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Journal of Biomedical Optics

Application of laser pulse stretching scheme for efficiently delivering laser energy in photoacoustic imaging
Author(s): Tianheng Wang; Patrick D. Kumavor; Quing Zhu
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Paper Abstract

High-energy and short-duration laser pulses are desirable to improve the photoacoustic image quality when imaging deeply seated lesions. In many clinical applications, the high-energy pulses are coupled to tissue using optical fibers. These pulses can damage fibers if the damage threshold is exceeded. While keeping the total energy under the Food and Drug Administration limit for avoiding tissue damage, it is necessary to reduce the peak intensity and increase the pulse duration for minimizing fiber damage and delivering sufficient light for imaging. We use laser-pulse-stretching to address this problem. An initial 17-ns pulse was stretched to 27 and 37 ns by a ring-cavity laser-pulse-stretching system. The peak power of the 37-ns stretched pulse reduced to 42% of the original, while the fiber damage threshold was increased by 1.5-fold. Three ultrasound transducers centered at 1.3-, 3.5-, and 6-MHz frequencies were simulated, and the results showed that the photoacoustic signal of a 0.5-mm-diameter target obtained with 37-ns pulse was about 98, 91, and 80%, respectively, using the same energy as the 17-ns pulse. Simulations were validated using a broadband hydrophone. Quantitative comparisons of photoacoustic images obtained with three corresponding transducers showed that the image quality was not affected by stretching the pulse.

Paper Details

Date Published: 10 May 2012
PDF: 9 pages
J. Biomed. Opt. 17(6) 061218 doi: 10.1117/1.JBO.17.6.061218
Published in: Journal of Biomedical Optics Volume 17, Issue 6
Show Author Affiliations
Tianheng Wang, Univ. of Connecticut (United States)
Patrick D. Kumavor, Univ. of Connecticut (United States)
Quing Zhu, Univ. of Connecticut (United States)

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