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Proceedings Paper

High frame rate photoacoustic computed tomography using coded excitation
Author(s): Masataka Azuma; Haichong K. Zhang; Kengo Kondo; Takeshi Namita; Makoto Yamakawa; Tsuyoshi Shiina
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Paper Abstract

Photoacoustic Computed Tomography (PACT) records signals from a wide range of angles to achieve uniform, highresolution images. A high-power laser is generally used for PACT, but the long acquisition time with a single probe is a problem due to the low pulse-repetition frequency (PRF). For PACT, this degrades image resolution and contrast because it is hard to scan with a small step interval. Moreover, in vivo measurement requires a fast image acquisition system to avoid motion artifacts. The problem can be resolved by using a high PRF laser, which provides only weak energy. Averaging measured signals many times can mitigate the low signal-to-noise issue, but the PRF is restricted by the acoustic time of flight, so this is a new source of measurement time increase. Here, we present the coded-excitation approach, which we previously proposed for linear scanning, to increase the PACT frame rate. Coded excitation irradiates temporally encoded pulses and enhances the signal amplitude through decoding. The PRF is thus not restricted to acoustic time of flight. Consequently, acquisition time can be shortened by increasing PRF, and the SNR increases for the same measurement time. To validate the proposed idea, we conducted experiments using a high PRF laser with a revolving motor and compared the performance of coded excitation to that of averaging. Results demonstrated that the contamination of a signal acquired from different angles was negligible, and that the scanning pitch was remarkably improved because the start point of decoding can be set in any code in the periodic sequence.

Paper Details

Date Published: 11 March 2015
PDF: 6 pages
Proc. SPIE 9323, Photons Plus Ultrasound: Imaging and Sensing 2015, 93232O (11 March 2015); doi: 10.1117/12.2079406
Show Author Affiliations
Masataka Azuma, Graduate School of Medicine, Kyoto Univ. (Japan)
Haichong K. Zhang, Johns Hopkins Univ. (United States)
Kyoto Univ. Graduate School of Medicine (Japan)
Kengo Kondo, Kyoto Univ. (Japan)
Takeshi Namita, Graduate School of Medicine, Kyoto Univ. (Japan)
Makoto Yamakawa, Kyoto Univ. (Japan)
Tsuyoshi Shiina, Graduate School of Medicine, Kyoto Univ. (Japan)

Published in SPIE Proceedings Vol. 9323:
Photons Plus Ultrasound: Imaging and Sensing 2015
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)

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