• Journal of Radiation Industry
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• v.11 no.3
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• pp.131-137
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• 2017

To compare the radiation dose and image noise of low dose computed tomography (CT) and high resolution CT using the fixed tube current technique and automatic tube current modulation (CARE Dose 4D). Chest CT and human anthropomorphic phantom were used the RPL (radiophotoluminescence) dosimeters. For image evaluation, standard deviation of mean CT attenuation coefficient and CT attenuation coefficient was measured using ROI analysis function. The effective dose was calculated using CTDIvol and DLP. CARE Dose 4D was reduced by 74.7% and HRCT by 64.4% compared to the fixed tube current technique in low dose CT of chest phantom. In CTDIvol and DLP, the dose of CARE Dose 4D was reduced by fixed tube current technique. For effective dose, CARE Dose 4D was reduced by 47% and HRCT by 46.9% compared to the fixed tube current method, and the dose of CARE Dose 4D was significantly different (p<.05). Noise in the image was higher than that in the fixed tube current technique. Noise difference in the image of CARE Dose 4D in low dose CT was significant (p<.05). The low radiation dose and the noise difference of the CARE Dose 4D were compared with the fixed tube current technique in low dose CT and HRCT using chest phantom. The radiation doses using CARE Dose 4D were in accordance with the national and international dose standards. CARE Dose 4D should be applied to low dose CT and HRCT for clinical examination.

• Korean Journal of Environmental Biology
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• v.18 no.2
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• pp.247-253
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• 2000

In order to investigate the stimulatory effect(hormesis) of low dose gamma-radiation on the seeding growth of old seeds with respect to antioxidant defense systems, various doses of gamma radiation to the 5-year-old dried seeds of Chinese cabbage (Brassica campestris L. cv Sulin eockaei). Compared to the new, 1-year- old seeds, old seeds irradiated by low does gamma radiation in the range of 1-2 Gy showed vigor growth as revealed by statistically significant increases both in the germination rates and the leaf size and fresh weight. Further, seedlings grown from seeds treated by low dose gamma radiation showed higher peroxidase and catalase activities than non-treated seedlings. These results suggest that the antioxidant defense systems could be closely related to the stimulatory effects of low dose radiation. [antioxidant enzyme, chinese cabbage, gamma radiation, germination rate, hormesis]

• Journal of Radiation Protection and Research
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• v.38 no.4
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• pp.166-171
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• 2013

While high-dose ionizing radiation results in long term cellular cytotoxicity, chronic low-dose (<0.2 Gy) of X- or ${\gamma}$-ray irradiation can be beneficial to living organisms by inducing radiation hormesis, stimulating immune function, and adaptive responses. During chronic low-dose-rate radiation (LDR) exposure, whole body of mice is exposed to radiation, however, it remains unclear if LDR causes changes in gene expression of the whole brain. Therefore, we aim to investigate expressed genes (EGs) and signaling pathways specifically regulated by LDR-irradiation ($^{137}Cs$, a cumulative dose of 1.7 Gy for total 100 days) in the whole brain. Using microarray analysis of whole brain RNA extracts harvested from ICR and AKR/J mice after LDR-irradiation, we discovered that two mice strains displayed distinct gene regulation patterns upon LDR-irradiation. In ICR mice, genes involved in ion transport, transition metal ion transport, and developmental cell growth were turned on while, in AKR/J mice, genes involved in sensory perception, cognition, olfactory transduction, G-protein coupled receptor pathways, inflammatory response, proteolysis, and base excision repair were found to be affected by LDR. We validated LDR-sensitive EGs by qPCR and confirmed specific upregulation of S100a7a, Olfr624, and Gm4868 genes in AKR/J mice whole brain. Therefore, our data provide the first report of genetic changes regulated by LDR in the mouse whole brain, which may affect several aspects of brain function.

• Korean Journal of Environmental Biology
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• v.19 no.1
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• pp.71-77
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• 2001

Pepper (Capsicum annuum L. cv. Jokwang and cv. Johong) seeds were irradiated with the doses of 0-50 Gy to investigate the effect of the low dose ${\gamma}$-radiation on the early growth and resistance to subsequent high dose of radiation. Following effect was observed in Johong cultivar but not in Jokwang cultivar Germination and early growth rate of Johong cultivar were noticeably increased at 4, 8 and 20 Gy irradiation group. Resistance to subsequent high dose of radiation of Johong cultivar increased at almost all of the low dose irradiation group. Especially it was highest at 4 Gy irradiation group. Plant groups of Johong cultivar showing the resistance to subsequent high dose of radiation, which had been pre-irradiated with 4 Gy and 8 Gy, were also higher in the carotenoid contents and enzyme activity than the plant group not irradiated previously.

• 대한방사선방어학회:학술대회논문집
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• 2010.04a
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• pp.48-51
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• 2010

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.4
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• pp.1773-1777
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• 2016

Diagnostic and therapeutic radiation fields are planned so as to reduce side-effects while maximising the dose to site but effects on healthy tissues are inevitable. Radiation causes strand breaks in DNA of exposed cells which can lead to chromosomal aberrations and cause malfunction and cell death. Several researchers have highlighted the damaging effects of high dose radiation but still there is a lacuna in identifying damage due to low dose radiation used for diagnostic purposes. Blood is an easy resource to study genotoxicity and to estimate the effects of radiation. The micronucleus assay and chromosomal aberration can indicate genetic damage and our present aim was to establish these with lymphocytes in an in vitro model to predict the immediate effects low dose radiation. Blood was collected from healthy individuals and divided into 6 groups with increasing radiation dose i.e., 0Gy, 0.10Gy, 0.25Gy, 0.50Gy, 1Gy and 2Gy. The samples were irradiated in duplicates using a LINAC in the radiation oncology department. Standard protocols were applied for chromosomal aberration and micronucleus assays. Metaphases were stained in Giemsa and 200 were scored per sample for the detection of dicentric or acentric forms. For micronuclei detection, 200 metaphases. Giemsa stained binucleate cells per sample were analysed for any abnormality. The micronuclei (MN) frequency was increased in cells exposed to the entire range of doses (0.1-2Gy) delivered. Controls showed minimal MN formation ($2.0%{\pm}0.05$) with triple MN ($5.6%{\pm}2.0$) frequency at the lowest dose. MN formation increased exponentially with the radiation dose thereafter with a maximum at 2Gy. Significantly elevated numbers of dicentric chromosomes were also observed, even at doses of 0.1-0.5Gy, compared to controls, and acentric chromosomes were apparent at 2Gy. In conclusion we can state that lymphocytes can be effectively used to study direct effect of low dose radiation.

• Archives of Pharmacal Research
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• v.20 no.3
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• pp.212-217
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• 1997

Induction of an adaptive response to ionizing radiation in mouse lymphoma (EL4) cells was studied by using cell survival fraction and apoptotic nucleosomal DNA fragmentation as biological end points. Cells in early log phase were pre-exposed to low dose of ${\gamma}$-rays (0.01 Gy) 4 or 20 hrs prior to high dose ${\gamma}$-ray (4, 8 and 12 Gy for cell survival fraction analysis; 8 Gy for DNA fragmentation analysis) irradiation. Then cell survival fractions and the extent of DNA fragmentation were measured. Significant adaptive response, increase in cell survival fraction and decrease in the extent of DNA fragmentation were induced when low and high dose .gamma.-ray irradiation time interval was 4 hr. Addition of protein or RNA synthesis inhibitor, cycloheximide or 5,6-dichloro-1-.betha.-d-ribofuranosylbenzimidazole (DRFB), respectively during adaptation period, the period from low dose ${\gamma}$-ray irradiation to high dose ${\gamma}$-ray irradiation, was able to inhibit the induction of adaptive response, which is the reduction of the extent DNA fragmentation in irradiated EL4 cells. These data suggest that the induction of adaptive response to ionizing radiation in EL4 cells required both protein and RNA synthesis.

• ETRI Journal
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• v.27 no.4
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• pp.449-452
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• 2005

The electrical characteristics of solid state devices such as the bipolar junction transistor (BJT), metal-oxide semiconductor field-effect transistor (MOSFET), and other active devices are altered by impinging photon radiation and temperature in the space environment. In this paper, the threshold voltage, the breakdown voltage, and the on-resistance for two kinds of MOSFETs (200 V and 100 V of $V_{DSS}$) are tested for ${\gamma}-irradiation$ and compared with the electrical specifications under the pre- and post-irradiation low dose rates of 4.97 and 9.55 rad/s as well as at a maximum total dose of 30 krad. In our experiment, the ${\gamma}-radiation$ facility using a low dose, available at Korea Atomic Energy Research Institute (KAERI), has been applied on two commercially available International Rectifier (IR) products, IRFP250 and IRF540.

• Journal of Radiation Protection and Research
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• v.20 no.2
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• pp.97-102
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• 1995

Adaptive response induced by low dose ${\gamma}-ray$ irradiation in human peripheral lymphocytes was examimed. Human lymphocytes were exposured to low dose of ${\gamma}-ray$ (priming dose, 0.01Gy) followed by high dose (challenging dose, 1.5Gy) after various time intervals (4, 7, 20 hours). Frequencies of micronuclei were enumerated in both primed and unprimed groups. Maximum reduction in frequency of micronuclei was observed when challenging dose irradiation was followed by priming dose after 4hr incubation period. When challenging doses were irradiated 7 or 20hr after priming dose, frequencies of micronuclei were reduced slighty. However, these reduction were not statistically significant. In this study, human peripheral lymphocytes were irradiated at Go phase and they showed adaptive response induced by low dose radiation. Since micronucleus assay is relatively simpler and faster than other methods, it may be a good tool for evaluating radiation-induced adaptive responses.

• Journal of Radiation Protection and Research
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• v.31 no.2
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• pp.53-63
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• 2006

The increased risk of cancer with exposure to low-dose radiation was estimated through longitudinal study for radiation workers at the nuclear power plants in Korea. The radiation dose data were collected from the Radiation Safety Management System(RSMS) of the Korea Hydro & Nuclear Power Co., Ltd(KHNP). The cancer risks with radiation exposure were evaluated in terms of relative mortality ratios(RMR) and relative incidence ratios(RIR) to the unexposed employees at the nuclear power plants, and of the standardized mortality ratios(SMR) and standardized incidence ratios(SIR). There were no significant increases of canters of all sites in the exposed group either in RIR[1.08, 95% confidence interval(CI) 0.74-1.58] or in RMR[1.21, CI 0.70-2.08]. Neither SIR[0.81, CI 0.28-0.96] nor SMR[0.86, CI 0.66-1.10] significantly deviated from 1.0 for cancers of all sites. The trend analysis did not identify evident dose-response relationship due to insufficient numbers of the cases. Consequently, it is concluded that increases in cancer risks in the radiation worker group exposed to low doses at the nuclear power plants in Korea are not identified at this time.