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19 May 2000 Ultimate sensitivity of time-resolved optoacoustic detection
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Proceedings Volume 3916, Biomedical Optoacoustics; (2000)
Event: BiOS 2000 The International Symposium on Biomedical Optics, 2000, San Jose, CA, United States
The major limitation in sensitivity of the optical tomography is associated with strong optical attenuation in human tissues. Opto-acoustic tomography overcomes this limitation utilizing detection of acoustic waves instead of detection of transmitted photons. Exceptional sensitivity of the opto-acoustic tomography allows early detection of small tumors located dep in human tissues, such as breast. This paper demonstrates that an optimally designed opto-acoustic imaging system can detect early 1-mm tumors with minimal blood content of only 7 percent at the depth of up to 7-cm within the breast attenuating laser irradiation 3.3 times per each 1-cm of its depth. A theoretical consideration of the ultimate sensitivity of piezo-detection in a wide ultrasonic frequency band is developed. The detection sensitivity is presented as a function of the ultrasonic frequency, tumor dimensions and optical absorption coefficient. Comparative analysis of piezo and optical interferometric detection of opto-acoustic transients is presented. The theoretical models of piezo detection were developed for the open-circuit and short-circuit schemes of operation. The ultimate sensitivity limited by thermal noise of electric capacitor of the piezo-element was estimated. It was shown that the limit of detection depends on the frequency band, the electric capacity of the transducer and the sped of sound in the piezo-element. Comparative analysis of various piezo-materials was made from the point of view of their utility for sensitive opto-acoustic detection.
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Alexander A. Oraevsky and Alexander A. Karabutov "Ultimate sensitivity of time-resolved optoacoustic detection", Proc. SPIE 3916, Biomedical Optoacoustics, (19 May 2000);

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