Nicholas J. Scott

Noncontact stimulation of the cavernous nerves in the rat prostate using a tunable-wavelength thulium fiber laser.

BACKGROUND AND PURPOSE Laser nerve stimulation has recently been studied in neuroscience as an alternative to electrical stimulation. Its advantages include noncontact stimulation, better spatial selectivity, and elimination of electrical stimulation artifacts. This study explored laser stimulation of the rat cavernous nerves as a potential alternative to electrical nerve mapping during nerve-sparing radical prostatectomy. MATERIALS AND METHODS The cavernous nerves were surgically exposed in 10 male rats. A thulium fiber laser stimulated the nerves, with a wavelength of 1870 nm, pulse energy of 7.5 mJ, radiant exposure of 1 J/cm2, pulse duration of 2.5 msec, pulse rate of 10 Hz, and 1-mm laser spot diameter, for a stimulation time of 60 sec. RESULTS AND CONCLUSION A significant increase in the intracavernosal pressure was detected on laser stimulation, with pressure returning to baseline values after stimulation ceased. This study demonstrates the feasibility of noncontact stimulation of the cavernous nerves using near-infrared laser radiation.

Thulium Fiber Laser Ablation of Urinary Stones Through Small-Core Optical Fibers

Complications during laser lithotripsy include optical fiber bending failure resulting in endoscope damage and low irrigation rates leading to poor visibility. Both problems are related to fiber diameter and limited by the holmium:YAG (Ho:YAG) laser (lambda = 2120 nm) multimode beam profile. This study exploits the thulium fiber laser (lambda = 1908 nm) beam profile for higher power transmission through smaller fibers. Thulium fiber laser radiation with 1 ms pulse duration, pulse rates of 10-30 Hz, and 70-mu m-diameter spot was coupled into silica fibers with 100, 150, and 200 mum core diameters. Fiber transmission, bending, and endoscope irrigation tests were performed. Damage thresholds for 100, 150, and 200 mum fibers averaged 40, 60, and > 80 W, respectively. Irrigation rates measured 35, 26, and 15 mL/min for no fiber, and 100 and 200 mum fibers. Thulium fiber laser energy of 70 mJ delivered at 20 Hz through a 100 mum fiber resulted in vaporization and fragmentation rates of 10 and 60 mg/min for uric acid stones. The thulium fiber laser beam profile provides higher laser power through smaller fibers than Ho:YAG laser, potentially reducing fiber failure and endoscope damage, and allowing greater irrigation rates for improved visibility.

Laser stimulation of the cavernous nerves in the rat prostate, in vivo: Optimization of wavelength, pulse energy, and pulse repetition rate

The cavernous nerves on the prostate surface are responsible for erectile function. Improved diagnostic techniques are necessary for identification of the nerves during prostate cancer surgery and preservation of sexual function after surgery. Electrical mapping of the nerves has been used as an intra-operative tool during prostate surgery, but it has proven inconsistent and unreliable. Non-contact optical stimulation of the cavernous nerves in the rat prostate has recently been demonstrated as a potential alternative to electrical nerve stimulation. The purpose of this study is to optimize the laser parameters to provide the maximum intracavernosal pressure response after optical nerve stimulation in the rat prostate. Optimal laser nerve stimulation parameters provided comparable response to electrical nerve stimulation. Optical nerve stimulation may represent a potential intra-operative diagnostic technique for use in laparoscopic and robotic nerve-sparing prostate cancer surgery.

Mid-IR Germanium Oxide Fibers for Contact Erbium Laser Tissue Ablation in Endoscopic Surgery

Endoscopic surgical applications of erbium lasers have been limited due to the lack of a suitable mid-IR optical fiber delivery system. Germanium oxide fibers are used for noncontact tissue ablation, but are not recommended for contact tissue ablation applications typically required during endoscopic surgery. This study describes the assembly and characterization of hybrid mid-IR fibers consisting of germanium oxide trunk fibers and sapphire fiber tips, and side-firing germanium oxide fibers with either 45deg angled tips or micromirrors. Average powers up to 8.5 W (850 mJ at 10 Hz) and transmission up to 70% was demonstrated through 450-mum-core, 1.5-m-long fibers, sufficient for endoscopic laser ablation of soft and hard tissues in contact mode.

Thulium fiber laser lithotripsy

Complications during laser lithotripsy include optical fiber bending failure resulting in endoscope damage and low irrigation rates leading to poor visibility. Both problems are related to fiber diameter and limited by the Holmium:YAG laser (λ = 2120 nm) multimode beam profile. This study exploits the Thulium fiber laser (λ = 1908 nm) beam profile for higher power transmission through smaller fibers. Thulium fiber laser radiation with 1-ms pulse duration, pulse rates of 10-30 Hz, and 70-μm-diameter spot was coupled into silica fibers with 100, 150, and 200 μm core diameters. Fiber transmission, bending, and endoscope irrigation tests were performed. Damage thresholds for 100, 150, 200 μm fibers averaged 40 W, 60 W, and > 80 W. Irrigation rates measured 35, 26, and 15 ml/min for no fiber, 100, and 200 μm fibers. Thulium fiber laser energy of 70-mJ delivered at 20 Hz through a 100 μm fiber resulted in vaporization and fragmentation rates of 10 and 60 mg/min for uric acid stones. The Thulium fiber laser beam profile provides higher laser power through smaller fibers than the Ho:YAG laser, potentially reducing fiber failure and endoscope damage and allowing greater irrigation rates for improved visibility.

Noninvasive thermal coagulation of deep subsurface tissue structures using a laser probe with integrated contact cooling

Cooling methods are used during cosmetic laser surgery to preserve a superficial layer of the skin surface. This study investigates contact cooling for sparing a deeper layer of the tissue surface during laser irradiation of subsurface tissues, with the goal of developing noninvasive laser therapy applications beyond cosmetic surgery. A laser probe was designed and tested for simultaneous laser irradiation and contact cooling of liver tissue, ex vivo. Gross and histologic examination was used to quantify thermal lesion dimensions. Liver lesions of 5.8-mm-diameter were created, while preserving the tissue surface to a depth of 1.5 mm. In vivo animal studies are planned to optimize the laser and cooling parameters for potential clinical applications.

Optical stimulation of the cavernous nerves in the rat prostate

Laser nerve stimulation has recently been studied as an alternative to electrical stimulation in neuroscience. Advantages include non-contact stimulation, improved spatial selectivity, and elimination of electrical stimulation artifacts. This study explores laser stimulation of the rat cavernous nerves, as a potential alternative to electrical nerve mapping during nerve-sparing radical prostatectomy. The cavernous nerves were surgically exposed in a total of 10 male rats. A Thulium fiber laser stimulated the nerves, with a wavelength of 1870 nm, pulse energy of 7.5 mJ, radiant exposure of 1 J/cm2, pulse duration of 2.5 ms, pulse rate of 10 Hz, and 1-mm laser spot diameter, for a stimulation time of 60 s. A significant increase in the intracavernosal pressure was detected upon laser stimulation, with pressure returning to baseline levels after stimulation. This study demonstrates the feasibility of non-contact laser stimulation of the cavernous nerves using near-infrared laser radiation.

NESSI and 'Alopeke: two new dual-channel speckle imaging instruments

NESSI and `Alopeke are two speckle imaging instruments for community use at the WIYN and Gemini-North telescopes. The two instruments were built at NASA ARC and include the capability for wide-field and traditional CCD imaging. Speckle interferometry utilizes extremely short exposures to produce interferograms from the turbulent atmosphere that are reconstructed into a diffraction-limited image, effectively giving space-based resolution from the ground. A primary role of these instruments is exoplanet validation for the Kepler, K2, TESS, and many RV programs. Contrast ratios of 6 or more magnitudes are easily obtained. The instrument uses two EMCCD cameras and two filter wheels to provide simultaneous dual-color observations in either narrowband or SDSS broadband filters to characterize detected companions. High resolution imaging enables the identification of blended binaries that contaminate many exoplanet detections, leading to incorrectly measured radii.

Mid-IR Germanium Oxide Fibers for Erbium:YAG and Erbium:YSGG Contact Laser Tissue Ablation in Endourology

Endoscopic surgical applications of Erbium:YAG and Erbium:YSGG lasers have been limited due to the lack of a suitable mid-IR optical fiber delivery system. Germanium oxide fibers are currently used in the clinic for non-contact tissue ablation, but are not recommended for contact tissue ablation applications typically required during endoscopic surgery in a fluid environment. This study describes the assembly and characterization of hybrid mid-IR fibers consisting of germanium oxide trunk fibers and sapphire fiber tips, and side-firing germanium oxide fibers with either 45° angled fiber tips or micro-mirrors. Average powers up to 8.5 W (850 mJ at 10 Hz) and transmission up to 70% was demonstrated through 450-μm-core, 1.5-meter-long fibers, sufficient for endoscopic laser ablation of soft and hard tissues in contact mode.

Holmium:YAG vs. Thulium fiber laser for high-power vaporization of canine prostate tissue

Direct studies comparing different lasers for treatment of BPH are lacking. This preliminary study compares continuous-wave (CW) vs. pulsed prostate tissue vaporization for the Thulium fiber laser and Holmium:YAG laser, both operating near the 1940 nm water absorption peak in tissue. A 50-W Thulium fiber laser (λ= 1908 nm) delivered CW laser radiation through a 600-μm silica fiber in non-contact mode with a 5-mm-diameter spot at the tissue surface. A Holmium:YAG laser (λ= 2120 nm) operated with an energy of 2 J, pulse rate of 25 Hz, and average power of 50 W, and delivered pulsed laser radiation through a 600-μm silica fiber with a 5-mm-diameter laser spot to achieve similar irradiances at the tissue surface. Tissue vaporization was performed in air with the prostate kept hydrated in saline. Tissue vaporization efficiency of both lasers was compared (n = 10 canine prostates for each laser group). Mean vaporization efficiency measured 5.30 ± 0.48 kJ/g vs. 4.13 ± 0.46 kJ/g for Thulium fiber and Holmium lasers (P < 0.05). Tissue vaporization rates measured 0.57 ± 0.05 g/min vs. 0.73 ± 0.07 g/min (P < 0.05). The Holmium:YAG laser vaporizes prostate tissue at a higher rate than the Thulium fiber laser, for the same average power delivered to the tissue. Both the Thulium fiber laser and Holmium:YAG lasers are capable of vaporizing prostate tissue at a rate > 1 g/min if operated at the high powers (100-W) typically used in the clinic.