• Journal of Radiation Protection and Research
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• v.39 no.4
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• pp.199-205
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• 2014

In the field of neutron detections, $^3He$ gas, the so-called "the gold standard," is the most widely used material for neutron detections because of its high efficiency in neutron capturing. However, from variable causes since early 2009, $^3He$ is being depleted, which has maintained an upward pressure on its cost. For this reason, the demands for $^3He$ replacements are rising sharply. Research into neutron converting materials, which has not been used well due to a neutron detection efficiency lower than the efficiency of $^3He$, although it can be chosen for use in a neutron detector, has been highlighted again. $^{10}B$, which is one of the $^3He$ replacements, such as $BF_3$, $^6Li$, $^{10}B$, $Gd_2O_2S$, is being researched by various detector development groups owing to a number of advantages such as easy gamma-ray discrimination, non-toxicity, low cost, etc. One of the possible techniques for the detection is an indirect neutron detection method measuring secondary radiation generated by interactions between neutrons and $^{10}B$. Because of the mean free path of alpha particle from interactions that are very short in a solid material, the thickness of $^{10}B$ should be thin. Therefore, to increase the neutron detection efficiency, it is important to make a $^{10}B$ thin film. In this study, we fabricated a $^{10}B$ thin film that is about 60 um in thickness for neutron detection using well-known technology for the manufacturing of a thin electrode for use in lithium ion batteries. In addition, by performing simple physical tests on the conductivity, dispersion, adhesion, and flexibility, we confirmed that the physical characteristics of the fabricated $^{10}B$ thin film are good. Using the fabricated $^{10}B$ thin film, we made a proportional counter for neutron monitoring and measured the neutron pulse height spectrum at a neutron facility at KAERI. Furthermore, we calculated using the Monte Carlo simulation the change of neutron detection efficiency according to the number of thin film layers. In conclusion, we suggest a fabrication method of a $^{10}B$ thin film using the technology used in making a thin electrode of lithium ion batteries and made the $^{10}B$ thin film for neutron detection using suggested method.

• Journal of the Korean Society of Radiology
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• v.5 no.2
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• pp.93-96
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• 2011

Currently, the development of direct conversion radiation detector using photoconductor materials is progressing in widely. Among of theses photoconductor materials, mercuric iodide compound than amorphous selenium has excellent absorption and sensitivity of high energy radiation. Also, the detection efficiency of signal generated in photoconductor film varies by electric filed and geometric distribution according to top-bottom electrode size. Therefore, in this work, the x-ray detection characteristics are investigated about the size of top electrode in $HgI_2$ photoconductor film. For sample fabrication, to solve the problem that is difficult to make a large area film, we used the spatial paste screen-print method. And the sample thickness is $150{\mu}m$ and an film area size is $3cm{\times}3cm$ on ITO-coated glass substrate. ITO(Indium-Tin-Oxide) electrode was used as top electrode using a magnetron sputtering system and each area is $3cm{\times}3cm$, $2cm{\times}2cm$ and $1cm{\times}1cm$. From experimental measurement, the dark current, sensitivity and SNR of the $HgI_2$ film are obtained from I-V test. From the experimental results, it shows that the sensitivity increases in accordance with the area of the electrode but the SNR is decreased because of the high dark current. Therefore, the optimized size of electrode is importance for the development of photoconductor based x-ray imaging detector.

• Journal of the Korean Society of Radiology
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• v.4 no.1
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• pp.5-9
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• 2010

In recent, a digital x-ray detector attracted worldwide attention and there are many studies to commercialize. There are two methods in digital x-ray detector. This method is an Indirect method and Direct method. This study is to see the differences between the digital x-ray detector based on a-Se used in the existing indirect conversion method and an x-ray conversion material that has better SNR(Signal-to-noise ratio) and property than the a-Se. To solve the problem that is difficult to make a large area film using Screen-Print method, we used a Screen-Print method. In this study, we used a polyclystal $HgI_2$ as x-ray conversion material and a sample thickness is $150{\mu}m$ and an area is $3cm{\times}3cm$. ITO(Indium-Tin-Oxide) electrode was used as top electrode using a Magnetron Sputtering System and each area is $3cm{\times}3cm$, $2cm{\times}2cm$ and $1cm{\times}1cm$ and then we evaluated darkcurrent, sensitivity and SNR of the $HgI_2$ film are measured, then we evaluated the electrical properties. And we used a current integration mode when I-V test. This experiment shows that the sensitivity increases in accordance with the area of the electrode but the SNR is decreased because of the high darkcurrent. Through fabricating of various thicknesses and optimal electrodes, we will optimize SNR in the future work.

• Korean Journal of Dental Materials
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• v.44 no.2
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• pp.151-161
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• 2017

The purpose of this study was to examine the effect of shade and thickness of resin-nanoceramic CAD-CAM block (RNB) on the microhardness of dual-cured resin cement, as well as to measure the number of photons transmitted through RNBs of different thicknesses and colors. One dual-cured resin cement was used to prepare resin cement specimens. Resin cement specimens were light-cured for 40 seconds through 3 shades (A1, A2, A3 in HT (high translucency) and LT (low translucency) respectively) and four thicknesses (1, 2, 3, 4 mm) of RNB specimens. Vickers microhardness measurements of resin cement specimens were performed using a Vickers hardness tester. The light transmission of RNB specimens was measured using a spectrometer (SpectroPro-500, Acton Research, Acton, MA, U.S.A.), and the translucency parameter was calculated using the CIEL*a*b* system. Data were statistically analyzed by ANOVA and Tukey's test. There was a significant decrease of microhardness of resin cement specimen with an overlay of 4 mm of RNB thickness and A3 shade in comparison to A1 and 1 mm, respectively (p<0.05). The translucency parameter values and light transmission of RNBs tested differed significantly, according to the thicknesses of the specimen (p<0.05). Light transmission is decreased with increase in the thicknesses of RNBs. Shade A1 transmitted more light than darker blocks. A decrease in microhardness of resin cement specimens was observed with increasing thickness and shade (A1 to A3) of RNBs.

• The Korean Journal of Nuclear Medicine Technology
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• v.21 no.1
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• pp.70-75
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• 2017

Purpose Radioactive iodine thyroid uptake (RAIU) rate is an examination which determines and seeks about general functions of thyroid gland. The size of thyroid gland is normally different between each person, also patients having thyroid diseases have had a variety of size of thyroid gland compared with others. The purpose of this study will investigate about the counting rate which is effected by the geometric factors through the length and volume changes of the source in RAIU rate. Materials and Methods I-131 185 kBq ($5{\mu}Ci$) were placed in a cylindrical phantom of 0.5 cm, 1 cm, 1.5 cm, and 3 cm in diameter, respectively, and saline was added to gradually increase the length by 1 cm in the horizontal and vertical directions to give a change in volume. The source was measured 20 times for 20 seconds from a distance of 25 cm to $364.4keV{\pm}20%$ energy ROI with Captus 3000 thyroid uptake system (Capintec, NJ, USA). Results When the source was located in the transverse direction of the detector, the consequence of one-way ANOVA is that even though the length of source is increased each diameter, there is mostly no significant difference. When the source was located in the longitudinal direction and the counting rate of length 1 cm at all diameter is set to 100%, the average is 92.57% for length 2 cm, 86.1% for 3 cm, 80.69% for 4 cm, 74.82% for 5 cm, and 69.68% at 6 cm. Conclusion According to this study, it is expected that the gap of RAIU rate has been depended on the thickness of thyroid gland as well as the diameter of the beaker. We know that the change of the volume with the increase of the length of the source had less effect on the change of the counting rate. Thus, in order to reduce the error in the measurement of the counting rate with the thyroid uptake rate equipment, an accurate counting rate can be relatively measured if the counting rate which is measured is corrected by thickness or the distance between the thyroid and the thyroid uptake rate equipment is changed.

• The Journal of Korean Society for Radiation Therapy
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• v.25 no.2
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• pp.145-151
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• 2013

Purpose: In this study, we analyzed how the dose change by field size effects on atomic number of shielding materials while using 6 MeV election beam. Materials and Methods: The parallel plate chamber is mounted in $25{\times}25cm^2$ the phantom such that the entrance window of the detector is flush with the phantom surface. phantom was covered laterally with aluminum, copper and lead which thickness have 5% of allowable transmission and then the doses were measured in field size $6{\times}6$, $10{\times}10$ and $20{\times}20cm^2$ respectively. 100 cGy was irradiated using 6 MeV electron beam and SSD (Source Surface Distance) was 100 cm with $10{\times}10cm^2$ field size. To calculate the photon flux, electron flux and Energy deposition produced after pass materals respectively, MCNPX code was used. Results: The results according to the various shielding materials which have 5% of allowable transmission are as in the following. Thickness change rate with field size of $6{\times}6cm^2$ and $20{\times}20cm^2$ that compared to the field size of $10{\times}10cm^2$ found to be +0.06% and -0.06% with aluminum, +0.13% and -0.1% with copper, -1.53% and +1.92% with lead respectively. Compare to the field size $10{\times}10cm^2$, energy deposition for $6{\times}6cm^2$ and $20{\times}20cm^2$ had -4.3% and +4.85% respectively without shielding material. With aluminum it had -0.87% and +6.93% respectively and with lead it had -4.16% and +5.57% respectively. When it comes to photon flux with $6{\times}6cm^2$ and $20{\times}20cm^2$ of field sizes the chance -8.95% and +15.92% without shielding material respectively, with aluminum the number -15.56% and +16.06% respectively and with copper the chance -12.27% and +15.53% respectively, with lead the number +12.36% and -19.81% respectively. In case of electron flux in the same condition, the number -3.92% and +4.55% respectively without shielding material respectively, with aluminum the number +0.59% and +6.87% respectively, with copper the number -1.59% and +3.86% respectively, with lead the chance -5.15% and +4.00% respectively. Conclusion: In this study, we found that the required thickness of the shielding materials got thinner with low atomic number substance as the irradiation field is increasing. On the other hand, with high atomic number substance the required thickness had increased. In addition, bremsstrahlung radiation have an influence on low atomic number materials and high atomic number materials are effected by scattered electrons.

• Journal of Radiation Protection and Research
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• v.32 no.3
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• pp.123-133
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• 2007

Z-axis automatic tube current modulation technique automatically adjusts tube current based on size of body region scanned. The purpose of the current study was to compare noise, and radiation dose of multi-detector row CT (MDCT) of lower extremity performed with Z-axis modulation technique of automatic tube current modulation with manual selection fixed tube current. Fifty consecutive underwent MDCT venography of lower extremity with use of a MDCT scanner fixed tube current and Z-axis automatic tube current modulation technique (10, 11 and 12 HU noise index, $70{\sim}450\;mA$). Scanning parameters included 120 kVp, 0.5 second gantry rotation time, 1.35:1 beam pitch, and 1 mm reconstructed section thickness. For each subject, images obtained with Z-axis modulation were compared with previous images obtained with fixed tube current (200, 250, 300 mA) and with other parameters identical. Images were compared for noise at five levels: iliac, femoral, popliteal, tibial, and peroneal vein of lower extremity. Tube current and gantry rotation time used for acquisitions at these levels were recorded. All CT examinations of study and control groups were diagnostically acceptable, though objective noise was significantly more with Z-axis automatic tube current modulation. Compared with fixed tube current, 2-axis modulation resulted in reduction of CTDIvol (range, $-6.5%{\sim}-35.6%$) and DLP (range, $-0.2%{\sim}-20.2%$). Compared with manually selected fixed tube current, 2-axis automatic tube current modulation resulted in reduced radiation dose at MDCT of lower extremity venography.

• Korean Journal of Digital Imaging in Medicine
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• v.5 no.1
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• pp.64-77
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• 2002

DR has had an important fact not only in the department of radiology but also in productivity or work efficiency of a whole hospital. The environment of DR has more various parameter than CR, so it is able to supply high quality of medical services. The current environment of radiology department in each hospital has been changed from Film-Screen system to DR through Full-PACS. This hospital which uses Full-PACS became to study the proper condition of CR and DDR and how the image quality of them is expressed among general photographing systems in the DR environment. From this experiment, the image quality of DDR is better than CR under the same exposure condition. And in the DDR system, the score of image which uses AEC is a little higher than the score which doesn't use it. Especially it can be known that the function of AEC of DDR is useful to improve the image quality in the part of skull and chest. (The function of AEC : It is the tool that detects the ionized current of x-ray which goes through objects with using the ion chamber which is in the detector. Also it controls the examination of X-ray when the proper density is reached.) Because the proper degree of density can be represented by this system, the photographing can be taken much easily without consideration of the exposure condition with the thickness of various objects. From the result of this experiment, it can be known that the selection of proper exposure condition plays an important rule to gain good Image Quality. More researches will be necessary about DDR system which has potential ability in the future.

• Journal of the Korean Society of Radiology
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• v.3 no.3
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• pp.37-40
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• 2009

In this study, we made a high efficiency x-ray detecting sensor using the lead oxide(PbO) that are used in direct method of x-ray detector. PbO with nano size particles is produced by sol-gel method for high efficiency. The produced PbO with nano size is deposited on ITO(Induim Tin Oxide) glass in several temperature using the PIB(particle-in-binder) method. The thickness of the deposited PbO is about $200{\mu}m$. Through the measurement of dark current, sensitivity and SNR(Signal To Noise Ratio), an electrical properties of the produced PbO film are analyzed. Therefore, we show that an electrical properties are changed according to a temperature and that the PbO film that was treated at $500^{\circ}C$ in O2 atmosphere is the most high efficiency x-ray detecting sensor.

• 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.