• Imaging Science in Dentistry
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• v.49 no.2
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• pp.139-151
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• 2019

Purpose: This study was performed to investigate the effect of exposure parameters on image quality obtained using a cone-beam computed tomography (CBCT) scanner and the relationship between physical factors and clinical image quality depending on the diagnostic task. Materials and Methods: CBCT images of a SedentexCT IQ phantom and a real skull phantom were obtained under different combinations of tube voltage and tube current (Alphard 3030 CBCT scanner, 78-90 kVp and 2-8 mA). The images obtained using a SedentexCT IQ phantom were analyzed technically, and the physical factors of image noise, contrast resolution, spatial resolution, and metal artifacts were measured. The images obtained using a real skull phantom were evaluated for each diagnostic task by 6 oral and maxillofacial radiologists, and each setting was classified as acceptable or unacceptable based on those evaluations. A statistical analysis of the relationships of exposure parameters and physical factors with observer scores was conducted. Results: For periapical diagnosis and implant planning, the tube current of the acceptable images was significantly higher than that of the unacceptable images. Image noise, the contrast-to-noise ratio (CNR), the line pair chart on the Z axis, and modulation transfer function (MTF) values showed statistically significant differences between the acceptable and unacceptable image groups. The cut-off values obtained using receiver operating characteristic curves for CNR and MTF 10 were useful for determining acceptability. Conclusion: Tube current had a major influence on clinical image quality. CNR and MTF 10 were useful physical factors that showed significantly associations with clinical image quality.

• Journal of radiological science and technology
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• v.36 no.2
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• pp.111-122
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• 2013

This study was carried out to reduce patient dose through focus-detector distance, kilovoltage, and a combination of copper filters. In the C, L-spine lateral, Skull AP views were obtained by making changes of 60-100 kV in tube voltage and of 100-200 cm in focus-detector distance and by adding a copper filter when using an auto exposure control device in the digital radiography equipment. The incident dose showed 90 kV, 0.3 mmCu in C-spine lateral with 0.06 mGy under the condition of 200 cm; 100 kV, 0.3 mmCu with 0.40 mGy under the condition of 200 cm and 90 kV 0.3 mmCu in Skull AP with the lowest value of 0.24 mGy under the condition of 140 cm. It was observed that entrance surface dose decreased the most when was increased by 150 cm, 70 kV (C-spine lateral), 81 kV (L-spine lateral). It was also found out that as the between the focus-detector increased in the expansion of the video decreased but the difference was not significant when the distance was 180 cm or more. Skull AP showed the most reduction in the entrance surface dose when the tube voltage was changed by 80 kV, 0.1 mmCu, and 120 cm. Therefore, when using the automatic exposure control device, it is recommended to use the highest tube voltage if possible and to increase focus-detector distance at least by 150~200 cm in wall and 120~140 cm in table in consideration of the radiotechnologist's physical conditions, and to combine 0.1~0.3 mmCu and higher filters. It is thus expected to reduce patient dose by avoiding distortion of images and reducing the entrance surface dose.

• Journal of radiological science and technology
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• v.15 no.1
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• pp.89-97
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• 1992

X-ray quality is identified numerically by half value layer(H.V.L) and the HVL is affected by the kVp and the amount of filtration in the useful beam. X-ray quality evaluated by H.L.D is influenced by kVp and filtration. Author had several experiments with phantom in diameter of 8 cm normal adult chest, for reduction of radiation dose of the patients in diagnostic radiology and got some results. 1. H.V.L is increased the thicker the filter and the higher the kVp. 2. If the kVp is increased from 60 to 120, the skin dose can be reduced as 34%(Skin dose of 60 kVp with 4 mmAl filter : 100%). 3. If the 4 mmAl filter with 60 kVp is added to x-ray tube, skin dose can be reduced as 23% than no filter. 4. Therefore high kVp and filtration can increase output to input dose ratio and 120 kVp and 4 mmAl filter were most effective for reduction of patient dose in chest radiography.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1119-1122
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• 2003

In this paper, the electric field distribution in dielectric tube with one layer and spherical dielectric in water was simulated. The reactor was made up of the spherical dielectric that is diameter 2.5[mm], ${\epsilon}_r$ : 5, 100, 1000, 5000 respectively and one glass plate being 2[mm] thickness, ${\epsilon}_r$ : 5 as electrode. The discharge gap was 7[mm]. As a result of the simulation, in case of being about the same value between the dielectric constant of spherical dielectric and water, when the reactor was applied to high voltage dielectric polarization characteristic was trending toward disappearance. To get more strong electric field, the dielectric constant should be higher comparatively, Increasing the spherical dielectric constant, the location of equippotential line was shifting from the interior to the exterior.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1143-1146
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• 2003

This paper was simulated the electric field distribution in dielectric tube with two layers and spherical dielectric in water. The reactor was made up of the spherical dielectric that is diameter : 2.5[mm], ${\epsilon}_r$ : 5, 25, 100, 1000, 5000 respectively and two glass plate being 2[mm] thickness, ${\epsilon}_r$ : 5 as electrode. The discharge gap was 9[mm]. As a result of the simulation, in case of being about the same value between the dielectric constant of spherical dielectric and water, when the reactor was applied to high voltage, dielectric polarization characteristic was trending toward disappearance. To get more strong electric field, the dielectric constant should be higher comparatively, Increasing the spherical dielectric constant, the location of equippotential line was shifting from the interior to the exterior.

• Journal of the Korean Society of Radiology
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• v.17 no.7
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• pp.1041-1047
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• 2023

Temporal bone CT, which is a high-resolution CT, uses a high tube voltage and a thin section thickness, so the scan dose is higher than that of adjacent areas. Accordingly, we applied changes to the reconstruction algorithm among the test conditions to find an algorithm with excellent sensitivity to lesions while reducing the test dose, and investigated its significance and the possibility of providing basic clinical data. As a result, when the tube voltage was lowered to 100 kVp and applied, the dose was reduced by about 35.6%, and when the definition algorithm was applied to the raw data acquired at 100 kVp, the SNR and CNR were excellent, and a statistically significant difference was shown when compared to other algorithms(p<0.05). And as a result of comparing structural similarity, the SSIM index was analyzed as 0.776, 0.813, and 0.741 for each ROI. Therefore, we believe that applying algorithm changes to temporal bone CT scans can partially reduce the dose generated from CT scans and are very meaningful in terms of basic clinical data.

• Journal of radiological science and technology
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• v.13 no.2
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• pp.31-36
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• 1990

We got the following results from the experiment and examination in order to measure the bone-marrow dose of the patients when we did chest or abdomen radiography in the hospitals located in Seoul City from Jan. 1989 until Feb. 1990. 1. In the exposure factors for chest radiography, tube voltage $60{\sim}69\;kVp$ took 48.3%, $80{\sim}89\;or\;90{\sim}99\;kVp$ took 13.8% respectively, $70{\sim}79\;kVp$ 10.3% and $100{\sim}129\;kVp$ 10.3%. In tube current and exposure times, $6{\sim}10\;mAs$ took 41.4%, $16{\sim}20\;mAs$ took 20.7% and $11{\sim}15\;mAs$ 13.8%, measure under 5mAs 10.4% orderly. 2. In chest radiography, the bone-marrow dose came to the minimum 3.48 mrad, to the maximum 35.67 mrad, to the mean 14.46 mrad, to the standard deviation 8.89 mrad. 3. Comparing bone-marrow doses of the patients when we used Bucky technique and non-Bucky technique, that of Bucky technique was very higher than that of non-Bucky technique. Because the result was that Bucky technique had the span of $6.09{\sim}35.67$ mrad, while non-Bucky technique had the span of $3.48{\sim}17.40$ mrad. 4. In the exposure factors for abdomen radiography, tube voltage of $70{\sim}79\;kVp$ was 63.0%, that of $80{\sim}89\;kVp$ was 22.2%, that of $60{\sim}69\;kVp$ was 11.1 %. Tube current and exposure times of $31{\sim}40\;kVp$ was 33.4%, that of $51{\sim}60\;mAs$ was 29.6% and that of $41{\sim}50\;mAs$ was 22.2%. 5. In abdomen radiography, the bone-marrow dose of the patients came to the minimum of 6.96 mrad, to the maximum of 60.90 mrad, to the mean of 35.73mrad, to the standard deviation of 12.65 mrad.

• Journal of the Korean Society of Radiology
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• v.16 no.3
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• pp.217-223
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• 2022

In this study, images taken using a grid and images taken using Air Gap Technique were evaluated in X-ray chest radiography. Subjective Evaluation The ROC (Receiver Operating Characteristic) evaluation was evaluated by 5 radiologists who had worked for more than 10 years in the radiology department of a university hospital. Objective evaluation SNR (Signal to noise ratio) was evaluated. As a result of the analysis, the Cronbach Alpha value was 0.714, which was significantly higher. In the Air Gap Technique, the distance between the phantom and the subject was set at 20 cm, and the image was taken with a tube voltage of 100 kVp, a tube current and a recording time of 8 mAs. In the ROC (Receiver Operating Characteristic) evaluation, the highest score was obtained with 18 score and an objective evaluation SNR (signal to noise ratio) of 6,149 scored. Also, in the imaging method using a grid, when the distance between the phantom and the constant receptor is 15 cm apart, and the tube voltage is 110 kVp, the tube current and the recording time are taken at 8 mAs, the ROC evaluation score is 19 and the objective evaluation SNR (Signal to noise ratio) is the highest with 6.622 scored. Therefore, if the Air Gap Technique imaging method is used, which overcomes the shortcomings such as delay in reading, increase in patient's exposure dose, and shortening of mechanical lifespan, as well as re-radiography due to the cut-off phenomenon of the grid that appears using the grid, the It is thought that it will be very helpful for chest imaging, including the case of using a portable X-ray imaging device.

• Journal of Environmental Science International
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• v.17 no.7
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• pp.817-826
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• 2008

Using high voltage electric fields induced by high voltage AC (10-12 kV/cm, 20 kHz) and pulsed (20-30 kV/cm, 40 Hz) electric field generator as a semipermanent and environment-friendly disinfecting apparatus, the disinfection effect of coliform group in the effluent of sewage plant was investigated. The effects of electric field strength, treatment time, discharge area of a discharge tube, water quality factors (electric conductivity, pH and SS) on its death rate were examined. The death rate of coliform group was increased with increasing electric field strength and treatment time. For AC and pulsed electric field generator, the critical electric field strength was 6 kV/cm and 2 kV/cm, respectively, and the critical treatment time was 5 min and 2 min, respectively, regardless of electric field strength. Comparing the death rate of coliform group by AC and pulsed electric fields used in this study, its death rate was higher for the latter than the former, but did not increase linearly with increasing electric field strength. The results obtained for the effects of discharge area, electric conductivity, pH and SS on the death rate of coliform group using AC electric field (12 kV/cm, 20 kHz) were as follows: its death rate showed the trend to increase linearly with increasing discharge area; for the effect of electric conductivity, its death rate was increased with increasing electric conductivity, regardless of ionic species, increased with increasing cationic valency, but was similar between the same cationic valency; the pH $5{\sim}9$ used in this study did not affect its death rate; its death rate was decreased with increasing SS concentration.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.82-88
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• 2014

Purpose: The purpose of study was to evaluate radiation dose for pediatric patients by changing tube voltage (kVp) and tube current (mA) at minimum conditions. By evaluating radiation dose, we want to provide dose reduction for pediatric patients and maintain good quality of SPECT/CT images. Materials and Methods: Discovery NM/CT 670 Scanne was used as SPECT/CT. Tube voltages are 80 and 100 kvP. Tube currents are 10, 15, 20, 25 mA. Using PMMA (Polymethyl methacrylate) Phantom, radiation dose which were calculated at center and peripheral dose and SNRD (Signal to Noise Ratio Dose) were evaluated. Using the CT performance phantom, spatial resolution was evaluated as the MTF (Modulation Transfer Function) graph. Jaszczak phantom was used for SPECT image evaluation by CNR (Contrast to Noise to Ratio). Results: Radiation dose using the PMMA phantom was higher peripheral dose than center dose about 7%. SNRD were 7.8, 8.2, 8.3, 8.8, 8.8, 9.9, 9.8, 9.6 for 80 kVp 10, 15, 20, 25 mA, 100 kVp 10, 15, 20, 25 mA. We can distinguish 35, 45, 70, 71, 52, 58, 90, 110 linepair for 80 kVp 10, 15, 20, 25 mA, 100 kVp 10, 15, 20, 25 mA at resolution with MTF. CNR of SPECT images using CT attenuation map were 57.8, 57.7, 57.1, 56.7, 56.6, 56.7, 56.7, 56.7% for 80 kVp 10, 15, 20, 25 mA, 100 kVp 10, 15, 20, 25 mA. Conclusion: In this study, radiation dose for pediatric patients showed decreased low dose condition. And SNRD value was similar in all condition. Resolution showed higher value at 100kVp than 80kVp. for CNR, there was no significant difference. we should take additional study to prove better quality and dose reduction.