Nuclear medicine in vitro tests are performed on an average of 14 million cases annually in Korea. $^{125}I$, a nuclear species mainly used for in vitro tests, was estimated to have a longer shelf-life than other nuclides because the half-life was longer than other nuclides. Most institutions have judged that the radioactive waste will be about 1/1000 of the original radioactivity when it was stored for a period corresponding to 10 times the half-life of the radioactive waste, and thus the disposal will be satisfied. However, as the amount of radioactive materials remaining in the waste generated by the mechanization and modernization of the inspection method was reduced, it is necessary to reasonably infer the storage period. As a result, the storage period can be calculated reasonably. Waste generated from this test include tubes, beads, vials, tips, and other miscellaneous flammable substances(tissue paper, gauze, paper, etc.). To estimate the reasonable storage of these wastes, the amount of residual radioactive material was measured using a DREAM GAMMA-10 counter, and the period was calculated based on this value. For the purpose of this study, all tubes and beads used for the tests during the year 2016 were measured at a medical checkup hospital in Seoul. A total of 398,879 testing tubes, with 4,155 tubes per box, with a minimum number of 2,792 and a maximum number of 4,374, were used. As a results indicate, the self-disposable period of the tube was measured as 14 days, the beads as 234 days, plastic vials as 177 days, and gauze as 365 days. It was deduced that there is no economical gain because it is not necessary to store for 1 year and 6 months, 10 times the half-life period of $^{125}I$, which was a conservative calculation method.

This work presents a novel configuration of front-end circuits for array-type SiPM-based radiation detectors to enable multiplexing to reduce the effective number of readout channels while maintaining high quality pulse information. The major component of the proposed configuration, a bootstrap amplifier exploiting the Miller effect, keep the same AC voltages of two sides of a detector, resulting in no effective detector capacitance between the nodes. This technique ideally allows combining channels without any performance degradation in terms of rise time and amplitude of signals that can be caused due to the accumulated capacitance when detectors are shorted in parallel in a signal multiplexing scheme. In order to verify the configuration, we designed and built a test board inserting a unity-gain amplifier between a 16-pixel SiPM array and a conventional charge-sensitive amplifier as a preamplifier. The simulated pulses at the output of the front-end system show that the bootstrap technique can successfully mitigate performance degradation of rise time and amplitude. This technique can be adopted in many applications that require a multiplexed readout of a large area of photodetectors, for instance, in cargo scanning technologies, radiation monitoring in nuclear plant facilities or developing advanced medical imaging instruments such as PET and SPECT.

The concerns about the potential contamination of drinking water with accidental nuclear matter have been escalated as more nuclear power plants are being constructed in many countries. Radiation monitoring systems in water environment are basically the same as the conventional ones in principle, but its structure needs to be adapted and modified so as to be suitable to the aquatic operation conditions. As a result, its specifications should be investigated in terms of the minimum detectable activity (MDA) as well as the effective detection distance (EDD) because they determine the radiation level that the monitoring system initiates the emergency action to prevent the water source from being contaminated early enough to avoid serious social commotion. In this study, the EDD and the MDA of the monitoring system fabricated by the Korea Atomic Energy Research Institute (KAERI) were measured with $^{68}Ga$ source. The $^{68}Ga$ source was mixed with water homogeneously in the experimental device, and detectable area was expanded gradually with detecting gamma emitted from $^{68}Ga$ source for EDD. Then, the gamma was also detected as a function of time for MDA, because the activity of $^{68}Ga$ decreases with its half-life. It turned out that the values were 29 cm and $5Bq{\cdot}l^{-1}$ in the experiments, respectively. Relatively short range of the EDD seems to be natural in water, but it suggests that multiple monitoring system need to be strategically installed in a body of water. the MDA value is far lower than the limitation for drinking water, which is $200Bq{\cdot}l^{-1}$ for $^{137}Cs$.

In order to experimentally analyze the artifacts of the chemical shift of water and oil, we made a phantom by mixing water and oil to change the turbo spin-echo (TSE) pulse sequence and various bandwidth (BW) and parameters. A phantom made of water and canola oil was prepared, and an eight-channel head coil of MRI 1.5 T and 3.0 T was used. The scan parameters were TR (5069 ms), TE (100 ms), water fat shift (0.999 and 1.891 pix) at 1.5 T and TR (3000 ms), TE (100 ms), and water fat shift (3.836 pix) at 3.0 T. In all sequences, a matrix ($256{\times}256$), field of view (FOV) (240 mm), and slice thickness were scanned at 3 mm; the frequency direction was RL (right-left), and the BW was calculated using the Philips ACR Bandwidth Calculator. The images were analyzed by obtaining the plot profile and the Fourier transform image. The signal-to-noise ratio (SNR), peak signal-to-noise ratio (PSNR), mean square error (MSE), root mean square error (RMSE), and maximum absolute error (MAE) were calculated to evaluate the images according to the 1.5T and 3.0T BWs of MR. In order to compare the image of chemical shift artifact, the layer of the chemical shift artifact was larger than that of 1.5T of BW 114.9 Hz compared to 217.5 Hz, and at 3.0T, 113.2 Hz compared to 218.1 Hz, and chemical shift artifact. The spatial frequency changes due to the Fourier transform were 1.5T and 3.0T. The reference image (BW 55.7 kHz) and the test image (BW 29.4 kHz) had the SNR of 7.753 dB, PSNR of 22.869 dB, RMSE of 26.808, and MAE of 7.758 in the 1.5T MRI. The reference image (BW 55.9 kHz) and the test image (BW 29 kHz) had the SNR of 17.79 dB, PSNR of 34.062 dB, RMSE of 33.401, and MAE of 5.971 in the 3.0 T MRI. The SNR and PSNR were measured at 1.5T and 3.0T when the BW parameter was changed. At the 1.5 T and 3.0 T MRI, there was a statistically significant difference (p-value<.05). The chemical shift artifacts occurred in the phantom of water and oil, and the artifact was less at 1.5 T than at 3.0 T, and the artifact decreased as the BW increased. In order to reduce the chemical shift artifact in MRI, it is considered appropriate to decrease the intensity of the field and to broaden the BW.

Radiation workers in nuclear medicine use radioisotopes for diagnostic evaluation and treatment, so Their risk of radiation exposure of the lens is greater than for other medical staff. Furthermore, the ICRP report 118 has suggested to reduce the occupational equivalent dose limit for the lens from $150mSv{\cdot}year^{-1}$ to 20 mSv in a year, averaged over defined periods of 5 years, with no single year exceeding 50 mSv. Therefore, the radiation worker in nuclear medicine may have risk to exceed the equivalent dose limit of the lens. To evaluate the performance of the shield for lens protection, the dose of the lens was measured using an ED3 electron dosimeter. During administration of the radiopharmaceuticals, lens dose was measured in non-shielding and with syringe shield, lead glass, and L-block. Also, based on the measured doses, Calculated the dose per 1 mCi of used radioisotope to help make the work plan. Additionally, compared the measurements of the OSL and ED3 over 6 month period to evaluate whether the lens dose of OSL could replace the ED3 measurements.

Many safety facilities are installed and operated in nuclear power plants. In particular, at the nuclear power plant, the gaseous radioactive waste which is exhausted in ventilation of the facility or generated in the power plant is emitted from the exhaust stack after filtering out the radioactive materials. The safety of equipment that monitors the emission of gaseous radioactive materials is very important. ANSI N13.1, the technical standard for emission gas radiation monitoring sampling design, was amended in 1999. There has been a need to verify that the sampling system meets the revised technical standards. It was difficult to directly carry out these evaluations in the field of nuclear power plants. Therefore, the efficiency of the HVAC duct was compared with that of the actual HVAC duct after shrinking (reduction ratio: 2.032 : 1) in the laboratory. The circular duct model and the scale down model were suitable for the sample collection position by satisfying all the flow rate, flow angle, particle distribution, trace gas distribution, and trace gas maximum values, which are the five sample collection position acceptance conditions of ANSI N13.1. The COVs of the real duct model, the flow velocity uniformity scale, and the Reynolds number equal-scale scale down model were 4.6%, 5.3% and 4.1%, respectively, and the COV difference between the actual duct model and the scale down model was less than 5%. The scale down model was validated. ANSI N13.1 (1999) confirmed that the scale-down model validity condition was satisfied. It is now possible to build other types of HVAC ducts in a miniature way to perform an empirical test of the performance of gas radiation monitors. This study was the first case that the actual HVAC duct was evaluated by the scale down model and its effectiveness was evaluated in Korea.

In this paper, we collected data related to the $4^{th}$ Industrial Revolution and provided basic information and tried to understand the perception of radiologists. In order to understand trends of the $4^{th}$ Industrial Revolution, we tried to analyze the tendency of news reporting by the press. The Korea Broadcasting Foundation's news Big Data Service 'Big Kinds'(www.bigkinds. or.kr) was used to select and review articles related to the medical field that were searched by the keyword "$4^{th}$ Industrial Revolution". We conducted a questionnaire survey using 'Naver Office' to investigate the recognition of current radiation workers. Statistical analysis was performed by SPSS23 Chi square test, and the significance was confirmed by age and career. Press reports increased sharply in 2017, mainly reported in Medicine & Medical. Among the patent applications related to the $4^{th}$ Industrial Revolution, medical devices accounted for more than 25%. Most radiologists say that there are many pessimistic responses to the job prospects and that they need to be acted on, but they have said that they are not proceeding or thinking clearly about the action. It is confirmed that the rate of the fourth industrial revolution is gradually increasing in the medical field, and universities, associations and medical institutions should establish and introduce curriculum to prepare for the $4^{th}$ industrial revolution. Also, it seems that each individual should increase the role and importance of radiologists in the era of the $4^{th}$ industrial revolution through active interest and voluntary participation.

In order to investigate the effect of set-up error on the dose delivery, this study evaluates the accuracy of dose delivery due to set-up error by applying a virtual brain tumor treatment plan using volumetric modulated rotational radiation therapy (VMAT). After obtaining a cross-sectional image with a CT device using Head Phantom, a treatment planning program was used to establish a VMAT treatment plan. Based on the treatment plan established, DQA was performed to assess the difference in dose delivery accuracy with set-up error. When the distance was changed to 7 mm with a distance of 1 mm on the basis of the measured value of 0 in the direction of Lat. and Vrt, a comparison was performed by deriving the average after 5 measurements each using a three dimensional array detector. We applied a virtual brain tumor treatment plan using VMAT. In the absence of set-up error, the measured values were 96.8%, 96.4%, 96.2% in Lat. ${\pm}1mm$, 96.2%, 95.9% in Lat. ${\pm}2mm$, 95.4%, 95.2% in Lat. ${\pm}3mm$, 92.0%, 90.1% in Lat. ${\pm}4mm$, 86.9%, 83.7% in Lat. ${\pm}5mm$, 85.6%, 80.3% in Lat. ${\pm}6mm$, 75.2%, 79.5% in Lat. ${\pm}7mm$, respectively. 96.1%, 96.1% in Vrt. ${\pm}1mm$, 95.9%, 95.7% in Vrt. ${\pm}2mm$, 95.1%, 95.1% in Vrt. ${\pm}3mm$, 91.4%, 91.5% in Vrt. ${\pm}4mm$, 88.6%, 88.3% in Vrt. ${\pm}5mm$, 83.1%, 85.6% in Vrt. ${\pm}6mm$, 79.1%, 77.2% in Vrt. ${\pm}7mm$ respectively. As the lateral and vertical error increases, the accuracy of the dose delivery decreases. In order to improve the accuracy of the dose delivery during VMAT treatment, we should try to reduce the error through accurate posture and appropriate image induction.

This study aims to obtain optimal spectrum for the proton distribution of the human brain using View Forum Analyzer with data transferred to PACS after acquiring magnetic resonance spectroscopy data using 3.0 T MRI. Spectrum resulting from magnetic resonance spectroscopy are useful for distinguishing chemical structures and different spectrum between normal and diseased tissues due to differences in biochemical information. Based on this basic theory, it is possible to obtain distinct spectral peaks by adjusting various parameters that can be changed in analyzer. Based on this study, we will provide MRS analysts with useful information on analysis methods and high diagnostic medical information for patients.

This study was carried out to examine radio-sensitivity to gamma-rays irradiated at different doses and to determine optimal dose for mutation breeding in sorghum [Sorghum bicolor(L.) Moench]. Ten cultivars were irradiated with gamma-rays at 100, 200, 300, 400, 500, 600, 700, and 1000 Gy. The germination rate of $M_1$ seeds was gradually decreased at doses higher than 300 Gy and showed no germination over 600 Gy. Likewise, the survival rate of $M_1$ seedling decreased at doses higher than 200 Gy and there were no survival over 500 Gy in all cultivars. However, the median lethal doses($LD_{50}$) and the median reduction doses($RD_{50}$) values of the tested sorghum cultivars were slightly different between cultivars. The $LD_{50}$ was 240(DINE-A-M), 225(IS225), 335(IS2868), 180(Moktak), 214(Banwoldang), 213(ChalI), 231(ChalII), 182(KLSO79125), 287(KLSO79075), and 274(Mesusu) Gy. The $RD_{50}$ was 179(DINE-A-M), 175(IS225), 210(IS2868), 142(Moktak), 174(Banwoldang), 163(ChalI), 175(ChalII), 159(KLSO79125), 199(KLSO79075), and 195(Mesusu) Gy depending on the plant height. Afterwards, we confirmed growth characteristics and mutants of the $M_2$ generation and then were collected mutant lines better than original cultivars. As a result, we suggest that the optimal doses of gamma-ray irradiations for mutation breeding of sorghum are 180 Gy(Moktak, KLSO79125), 200 Gy(DINE-A, IS645, Banwoldang, ChalI, ChalII), 250 Gy(KLSO79075, Mesusu), and 300 Gy(IS2868). By irradiation of gamma-rays at the suggested optimal doses, we constructed $M_2$ lines for sorghum breeding.

We measure the dose of lead glass according to the change of tube voltage of X-ray and compare the shielding ability to confirm the shielding rate. The lead glass used for the X-ray shielding material was 6.5 mm in thickness and 1.5 mmPb in the lead equivalent. The tube voltage was measured at 60, 70, 80, 90, 100, 110, 120 kVp and tube current of 10 mAs. At the tube voltage of 60 kVp, the dose was shielded by 90.3% and the dose rate was shielded by 89.9%. At the tube voltage of 120 kVp, the dose was blocked by 31.6% and the dose rate was blocked by 34.7%. As the tube voltage increased, the shielding rate decreased. At the tube voltage of 60 kVp, the dose shielding rate was as high as 90.3%, but as the tube voltage increased to 120 kVp, the shielding rate decreased to 31.6%. There is a significant difference in dose depending on the use of lead glass (p-value <.05). By measuring the shielding ability of the lead glass according to the change of the tube voltage of the X-ray, the dose shielding rate was 31.6~90.3% and the dose shielding rate was 34.7~89.9%. We could confirm the shielding effect of lead glass according to the investigation of X-ray. We should make efforts to reduce the exposure by using the characteristics of lead glass by referring to these results.

This study examines Poly vinylidene fluorine (PVDF) membrane modification by glycidyl methacrylate (GMA) using the radiation induced graft polymerization. To evaluate the effects of GMA monomer concentrations and absorbed doses, various experimental conditions were tested in the laboratory. The morphology of membrane surface was significantly changed by increasing radiation intensity and GMA concentration. The roughness of membrane surface was decreased from 480 nm to 210 nm. The sulfonyl group and elemental sulfur on the membrane surface were analyzed using FT-IR and EDS. The concentration of elemental sulfur was increased as degree of grafting was increased. The water flux of grafted membrane showed 10 times higher than that of virgin membrane. Additionally, the grafted membrane shows good flux recovery in wastewater filtration. This result leads to the PVDF membrane was effectively functionalized by radiation-induced grafting polymerization.

During decommissioning of a nuclear facility, the radiation dose to workers should be managed not to exceed a certain level. The objective of this study was to review decommissioning organization and target doses for management of radiation exposure to workers at nuclear facilities. The review was performed for the 7 nuclear facilities in the US, including commercial nuclear power plants, research and experimental reactor, and other nuclear facilities. For all the facilities, decommissioning organizations were established and given in decommissioning activities report and decommissioning plan. Certain department and associated supervisors were in charge of radiation protection of workers. They had an authority to stop radiation works not to exceed a certain level. In 10 CFR 20, only dose limits not target doses are given. Therefore, each facility set its own target doses and applied it during the facility decommission. The target doses were set 50~100% ($25{\sim}50mSv{\cdot}year^{-1}$) level of dose limits for the commercial nuclear power plants and 10~50% ($5{\sim}25mSv{\cdot}year^{-1}$) level of dose limits for the research and experimental nuclear plant and other nuclear facilities. It is suggested that 70~90% ($14{\sim}18mSv{\cdot}year^{-1}$) level of dose limits is appropriate for near future decommissioning of a commercial nuclear power plant considering target doses for previous decommission of nuclear facilities in other country and management dose limits set for operational nuclear power plants in Korea.

This research is to compare noise and quantity of exposed ray at abdomen with two medical equipment company, GE and Siemens. As well as figuring out which one has high or low quantity of exposed ray and advantages of each equipment in certain areas. This research used SIEMENS (Somatom Definition Flash, Germany) and GE (Discovery CT 750 HD, USA) in 'C' University as CT equipments. For dummy, this research used Rando phantom (Art-20x fluke biomedical, USA) in condition of care dose 4D and care Kv System with Siemens and GE respectively. For slice thickness, this research used 3 mm for Siemens and 3.75 mm for GE and scanned abdomen 4 times with same FOV 38 cm and 80, 100, 120, 140 kVp. This research is to figure out correlation between noise and quantity of rays from changes of tube voltage in each company's equipment for abdominal phantom. Also this paper got the results that average value of noise decreases and values of CTDlvol and DLP increases by increasing tube voltage to 80, 100, 120, 140 kVp respectively. From above research, there is a difference in quantity of ray for patients by type of equipment, even scanning same area. Therefore, there should be appropriate management criteria. With this perception, the limitation of this research used only two different companies' equipment and used standardized phantom that excludes different characteristics by each patient. To increase quality of image with decreasing unnecessary quantity of rays, there should be additional technology development.