• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.12
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• pp.2310-2316
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• 2016

We studied the effect of $Co^{60}$ gamma-radiation on the fiber Bragg gratings (FBGs) by irradiation time of UV Krypton fluoride (KrF) excimer laser among grating processing parameters. The FBGs were fabricated in a different UV laser irradiation time at 30, 60, 90, and 120 seconds using the same commercial Ge-doped silica core fiber (SMF-28e). It was exposed to gamma-radiation up to a high dose of 34.3 kGy at the dose rate of 106 Gy/min, and then it was analyzed radiation effects by measuring the radiation-induced change in the temperature sensitivity coefficient and Bragg wavelength shift. According to the experimental results, We confirmed that the UV laser irradiation period for grating inscription has a highly effect on the radiation sensitivity of the FBGs. The radiation-induced Bragg wavelength shift by the change of laser irradiation conditions showed a difference more than about 50 %.

• Journal of radiological science and technology
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• v.45 no.2
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• pp.165-170
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• 2022

Staphylococcus aureus is a major pathogen that causes clinical infections in humans and can also cause massively colonized in lesion skin, particularly in atopic dermatitis patients. This study investigated the effects of photodynamic inactivation with radachlorin and diode laser irradiation on the viability of S. aureus in vitro and assessed the effects of the dose of laser transmission. In the PDI group, 5 𝜇L of S. aureus suspension and 5 𝜇L of radachlorin were inoculated in a 55 mm petri dish (63.6 cm²). The samples were placed in a 37° incubator for 30 min and then irradiated with light (660 nm diode laser). After laser irradiation, the cells were stored for 24 h at 37° in an incubator with 5% CO2, and the number of colonies was counted. All CFU/mL of S. aureus were reduced by diode laser in the presence of radachlorin, with a killing rate of 87.9% at an energy dose of 9 J/cm². This study contribute to treat colonized with S. aureus in atopic dermatitis patients and wound infections by providing information on the optimal dose of laser transmission using PDI to eliminate S. aureus.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.638-640
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• 2018

In this paper, FBG sensor is fabricated using 800nm femtosecond laser. The sensor was irradiated with a cumulative dose of 100 kGy gamma ray, and the effect of radiation on the FBG coating material was evaluated.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.961-963
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• 2015

In this study, we studied the effect of $Co^{60}$ gamma-radiation on the fiber Bragg gratings written by femtosecond UV laser in single mode optical fibers. The fiber Bragg gratings were exposed to gamma-radiation up to a dose of about 31.6 kGy at the dose rate of 106 Gy/min. According to the experimental data and analysis results, we confirmed Bragg gratings written by femtosecond laser have the excellent radiation-hardened characteristics for high radiation environments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.711-713
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• 2017

Fiber Brag grating sensors were written in standard Ge-doped telecom optical fiber (Corning SMF-28) using an 800nm femtosecond laser and a phase mask. It were exposed to gamma-radiation up to a dose of 100 kGy to evaluate the radiation effect. The fs-FBG-2 sensor showed incomplete optical characteristics during irradiation, but the fs-FBG-1 sensor showed excellent radiation resistance with Bragg wavelength shift(BWS) of less than 10pm at a dose of 100 kGy.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.161-166
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• 2016

We studied the effect of $Co^{60}$ gamma-radiation on the FBGs by a variation of grating the fabrication parameters. The FBGs were fabricated in a different UV KrF laser intensity using the same boron co-doped photo-sensitive fiber and exposed to gamma-radiation up to a dose of 33.8 kGy. According to the experimental data and analysis results, We confirmed that the laser intensity for grating inscription has a highly effect on the radiation sensitivity of the FBGs and the radiation-induced Bragg wavelength shift by the change of laser process condition showed a difference more than about 30 %.

• Radiation Oncology Journal
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• v.19 no.4
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• pp.301-305
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• 2001

Purpose : This study was peformed for the evaluation of the feasibility and toxicity of hypofractionated radiation therapy for early glottic cancer Methods and Materials : From February 1999 to February 2000, 20 patients with Histologically confirmed Stage I, II glottic cancer were enrolled into this study. There were 18 males and 2 females, the median age of the patients was 59 years. The distribution of stage distribution was as fellows; T1aN0-16 patients, T1bN0-1 patient, T2N0-3 patients. Eighteen patients underwent laryngomicroscopic biopsy only, and two patients underwent laser cordectomy. All patients received radical radiation therapy (2.5 Gy per fraction, 24 fractions, total 60 Gy). Median duration of treatment was 36 days (range $31\~45\;days$). Results : Radiation therapy were well tolerated. Most common acute reactions were odynophagia and hoarseness, and these reactions resolved after radiation therapy. There were one case of RTOG grade 3 odynophagia $(5\%)$, six cases of grade 3 hoarseness $(30\%)$. Response of radiation therapy was evaluated one month after completion of treatment. All patients revealed complete response. During follow up, total three cases of treatment failure were detected. two cases were local recurrence in 10 and 13 months of radiation therapy and one case was local recurrence and distant metastasis in 2 months of radiation therapy. Conclusion : This hypofractionated radiation therapy schedule was feasible and effective for control of early glottic cancer But longer follow up time would be required to assess the long-term disease control and the late complication by shortening radiation therapy duration.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.313-318
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• 2019

To improve the sensitivity, a detector using a block scintillator was developed. In the pixelated scintillator, a reflector is located between pixels to move the light generated from the scintillator to the photosensor as much as possible, and sensitivity loss occurs in the reflector portion. In order to improve the sensitivity and to have the characteristics of the pixelated scintillator, the block scintillator was processed into a scintillator in pixel form through three-dimensional laser engraving. The energy spectra and energy resolution of each pixel were measured, and sensitivity analysis of block and pixel scintillator was performed through GATE simulation. The measured global energy resolution was 20.7%, and the sensitivity was 18.5% higher than that of the pixel scintillator. When this detector is applied to imaging devices such as gamma camera and positron emission tomography, it will be possible to shorten the imaging time and reduce the dose of patient by using less radiation source.

• Radiation Oncology Journal
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• v.20 no.2
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• pp.155-164
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• 2002

Purpose : A ginkgo biloba extract (GBE) has been known as a hypoxic cell radiosensitizer. Its mechanisms of action are increase of the red blood cell deformability, decrease the blood viscosity, and decrease the hypoxic cell fraction in the tumor. The aims of this study were to estimate the effect of GBE on fractionated radiotherapy and to clarify the mechanism of action of the GBE by estimating the blood flow in tumor and normal muscle. Materials and Methods : Fibrosarcoma (FSall) growing in a C3H mouse leg muscle was used as the tumor model. When the tumor size reached 7 mm in diameter, the GBE was given intraperitoneally at 1 and 25 hours prior to irradiation. The tumor growth delay was measured according to the various doses of radiation (3, 6, 9, 12 Gy and 15 Gy) and to the fractionation (single and fractionated irradiation) with and without the GBE injection. The radiation dose to the tumor the response relationships and the enhancement ratio of the GBE were measured. In addition, the blood flow of a normal muscle and a tumor was compared by laser Doppler flowmetry according to the GBE treatment. Results : When the GBE was used with single fraction irradiation with doses ranging from 3 to 12 Gy, GBE increased the tumor growth delay significantly (p<0.05) and the enhancement ratio of the GBE was 1.16. In fractionated irradiation with 3 Gy per day, the relationships between the radiation dose (D) and the tumor growth delay (TGD) were TGD $(days)=0.26{\times}D$ (Gy)+0.13 in the radiation alone group, and the TGD $(days)=0.30{\times}D$ (Gy)+0.13 in the radiation with GBE group. As a result, the enhancement ratio was 1.19 ($95\%$ confidence interval; $1.13\~1.27$). Laser Doppler flowmetry was used to measure the blood flow. The mean blood flow was higher in the muscle (7.78 mL/100 g/min in tumor and the 10.15 mL/100 g/min in muscle, p=0.005) and the low blood flow fraction (less than 2 mL/100 g/min) was higher in the tumor $(0.5\%\;vs.\;5.2\%,\;p=0.005)$. The blood flow was not changed with the GBE in normal muscle, but was increased by $23.5\%$ ( p=0.0004) in the tumor. Conclusion : Based on these results, it can be concluded that the GBE enhanced the radiation effect significantly when used with fractionated radiotherapy as well as with single fraction irradiation. Furthermore, the GBE increased the blood flow of the tumor selectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1980-1986
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• 2016

In this study, we studied the gamma-radiation effect of fiber Bragg gratings (FBGs) on the high temperature annealing condition after grating inscription using a KrF UV laser (248 nm). The FBGs were fabricated in a different annealing temperature using the same commercial Ge-doped silica core fiber (SMF-28e) and exposed to gamma-radiation up to a dose of 31 kGy at the dose rate of 115 Gy/min. The high temperature annealing procedure for grating stabilization was applied to change the radiation sensitivity of the FBGs. According to the experimental data and analysis results, the gratings that were stabilized at different temperatures at 100, 150 and $200^{\circ}C$ have clearly shown that exposure to higher temperatures increases their radiation sensitivity. The radiation-induced Bragg wavelength shift (BWS) was shown a difference of up to about a factor of two depending on the annealing temperature conditions of the gratings.