• 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.

• Journal of radiological science and technology
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• v.44 no.4
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• pp.301-306
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• 2021

The skull has peripheral organs such as the crystalline lens and thyroid gland, which are highly radiosensitive, but the examination is performed without considering the uneven dose distribution due to the heel effect at the time of the current Skull Town's examination. However, no studies have been conducted on the exposure dose of surrounding organ tissues due to the difference in image density due to the heel effect and the non-uniformity of the dose. Using the cathode (-) and anode (+) set on the Tube to measure the scattered radiation along the Tube direction as a guide, change 30° and 37° in the cathode direction and 30° and 37° in the anode direction. It was given and investigated 5 times to obtain scattered radiation. image measurements were SNR, PSNR, RMSE, and MAE. Measurement results Measurement results of surrounding organ doses when the Tube direction was 30° and 37° The dose was low when the direction was cathodic in all organs (p<0.000). Both cathodes were higher in the image measurements(p<0.04). Continuous research may be needed for diagnostically valuable imaging and minimization of patient exposure dose.

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4698-4707
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• 2022

As part of the ICRP Task Group 103 project, we developed ten thyroid models for the pediatric mesh-type reference computational phantoms (MRCPs). The thyroid is not only a radiosensitive target organ needed for effective dose calculation but an important source region particularly for radioactive iodines. The thyroid models for the pediatric MRCPs were constructed by converting those of the pediatric voxel-type reference computational phantoms (VRCPs) in ICRP Publication 143 to a high-quality mesh format, faithfully maintaining their original topology. At the same time, we improved several anatomical parameters of the thyroid models for the pediatric MRCPs, including the mass, overlying tissue thickness, location, and isthmus dimensions. Absorbed doses to the thyroid for the pediatric MRCPs for photon external exposures were calculated and compared with those of the pediatric VRCPs, finding that the differences between the MRCPs and VRCPs were not significant except for very low energies (<0.03 MeV). Specific absorbed fractions (target ⟵ thyroid) for photon internal exposures were also compared, where significant differences were frequently observed especially for the target organs/tissues close to the thyroid (e.g., a factor of ~1.2-~327 for the thymus as a target) due mainly to anatomical improvement of the MRCP thyroid models.

• Radiation Oncology Journal
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• v.24 no.2
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• pp.128-137
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• 2006

Purpose: We investigated whether a relationship exists between tumor control dose 50 ($TCD_{50}$) or tumor growth delay (TGD) and radiation induced apoptosis (RIA) in syngeneic murine tumors. Also we investigated the biological markers that can predict radiosensitivity in murine tumor system through analysis of relationship between $TCD_{50}$, TGD, RIA and constitutive expression levels of the genetic products regulating RIA. Materials and Methods: Syngeneic murine tumors such as ovarian adenocarcinoma, mammary carcinoma, squamous cell carcinoma, fibrosarcoma, hepatocarcinoma were used In this study. C3H/HeJ mice were bred and maintained in our specific pathogen free mouse colony and were $8{\sim}12$ weeks old when used for the experiments. The tumors, growing in the right hind legs of mice, were analyzed for $TCD_{50}$, TGD, and RIA at 8 mm in diameter. The tumors were also analyzed for the constitutive expression levels of $p53,\;p21^{WAF1/CIP1},\;BAX,\;Bcl-2,\;Bcl-X_L,\;Bcl-X_S$, and p34. Correlation analysis was peformed whether the level of RIA were correlated with $TCD_{50}$ or TGD, and the constitutive expression levels of genetic products regulating RIA were correlated with $TCD_{50}$, TGD, RIA. Results: The level of RIA showed a significant positive correlation (R=0.922, p=0.026) with TGD, and showed a trend to correlation (R=-0.848), marginally significant correlation with $TCD_{50}$ (p=0.070). It indicates that tumors that respond to radiation with high percentage of apoptosis were more radiosensitive. The constitutive expression levels of $p21^{WAF1/CIP1}$ and 34 showed a significant correlation either with $TCD_{50}$ (R=0.893, p=0.041 and R=0.904, p=0.035) or with TGD (R=-0.922, p=0.026 and R=-0.890 p=0.043). The tumors with high constitutive expression levels of $p21^{WAF1/CIP1}$ or p34 were less radiosensitive than those with low expression. Conclusion: Radiosensitivity may be predicted with the level of RIA in murine tumors. The constitutive expression levels of $p21^{WAF1/CIP1}$ or p34 can be used as biological markers which predict the radiosensitivity.

• Journal of the Korean Society of Radiology
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• v.10 no.6
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• pp.435-442
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• 2016

This study was an investigation of the anode heel effect caused by changing the angle of the x-ray tube. We established the following conditions for experimental measurements: 70 kV, 30 mAs, focus-detector distance of 100cm, and a collimator setting of $35{\times}43cm^2$. The measurement points were set up at the center of the collimator and extended to each side in intervals of 3.5cm, with points A1, A2, A3, A4, A5, A6 on the anode side and points C1, C2, C3, C4, C5, C6 on the cathode side. We measured the entrance surface dose from point A6 to point C6 with each point perpendicular to an x-ray tube. And we did the same when measuring different angles of the x-ray tube from 15 to 30 degrees for every point on the anode and cathode sides. Using perpendicular x-ray tube, we found that the entrance surface dose of the A5 point was three times higher than that of the C5 point. Thus, we conclude that if the anode side is placed near highly radiosensitive organs, then there will be less radiation exposure when using a perpendicular x-ray tube. When imaging using x-ray tube angles, an angle to the cathode side can reduce the gap of the entrance surface dose on both the anode and cathode sides. When imaging areas where there are differences in thickness between the upper and lower sides, the angle to the cathode side that is closer to the thicker area can reduce the gap of the entrance surface dose and capture a higher quality image.

• Imaging Science in Dentistry
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• v.31 no.3
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• pp.135-143
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• 2001

Purpose : To evaluate the effect of all-trans-retinoic acid on radiosensitivity and radiation-induced apoptosis in NHOK, HEp-2 and FaDu cell lines. Material and Methods: We measured the changes in survival fraction at 2 Gy (SF2), α and β after treatment of retinoic acid (1μM) prior to irradiation with doses of 2, 4, 6 and 10 Gy and correlated the radiosensitizing effect of retinoic acid with them. Also, apoptosis induction was assayed with the flow cytometry on days 1,2, 3, 4 and 5 after irradiation (2, 10 and 20 Gy) combined with retinoic acid. Results and Conclusion: SF2 values for NHOK, HEp-2 and FaDu cell lines were 0.54, 0.64 and 0.41, respectively and the cell line of FaDu was the most radiosensitive. For cell lines of NHOK and HEp-2, pretreatment of cells with retinoic acid resulted in a significant decrease of the SF2 values. The α/β ratios of x-ray survival curve were 8.714 (NHOK), 4.098 (HEp-2) and 11.79 (FaDu). The α/β ratio for NHOK decreased on pretreatment with retinoic acid, whereas those for HEp-2 and FaDu increased. Radiation induced apoptosis in all cell lines but, retinoic acid did not affect the apoptosis.

• Journal of Radiation Protection and Research
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• v.22 no.3
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• pp.153-160
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• 1997

The frequencies of ${\gamma}$-ray-induced micronuclei (MN) in cytokinesis-blocked (CB) lymphocytes at several doses were measured in three donors of human and C57BL/6 mice. Measurements performed after irradiation showed a dose-related increases in MN frequency in each of the donors studied. The relative sensitivity of mouse in spleen lymphocytes (SLs) compared with human peripheral blood lymphocytes (PBLs) was estimated by best fitting linear-quadratic model based on the radiation-induced MN data over the range from 0 cGy to 400 cGy. In the case of MN frequency with 0.2 per CB cell, the relative sensitivity of mouse SLs was 1.67. Compared with the radiation-induced MN formation in the PBLs of human, the SLs of mouse were more radiosensitive. Using this MN assay with human PBLs and mouse SLs, studies were performed to determine whether the water fraction of ginseng (Panax ginseng C.A.Meyer) against radiation-induced MN in human PBLs after in vitro irradiation (3Gy) and in SLs of C57BL/6 mice after in vivo irradiation (3Gy). The frequency of MN in human PBLs was reduced by water fraction of ginseng (0.5mg/ml of medium) both pre-and post treatment (p<0.0l) in vitro. In addition, the frequency of MN in mouse SLs was also reduced by pretreatment of ginseng (2mg/ml of drinking water for 7days) in vivo. The data suggested that the ginseng may reduce cell damage caused by ${\gamma}$-rays in vitro and in vivo. Further studies are needed to characterize better the protective nature of ginseng extract, its fractions and compounds.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.8
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• pp.3301-3306
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• 2015

Nucleolin (C23) is an important anti-apoptotic protein that is ubiquitously expressed in exponentially growing eukaryotic cells. In order to understand the impact of C23 in radiation therapy, we attempted to investigate the relationship of C23 expression with the radiosensitivity of human non-small cell lung cancer (NSCLC) cells. We investigated the role of C23 in activating the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), which is a critical protein for DNA double-strand breaks (DSBs) repair. As a result, we found that the expression of C23 was negatively correlated with the radiosensitivity of NSCLC cell lines. In vitro clonogenic survival assays revealed that C23 knockdown increased the radiosensitivity of a human lung adenocarcinoma cell line, potentially through the promotion of radiation-induced apoptosis and adjusting the cell cycle to a more radiosensitive stage. Immunofluorescence data revealed an increasing quantity of ${gamma}$-H2AX foci and decreasing radiation-induced DNA damage repair following knockdown of C23. To further clarify the mechanism of C23 in DNA DSBs repair, we detected the expression of DNA-PKcs and C23 proteins in NSCLC cell lines. C23 might participate in DNA DSBs repair for the reason that the expression of DNA-PKcs decreased at 30, 60, 120 and 360 minutes after irradiation in C23 knockdown cells. Especially, the activity of DNA-PKcs phosphorylation sites at the S2056 and T2609 was significantly suppressed. Therefore we concluded that C23 knockdown can inhibit DNA-PKcs phosphorylation activity at the S2056 and T2609 sites, thus reducing the radiation damage repair and increasing the radiosensitivity of NSCLC cells. Taken together, the inhibition of C23 expression was shown to increase the radiosensitivity of NSCLC cells, as implied by the relevance to the notably decreased DNA-PKcs phosphorylation activity at the S2056 and T2609 clusters. Further research on targeted C23 treatment may promote effectiveness of radiotherapy and provide new targets for NSCLC patients.

• Radiation Oncology Journal
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• v.14 no.4
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• pp.255-264
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• 1996

Purpose : Paclitaxel is a chemotherapeutic agent with potent microtubule stabilizing activity that arrests cell cycle in $G_2$-M Because $G_2$-M is the most radiosensitive Phase of the cell cycle, paclitaxel has potential as a cell cycle- specific radiosensitizer. This study was designed to investigate the ability of paclitaxel to increase the radiotoxicity in normal small bowel mucosa of the rat. materials and Methods : A sigle intraperitoneal infusion of paclitaxel (10mg/kg), and a single irradiation(8 Gy, x-ray) to the whole abdomen and combination of radiation(8 Gr, x-ray) 24 hours after paclitaxel infusion in the rats were done. The changes of jejunal mucosa, and kinetics of mitotic arrest and apoptosis in the jejunal crypt were defined at 6 hours - 5 days after each treatment histologically. Results : Paclitaxel blocked jejunal crypt cell in mitosis and induced minmal apoptosis. Mitotic arrest by paclitaxel was peaked at 6 hours after infusion and returned to normal by 24 hours. Radiation induced apoptosis and peaked at 6 hours and returned to normal by 24 hours. Combination of paclitaxel and radiation blocked crypt cell in mitosis at 3 days and induced apoptosis slightly at 6 hours and 24 hours and returned to normal by 3 days. The incidence of apoptosis in combined group at 6 hours was slightly higher than normal control but significantly lower than radiation alone group. The major changes of jejunal mucosa were nuclear vesicle and atypia which were appeared at 6 hours - 3 days and returned to normal by 5 days The degree of the mucosal changes are not different in 3 groups except for absence of inflmmatory reaction in radiation group. Conclusion : Mitotic arrest by paclitaxel was peaked at 6 hours and returned to normal by 24 hours and paclitaxel induced minimal apoptosis. Radiation induced apoptosis, peaked at 6 hours and returned to normal by 24 hours. Radiation-induced apoptosis was less in combined group which suggested that paclitaxel have a radioprotective effect when radiation was given 24 hours after paclitaxel infusion.

• Radiation Oncology Journal
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• v.11 no.2
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• pp.439-448
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• 1993

The B-type gamma knife unit was installed at Kyung-Hee University Hospital in March 1992. The selective beam plugging method can be used to reduce the low percentage isodose profiles of normal sensitive organ and to modify the isodose curves of treatment volume for better shaping of the target volume. For representing the changes of the low percentage isodose profiles, the variations of dose distribution for several cases were discussed in this paper. The film dosimetry was peformed for the evaluation of calculated isodose profiles predicted by KULA dose planning system. The results were verified by RFA-3 automatic densitometry. The clinical application of selective beam shielding method was peformed in 17 patients in 100 patients who have undergone gamma knife radiosurgery for a year. The calculated and the measured isodose profiles for the high percentage regions were well consistent with each other. When the target of pituitary tumor is macro-size, the selective beam shielding method is the most applicable method. When the target size, however, is small, the correct selection of the proper helmet size is very important. All patients were exposed almost about 3~12 Gy for brain stem, and 3~11.2 Gy for optic apparatus. It is recommended that the same or other plugging patterns with multiple isocenters should be used for protection of the radiosensitive normal structures with precise treatment of CNS lesions.