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Proceedings Paper

Gaussian versus flat-top spatial beam profiles for optical stimulation of the prostate nerves
Author(s): Serhat Tozburun; Gwen A. Lagoda; Arthur L. Burnett; Nathaniel M. Fried
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Paper Abstract

The cavernous nerves (CN) course along the prostate surface and are responsible for erectile function. Improved identification and preservation of the CN's is critical to maintaining sexual potency after prostate cancer surgery. Noncontact optical nerve stimulation (ONS) of the CN's was recently demonstrated in a rat model, in vivo, as a potential alternative to electrical nerve stimulation (ENS) for identification of the CN's during prostate surgery. However, the therapeutic window for ONS is narrow, so optimal design of the fiber optic delivery system is critical for safe, reproducible stimulation. This study describes modeling, assembly, and testing of an ONS probe for delivering a small, collimated, flat-top laser beam for uniform CN stimulation. A direct comparison of the magnitude and response time of the intracavernosal pressure (ICP) for both Gaussian and flat-top spatial beam profiles was performed. Thulium fiber laser radiation (λ=1870 nm) was delivered through a 200-μm fiber, with distal fiber tip chemically etched to convert a Gaussian to flat-top beam profile. The laser beam was collimated to a 1-mm-diameter spot using an aspheric lens. Computer simulations of light propagation were used to optimize the probe design. The 10-Fr (3.4-mm-OD) laparoscopic probe provided a constant radiant exposure at the CN surface. The probe was tested in four rats, in vivo. ONS of the CN's was performed with a 1-mm-diameter spot, 5-ms pulse duration, and pulse rate of 20 Hz for a duration of 15-30 s. The flat-top laser beam profile consistently produced a faster and higher ICP response at a lower radiant exposure than the Gaussian beam profile due, in part, to easier alignment of the more uniform beam with nerve. The threshold for ONS was approximately 0.14 J/cm2, corresponding to a temperature increase of 6-8°C at the CN surface after a stimulation time of 15 s. With further development, ONS may be used as a diagnostic tool for identification of CN's during prostate cancer surgery.

Paper Details

Date Published: 2 March 2010
PDF: 6 pages
Proc. SPIE 7548, Photonic Therapeutics and Diagnostics VI, 75484W (2 March 2010); doi: 10.1117/12.852994
Show Author Affiliations
Serhat Tozburun, The Univ. of North Carolina at Charlotte (United States)
Gwen A. Lagoda, Johns Hopkins Medical Insitutions (United States)
Arthur L. Burnett, Johns Hopkins Medical Insitutions (United States)
Nathaniel M. Fried, The Univ. of North Carolina at Charlotte (United States)
Johns Hopkins Medical Insitutions (United States)

Published in SPIE Proceedings Vol. 7548:
Photonic Therapeutics and Diagnostics VI
Anita Mahadevan-Jansen; Andreas Mandelis; Brian Jet-Fei Wong M.D.; Nikiforos Kollias; Henry Hirschberg M.D.; Kenton W. Gregory M.D.; Reza S. Malek; E. Duco Jansen; Guillermo J. Tearney; Steen J. Madsen; Bernard Choi; Justus F. R. Ilgner; Haishan Zeng; Laura Marcu, Editor(s)

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