• Radiation Oncology Journal
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• v.16 no.4
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• pp.517-529
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• 1998

Purpose : Although many studies have investigated the dosimetric aspects of stereotactic radiosurgery in terms of target volume, the absorbed doses at extracranial sites: especially the lens or thyroid - which are sensitive to radiation for deterministic or stochastic effect -have infrequently been reported. The aim of this study is to evaluate what effects the parameters of radiosurgery have on the absorbed doses of the lens and thyroid in patients treated by stereotactic radiosurgery, using a systematic plan in a humanoid phantom. Materials and Methods : Six isocenters were selected and radiosurgery was planned using the stereotactic radiosurgery system which the Department of Therapeutic Radiology at Seoul National University College of Medicine developed. The experimental radiosurgery plan consisted of 6 arc planes per one isocenter, 100 degrees for each arc range and an accessory collimator diameter size of 2 cm. After 250 cGy of irradiation from each arc, the doses absorbed at the lens and thyroid were measured by thermoluminescence dosimetry. Results : The lens dose was 0.23$\pm$0.08$\%$ of the maximum dose for each isocenter when the exit beam did not pass through the lens and was 0.76$\pm$0.12$\%$ of the maximum dose for each isocenter when the exit beam passed through the lens. The thyroid dose was 0.18$\pm$0.05$\%$ of the maximum dose for each isocenter when the exit beam did not pass through the thyroid and was 0.41$\pm$0.04$\%$ of the maximum dose for each isocenter when the exit beam Passed through the thyroid. The passing of the exit beam is the most significant factor of organ dose and the absorbed dose by an arc crossing organ decides 80$\%$ of the total dose. The absorbed doses of the lens and thyroid were larger as the isocenter sites and arc planes were closer to each organ. There were no differences in the doses at the surface and 5 mm depth from the surface in the eyelid and thyroid areas. Conclusion : As the isocenter and arc plane were placed closer to the lens and thyroid, the doses increased. Whether the exit beams passed through the lens or thyroid greatly influenced the lens and thyroid dose. The surface dose of the lens and thyroid consistently represent the tissue dose. Even when the exit beam passes through the lens and thyroid, the doses are less than 1$\%$ of the maximum dose and therefore, are too low to evoke late complications, but nevertheless, we should try to minimize the thyroid dose in children, whenever possible.

• Journal of Radiation Protection and Research
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• v.40 no.4
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• pp.244-251
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• 2015

The containment filtered venting system reduces the range of the contamination area around the nuclear power plant by strengthening the integrity of the containment building. In this study, the probabilistic assessment code MACCS2 was used to assess the effect of the CFVS to off-site. The accident source term was selected from a Probabilistic Safety Analysis report of SHINKORI 1&2 Nuclear Power Plant. The three source term categories from 19 STC were chosen to evaluate the effective dose and thyroid dose of residents around the power plant and the dose with CFVS and without CFVS were compared. The dose was calculated according to the distance from the nuclear power plant, so the damage scale based on the distance that exceeds the IAEA criteria for effective dose (100 mSv per 7 days) and thyroid dose (50 mSv per 7 days) were compared. The effective dose reduction rates of the STC-3, STC-4, STC-6 were about 95-99% in the whole range (0~35 km), 96-98% for the thyroid dose. There are similar results between effective dose and thyroid dose. After applying the CFVS, the damage scale that exceeds the effective dose criteria was about 1 km (mean). Especially, the STC-4 damage scale was decreased from 26 km (mean) to 1.2 km (mean) significantly. The damage scale that exceed the thyroid dose criteria was decreased to 2~3 km (mean). The STC-4 damage scale was also decreased significantly as compared to STC-3, STC-6 in terms of effective dose.

• Journal of the Korean Society of Radiology
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• v.13 no.6
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• pp.889-894
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• 2019

Upper gastrointestinal series is an examination that uses X-rays. It is important to defend against exposure to radiation during upper gastrointestinal examination because the organs, such as thyroid gland, lens, breasts, and gonads, with relatively high biological sensitivity to radiation are distributed on the examination area. We have made a whole body phantom that can change the depth of organs. radiation dose of eye, thyroid gland, breast and gonads were measured by the same procedure as the actual upper gastrointestinal examination. When performed only fluoroscopy the mean dose reduction of lens, thyroid gland, breast and gonads was 62.2%. The mean dose reduction of lens, thyroid gland, breast and gonads was 59.0% when both fluoroscopy and spot shoot were performed. Therefore, when performed upper gastrointestinal examination it was confirmed that shielding of the lens, thyroid gland, breast and gonads was effective in decreasing the exposure dose. The manufactured human phantom can be used in measuring radiation dose for deep organ because it can adjust the height corresponding to the organs located in the human body.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.265-272
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• 2014

Purpose : To reduce the radiation dose to the thyroid that is affected to scattered radiation, the shield was used. And we evaluated the shielding effect for the thyroid during whole brain radiation therapy. Materials and Methods : To measure the dose of the thyroid, 300cGy were delivered to the phantom using a linear accelerator(Clinac iX VARIAN, USA.)in the way of the 6MV X-ray in bilateral. To measure the entrance surface dose of the thyroid, five glass dosimeters were placed in the 10th slice's surface of the phantom with a 1.5 cm interval. The average values were calculated by measured values in five times each, using bismuth shield, 0.5 mmPb shield, self-made 1.0 mmPb shield and unshield. In the same location, to measure the depth dose of the thyroid, five glass dosimeters were placed in the 10th slice by 2.5 cm depth of the phantom with a 1.5 cm interval. The average values were calculated by measured values in five times each, using bismuth shield, 0.5 mmPb shield, self-made 1.0 mmPb shield and unshield. Results : Entrance surface dose of the thyroid were respectively 44.89 mGy at the unshield, 36.03 mGy at the bismuth shield, 31.03 mGy at the 0.5 mmPb shield and 23.21 mGy at a self-made 1.0 mmPb shield. In addition, the depth dose of the thyroid were respectively 36.10 mGy at the unshield, 34.52 mGy at the bismuth shield, 32.28 mGy at the 0.5 mmPb shield and 25.50 mGy at a self-made 1.0 mmPb shield. Conclusion : The thyroid was affected by the secondary scattering dose and leakage dose outside of the radiation field during whole brain radiation therapy. When using a shield in the thyroid, the depth dose of thyroid showed 11~30% reduction effect and the surface dose of thyroid showed 20~48% reduction effect. Therefore, by using the thyroid shield, it is considered to effectively protect the thyroid and can perform the treatment.

• Journal of radiological science and technology
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• v.28 no.2
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• pp.117-122
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• 2005

According to the Para. 5 of Art 2 of the Korean Nuclear Safety Regulations, which was revised in 1999, internal dose assessment as well as external one should be performed by law for employees at a nuclear power plant from 2003, and their estimate errors should also be within 50%. Thus, more accurate internal dosimetry becomes important. Corresponding to such regulation revision, we are developing a more accurate thyroid-uptake internal dosimetric system and have developed a Monte Carlo simulation code, the so-called CALEFF, to calculate the detection efficiency of the dosimetric system. In this paper, we calculated detection efficiencies with various test conditions by using the CALEFF code and discussed their characteristics. We may use the detection efficiency calculated by the code in calibrating the thyroid internal dose from measured data.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.1118-1123
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• 2009

Ten hospitals from the Gwangju area were used to examine shallow dose to eyes and thyroid from panoramagraphy. Thermoluminescent dosimeter (TLD) and Photoluminescent dosimeter (PLD) were used as measurement devices at each hospital. ICRP 60 and ICRP 73 set standards for acceptability for eyes at 15mSv and thyroid at 1mSv per year. Left eye measures with TLD and PLD resulted in 0.19mSv and 0.24mSv respectively. Right eye measures with TLD and PLD resulted in 0.23mSv and 0.25mSv respectively. Thyroid measures with TLD and PLD resulted in 0.08mSv and 0.25mSv respectively with both measures not exceeding standards for acceptance. There was a significant difference in comparing the left eye and thyroid for TLD and PLD (p<0.01). There was no significant difference with the right eye (p>0.05). The absorbed dose measurements for eyes and thyroid using TLD and PLD in regards to panorama devices at each hospital were within the ICRP 60 recommendations; however, with the possibility of stochastic effect, all dose levels were taken into consideration.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2278-2284
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• 2012

Exposure-dose reducing effect was measured by using bolus, a tissue-equivalent material as a shield to obtain useful diagnostic images while minimizing the radiation exposure of thyroid which is highly sensitive to radiation during panoramic radiography. The experiment was performed within the period of 1 June 2001 through 30 June 2011 by measuring entrance surface dose and deep dose at the thyroid-corresponding site of a head and neck phantom. As a result, the entrance surface dose in the thyroid for using no shield was 43.84 ${\mu}Gy$ on the average, and the thyroid shield of bolus 10 mm in thickness reduced the dose by 15.45 ${\mu}Gy$(35.24%) to 28.39 ${\mu}Gy$ on the average. The use of a 20 mm thyroid shield resulted in the dose of 25.38 ${\mu}Gy$ on the average, a 18.46 ${\mu}Gy$(42.10%) drop from 43.84 ${\mu}Gy$ for using no shield. On the site 20 mm below the surface, a thyroid shield 10 mm in thickness had no dose-reducing effect, while a 20 mm thyroid shield reduced the dose by 0.06 mSv(20%).

• Progress in Medical Physics
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• v.18 no.4
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• pp.187-193
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• 2007

In an effort to assess the internal absorbed dose of radionuclides that is suitable to Koreans' physiological characteristics, we asked 28 male Koreans to take $^{131}|$ orally, determined the thyroidal uptake and daily urination ratio, and assessed the absorbed dose by organ. As a result, first, 24 hours after administering, the average thyroidal uptake and the daily urination ratio registered 19.70% and 71.12%, respectively. Second, the whole body effective dose according to the thyroidal uptake calculated herein and the existing ICRP-suggested thyroidal uptake of 30% offered 1.464E-08 Sv and 2.189E-08 Sv, respectively, showing a 1.5 times difference. To evaluate the quantity of the absorbed dose of radioactive iodine, we can better reduce the error in assessing the body exposure dose by conducting measurement according to human races rather than depending on the existing ICRP data.

• Journal of Radiation Protection and Research
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• v.19 no.1
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• pp.69-80
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• 1994

The TCMI(Three-Compartment Model for iodine) computer code has been developed, which is based on the three-compartment model and the respiratory model recommended in ICRP publication 54. This code is able to evaluate the thyroid burden, dose equivalent, committed dose equivalent and urinary excretion rate as time-dependent functions from the input data: working time and the radioiodine concentration in air. Using the TCMI code, the time-dependent thyroid burdens, the thyroid doses and the urinary excretion rates were calculated for three specific exposure patterns : acute, chronic and periodic. Applicability as an internal dose evaluation method has been assessed by comparing the results with some operational experiences. Simple equations and tables are provided to be used in the evaluation of the thyroid burden and the resulting doses for given I-131 concentration in air and the working time.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.147-151
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• 2019

In chest and abdomen CT scans, the radiation exposure doses by scattering lines were measured at the eyeball and thyroid. Radiation exposure was investigated by using shielding devices. The chest and abdomen CT scan protocols used in the real examination were applied to measure and compare radiation doses before and after the use of shielding devices at the eyeball and the thyroid. The radiaton doses were measured with OSLD dosimeters. Barium, tungsten sheets, goggles and neck shields were used to protect the scattered X-ray. The chest CT scans showed respectively 3.01 mSv and 6.21 mSv at the eyeball and the thyroid by the scattered X-ray. The abdomen CT scans showed 0.55 mSv and 3.22 mSv for the eyeball and the thyroid respectively. Barium and tungsten sheets had 11% to 13% protection rates at the eyeball and the thyroid for chest CT scan, and 34% to 49% reduction in radiation dose for the abdomen CT scan. Because of the significant radiation dose, which causes cataracts and thyroid cancer by the repeated and continuous radiation exposure, for the chest and the abdomen CT scans, it is required to use shielding devices to reduce radiation dose for examinations.