• Journal of the Korean Society of Radiology
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• v.16 no.4
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• pp.471-476
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• 2022

The purpose of this study was to study the probability of cancer occurrence due to photoneutron dose exposure of the colon and thyroid gland, which are normal organs, in 3D CRT, IMRT 5 portals, and IMRT 9 portals, which are radiotherapy methods for prostate cancer. The total prescribed dose for prostate cancer was 6600 cGy, 220 cGy per dose, and 30 divided irradiations were applied for the total number of times. After setting up the Rando phantom on the treatment table (couch) of the medical linear accelerator used in the experiment, an optically stimulated luminescence albedo neutron dosimeter was placed on the corresponding area of the large intestine and thyroid gland of the phantom for measurement. During 3D CRT of prostate cancer, the probability of secondary cancer due to photoneutron dose to the colon and thyroid gland, which are normal organs, was 1.8 per 10,000 people. And IMRT 5 portals were 8.7 per 10,000 people, which was about 5 times larger than 3D CRT. IMRT 9 portals derived the result that there is a probability that 1.2 people per 1,000 people will develop cancer. Based on this study, the risk of secondary radiation exposure due to the dose of photoneutrons generated during radiation therapy is studied, and it is thought that it will be used as useful data for radiation protection in relation to the stochastic effect of radiation in the future.

• Journal of the Korean Society of Radiology
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• v.16 no.1
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• pp.45-51
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• 2022

This study compared DLP values along with phantom entrance surface doses and the image quality of chest CT scans made using a Care Dose 4D+Care kV System, scans that are made using only the Care Dose 4D function, and scans that are made with changes made by applying 80 kVp, 100 kVp, 120 kVp, and 140 kVp to the Care Dose 4D and tube voltage to search for methods to maintain the highest image quality with minimal patient doses. It was shown that DLP values decreased 6.727% when scans were taken with Chest Care Dose 4D + Care kV semi 100 and 6.481% when scans were taken with Chest Care Dose 4D + Care kV. With Chest Non as a standard, skin surface doses decreased 16.519% when scans were taken with Chest Care Dose 4D + Care kV semi 100 and 15.705% when scans were taken with Chest Care Dose 4D + Care kV. With comparisons of image quality, when comparisons were made with Chest Non, comparisons made of SNR values and CNR values in all scanning conditions including Care Dose 4D + Care kV showed that there were no significant differences at P>0.05. Imaging using Chest Care Dose 4D + Care kV in chest CT showed that exposure doses decreased similarly to result values gained from the best conditions through manual adjustments of kV and mAS, and there were no significant differences in image SNR and CNR. If the Chest Care Dose 4D + Care kV function is used, image quality is maintained and patient exposure to radiation can be reduced.

• Journal of the Korean Society of Radiology
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• v.16 no.4
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• pp.387-394
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• 2022

120 kVp FBP reconstruction image standard by using raw data after scanning by changing tube voltage among the NECK CT protocols that are broad applied in clinical practice using a human phantom including thyroid gland The usefulness of the DLIR reconstruction technique was investigated. As a result, CTDIvol decreased when the DLIR reconstruction technique was applied, and in particular, the image quality obtained under the same standard scanning conditions at a lower dose for ASIR-V and DLIR reconstruction was reached than when FBP was applied at the same kVp In addition, as a result of SNR and CNR analysis, the DLIR reconstructed image was analyzed with high SNR and CNR values, and SSIM analysis, the SSIM index of the 100 kVp, DLIR reconstructed image was measured to be close to 1, and it was analyzed that the similarity of the reconstructed image to the original image was high (p>0.05). If the results of this study are used to supplement clinical image evaluation and further develop an algorithm applicable to various anatomical structures, it is thought that it will be useful for clinical application as it is possible to maintain the image quality while lowering the examination dose.

• Journal of Industrial Convergence
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• v.21 no.1
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• pp.9-31
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• 2023

This study is a study on the different cognitive systems and different knowledge systems of members participating in complex and diverse consulting projects, and it is a study on team collaboration that affects the team performance of the project. The purpose of this study is to analyze the mediating effects of team shared cognition, team transactive memory, team knowledge integration, and team efficacy in the cognitive interaction process of a consulting project. This study established a research model and research hypothesis based on previous studies. Data were collected from consultants who actually participated in the consulting project. To empirically analyze the research hypothesis, demographic analysis, validity and reliability analysis, structural model analysis for hypothesis verification, and mediating effect analysis using phantom variables were performed. As a result of the study, in order to increase team performance, it is necessary to improve team shared cognition and team transactive memory, which are cognitive systems, and team knowledge integration, which is a knowledge system, must also be improved. Therefore, there is a need for a sense of team efficacy that integrates disparate cognitive and knowledge systems, trusts each other's expertise, and enables successful team work. In addition, future studies on sub-factors of cognitive processes are needed.

• Korean Journal of Culture and Social Issue
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• v.20 no.4
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• pp.443-467
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• 2014

The purpose of this study was to analysis the causal model between self-directedness, learning flow, career decision and self-efficacy, and career exploration behavior of undergraduate students. A survey was conducted on 604 undergraduate students, and Structural Equation Modeling was used to analyze. The major findings were as follows: First, learning flow and career decision self-efficacy were found to have positive impacts on career exploration behavior. However, self-directedness was found to have no significant direct impacts on career exploration behavior. Second, self-directedness was found to have positive impacts on learning flow and career decision self-efficacy. Finally, learning flow and career decision self-efficacy were found to have perfect mediating effects on the relationships between self-directedness and career exploration behavior. Considering the size of the specific indirect effect, the mediating effects of learning flow was relatively larger than those of career decision self-efficacy. Based on the results, discussions to increase career exploration behavior were made as well as suggestions for future research.

• Journal of radiological science and technology
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• v.46 no.4
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• pp.315-323
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• 2023

Post-mortem computed tomography (PMCT) is commonly employed in the field of forensic pathology. PMCT was mainly performed using a whole-body scan with a wide field of view (FOV), which lead to a decrease in spatial resolution due to the increased pixel size. This study aims to evaluate the potential for developing a super-resolution model based on conditional generative adversarial networks (CGAN) to enhance the image quality of CT. 1761 low-resolution images were obtained using a whole-body scan with a wide FOV of the head phantom, and 341 high-resolution images were obtained using the appropriate FOV for the head phantom. Of the 150 paired images in the total dataset, which were divided into training set (96 paired images) and validation set (54 paired images). Data augmentation was perform to improve the effectiveness of training by implementing rotations and flips. To evaluate the performance of the proposed model, we used the Peak Signal-to-Noise Ratio (PSNR), Structural Similarity Index Measure (SSIM) and Deep Image Structure and Texture Similarity (DISTS). Obtained the PSNR, SSIM, and DISTS values of the entire image and the Medial orbital wall, the zygomatic arch, and the temporal bone, where fractures often occur during head trauma. The proposed method demonstrated improvements in values of PSNR by 13.14%, SSIM by 13.10% and DISTS by 45.45% when compared to low-resolution images. The image quality of the three areas where fractures commonly occur during head trauma has also improved compared to low-resolution images.

• Journal of the Korean Society of Radiology
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• v.17 no.4
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• pp.573-579
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• 2023

This study compares dose difference between the presence or absence of grid in Chest PA radiography using auto exposure control and compares image quality among presence, absence or virtual grid, and proposes a new clinically useful grid combination for chest radiography. The human body phantom was placed Chest PA position and the dosimeter was placed at T6. The same irradiation conditions and field size were applied. 30 images were obtained in the state in which grid was applied and in the state in which grid was not applied, and an additional 30 images in which the virtual grid was applied to the image without the grid were obtained. Radiation dose was presented to entrance surface dose. The image quality was analyzed by comparing the signal-to-noise and contrast-to-noise ratio. ESD decreased by 48% when the grid was not used, compared to when the grid was used. SNR and CNR increased by 32% and 30% compared to grid use when grid was not used, respectively. In the case of using the virtual grid, it increased by 18% and 16% respectively, compared to the case of using the grid. As a result of this study, it is believed that when using a virtual grid instead of a grid, the quality of the image can be maintained while reducing the patient dose.

• Journal of the Korean Society of Radiology
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• v.17 no.2
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• pp.207-213
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• 2023

Computed tomography (CT) images are used as the basis for proton Bragg peak position estimation and treatment plan simulation. During the Hounsfield Unit (HU) based proton stopping power ratio (SPR) estimation, small differences in the patient's density and elemental composition lead to uncertainty in the Bragg peak positions along the path of the proton beam. In this study, we investigated the potential of dual-energy computed tomography image-based proton SPRs prediction accuracy to reduce the uncertainty of Bragg peak position prediction. Single- and dual-energy images of an electron density phantom (CIRS Model 062M electron density phantom, CIRS Inc., Norfolk, VA, USA) were acquired using a computed tomography system (Somatom Definition AS, Siemens Health Care, Forchheim, Germany) to estimate the SPRs of the proton beam. To validate the method, it was compared to the SPRs estimated from standard data provided by the National Institute of Standards and Technology (NIST). The results show that the dual-energy image-based method has the potential to improve accuracy in predicting the SPRs of proton beams, and it is expected that further improvements in predicting the position of the proton's Bragg peak will be possible if a wider variety of substitutes with different densities and elemental compositions of the human body are used to predict the SPRs.

• The Korean Journal of Nuclear Medicine Technology
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• v.27 no.1
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• pp.47-54
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• 2023

Purpose PET-CT imaging require an appropriate quality assurance system to achieve high efficiency and reliability. Quality control is essential for improving the quality of care and patient safety. Currently, there are performance evaluation methods of UN2-1994 and UN2-2001 proposed by NEMA and IEC for PET-CT image evaluation. In this study, we compare phantom images with the same experiments before and after PET-CT 3D normalization and well counter correction and evaluate the usefulness of quality control. Materials and methods Discovery 690 (General Electric Healthcare, USA) PET-CT equiptment was used to perform 3D normalization and well counter correction as recommended by GE Healthcare. Based on the recovery coefficients for the six spheres of the NEMA IEC Body Phantom recommended by the EARL. 20kBq/㎖ of ¹⁸F was injected into the sphere of the phantom and 2kBq/㎖ of ¹⁸F was injected into the body of phantom. PET-CT scan was performed with a radioacitivity ratio of 10:1. Images were reconstructed by appliying TOF+PSF+TOF, OSEM+PSF, OSEM and Gaussian filter 4.0, 4.5, 5.0, 5.5, 6.0, 6,5 mm with matrix size 128×128, slice thickness 3.75 mm, iteration 2, subset 16 conditions. The PET image was attenuation corrected using the CT images and analyzed using software program AW 4.7 (General Electric Healthcare, USA). The ROI was set to fit 6 spheres in the CT image, RC (Recovery Coefficient) was measured after fusion of PET and CT. Statistical analysis was performed wilcoxon signed rank test using R. Results Overall, after the quality control items were performed, the recovery coefficient of the phantom image increased and measured. Recovery coefficient according to the image reconstruction increased in the order TOF+PSF, TOF, OSEM+PSF, before and after quality control, RCmax increased by OSEM 0.13, OSEM+PSF 0.16, TOF 0.16, TOF+PSF 0.15 and RCmean increased by OSEM 0.09, OSEM+PSF 0.09, TOF 0.106, TOF+PSF 0.10. Both groups showed a statistically significant difference in Wilcoxon signed rank test results (P value<0.001). Conclusion PET-CT system require quality assurance to achieve high efficiency and reliability. Standardized intervals and procedures should be followed for quality control. We hope that this study will be a good opportunity to think about the importance of quality control in PET-CT

• Journal of the Korean Society of Radiology
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• v.17 no.3
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• pp.449-457
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• 2023

Shielding for reducing exposure dose can make the diagnosis limited. The purpose of this study is to increase the efficiency of radiation protection and minimize the loss of image information by producing the shielding made of the water and the contrast medium which has different proportion and finding out the ideal proportion of them. Each shielding materials were made of water and water-soluble iodine contrast medium with the different proportion. The attenuation rate of absorbed dose was evaluated by the shielding materials in the plastic contents for measuring the efficiency of the radiation protection. As a result, the higher ratio of the contrast medium, the more efficient it is for radiation attenuation. The anatomical structure was observed most properly in case of the solution with 20 ml of the contrast medium and most difficultly in case of more than 60 ml of the contrast medium. In case of the signal intensity between skeleton and gas, the difference of average value had a significant as p < 0.001. Shielding with contrast medium attenuates less than the conventional shielding but in the examination for the sensitive part to radiation, it can be used to minimize the loss of the image information and reduce the exposure dose.