• Progress in Medical Physics
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• v.22 no.4
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• pp.198-205
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• 2011

Gamma irradiator is widely used for cell, animal experiment, irradiation for blood, dose measurement, and education. Biobeam8000 gamma irradiator (STS Steuerungstechnik &. Strahlenschutz GmbH, Braunschweig, Germany, Cs137, 81.4 TBq) that KIRAMS (Korea Institute of Radiological and Medical Science) has is a irradiation device that enables to be used in large-capacity of 7.5 L and extensive area. Cs-137 source moves range of 24 cm back-and-forth in a regular cycle in beaker for uniform irradiation and a beaker that puts a specimen like existing radiation irradiator such as Gammacell3000 rotates $360^{\circ}$ during irradiation. Precise dose information according to the location of radiation source would be needed because of the movement of radiation source, whereas radiation could be uniformly irradiated in comparison with existing gamma irradiator. In this study, dose distribution of the inside beaker located in Biomeam8000 gamma irradiator was measured using glass dosimeter, and dose evaluation and distribution regarding dose linearity and dose reproducibility were implemented based on measurement results. This aims to show guideline for efficient use of irradiator based on measurement result when doing experiment or radiation exposure.

• Progress in Medical Physics
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• v.24 no.3
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• pp.140-144
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• 2013

In this research, the glass dosimeter was calibrated to measure the standard absorbed dose of the Cs-137 irradiator and absorbed dose in a biological sample. Absorbed dose in water for Cs-137 gamma ray was determined by the IAEA TRS-277 protocol. The PTW-TM30013 ion chamber and the PTW-TM41023 water phantom were utilized for measuring absorbed dose and the value was compared with the reading from DoseAce GD-302M glass dosimeter from Asahi Techno Glass Corporation for its calibration. The uncertainty of measurement ($1{\sigma}$) of the calibrated glass dosimeter was 2.7% and this result would be applied to improve the accuracy in measurement of absorbed dose in a biological sample.

• Progress in Medical Physics
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• v.22 no.3
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• pp.124-130
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• 2011

In this study the dosimetric evaluation for a biological sample irradiated by gamma rays from Cs-137 irradiator (Gamma Irradiator, Chiyoda Technol Co., Japan) was performed for radiobiological experiment. A spherical water with a diameter of 3 cm was assumed as a biological sample. The absorbed dose were determined by the air kerma based dosimetric calculation system. The theoretical and Monte Carlo calculations (MCNPX) were performed and compared to evaluate measured air kerma and determined absorbed dose respectively. As a result of comparison with theoretical calculation, the measured air kerma was in good agreement within 3.1% at the distance of 100 and 200 cm from the source. In comparison with Monte Carlo results the determined absorbed dose along the central axis was in good agreement within 1.9% and 3.7% at 100 cm and 200 cm respectively. Although the preliminary results were obtained in this study these results were used as a basis of dosimetric evaluation for radiobiological experiment. Extended study will be performed to evaluate the dose in various conditions of biological samples.

• Progress in Medical Physics
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• v.25 no.3
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• pp.123-127
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• 2014

The Cs-137 irradiator is widely used to irradiate biological samples for radiobiological research. To obtain the accurate outcomes, correct measurements of the delivered absorbed dose to a sample is important. The IAEA protocols such as TRS-277 and TRS-398 were recommended for the Cs-137 reference dosimetry. However in TRS-398 protocol, currently known as the most practical dosimetry protocol, the quality factor ($k_{Q,Q_0}$) for Cs-137 gamma rays is not suggested. Therefore, the use of TRS-398 protocol is currently unavailable for the Cs-137 dosimetry directly. The calculation method previously introduced for high energy photon beams in radiotherapy was used for deriving the Cs-137 beam qualities ($k_{Q,Q_0}$) for the 15 commercially available farmer type ionization chambers in this study. In conclusion, $k_{Q,Q_0}$ values were ranged from 0.998 to 1.002 for Cs-137 gamma rays. These results can be used as the reference and dosimeter calibrations for Cs-137 gamma rays in the future radiobiological researches.

• Imaging Science in Dentistry
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• v.34 no.3
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• pp.137-144
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• 2004

Purpose: To investigate the effects of low dose irradiation on the calcium content and calcific nodule formation of the MC3T3-El osteoblastic cell line. Materials and Methods: Cells were irradiated with a single dose of 0.2, 0.4 and 0.6 Gy at a dose rate of 5.38 Gy/min using Cs-137 irradiator. After irradiation, the calcium content and calcific nodule formation were examined on the 1st, 2nd, 3rd and 4th week. Results: We did not find any significant difference of total calcium content after irradiation of 0.2, 0.4 and 0.6 Gy when compared with the unirradiated control group. There was no significant difference of total calcium content between 0.2, 0.4 and 0.6 Gy irradiated groups. We found an increased tendency of the calcific nodule formation after irradiation of 0.2, 0.4 and 0.6 Gy when compared with the unirradiated control group without significant difference of calcific nodule formation between 0.2, 0.4 and 0.6 Gy irradiated groups. Conclusion : The results showed an increased tendency of the calcific nodule formation after low dose irradiation. However, this tendency did not increase with the increase of irradiation dose.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.25 no.2
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• pp.343-362
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• 1995

The purpose of this study was to investigate chronic radiation effects on the basal cell of the rat tongue epithelium according to different irradiation timing. Forty-two female rats were devided into 5 experimental groups according to different irradiation timing and were irradiated single dose of 396cGy by MK cell irradiator using Cs-137. Experimental rats were sacrificed at the 2nd week, 4th week and 6th week after birth. The specimens were examined with light microscope and transmission electron microscope. The following results were obtained. 1. The first changes after irraditation were vacuoles. The vacuoles were chiefly observed in the cytoplasm, perinuclei area, and nuclei. 2. The most severe degenerative changes in the basal cell layer were observed in all experimental groups. ; cellular disarrangement, vacuole formation, widening of intercellular space, enlarged mitochondria & rER, and chromatin clumping were seen. 3. The cellular degenerative changes were most severe at the 4th week after birth in all experimental group, and the basal cell hyperplasia was seen at the 6th week in the most of experimental groups 4. The experimental groups 3 and 4 show more severe and more prolonged cellular degeneration than experimental groups 1 and 2, which were irradiated in pregnancy, and experimental group 5, which was irradiated after tongue maturation.

• The Korean Journal of Nuclear Medicine
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• v.34 no.2
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• pp.144-153
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• 2000

Purpose: The purpose of this study was to evaluate the relationship between radiation-induced activation of DNA repair genes and radiation induced apoptosis in A431 cell line. Materials and Methods: Five and 25 Gys of gamma radiation were given to A431 cells by a Cs-137 cell irradiator. Apoptosis was evaluated by flow cytometry using annexin V-fluorescein isothiocyanate and propidium iodide staining. The expression of DNA repair genes was evaluated by both Northern and Western blot analyses. Results: The number of apoptotic cells increased with the increased radiation dose. It increased most significantly at 12 hours after irradiation. Expression of p53, p21, and hRAD50 reached the highest level at 12 hours after 5 Gy irradiation. In response to 25 Gy irradiation, hRAD50 and p21 were expressed maximally at 12 hours, but p53 and GADD45 genes showed the highest expression level after 12 hours. Conclusion: Induction of apoptosis and DNA repair by ionizing radiation were closely correlated. The peak time of inducing apoptosis and DNA repair was 12 hours in this study model. hRAD50, a recently discovered DNA repair gene, was also associated with radiation-induced apoptosis.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.27 no.1
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• pp.107-122
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• 1997

Radiation sensitivity data was generated for two human cancer cell lines(KB, RPMI 2650) and human primary gingival fibroblast was tested three times using a viable cell number counting with a hemocytometer, MTT(3-[4,5-Dimethylthiazol2-yl]-2,5-diphenyl tetrazolium bromide) assay, and LDH(Lactate dehydrogenase) assay. Single irradiation of 2, 4, 6, 10, 15, 20Gy were applied to the tumor cell lines and the primary cultured gingival fibroblast The two fractions of 4Gy and 10Gy were seperated with a 4 hour time interval. The irradiation was done with 241.5cGy/min dose rate using /sup 137/Cs MK cell irradiator at room temperature. The obtained results were as followed : 1. There was significantly different viable cell numbers as the amount of radiation dose on the tested cells were cell number counted with a hemocytometer. In fractions, there were more viable cells remaining. 2. Phase-contrast microscopically, radiation-induced morphologic changes were pronounced on the tumor cells, however, almost no differences on the gingival fibroblast. 3. There was significantly different absorbance at 2Gy on RPMI 2600, 4Gy on KB and GF in MTT assay. In fractions, the absorbance was significantly higher on KB. 4. The level of extracellular LDH activity in the experimental group was significantly higher in the 2-4Gy than the control group. 5. The total level of extracellular and intracellular LDH activity was decreased as increased amounts of radiation dose was applied.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.25 no.2
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• pp.483-499
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• 1995

Mandibular first molars of the rats were undertaken to observe the radiosensitivity of amelogenesis. Twenty four Sprague-Dawley rats received 396cGy radiation with the MK Cell irradiator using Cs-137, and twenty four rats served as control. They were devided into two groups; Group 1 which received radiation at the 14th day after gestation and group 2 which received radiation at the 19th day after gestation. Light Microscopy and Transmitted Electron Microscopy investigation was undertaken in the group 1 at the 15th, 18th, 20th, 22nd(2 days after birth), and 25th day(5 days after birth) after gestation, and in the group 2 at the 21th(birth day), 22nd(2 days after birth), and 25th(5 days after birth) day after gestation. The following histopathologic findings were obtained. 1. Compared with control group, experimental group showed a delayed formation of enamel and dentin due to slow rate of differentiation of undifferentiated mesenchymal cells. 2. In the experimental groups, the arrangement of the inner enamel epithelium was irregular and there were many vacuoles in the cytoplasm. There were dilated rER and mitochondria, increase of the intercellular space, and loss of the cellular polarity. 3. In the group 1, early enamel without Tomes' process, and early organic matrix was observed at the 25th day after gestation. 4. In the group 2, histopathologic changes were similar to those of the group 1, but the degree of changes was more severe than that of the group 1.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.1
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• pp.59-71
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• 1998

The radiation-induced apoptosis was studied for two human cancer cell lines (KB cells, RPMI 2650 cells) and the human gingival fibroblast cell line (HGF-1 cells). The single irradiation of 2, 10, 20Gy was done with 241.5 cGylmin dose rate using the /sup 137/Cs MK cell irradiator. The cells were stained with propidium iodide and examined under the fluoro-microscope and assayed with the flow cytometry a day after irradiation. Also, the LDH assay was done to determine the amount of necrotic cells. The obtained results were as follows: 1. On the fluoro-microscope, many fragmented nuclei were detected in the KB, RPMI 2650, and HGF-1 cells after irradiation. 2. On the DNA content histogram obtained from the flow cytometry, the percentages of the pre-Gl peak of the control and 2, 10 and 20Gy irradiation group were 4.5, 55.0, 52.3, and 66.6％ on KB cells, 2.7, 3.3, 31.8, and 32.6％ on RPMI 2650 cells and 2.8, 21.8, 30.4, and 40.2％ on HGF-1 cells respectively. 3. The number of Gl-stage cells was abruptly decreased after 2Gy irradiation on KB cells and 10Gy irradiation on RPMI 2650 cells, But there was a slight decrease without regard to irradiation dose on HGF-1 cells. 4. There was no significantly different absorbance in extracellular LDH assay along the experimental cell lines.