Circumferential irradiation for interstitial coagulation of urethral stricture

Abstract

An optical diffuser was developed to achieve radially uniform light irradiation by micro-machining helical patterns on the fiber surface for endoscopically treating urethral stricture. Spatial emission from the diffuser was evaluated by goniometric measurements. A computational model was developed to predict spatio-temporal heat distribution during the interstitial coagulation. The fabricated diffuser yielded circumferential light distribution with slightly concentrated energy at the proximal end. Both simulation and tissue testing demonstrated approximately 1-mm coagulation thickness at 6 W for 10 sec with 1470 nm. The proposed optical diffuser may be a feasible tool to treat the urethral stricture in a uniform manner.

Ex vivolaser lipolysis assisted with radially diffusing optical applicator

“…16 Figure 1 shows an experimental setup for ex vivo laser lipolysis tests. Prior to the tests, all the samples were stored at room temperature (20°C) to minimize any dehydration and structural deformation.…”

“…Initially, both threshold time and temperature rise during laser liquefaction were investigated as a function of power level (8,12,16, and 20 W) for a diffusing applicator. The irradiation times were varied from 1 to 30 s with an increment of 1 s at each applied power until the fat liquefaction commenced.…”

“…However, the low heat absorption by the adipose tissue often induced severe thermal damage to the collagen in the subcutaneous adipose tissue. 16 Laser micromachining creates the predetermined lozenge patterns on the fiber surface, eventually scattering laser light in a radial direction. 10,14 Lately, the wavelengths ranging from 1320 to 2100 nm were used with flat fibers as both fat and water attain high light absorption.…”

“…On account of higher light absorption than 1064 nm, the 980-nm wavelength was employed instead, but the clinical results demonstrated that the wavelength was less effective for skin tightening. 16,17 In turn, the circumferential irradiation is associated with the decreased irradiance along the 1-cm long diffuser tip, which entails uniform thermal denaturation in the tubular tissue without any carbonization on the tissue-fiber interface. 15 As a result, patients experience fewer complications such as burns.…”

Endoluminal application of glass-capped diffuser for ex vivo endovenous photocoagulation

“…To remove any residual debris on the fiber surface and to increase the visibility of degradation, each fiber was carefully cleaned by an ultrasonic cleaner (SH‐1025, Saehan ultrasonic Co. Ltd., Seoul, Korea) to ensure no accidental scratches. Then, spatial light distributions from both the flat and the diffusing fibers were quantitatively measured by a homemade goniometer in conjunction with 2 mW HeNe laser light . Polar and longitudinal emissions were measured for the flat and the diffusing fibers, respectively before and after the temperature measurements in the blood ( N = 3) .…”