A whole body counter (WBC) is used in nuclear power plants (NPPs) to identify and measure internal radioactivity of workers who is likely to ingest or inhale radionuclides. A WBC has several counting geometries, i.e. the thyroid, lung, whole body and gastrointestinal tract, considered with the location where radionuclides are deposited in the body. However, only whole body geometry is normally used to detect internal radioactivity during whole body counting at NPPs. It is overestimated internal exposure dose because this measured values are indicated as the most conservative radioactivity values among the them of other's geometry. It is often possible to estimate external contamination as internal contamination due to radionuclides attached to the skin of radiation workers and this leads to an excessively conservative estimation of radioactive contamination. In this paper, the reanalysis of previous experiments for radioactivity depending on the counting geometry of WBC using phantoms and standard radiation sources was carried out in order to improve overestimated internal exposure dose. Quantitative criteria could be used for selecting the optimal WBC counting geometry. Furthermore, discrimination guideline according to ratio of count rates of the upper and lower detectors of the WBC is provided through statistical analysis method.

High-frequency electron accelerators are widely used in the various radiation equipment such as container inspection device, non-destructive inspection system and radiation therapy. The RF characteristics of S-band (2856 MHz) side-coupled structures for accelerator cavity were measured by using E-antenna (in refection), part of the half cell cavity was found to be out of error bound from resonance frequency, and thus was re-processed. When the error bound of the frequency is within 2 MHz, it can be reduced by using external tuning device. But if the error bound is bigger than 10 MHz, external tuning device cannot be used. In this study, Based on the result of accelerator cavity simulation and the precise machining, accelerating cell part and side-coupling cell were reprocessed to produce accelerator cavity frequency that is fit to purpose.

To distinguish urinary stones, we tried to identify the components of urinary stone using HU of nonenhancement MDCT. HU was measured according to the tube voltage and the slice thickness of the section of urinary stone. After injecting urinary stone into a small plastic bottle, experimental phantom was prepared using pork similar to human body. 640 slice MDCT. HU of urinary stone was measured according to each tube voltage and slice thickness in the obtained images. HU of urinary stones according to tube voltage were 135 kVp ($373.68{\pm}30.20HU$), 100 kVp ($525.94{\pm}44.93HU$) and 80 kVp ($691{\pm}80.80HU$), and the slice thickness was 0.5 mm ($752{\pm}25.71HU$) minimum ($545.96{\pm}29.89HU$), 1.5 mm ($462.68{\pm}46.35HU$), 2 mm ($360.43{\pm}66.19HU$). It was found that the HU of urinary stone was increased with decreasing tube voltage, and the HU of urinary stone was decreased with increasing thickness of the section. Non-enhancement MDCT for urinary stone is thought to be useful for the diagnosis of urinary stone using thin slice thickness using low tube voltage.

Cellulose degradation improved mutants, LER120, LER121, LER277R80, LER277R88, and LER277R140 were induced from Lentinula edodes KACC42378 using gamma ray radiation ($^{60}Co$) at the dose of $LD_{99}$ (0.94kGy). To understand the cellulase activity enhanced mechanism in these mutants, we examined the expression of cellulase genes, cellobiohydrolase (cel7A and cel6B), endoglucanase (Lecel5A and Lecel12A) and ${\beta}$-glucosidase (Lxyl-p1 and LebglA) using the qRT-PCR. The expression of LebglA was significantly up-regulated in all mutants (LER120; 6.5 fold, LER121; 10.2 fold, LER277R80; 2.0 fold, LER277R88; 17.6 fold, LER277R140; 18.5 fold) compared with that of the wild type (WT) in the 1% carboxymethylcellulose (CMC) media, while the expression of cellobiohydrolases and endoglucanases did not changed. To clarify the mutation on the sequences of the LebglA by radiation, we cloned LebglA coding DNA sequence (CDS). There was no sequence variations between LebglA CDSs of each mutant and WT. Based on commonly up-regulation of LebglA expression in all cellulose degradation improved mutants, LebglA could play a principal role in cellulose degradation of L. edodes and ${\beta}$-glucosidase specific regulator gene(s) might be turned on in mutants in this study.

Shielding radiation devices is a very important factor in securing the safety of users. In general, the best method of shielding radiation is to make the shielding material thick enough to minimize the amount of radiation leakage. However, since the shielding materials are very heavy, it would be necessary to consider the mass of the total system with a sufficient shielding structure for mobile systems. In this study, we investigate different materials for shielding of mobile micro-CT and evaluate the shielding performance with respect to the shielding position and the total weight of the system. The purpose of the shielding materials optimization is to compare the shielding ability with respect to the weight of the shielding material and to select the material that is sufficiently light while maximizing the shielding effect. The shield location measurement is based on the amount of leakage radiation when the shield is installed inside and outside of the micro-CT system housing. The materials used in this study are lead and tungsten with thicknesses ranging from 1 mm to 5 mm. Tungsten showed the same shielding performance at half of the lead thickness with the density less than twice the density of lead, making the tungsten shielding much lighter. In case of the shielding position, the inner shielding of the housing showed a higher shielding performance when compared to that of the outer housing.

We have started this study in an attempt to measure facility spaces' Radon density and minimize Radon damages to human health accounting for measurement values. The subject of this study is a general hospital situated within the Seoul metropolitan area, the Seoul Medical Center. The Radon density measurement points were dispersed as following for comparison among spatial categorization: 17 spots within office areas(places where only hospital employees occupy), 25 spots within patients' waiting area (occupied by employees, patients, patient caretakers, general passerby), 22 spots within treatment areas (occupied by employees or patients). For comparison among building levels, 10 places were picked within the basement area (5 on the first basement level, 1 on the second basement level, 2 on the third basement level, 2 on the fourth basement level), 54 places above ground (25 on the first floor, 27 on the second, 2 on the third). For comparison based on the factor of window existence, 21 spots without windows and 43 spots with windows were compared. Measurement was carried out for the duration of four months by Alpha track detectors with the removal of LR-115 tapes. These detectors are fixed to the wall with a one meter length string hanging from a half-circle shaped link fixed upright at a right angle on the ceiling at the center of the measurement area. As a manual detector, for Alpha track detector measurement to be properly conducted, it should be used under minimized circumstantial changes from the usual status quo for the duration of measurement. Study collaborators have kept the environmental factors constant while measuring Radon density, with indoors detectors being comprised of two types, passive and active detectors. These two types could be differentiated apart by their electric power source. Passive detectors are easier to maneuver and are more economical in their costs than their active counterparts. Few demerits persist, however, in that passive detectors have more difficulty achieving prompt long term measurements and are more prone to lowered reliability in their measurements due to external environmental factors. Despite these shortcomings, for its relative low costs and efficiency, collaborators have decided on using Alpha track detector LR-115 device for the purpose of this study. The mean Radon concentration level of the 21 places with windows was $58.00Bq{\cdot}m^{-3}$, with the 43 places without windows mean level being $62.93Bq{\cdot}m^{-3}$, The mean difference of approximately $5Bq{\cdot}m^{-3}$ with windowed places being lower in Radon concentration levels were nonsignifican t (p>0.05). The reason why lower Radon density was measured in windowed areas could be postulated to be due to airing and emission of Radon from measured indoors to outdoors. In the comparisons between workspace categorizations, the mean Radon density level of the 17 places within office areas (occupied only by hospital employees) was $58.18Bq{\cdot}m^{-3}$, a mean of $64.50Bq{\cdot}m^{-3}$ in 22 patient waiting areas (occupied by employees, patients, caretakers, and passersby), and a mean of $61.31Bq{\cdot}m^{-3}$ was achieved in 22 treatment areas. Radon density level was ranked from highest to lowest from office areas, treatment areas, and patient waiting areas. There were, however, no statistical significance achieved among the three spatial categorizations(p>0.05). We could postulate lower Radon level was achievable through frequent airing from multiple windows. Comparisons between floor levels led to the result of mean of $55.90Bq{\cdot}m^{-3}$ in the 10 areas in the basement levels, and mean of $62.31Bq{\cdot}m^{-3}$ in the 54 areas in the above ground level floors. While not achieving statistical significance (p>0.05), Radon levels were measured to be $7Bq{\cdot}m^{-3}$ lower in the basement areas compared to the above ground levels. Based on these results, we believe reducing lung cancer inducing Radon density by appropriately measuring and controlling radon concentration levels would be conducive to lowering radiation exposure to on facility employees, patients, and caretakers.

It is to find optimize quantity of ray that can decrease metal artifact caused by artificial hip joint, etc. when deciphering an image by monochromatic X-ray. To compare change of CT number value and noise value of metal artifact in animal tested image, 4 areas were selected and changed keV to measure CT number and noise value at each keV then CNR (Contrast to Noise Ratio) value is calculated. From computer analysis result, 62keV is the point where can get the metal artifact minimized image, but this paper figured out that it is possible to get the metal artifact minimized image from 90 keV. Therefore, it is possible to get diagnosable image that minimized metal artifact by reconstruction in condition of 90 keV when having CT scan for patients who had artificial metal substance enthesis such as pedicle screw enthesis and artificial coxaenthesis.

The details of the radiation used in the current veterinary hospitals have been regulated by the regulations of animal diagnostic radiators. However, veterinary hospitals with a total workload of less than $10mA{\cdot}min$ per week are excluded from the legal obligation to administer radiation safety management. This study investigated the actual situation of small animal hospitals. Based on the results of this survey, the radiation dose of the radiation workers was measured and evaluated. The results of this study will be a meaningful assessment of small animal hospitals that are excluded from legal objectives.

The purpose is to improve the accuracy of dose reduction and adrenal gland diagnosis by analyzing the HU and evaluating the effective dose of contrast CT scan of the adrenal gland in order to evaluate the accuracy of contrast enhancement of adrenal adenomas. We analyzed the dose information of patient DICOM file that underwent CT scan of adrenal gland examination. CT scan of the adrenal gland performed pre contrast, portal phase, a 3 minute delay and a 15 minute delay. The HU measurement selects the largest region of adrenal lesion. And, mean, standard deviation, and area of the adrenal lesion were analyzed by ROI. Absolute percentage washout (APW) and relative percentage washout (RPW) calculated and the adrenal adenomas diagnosed by threshold value of the percentage washout rate were above APW 60% and RPW 40%. Effective dose was calculated based on DLP of DICOM dose report for adrenal CT scan. HU analyzed of the adrenal gland by calculating APW and RPW. The APW and RPW were analyzed by 52% and 41.8% at 3 minute delay, 73.5% and 59% at 15 minute delay, respectively. The diagnosis of adrenal adenomas was consistent with APW (73.5%) and RPW (59%) above the threshold at 15 minute delay. The effective dose of adrenal CT scan was 16.08 mSv. Therefore, it is necessary for radiation dose reduction.