Temperature-controlled optical stimulation of the rat prostate cavernous nerves

Abstract

Abstract. Optical nerve stimulation (ONS) may be useful as a diagnostic tool for intraoperative identification and preservation of the prostate cavernous nerves (CN), responsible for erectile function, during prostate cancer surgery. Successful ONS requires elevating the nerve temperature to within a narrow range (∼42 to 47°C) for nerve activation without thermal damage to the nerve. This preliminary study explores a prototype temperature-controlled optical nerve stimulation (TC-ONS) system for maintaining a constant (AE1°C) nerve temperature during short-term ONS of the rat prostate CNs. A 150-mW, 1455-nm diode laser was operated in continuous-wave mode, with and without temperature control, during stimulation of the rat CNs for 15 to 30 s through a fiber optic probe with a 1-mm-diameter spot. A microcontroller opened and closed an in-line mechanical shutter in response to an infrared sensor, with a predetermined temperature set point. With TC-ONS, higher laser power settings were used to rapidly and safely elevate the CNs to a temperature necessary for a fast intracavernous pressure response, while also preventing excessive temperatures that would otherwise cause thermal damage to the nerve. With further development, TC-ONS may provide a rapid, stable, and safe method for intraoperative identification and preservation of the prostate CNs. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Optical Stimulation of Neurons

“…This probe showed similar results to those from previous work using a fibre [ 61 ] and may allow easier targeting of nerves for INS. This probe was adapted [ 146 ] to provide temperature monitoring and feedback with the continuous wave stimulation technique [ 75 ]. An IR sensor monitored the temperature on the surface of the nerve and controlled the laser power, allowing a fast ramp up in temperature without increasing to levels that may cause damage.…”

“…Holographic patterning of light onto neural tissue was demonstrated by [ 122 , 151 ]. This technique uses a spatial light modulator to deliver light to individual neurons that have been photo-sensitised with optogenetic treatments or by using photo-absorbers [ 146 ].…”

Identifying optimal parameters for infrared neural stimulation in the peripheral nervous system

“…8,9,[30][31][32] The application of INS in animal models for surgical guidance includes use in the prostate, bladder, and base of the skull to minimize collateral nerve damage that can give rise to urinary incontinence, sexual impotence, and facial paralysis, respectively. 16,17,[33][34][35] Together, these studies substantiate INS as a potentially valuable clinical tool in both the central and peripheral nervous systems.…”

“…Optical neuromodulation has had a profound impact on both clinical and basic research due to its spatial selectivity. In clinical applications where high spatial resolution is required including prostatectomies, 16,33,34 rhizotomies, 29 and skull base surgeries, 35 optical methods could offer a superior alternative to electrical stimulation. With optogenetics, selective neural excitation requires targeting genetically altered neurons.…”

Direct Administration of Nerve-Specific Contrast to Improve Nerve Sparing Radical Prostatectomy

“…In addition, these imaging probe based technologies often require that the probe be in direct contact with the nerve tissue, generating point based measurements instead of images and potentially interferring with minimally invasive procedures. Non-imaging technologies such as optical nerve stimulation have also been used to identify nerves by measuring intracavernous pressure upon stimulation of nerve tissue, however without direct imaging capability and a lag time of 2-5 s between stimulation and measurement, real time nerve identification is again difficult to achieve 23 - 26 . The utility of fluorescence image-guided surgery has been demonstrated using developed imaging systems, such as the FLARE 14 , 16 , 17 , 27 - 29 , Fluobeam 800 30 , Photodynamic eye 31 , HyperEye Medical System 32 , and the FDA approved fluorescence-imaging channel in the da Vinci surgical robot (Intuitive Surgical, Inc., Sunnyvale, CA).…”