Mr. Trung Hau Nguyen Profile

Trung Hau Nguyen

at Pukyong National Univ

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Author

Publications (2)

Proceedings Article | 27 April 2016 Presentation

Application of novel optical diffuser for urethral stricture treatment (Conference Presentation)

Trung Hau Nguyen, Yun-Hee Rhee, Jin-Chul Ahn, Hyun Wook Kang

Proceedings Volume 9689, 96891H (2016) https://doi.org/10.1117/12.2212217

KEYWORDS: Tissues, Diffusers, Tissue optics, Optical fibers, Laser therapeutics, Laser tissue interaction, Optical fabrication, In vitro testing, Liver, Energy efficiency

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Optical fibers have frequently been used for photothermal laser therapy due to its efficiency to deliver laser energy directly to tissue. The aim of the current study was to develop a diffusing optical fiber to achieve radially uniform light irradiation for endoscopically treating urethral stricture. The optical diffuser was fabricated by micro-machining helical patterns on the fiber surface using CO2 laser light at 5 W. Visible light emission (632 nm) and spatial emissions (including polar, azimuthal, and longitudinal emissions) of the fiber tip were evaluated to validate the performance of the fabricated diffuser. Prior to tissue tests, numerical simulation on heat distribution was developed to estimate the degree of tissue coagulation depth during interstitial coagulation. Due to a high absorption coefficient by tissue water, 1470 nm laser was used for photothermal therapy treatment of urethral stricture to obtain a more precise depth profile. For in vitro tissue tests, porcine liver tissue was irradiated with three different power levels (3, 6, and 9 W) at various irradiation times. Porcine urethral tissue was also tested with the diffuser for 10 sec at 6 W to validate the feasibility of circumferential photothermal treatment. The treated tissue was stained with hematoxylin and eosin (H and E) and then imaged with an optical transmission microscope. The spatial emission characteristics of the diffusing optical fiber presented an almost uniform power distribution along the diffuser tip (less than 10% deviation) and around its circumference (less than 5% deviation). The peak temperature in simulation model at the tissue interface between the glass-cap and the tissue was 373 K that was higher than that at the distal end. The tissue tests showed that higher power levels resulted in lower coagulation thresholds (e.g., 1 sec at 9 W vs 8 sec at 3 W). Furthermore, the coagulation depth was approximately 20% thinner than the simulation results (p<0.001). The extent of coagulation thickness in urethral tissue was measured to be 1.3±0.2 mm, which was slightly thicker (18%) than the liver testing (1.1±0.1 mm) under the same conditions (p < 0.001). The proposed optical diffuser may be a feasible tool to treat the urethral stricture in a uniform manner.

Proceedings Article | 26 February 2015 Paper

Photoactive dye enhanced tissue ablation for endoscopic laser prostatectomy

Minwoo Ahn, Trung Hau Nguyen, Van Phuc Nguyen, Junghwan Oh, Hyun Wook Kang

Proceedings Volume 9303, 93031D (2015) https://doi.org/10.1117/12.2077096

KEYWORDS: Laser ablation, Laser tissue interaction, Tissue optics, Tissues, Absorption, Prostate, Absorbance, Endoscopy, Laser therapeutics, Natural surfaces

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