4 March 2013 Optical-resolution photoacoustic micro-endoscopy with ultrasound array system detection
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Abstract
Recently we demonstrated the feasibility of Optical-Resolution Photoacoustic Micro-Endoscopy (OR-PAME) using an image guide fiber. However, the use of an ultrasound transducer for signal collection limited useful applications. We demonstrate detection of OR-PAM signals using an external array transducer in order to make endoscopic imaging practical for clinical use for the first time. The array system is able to visualize the placement of the image-guide fiber using pulse-echo ultrasound then switch to an OR-PAME acquisition mode. Photoacoustic signals are captured by a Verasonics ultrasound system using an L7-4 linear array transducer. A high-repetition-rate 532-nm fiber laser was used as the excitation source. This light was focused and raster­ scanned into a 800m-diameter image-guide fiber bundle consisting of 30,000 individual fiber elements. The operator finds the end of the endoscope using a flash ultrasound imaging mode, then captures endoscopic data by clicking a button. This activates the motion of scanning mirrors into the end of the image guide, and engages an endoscopic capture sequence. Endoscopic data are used to form a maximum amplitude image by simply taking the maximum of the absolute value of the signal across the 64 center channel lines used for capture. Using this technique, we have captured images of carbon fibers with a resolution of 6 microns at an SNR of greater than 30dB. Electronic focusing is expected to improve the SNR. The use of an ultrasound array transducer for both endoscope guidance and data collection allows for a much smaller endoscope footprint while opening up clinical possibilities.
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Tyler Harrison, Tyler Harrison, Parsin Hajireza, Parsin Hajireza, Alexander Forbrich, Alexander Forbrich, Roger Zemp, Roger Zemp, } "Optical-resolution photoacoustic micro-endoscopy with ultrasound array system detection", Proc. SPIE 8581, Photons Plus Ultrasound: Imaging and Sensing 2013, 85810C (4 March 2013); doi: 10.1117/12.2004887; https://doi.org/10.1117/12.2004887
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