• Journal of the Korean Society of Radiology
• /
• v.14 no.5
• /
• pp.635-642
• /
• 2020

The purpose of this study was to analysis the effects of shielding area of field configuration with changing of sensitivity and density on tube current (milliampere-seconds, mAs) and image quality in automatic exposure control (AEC) system. The equipment used a digital radiography device (Digital Diagnost, Philips, Netherlands), which has a integral type with an X-ray tube and an indirect digital detector. The AEC system conditions were consisted of 9 setting environments, that mode changing of the sensitivity (S200, S400, S800) and the density (+2.5, 0, -2.5). The tube current evaluated automatically exposed mAs under 81 combination conditions crossed by AEC conditions in fixed at 40 kVp. The image quality evaluated the radiographic images that selected valid images by visual assessment the radiographic images of the self-produced conical pyramid phantom and then measured their signal to noise ratio (SNR). As a result, the maximum tube current was 60.0 mAs that automatically exposed conditions were the 100% of shielding area and the sensitivity of S200 and the density of +2.5. The minimum tube current was 0.9 mAs with non-shielding area and the sensitivity of S800 and the density of -2.5. When the shielded area 0% with the sensitivity of S200 and the density of +2.5, the maximum SNR was the highest as 25.2. But when the shielded area 25% with the sensitivity of S800 and the density of -2.5, the minimum SNR was the lowest as 4.7.

• Journal of Korean Foot and Ankle Society
• /
• v.20 no.3
• /
• pp.112-115
• /
• 2016

Purpose: We aimed to investigate the safety zone for Achilles tendon insertion in the posterior aspect of the calcaneus via the use of magnetic resonance imaging (MRI) when planning for insertional Achilles tendinopathy. Materials and Methods: This study included 95 patients. The MRI of midsagittal plane of the ankle joint was used to measure the proximal and distal insertion point for the Achilles tendon in the posterior aspect of the calcaneus. Patients were divided into three groups according to the proportion of the distal insertion point out of the entire calcaneal length: the proximal, middle, and distal insertion groups. Results: The mean proximal and distal insertion points for the Achilles tendon were measured as 1.05 cm (0~2.11 cm) and 2.36 cm (1.60~2.93 cm), respectively. When the posterior aspect of the calcaneus was used as the reference plane, none of the patients was in the proximal insertion group, while 75 and 20 patients were in the middle and distal insertion groups, respectively. The insertion portion was longer in the distal insertion group ($1.47{\pm}0.25cm$) than in the middle insertion group ($1.27{\pm}0.35cm$). Statistically significant differences with respect to the length of the insertion portion were observed between the two groups (p=0.008). Conclusion: Removal of more than 1 cm below the superior margin of the posterior calcaneus may be dangerous. An MRI study on the Achilles tendon of patients without hindfoot deformity or tendinopathy revealed various insertional characteristics. Preoperative MRI evaluation is safer than relying solely on the simple radiological assessment when planning for insertional Achilles tendinopathy.

• Journal of the Korean Society of Radiology
• /
• v.12 no.2
• /
• pp.193-199
• /
• 2018

In this research, 15 patients were diagnosed with 1.5T and 3.0T MRI instruments (Philips, Medical System, Achieva) to minize Ferromagnetic artifact and find the optimized Tesla. Based on the theory that the 3.0T, when compared to 1.5T, show relatively high signal-to-ratio(SNR), Scan time can be shortened or adjust the image resolution. However, when using the 3.0T MRI instruments, various artifact due to the magnetic field difference can degrade the diagnostic information. For the analysis condition, area of interest is set at the background of the T1, T2 sagittal image followed by evaluation of L3, L4, L5 SNR, length of 3 parts with Ferromagnetic artifact, and Histogram. The validity evaluation was performed by using the independent t test. As a result, for the SNR evaluation, mere difference in value was observed for L3 between 1.5T and 3.0T, while big differences were observed for both L4, and L5(p<0.05). Shorter length was observed for the 1.5T when observing 3 parts with Ferromagnetic artifact, thus we can conclude that 3.0T can provide more information on about peripheral tissue diagnostic information(p<0.05). Finally, 1.5T showed higher counts values for the Histogram evaluation(p<0.05). As a result, when we have compared the 1.5T and 3.0T with SNR, length of Ferromagnetic artifact, Histogram, we believe that using a Low Tesla for Spine MRI test can achieve the optimal image information for patients with disk operation like PLIF, etc. in the past.

• Journal of the Korean Society of Radiology
• /
• v.12 no.2
• /
• pp.139-148
• /
• 2018

Assessment of NPP(Nuclear Power Plant) decommissioning cost is very important for safe decommissioning of nuclear power plants. In the United States, which has the most NPP decommissioning experience, the cost evaluation study has been conducted since the 1970s in order to decommissioning nuclear facilities. The US NRC has conducted studies on decommissioning technology, safety and cost for a variety of reactor type and nuclear installations. In the total decommissioning costs, the end of operation licenses accounted for the largest portion, followed by spent fuel management and site restoration. In case of immediate decommissioning, spent fuel management cost increased compared to delayed decommissioning, and delayed deocmmissioning increased the cost of terminating the operation license. However, in general, delayed decommissioning does not show any significant benefit as compared with immediate decommissioning. It is necessary to consider the evaluation according to the site conditions when evaluating the cost of decommissioning domestic nuclear power plants. Also, in Korea, IAEA recommendations were applied to reorganize the radioactive waste classification system. Therefore, it is necessary to develop a method to appropriately use the decommissioning data of the preceding US Nuclear Power Plant in the new classification system when estimating the amount of radioactive waste generated during decommissioning. In particular, the establishment of the evaluation methodology for the waste to be disposed of will be an important factor in securing the accuracy of the decommissioning cost. In addition, it is necessary to construct information data that can be applied to facility characteristics and work characteristics in order to evaluate the cost of demolition of domestic nuclear power plants.

• Journal of the Korean Society of Radiology
• /
• v.11 no.3
• /
• pp.109-115
• /
• 2017

The purpose of this study was to evaluate the clinical efficacy of 128 MDCT (multi-detector computed tomography) for reducing the CareDose 4D dose and comparing the image quality with the fixed tube current technique. For this purpose, we conducted the phantom and clinical studies to evaluate the exposure dose and image of the subject before and after applying the CareDose 4D system in abdominal examination using 128 MDCT. In the phantom study, ROI (Region of interest) was located at the center, 3, 6, 9, 12 o'clock, into two groups: group A without CareDose 4D and Group B applied were measured. In the clinical study, ROI was located at the liver 8 segments, divided into two groups too. The measured items were CT number, noise, and dose length product (DLP) dose. The result of CTDIvol (CT Dose Index volume) measurements in phantom and clinical studies were lower than those before CareDose 4D application, and dose and effective dose were also measured lower (p<.05). There was no difference in CT number before and after application (p>.05). In conclusion, using CareDose 4D, we can obtain optimal image information without deteriorating image quality while reducing patient dose.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2005.06a
• /
• pp.464-473
• /
• 2005

Methodologies of NEWTRIT model, NRC model and AIRDOS-EPA model, which are off-site dose assessment models for regulatory compliance from routine releases of tritium into the environment, were investigated. Using the domestic data, if available, the predictive results of the models were compared. Among them, recently developed NEWTRIT model considers only doses from organically bounded tritium (OBT) due to environmental releases of tritiated water (HTO). A total dose from all exposure pathways predicted from AIRDOS-EPA model was 1.03 and 2.46 times higher than that from NEWTRIT model and NRC model, respectively. From above result, readers should not have an understanding that a predictive dose from NRC model may be underestimated compared with a realistic dose. It is because of that both mathematical models and corresponding parameter values for regulatory compliance are based on the conservative assumptions. For a dose by food consumption predicted from NEWTRIT model, the contribution of OBT was nearly equivalent to that of HTO due to relatively high consumption of grains in Korean. Although a total dose predicted from NEWTRIT model is similar to that from AIRDOS-EPA model, NEWTRIT model may be have a meaning in the understanding of phenomena for the behavior of HTO released into the environment.

• Journal of Oral Medicine and Pain
• /
• v.38 no.2
• /
• pp.175-185
• /
• 2013

Objective : Condyle hypoplasia in temporomandibular joint(TMJ) is often observed in several radiographic views. Mandibular Condyle hypoplasia is frequently confused with osteoarthritis with bony changes in TMJ. This paper investigated clinical characteristics of mandibular condyle hypoplasia as compared with TMJ osteoarthritis. Material and method : 276 patients with TMD were taken clinical and radiological examination and were divided into study group, 189 patients diagnosed with mandibular condyle hypoplasia, and control group, 87 patients diagnosed with TMJ osteoarthritis. And clinical features(Onset, Overjet, Overbite, Noise, Locking, NAS of noise, LOM, pain, MCO, and site of diagnosis and pain)of the two groups were compared. Results : 1. Mandibular condyle hypoplasia and TMJ osteoarthritis were similar in many of the clinical features. 2. Mandibular condyle hypoplasia concordance rates of the radiographic diagnosis site and the pain site was significantly lower than TMJ osteoarthritis. 3. Bilateral mandibular condyle hypoplasia group had more occlusal discomfort, and clenching habits than unilateral mandibular condyle hypoplasia group. 4. Unilateral mandibular condyle hypoplasia group had more unilateral chewing habits and LOM than unilateral TMJ osteoarthritis group. Unilateral TMJ osteoarthritis group had more morning stiffness and higher concordance rates of the radiographic diagnosis site and the click sound site than unilateral mandibular condyle hypoplasia group. 5. Bilateral mandibular condyle hypoplasia group had more usual headaches and overjet than bilateral TMJ osteoarthritis group. Conclusion : Mandibular condyle hypoplasia has somewhat distinguishing clinical characteristics as compared with TMJ osteoarthritis.

• Journal of Radiation Protection and Research
• /
• v.34 no.3
• /
• pp.129-136
• /
• 2009

During the maintenance period at Korean nuclear power plants, internal exposure of radiation workers occurred by the inhalation of $^{131}I$ released to the reactor building when primary system opened. The internal radioactivity of radiation workers contaminated by $^{131}I$ was measured using a whole body counter. Intake estimation and the calculation of committed effective dose were also conducted conforming to the guidance of internal dose assessments from publications of International Commission on Radiological Protection. Because the uptake and excretion of $^{131}I$ in a body occur quickly and $^{131}I$ is accumulated in the thyroid gland, the estimated intakes showed differences depending on the counting time after intake. In addition, since ICRP publications do not provide the intake retention fraction (IRF) for whole body of $^{131}I$, the IRF for thyroid was substitutionally used to calculate the intake and subsequently this caused more error in intake estimation. Thus, intake estimation and the calculation of committed effective dose were conducted by manual calculation. In this study, the IRF for whole body was also calculated newly and was verified. During this process, the estimated intake and committed effective dose were reviewed and compared using several computer codes for internal dosimetry.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.12 no.1
• /
• pp.59-68
• /
• 2014

The public's access to the disposal facilities should be restricted during the institutional control period. Even after the institutional control period, disposal facilities should be designed to protect radiologically against inadvertent human intruders. This study is to assess the effective dose equivalent to the inadvertent intruder after the institutional control period thorough the GENII. The disposal unit was allocated with different kind of radioactive waste and the effects of the radiation dose to inadvertent intruder were evaluated in accordance with the institutional control period. As a result, even though there is no institutional control period, all were satisfied with the regulatory guide, except for the disposal unit with only spent filter. However, the disposal unit with only spent filter was satisfied with the regulatory guide after the institutional control period of 300 years. But the disposal unit with spent filter mixed with dry active waste could shorten the institutional control period. So the institutional control period can be reduced through the mixing the other waste with spent filter in disposal unit. Therefore, establishing an appropriate plan for the disposal unit with spent filter and other radioactive waste will be effective for radiological safety and reduction of the institutional control period, rather than increasing the institutional control period and spending costs for the maintenance and conservation for the disposal unit with only spent filter.

• Journal of Radiation Protection and Research
• /
• v.37 no.3
• /
• pp.116-122
• /
• 2012

A short-term atmospheric dispersion factor (${\chi}/Q$) is an essential element for radiological dose assessment following a hypothetical accidental releases of light-water nuclear power plants. The U. S. NRC developed PAVAN program to comply with the U. S. NRC's Regulatory Guide 1.145. Meteorological data is an essential element for atmospheric dispersion, and PAVAN uses a joint frequency distribution data, which represents the occurrence probability of wind speed and wind direction for atmospheric stability. Using the meteorological data measured at Kori and Wolsung sites for the last 5 years (from 2006 to 2010), a variety of joint frequency distribution data were prepared to evaluate ${\chi}/Q$ values with different wind speed classifications (U. S. NRC's recommendation and even distribution of occurrence probability) and periods of meteorological data to be analyzed (1 year, 2 year, 3 year, 4 year, 5 year). As a result, it was found that the influence of the wind speed classification on ${\chi}/Q$ values is little, while the influence of the periods of meteorological data to be analyzed is relatively significant, representing more than 1.5 times in the ratio of maximum to minimum values.