Ms. Ngot Thi Pham Profile

Ngot Thi Pham

at Pukyong National Univ

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Publications (2)

SPIE Journal Paper | 20 April 2017 Open Access

Real-time temperature monitoring with fiber Bragg grating sensor during diffuser-assisted laser-induced interstitial thermotherapy

Ngot Thi Pham, Seul Lee Lee, Suhyun Park, Yong Wook Lee, Hyun Wook Kang

JBO, Vol. 22, Issue 04, 045008, (April 2017) https://doi.org/10.1117/12.10.1117/1.JBO.22.4.045008

KEYWORDS: Fiber Bragg gratings, Tissues, Temperature metrology, Diffusers, Laser tissue interaction, Liver, Sensors, Fiber lasers, Natural surfaces, Tissue optics

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Proceedings Article | 19 April 2017 Presentation

Temperature monitoring with FBG sensor during diffuser-assisted laser-induced interstitial thermotherapy (Conference Presentation)

Ngot Pham, Seul Lee Lee, Yong Wook Lee, Hyun Wook Kang

Proceedings Volume 10038, 100380B (2017) https://doi.org/10.1117/12.2251369

KEYWORDS: Technetium, Laser therapeutics, Fiber Bragg gratings, Sensors, Tissues, Temperature sensors, Temperature metrology, Heat therapy, Diffusers, Electromagnetic interference

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Temperature variations are often monitored by using sensors operating at the site of treatment during Laser-induced Interstitial Thermotherapy (LITT). Currently, temperature measurements during LITT have been performed with thermocouples (TCs). However, TCs could directly absorb laser light and lead to self-heating (resulting in an over-estimation). Fiber Bragg grating (FBG) sensors can instead overcome this limitation of the TCs due to its insensitivity to electromagnetic interference. The aim of the current study was to quantitatively evaluate the FBG temperature sensor with a K-type thermocouple to real-time monitor temperature increase in ex vivo tissue during diffuser-assisted LITT. A 4-W 980-nm laser was employed to deliver optical energy in continuous mode through a 600-µm core-diameter diffusing applicator. A goniometric measurement validated the uniform light distribution in polar and longitudinal directions. The FBG sensor showed a linear relationship (R2 = 0.995) between wavelength shift and temperature change in air and tissue along with a sensitivity of ~ 0.0114 nm/˚C. Regardless of sensor type, the measured temperature increased with irradiation time and applied power but decreased with increasing distance from the diffuser surface. The temperature elevation augmented the degree of thermal coagulation in the tissue during LITT (4.0±0.3-mm at 99˚C after 120-s). The temperature elevation augmented the degree of thermal coagulation in the tissue during LITT s irradiation). The FBG-integrated diffuser was able to monitor the interstitial temperature in tubular tissue (porcine urethra) real-time during laser treatment. However, the thermal coagulation thickness of the porcine urethra was measured to be 1.5 mm that was slightly thicker (~20%) than that of the bovine liver after 4-W 980-nm laser for 48 s. The FBG temperature sensor can be a feasible tool to real-time monitor the temporal development of the temperature during the diffuser-assisted LITT to treat urethral disease.

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