• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.487-494
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• 2020

The distance between the source and the detector, the diameter of the detector, and the volume effect of the radiation source result in a change in solid angle at the detector entrance, which affects the determination of detection efficiency by causing a difference in path length within the detector. A typical analysis method for calculating solid angles was useful only for a source (⁶⁰Co) with a simple geometric structure, so in this experiment, the distance between the detector and the source was measured by switching on for up to 25 cm with the reference point of window cap 0.5 cm. In addition, 450 and 1000 ㎖ Marinelli beaker of standard volumetric sources were closely adhered to the detector. For circular point sources co-axial with the detector, the change in the solid angle to the distance from the detector window is equal to half the square radius of the source versus the square radius of the detector, if the resulting relationship of the calculation analysis results in the detector being less than the radius of the source. Since the solid angular difference is 0.5 the result of Monte Carlo is acceptable. The relationship between detector and source distance is shown. Solid angles have been verified to decrease rapidly with distance. Measurement and simulation results for a volumetric source show a difference of ±1.01% from a distance of 0 cm and less than 4 % when the distance is reduced to 5 and 10 cm. It can be seen that the longer distance, the smaller efficiency angle, and the exponential increase in attenuation as the energy decreases, is reflected in the calculation of efficiency. Thus, the detection efficiency has proved sufficient for the use of solid angle and Monte Carlo codes.

• Toxicological Research
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• v.22 no.4
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• pp.417-422
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• 2006

Cytogenetic and hematological analysis was performed in peripheral blood obtained from cattle bred in the high background radiation areas (HBRA, Goesan-gun, Cheongwon-gun, Boeun-gun) and a control area. The frequencies of gamma-ray induced micronuclei (MN) in the cytokinesis-blocked (CB) lymphocytes at several doses were measured in 3 cattle. An estimated dose of radiation was calculated by a best fitting linear-quadratic model based on the radiation-induced MN formation from the bovine lymphocytes exposed in vitro to radiation over the range from 0 mGy to 1,969 mGy. The measurements performed after irradiation showed dose-related increases in the MN frequency in each donors. The results were analyzed using a linear-quadratic model with a line of best fit of $y=(0.0583{\pm}0.0137)D+(0.0366{\pm}0.0081)D^2+(0.0093{\pm}0.0015)$ (y=number of MN/CB cells and D=irradiation dose in Gy). MN rates per 1,000 CB lymphocytes of cattle from the Goesan-gun, Cheongwon-gun, Boeun-gun and the control area were $6.50{\pm}2.72,\;9.00{\pm}4.50,\;10.89{\pm}4.23\;and\;9.60{\pm}4.70$, respectively. The MN frequencies of CB lymphocytes from cattle bred in 4 areas mean that the values are within the background variation in this experiment. The MN frequencies and hematological values were similar regardless of whether the cattle were bred in the HBRA or the control area.

• Journal of Plant Biotechnology
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• v.30 no.1
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• pp.19-25
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• 2003

Radiation technique in agriculture was initiated to develop mutant rice. Seeds of Daechungbyeo rice were irradiated with 250 Gy gamma ray for the purpose of inducing and selecting rice variants. Some quantitative traits of the variants in M$_{8}$ generation were evaluated and RAPD analysis was carried out. Variants showed a wider range of agronomic characteristics in both a positive and a negative direction compared with their original variety. The new mutants were characterized by an increased or decreased in plant height, lodging resistance and shorter panicle. RAPD analysis showed that polymorphic bands were presented in most of the primers. In comparison with the original variety, variants were classified into four groups through UPGMA analysis. Among mutants no. 91, 139, 140 and 141 was ranked as salt tolerance and the proline content of these mutants was more increased than that of original variety. The lines of 139, 140 and 141 had the highest genetic distance as compared to original variety in the dendrogram. It is expected that such variants will be useful not only for studying molecular genetics but also for breeding research and genetic analysis.s.

• Journal of radiological science and technology
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• v.35 no.4
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• pp.353-360
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• 2012

Diverse designs of collimator have been applied to Single Photon Emission Computed Tomography (SPECT) according to the purpose of acquisition; thus, it is necessary to reflect geometric characteristic of each collimator for successive image reconstruction. This study carry out reconstruction algorithm for imaging system in nuclear medicine with pinhole collimator. Especially, we study to solve sampling problem which caused in the system model of pinhole collimator. System model for a maximum likelihood expectation maximization (MLEM) was developed based on the geometry of the collimator. The projector and back-projector were separately implemented based on the ray-driven and voxel-driven methods, respectively, to overcome sparse sampling problem. We perform phantom study for pinhole collimator by using geant4 application for tomographic emission(GATE) simulation tool. The reconstructed images show promising results. Designed iterative reconstruction algorithm with unmatched system model effective to remove sampling problem artefact. Proposed algorithm can be used not only for pinhole collimator but also for various collimator system of imaging system in nuclear medicine.

• Journal of radiological science and technology
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• v.30 no.3
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• pp.237-243
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• 2007

Phantoms are very necessary for quality assurance of radio nuclides imaging systems to maintain standards and to ensure reproducibility of test. General quality assurance and instrument quality control are essential in every hospital. The human tissue equivalent materials are aluminum, areryl, water and epoxy..etc. It is very important to select optimum equivalant materials for a phantoms in QC. Especially, paraffin is very similar with human soft tissue in X or Gamma-ray physical characteristics and easy to buy with economically. We made a paraffin thyroid phantom and compare with thyroid areryl phantom, also used commercially in practice. Two small size cold spots(3 and 6 mm diameter) and a hot spot(3 mm diameter) embeded in paraffin phantom. And imaged with $^{99m}TcO_4$ by camera for analysis about spatial resolution and noise at the hot and cold spots. We got some results as below : 1. No difference in counting rate and noise between both arcryl and paraffin thyroid phantoms. 2. The best spatial resolution can be seen 6 cm distance between pinhole collimator and thyroid phantoms(arcryl and paraffin). 3. More optimal spatial resolution could acquired in paraffin thyroid phantom. Paraffin is very similar with human soft tissue in atomic number, density and relative absorbtion function, and can be shaped easily what we wanted. So we can recommendation paraffin as quality assurance phantom because its usefulness, economical benefit and purchasability.

• Journal of the Korean Society of Radiology
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• v.5 no.3
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• pp.103-110
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• 2011

The effect on active transport of $K^+$ and $Na^+$ of cell membrane model which irradiated by radiation was investigated. The cell membrane model used in this experiment was a $Na^+$ type sulfonated copolymerized membrane of styrene and divinylbenezene. The initial flux of the ion was increased with increase of both $H^+$ ion concentration. In this experiment range(pH $0.5^{-3}$), the initial flux of $K^+$ which was not irradiated by radiation was found to be from $7.9{\times}10^{-4}$ to $7.49{\times}10^{-3}mole/cm^2{\cdot}h$ and that of Na+ from $10.6{\times}10^{-4}$ to $7.68{\times}10^{-3}mole/cm^2{\cdot}h$. The initial flux of $K^+$ which was irradiated by radiation was found to be from $35.0{\times}10^{-4}$ to $42.4{\times}10^{-3}mole/cm^2{\cdot}h$ and that of $Na^+$ from $52.0{\times}10^{-4}$ to $43.3{\times}10^{-3}mole/cm^2{\cdot}h$. The membrane was selective for $K^+$ and the ratio $K^+/Na^+$ was about 1.10. And the driving force of pH of irradiated membrane was significantly increased about 4-5 times than membrane which was not irradiated. As active transport of $K^+$ and $Na^+$ of cell membrane model were abnormal, cell damages were appeared at cell.

• Korean Journal of Veterinary Research
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• v.45 no.4
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• pp.469-475
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• 2005

Cytogenetic and hematological analysis was performed in peripheral blood obtained from pigs bred in the high background radiation areas (HBRA) (Cheongwon-gun and Boeun-gun) and a control area. The frequencies of gamma-ray induced micronuclei (MN) in the cytokinesis-blocked (CB) lymphocytes at several doses were measured in three pigs. An estimated dose of radiation was calculated by a best fitting linear-quadratic model based on the radiation-induced MN formation from the swine lymphocytes exposed in vitro to radiation over the range from 0 mGy to 1,969 mGy. The measurements performed after irradiation showed dose-related increases in the MN frequency in each donors. The results were analyzed using a linear-quadratic model with a line of best fit of $y=0.0005404D^2+0.04237D+0.00833$ [y = number of MN/cytokinesis-blocked (CB) cells and D = irradiation dose in Gy]. MN rates per 1,000 CB lymphocytes of pig from the HBRA (Cheongwon-gun, Boeun-gun) and the control area were $6.70{\pm}2.36$, $9.00{\pm}3.50$ and $11.00{\pm}2.98$, respectively. The MN frequencies of CB lymphocytes from pigs bred in three areas means that the values are within the background variation in this experiment. The MN frequencies and hematological values were similar regardless of whether the pigs were bred in the HBRA or the control area.

• Journal of Chest Surgery
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• v.30 no.8
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• pp.739-746
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• 1997

A variety of experiments concerning the development of ideal prosthetic grafts for correcting circumferential tracheal defects have been performed. The requirements for an ideal tracheal prosthesis are impermeability to air, consistency to prevent collapse, and acceptance by the host tissue causing a minimum inflammatory reaction, allowing fibroblastic infiltration and epithelialization. The synthetic material, polyurethane(PU), is known as a biocompatible polymer with an inert component. In this study, the tracheal prosthesis was made from microporous PU(30 micrometer in diameter) coated with gelatin and reinforced with isoplastic rings. This procedure provides the prosthesis with a compression strength. The out side diame er of the prosthesis was 20 mm with a length of 30 mm. The gelatin used in the study was obtained from pig skin and immobilized and cross-linked by irradiation(60 Co gamma ray) to promote host tissue incorporation and render the prosthesis epithelization after implantation. Animal experiments using 10 mongrel dogs were performed to compare three kinds of prosthesis; gelatin coated polyurethane graft, uncoated polyurethane graft, and prosthesisf pericadium complex graft. After 6 weeks of implantation, the epithelialization of implants was seen on the gelatin-coated and prosthesisfpericadium complex grafts. Implanted prosthesis were complicated by airway obstruction due to anastomosis granuloma. Early tracheal stenosis was found in the uncoated graft group. Two kind of anastomosis techniques were tested on the gelatin-coated prosthesis. Everted anastomosis resulted severe granuloma than the inverted anastomosis. In the prosthesislpericadium complex graft, bacteria and inflammation at a anastomotic site was found. Based on these results, gelatin coated porous polyurethane trachea prosthesis is biocompatible and may be useful in clinical application with further investigation.

• Journal of Sensor Science and Technology
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• v.7 no.2
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• pp.131-139
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• 1998

$CdS_{0.67}Se_{0.33}$ single crystal was grown by vertical sublimation method of closed tube physical vapour deposition. The (0001) growth plane of oriented single crystals was confirmed from the back-ref1ection Laue patterns. From the Hall effects by van der Pauw method, the as-grown $CdS_{0.67}Se_{0.33}$ single crystals were found to be n-type semiconductors. The mobility appeared to be decreased by lattice scattering at temperature range from 150K to 293K and by impurity scattering at temperatures ranging from 30K to 150K In order to explore its applicability in photoconductive cells, we measured the ratio of photo-current to dark-current (pc/dc), maximum allowable power dissipation (MAPD), spectral response and response time respectively. The results indicated that for the samples annealed in Cu vapour the photoconductive characteristics are best. We obtained sensitivity of 0.99, the value of pc/de of $1.84{\times}10^{7}$, the MAPD of 323mW and the rise and decay time of 9.3 ms and 9.7 ms, respectively.

• Journal of Sensor Science and Technology
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• v.23 no.2
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• pp.134-141
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• 2014

A stoichiometric mixture of evaporating materials for $BaIn_2Se_4$ epilayers was prepared from horizontal electric furnace. To obtain the single crystal thin films, $BaIn_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were $620^{\circ}C$ and $400^{\circ}C$, respectively. The crystalline structure of the epilayers was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $BaIn_2Se_4$ epilayers measured from Hall effect by van der Pauw method are $8.94{\times}10^{17}cm^{-3}$ and 343 $cm^2/vs$ at 293 K, respectively. The temperature dependence of the energy band gap of the $BaIn_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)$=2.6261 eV-$(4.9825{\times}10^{-3}eV/K)T^2/(T+558 K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $BaIn_2Se_4$ have been estimated to be 116 meV and 175.9 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $BaIn_2Se_4/GaAs$ epilayer. The three photocurrent peaks observed at 10 K are ascribed to the $A_1-$, $B_1$-exciton for n = 1 and $C_{21}$-exciton peaks for n=21.