• Journal of Radiation Protection and Research
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• v.48 no.2
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• pp.59-67
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• 2023

Background: This study aims to reevaluate natural radiation exposure, following up on our previous study conducted in 2019, and to assess the associated risk of lung cancer to the public residing in the gold mining areas of Betare-Oya, east Cameroon, and its vicinity. Materials and Methods: Gamma-ray spectra collected using a 7.62 cm×7.62 cm in NaI(Tl) scintillation spectrometer during a car-borne survey, in situ measurements and laboratory measurements performed in previous studies were used to determine the outdoor absorbed dose rate in air to evaluate the annual external dose inhaled by the public. For determining internal exposure, radon gas concentrations were measured and used to estimate the inhalation dose while considering the inhalation of radon and its decay products. Results and Discussion: The mean value of the laboratory-measured outdoor gamma dose rate was 47 nGy/hr, which agrees with our previous results (44 nGy/hr) recorded through direct measurements (in situ and car-borne survey). The resulting annual external dose (0.29±0.09 mSv/yr) obtained is similar to that of the previous study (0.33±0.03 mSv/yr). The total inhalation dose resulting from radon isotopes and their decay products ranged between 1.96 and 9.63 mSv/yr with an arithmetic mean of 3.95±1.65 mSv/yr. The resulting excess lung cancer risk was estimated; it ranged from 62 to 216 excess deaths per million persons per year (MPY), 81 to 243 excess deaths per MPY, or 135 excess deaths per MPY, based on whether risk factors reported by the U.S. Environmental Protection Agency, United Nations Scientific Committee on the effects of Atomic Radiation, or International Commission on Radiological Protection were used, respectively. These values are more than double the world average values reported by the same agencies. Conclusion: There is an elevated level of risk of lung cancer from indoor radon in locations close to the Betare-Oya gold mining region in east Cameroon. Therefore, educating the public on the harmful effects of radon exposure and considering some remedial actions for protection against radon and its progenies is necessary.

• Journal of Radiation Protection and Research
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• v.23 no.4
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• pp.211-218
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• 1998

The distributional effects of radioactive materials on external gamma exposure have been analyzed. An approximate method for estimating external gamma dose given from an arbitrary distribution of radioactive material has been developed. The minimum gamma exposure given from a point source is shown at 0.07 MeV if the source to receptor distance is shorter than 10 m. But if the receptor to point source distance is longer than 20 m, gamma exposure rate increases monotonously according to the average gamma energy. For the analysis of the effects of volume source, we estimated the gamma dose given from different size of hemisphere in which radioactive materials are distributed uniformly. When the radius of hemisphere is longer than 40 m, external gamma dose rate increases monotonously. The gamma dose rate given from the radioactive materials deposited on the ground shows the minimum value at 0.07 MeV in any case. The analysis shows that external gamma exposure is strongly dependent on the distribution of radioactive materials in the environment and gamma energy.

• Journal of Radiation Protection and Research
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• v.19 no.3
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• pp.209-221
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• 1994

In the case of a severe accident of a nuclear power plant, the whole body dose and the relative importance of the radionuclides during the lifetime of an exposed person were estimated for each exposure pathway with distances from the release point. The external exposure pathways due to immersion of radioactive cloud and deposition of radioactive materials on the ground, and the internal exposure pathways due to inhalation and ingestion of contaminated foodstuffs were considered. The effects due to the ingestion of contaminated foodstuffs were estimated considering the variation of radioactive concentration in the foodstuffs according to deposition time and elapsed time after deposition using a dynamic ingestion pathway model applicable to Korean environment, named 'KORFOOD'. As the results up to 80 km from the release point, the effects due to ingestion of contaminated foodstuffs showed the highest contribution to total exposure dose. The contribution of I isotopes was the highest in the case of the external dose due to immersion of radioactive cloud and internal dose due to inhalation. The contribution of Cs isotopes was highest in the case of the external dose due to deposition of radioactive materials on the ground. In the case of the internal dose due to ingestion of contaminated foodstuffs, Cs deposition in summer and Sr deposition in winter, respectively, were the most dominant radionuclide to whole body.

• Radiation Oncology Journal
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• v.1 no.1
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• pp.103-109
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• 1983

47 out of 56 cases of intact uterine cervix cancer treated by radiation at the Hanyang University Hospital were followed 18 months or more after treatment. (7 patients died before 18 months, 2 cases lost to follow-up). Age distribution reveal 5 cases in 30's, 18 cases in 40's, 17 cases in 50's, 7 cases in 60's. Histologically, all cases were squamous cell type except one case of adenocarcinoma. 1. 45 cases were treated by combined external Co-60 irradiation and intracavitary irradiation by Cs-137 small sources. 1 case was treated by external irradiation only, and 1 case by intracavitary only. 2. Rectal injuries were observed in 13 cased (27.6%), 4 cases in Grade 1, 8 cased in Grade 2 and 1 cases in Grade 3 which needed surgical management. 3. Average intervals of rectal injury following treatment was 9.2 months varying from 5 to 15 months. 4. Relation between rectal injury and point A dose reveal 6 cases between 7000-7999 rad and 6 cases between 8000-8999 rad and 1 case above 9000 rad. Even though there is no direct relation between point A dose and rectal injury, it is expected that rectal injury increases as point A dose increase. 5. In the normal condition, rectal injury can't be attributed to one major cause. Radiation dose, small source distribution, general condition of patients, local anatomy of the individual patient, history of PID and previous surgery, all play complex roles.

• The Journal of Korean Society for Radiation Therapy
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• v.14 no.1
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• pp.175-186
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• 2002

The purpose of this study is directly measure and evaluate about absorbed dose change according to nominal energy and electron cone or medical accelerator on isodose curve, percentage depth dose, contaminated X-ray, inhomogeneous tissue, oblique surface and irradiation on intracavitary that electron beam with high energy distributed in tissue, and it settled standard data of hish energy electron beam treatment, and offer to exactly data for new dote distribution modeling study based on experimental resuls and theory. Electron beam with hish energy of $6{\sim}20$ MeV is used that generated from medical linear accelerator (Clinac 2100C/D, Varian) for the experiment, andwater phantom and Farmer chamber md Markus chamber und for absorbe d dose measurement of electron beam, and standard absorbed dose is calculated by standard measurements of International Atomic Energy Agency(IAEA) TRS 277. Dose analyzer (700i dose distribution analyzer, Wellhofer), film (X-OmatV, Kodak), external cone, intracavitary cone, cork, animal compact bone and air were used for don distribution measurement. As the results of absorbed dose ratio increased while irradiation field was increased, it appeared maximum at some irradiation field size and decreased though irradiation field size was more increased, and it decreased greatly while energy of electron beam was increased, and scattered dose on wall of electron cone was the cause. In percentage depth dose curve of electron beam, Effective depth dose(R80) for nominal energy of 6, 9, 12, 16 and 20 MeV are 1.85, 2.93, 4.07, 5.37 and 6.53 cm respectively, which seems to be one third of electron beam energy (MeV). Contaminated X-ray was generated from interaction between electron beam with high energy and material, and it was about $0.3{\sim}2.3\%$ of maximum dose and increased with increasing energy. Change of depth dose ratio of electron beam was compared with theory by Monte Carlo simulation, and calculation and measured value by Pencil beam model reciprocally, and percentage depth dose and measured value by Pencil beam were agreed almost, however, there were a little lack on build up area and error increased in pendulum and multi treatment since there was no contaminated X-ray part. Percentage depth dose calculated by Monte Carlo simulation appeared to be less from all part except maximum dose area from the curve. The change of percentage depth dose by inhomogeneous tissue, maximum range after penetration the 1 cm bone was moved 1 cm toward to surface then polystyrene phantom. In case of 1 cm and 2 cm cork, it was moved 0.5 cm and 1 cm toward to depth, respectively. In case of air, practical range was extended toward depth without energy loss. Irradiation on intracavitary is using straight and beveled type cones of 2.5, 3.0, 3.5 $cm{\phi}$, and maximum and effective $80\%$ dose depth increases while electron beam energy and size of electron cone increase. In case of contaminated X-ray, as the energy increase, straight type cones were more highly appeared then beveled type. The output factor of intracavitary small field electron cone was $15{\sim}86\%$ of standard external electron cone($15{\times}15cm^2$) and straight type was slightly higher then beveled type.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.566-570
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• 1997

The effect of average gamma energy on the external radiation dose has been analyzed. Cloud- and groundshine have been calculated according to the average gamma energy. Monte Carlo integration method was used for the calculation of cloudshine and Romberg quadrature method was adopted for groundshine. The analysis shows that the external gamma exposure is strong]y dependent on the gamma energy and the distribution of radiation sources.

• Journal of Radiation Protection and Research
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• v.41 no.1
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• pp.1-6
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• 2016

Background: It is very difficult to set a regulatory guidance or criteria for the protection of non-human species from the ionizing radiation, because there are no generally or internationally accepted methods for demonstrating the compliance with such criteria. It is needed that Korea develop the primary dose rate standards for the protection of both aquatic and terrestrial biota in the near future. Materials and Methods: The potential dose rates due to both external and internal radiation exposures to marine organisms such as plaice/flounder, gray mullet, and brown seaweed collected within territorial seas around the Korean Peninsula were estimated. Results and Discussion: The total dose rates to plaice/flounder, gray mullet and brown seaweed due to $^{40}K$, a primordial radionuclide in marine environment, were found to be 0.2%, 0.08% and 0.3% of approximately the values of the Derived Consideration Reference Levels (DCRLs, i.e. $1-10mGy{\cdot}d^{-1}$), respectively, as suggested by the International Commission on Radiological Protection (ICRP) publication 124. The total dose rates to marine fishes and brown seaweed due to anthropogenic radionuclides such as $^{90}Sr$, $^{137}Cs$ and $^{239+240}Pu$ were considered to be negligible compared to the total dose rate due to $^{40}K$. The external exposure to benthic fish due to all radionuclides was much higher than that of pelagic fish. Conclusion: From this study, it is recommended that the further study is required to develop a national regulatory guidance for the evaluation of doses to non-human species.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.843-852
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• 2019

In the present study, we established a comprehensive dataset of dose coefficients (DCs) of the new meshtype ICRP reference computational phantoms (MRCPs) for idealized external exposures of photons and electrons with the Geant4 code. Subsequently, the DCs for the nine organs/tissues, calculated for their thin radiosensitive target regions, were compared with the values calculated by averaging the absorbed doses over the entire organ/tissue regions to observe the influence of the thin sensitive regions on dose calculations. The result showed that the influences for both photons and electrons were generally insignificant for the majority of organs/tissues, but very large for the skin and eye lens, especially for electrons. Furthermore, the large influence for the skin eventually affected the effective dose calculations for electrons. The DCs of the MRCPs also were compared with the current ICRP-116 values produced with the current ICRP-110 reference phantoms. The result showed that the DCs for the majority of organs/ tissues and effective dose were generally similar to the ICRP-116 values for photons, except for very low energies; however, for electrons, significant differences from the ICRP-116 values were found in the DCs, particularly for superficial organs/tissues and skeletal tissues, and also for effective dose.

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.1949-1958
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• 2023

The International Commission on Radiological Protection (ICRP) Publication 116 was released to provide a comprehensive dataset of the dose coefficients (DCs) for external exposures produced with the adult reference voxel phantoms of ICRP Publication 110. Although an advanced skeletal dosimetry method for photons and neutrons using fluence-to-dose response functions (DRFs) was introduced in ICRP Publication 116, the ICRP-116 skeletal DCs were calculated by using the simple method conventionally used (i.e., doses to red bone marrow and endosteum approximated by doses to spongiosa and/or medullary cavities). In the present study, the photon and neutron DRFs were used to produce skeletal DCs of the ICRP-110 reference phantoms, which were then compared with the ICRP-116 DCs. For photons, there were significant differences by up to ~2.8 times especially at energies <0.3 MeV. For neutrons, the differences were generally small over the entire energy region (mostly <20%). The general impact of the DRF-based skeletal DCs on the effective dose calculations was negligibly small, supporting the validity of the ICRP-116 effective DCs despite their skeletal DCs derived from the simple method. Meanwhile, we believe that the DRF-based skeletal DCs could be beneficial in better estimates of skeletal doses of individuals for risk assessments.

• The Journal of the Korea Contents Association
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• v.13 no.12
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• pp.860-868
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• 2013

The purpose of this study is to ensure safety by measuring External radiation dose ratio (ERDR) by traits of patients in many ways after administering radiopharmaceutical($^{18}F$-FDG) for PET Torso scan, and to decrease ERDR of those to RI technologist, caretakers, and those who frequently exposed to radiation by arousing attention to radiation dose. Radiopharmaceutical was administered to 80 patients who conducted PET Torso from January to June, 2013. Radiation dose emitted from the patients was measured according to body shape(BMI), water hydration, height, amount of radiation administration. From the moment immediately after the radiopharmaceutical was administered, ERDR was measured by personal traits of patients. The radiation dose increased in proportion to the administered amount of the radiopharmaceutical, and there was no significant difference depending on the body shape of the patients. When water was supplied and the height was normal, the radiation dose was lower compared with the cases where water was not supplied and height was not normal. There is a need for making efforts to minimize the working time through sufficient education and mock training before those who RI technologist with sources of radiation for complying the radiation safety management rule. And they should minimize the ERDR by wearing a protective gear.