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KEYWORDS

Nanorods

Gold

Toxic industrial chemicals

Absorption

Photoacoustic spectroscopy

Ultrasonics

Laser irradiation

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