DocumentCode :
2003318
Title :
Feasibility study of multispectral photoacoustic coded excitation using orthogonal unipolar Golay codes
Author :
Mienkina, Martin P. ; Eder, Annika ; Schmitz, Georg ; Friedrich, Claus-Stefan ; Gerhardt, Nils C. ; Hofmann, Martin R.
Author_Institution :
Inst. of Med. Eng., Ruhr-Univ. Bochum, Bochum, Germany
fYear :
2009
fDate :
20-23 Sept. 2009
Firstpage :
108
Lastpage :
111
Abstract :
Photoacoustic (PA) imaging is a new imaging modality based on the generation of ultrasound in biological tissue by laser irradiation. It would be desirable to use laser diodes as excitation sources for PA since they are less expensive and more compact than commonly used Nd:YAG lasers. Laser diodes exhibit a higher pulse repetition frequency (PRF) and a lower pulse energy compared to Nd:YAG lasers. In order to increase the SNR of PA imaging using laser diodes, we propose multispectral photoacoustic coded excitation (MS-PACE) based on orthogonal unipolar Golay codes (OUGC). This concept allows acquiring photoacoustic data generated by two laser diodes at two different wavelengths simultaneously and separating them afterwards. The SNR gain and coding gain compared to time equivalent averaging is analytically derived. Furthermore, the feasibility of the concept is experimentally verified. Two laser diodes, emitting light at 850 nm and 905 nm, are triggered according the OUGC scheme. They irradiate a metal slab. The resulting PA signals are acquired using a reconfigured clinical ultrasound system with an 128 element linear array. The data are decoded and images are formed using a delay-and-sum algorithm. Using an 8 bit sequence the SNR is increased by 8.68 dB (905 nm) and 8.87 dB (850 nm). These results are in good agreement with the theoretical SNR gain of 9.03 dB. The resulting images allow a clear discrimination of both wavelengths, demonstrating the feasibility of MS-PACE using OUGC.
Keywords :
Golay codes; acoustic imaging; biological tissues; biomedical ultrasonics; laser applications in medicine; photoacoustic effect; semiconductor lasers; MS-PACE; YAG:Nd; biological tissue; gain 9.03 dB; laser diodes; laser irradiation; multispectral photoacoustic coded excitation; orthogonal unipolar Golay codes; photoacoustic imaging; pulse energy; pulse repetition frequency; ultrasound generation; wavelength 850 nm; wavelength 905 nm; Biological tissues; Decoding; Delay; Diode lasers; Frequency; Gain; Laser excitation; Optical pulses; Slabs; Ultrasonic imaging; component; laser diode; optoacoustic; orthogonal Golay code; photoacoustic;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Ultrasonics Symposium (IUS), 2009 IEEE International
Conference_Location :
Rome
ISSN :
1948-5719
Print_ISBN :
978-1-4244-4389-5
Electronic_ISBN :
1948-5719
Type :
conf
DOI :
10.1109/ULTSYM.2009.5441941
Filename :
5441941
Link To Document :
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