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Application of laser pulse stretching scheme for efficiently delivering laser energy in photoacoustic imaging. | LitMetric

Application of laser pulse stretching scheme for efficiently delivering laser energy in photoacoustic imaging.

J Biomed Opt

University of Connecticut, Electrical and Computer Engineering Department, Storrs, Connecticut 06269, USA.

Published: June 2012

AI Article Synopsis

  • High-energy, short-duration laser pulses enhance the quality of photoacoustic imaging for deep tissue lesions but risk damaging optical fibers if the energy exceeds their threshold.
  • To mitigate fiber damage while ensuring effective imaging, a laser-pulse-stretching method was implemented that lengthened the pulse duration from 17 ns to 27 and 37 ns, reducing peak power by 42% and increasing the fiber damage threshold by 1.5 times.
  • Simulations with ultrasound transducers showed that the photoacoustic signals from a small target using the stretched 37-ns pulse maintained 80-98% of the original energy efficiency, confirming that pulse stretching did not degrade image quality.

Article 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.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3381029PMC
http://dx.doi.org/10.1117/1.JBO.17.6.061218DOI Listing

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