• Journal of the Korean Society of Radiology
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• v.11 no.5
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• pp.379-385
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• 2017

This study identifies the optimal tube voltages depending on the changes in the patient's body type for limb tests using a digital radiography (DR) system. For the upper-limp test, the dose area product (DAP) was fixed at $5.06dGy{\ast} cm^2$, and for the lower-limb test, the DAP was fixed at $5.04dGy{\ast} cm^2$. Afterwards, the tube voltage was changed to four different stages and the images were taken three times at each stage. The thickness of the limbs was increased by 10 mm to 30 mm to change in the patient's body type. For a quantitative evaluation, Image J was used to calculate the contrast to noise ratio (CNR) and signal to noise ratio (SNR) among the four groups, according to the tube voltage. For statistical testing, the statistically significant differences were analyzed through the Kruskal-Wallis test at a 95% confidence level. For the qualitative analysis of the images, the pre-determined items were evaluated based on a 5-point Likert scale. In both upper-limb and lower-limb tests, the more the tube voltage increased, the more the CNR and SNR of the images decreased. The test on the changes depending on the patient's body shape showed that the more the thickness increased, the more the CNR and SNR decreased. In the qualitative evaluation on the upper limbs, the more the tube voltage increased, the more score increased to 4.6 at the maximum of 55kV and 3.6 at 40kV, respectively. The mean score for the lower limbs was 4.4, regardless of the tube voltage. The more either the upper or lower limbs got thicker, the more the score generally decreased. The score of the upper limps sharply dropped at 40kV, whereas that of the lower limps sharply dropped at 50kV. For patients with a standard thickness, the optimized images can be obtained when taken at 45kV for the upper limbs, and at 50kV for the lower limbs. However, when the thickness of the patient's limbs increases, it is best to set the tube voltage at 50 kV for the upper limbs and at 55 kV for the lower limbs.

• Journal of the Korean Society of Radiology
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• v.13 no.7
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• pp.1035-1043
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• 2019

The object of is this research is to find out the optimal Tesla by evaluating SNR and CNR, after testing 1.5 T and 3.0 T. The randomly selected patients tested by nasopharynx MRI transmitted in PACS were applied to the research. Two MRI units(1.5 T, 3.0 T) was used for analyzing the data. As a method of analysis, in T1W highlighting and T1 fat removal images, we set up a certain area of interest and evaluated the SNR and CNR on tongue, spinal cord, masseter muscle, fat, parotid gland, and tumor tissue. We evaluated the SNR and CNR by quantitative analysis of six tissue, measuring the quality of images for uniform fat removal, magnetic sensitivity artifact on a four-point scale by qualitative analysis. The statistical significance of this date analysis was based on independent sample verification and was accepted when the P value was less than 0.05. As a result of analysis of both devices, 3.0 T was high in the quantitative evaluation, while 1.5 T was high in the qualitative evaluation. Considering the advantages and disadvantages of each device, and if the device is selected complementarily and applied to patients, it is believed that it will provide the optimal information.

• 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.7
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• pp.1025-1031
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• 2023

We aimed to evaluate the radiation dose and image quality by changing the Scout view voltage in low-dose chest CT (LDCT) and applying scan parameters such as AEC (auto exposure control) and ASIR (adaptive statistical iterative reconstruction) to find the optimal protocol. Scout view voltage was varied at 80, 100, 120, 140 kV and after measuring the dose 5 times using the existing low-dose chest CT protocol, the appropriate kV was selected for the study using the Dose report provided by the equipment. After taking a basic LDCT shot at 120 kV, 30 mAs, ASIR 50% was applied to this condition. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were assessed by measuring Background noise (B/N). For dose comparison, CTDI_vol and DLP provided by the equipment were compared and analyzed using the formulas. The results indicated that the protocol of scout 140 + LDCT + ASIR 50 + AEC reduced radiation exposure and improved image quality compared to traditional LDCT, providing an optimal protocol. As demonstrated in the experiment, LDCT screenings for asymptomatic normal individuals are crucial, as they involve concerns over excessive radiation exposure per examination. Therefore, applying appropriate parameters is important, and it is expected to contribute positively to the public health in future LDCT based health screenings.

• Journal of the Korean Society of Radiology
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• v.13 no.5
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• pp.699-704
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• 2019

It is important to minimize the exposure dose during an examination and obtain good quality images at the same time. This study compared the beam harding effect according to the baseline superior orbito meatal line(SOML), orbito meatal line(OML), inferior orbito metal line(OML) and measured the exposure dose of the lens, especially in brain CT examinations, which generally apply to head diease patients. The beam harding effect assessment of each image along the baseline was performed quantitatively using the Image J program, and the exposure dose of the lens was detected by OSLDs and compared. As a result, As a result, when the SOML was used as the reference line, the dose of the lens was decreased by 85.08% at 80 kV and by 79.7% at 80 kV, compared to when IOML was used as the baseline. If the gantry angle at brain CT was parallel scan to SOML, there were no significant differences in the exposure to the lens and between the OML and IOML. Therefore, this study has shown that it is efficient to have a parallel scan on SOML as a protocol during Brain CT examinations.

• Journal of the Korean Society of Radiology
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• v.13 no.4
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• pp.623-628
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• 2019

The aim of this study was to design fast non local means (FNLM) noise reduction algorithm and to confirm its application feasibility in light microscopic image. For that aim, we acquired mouse first molar image and compared between previous widely used noise reduction algorithm and our proposed FNLM algorithm in acquired light microscopic image. Contrast to noise ratio, coefficient of variation, and no reference-based evaluation parameter such as natural image quality evaluator (NIQE) and blind/referenceless image spatial quality evaluator (BRISQUE) were used in this study. According to the result, our proposed FNLM noise reduction algorithm can achieve excellent result in all evaluation parameters. In particular, it was confirmed that the NIQE and BRISQUE evaluation parameters for analyzing the overall morphologcal image of the tooth were 1.14 and 1.12 times better than the original image, respectively. In conclusion, we demonstrated the usefulness and feasibility of FNLM noise reduction algorithm in light microscopic image of small animal tooth.

• Journal of the Korean Society of Radiology
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• v.13 no.7
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• pp.1025-1033
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• 2019

Although magnetic resonance imaging without linear hardening of CT is recognized as a method of obtaining high contrast of tissue and excellent resolution image in brain disease and head and neck examination, magnetic susceptibility artifact is generated in case of metal implants in the oral cavity, which is an obstacle to image diagnosis. Therefore, an effort was made in this thesis to find a method to reduce artifacts caused by dental implants and prosthesis in MRI. Implant-induced artifacts in magnetic resonance imaging showed that the signal size increased with shorter TE in GE technique and was inconsistent with water temperature change. In SE technique as well, the signal size of water was generally higher than that of air, but the signal to noise ratio (SNR) was not different by air and temperature. In EPI technique, images with fewer artifacts were obtained quantitatively and qualitatively when there was more water than air, and the signal to noise ratio was measured the highest, especially at water temperatures of 20° and 30°. In conclusion, when examining using the EPI technique rather than the SE or the GE technique, obtaining brain diffusion using a 20° and 30° water bag reduces the magnetic susceptibility artifacts caused by implants and prosthesis, suggesting that it may provide images with high diagnostic value.

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.637-645
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• 2017

The objective of this study was to find the optimum test device for the cerebral blood vessels by comparing and analyzing the SNR and CNR methods for images of three devices (i.e., MRA, CTA, and DSA). The study targeted 90 patients who underwent cerebral angiography from November 2016 to May 2017. The measuring parts were measured by using Rt MCA, Lt MCA, and ACA Image J. The results of quantitative analysis showed that the mean SNR of MRA, the CNR of MRA, the signal strength of MRA, the mean SNR of CTA, the CNR of CTA, the signal strength of CTA, the SNR of DSA, the CNR of DSA, and the signal strength of DSA were evaluated as 254.87, 178.13, 326.81, 74.75, 62.2, 356.66, 26.85, 25.89, and 4400.69, respectively (p<0.05). As a result, both SNR and CNR methods measured it in the order of MRA>CTA>DSA. Statistical significance was determined by using ANOVA analysis at p<0.05 and Bonferroni method was used as a post-hoc analysis SPSS. In conclusion, the results of this study revealed that the optimum imaging devices were MRA, CTA, and DSA after evaluating randomly selected patients with cerebrovascular disease.

• Journal of the Korean Society of Radiology
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• v.14 no.2
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• pp.139-148
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• 2020

The purpose of this study is to propose a method to optimize the performance of Digital Radiography (DR) by analyzing the effect of exposure time change on the stability of radiation output and image quality. The experimental method was used to change the exposure time to 50 msec, 100 msec, 200 msec, and 400 msec so that the Percentage Average Error (PAE), Time-to-Radiation Dose Curve, Signal to Noise Ratio (SNR), Contrast to Noise Ratio (CNR) and theses analysis were performed to evaluate the normal operation of parameters, radiation output and image quality. As a result, all the parameters used in the experiment showed the Percentage Average Error in the normal range, and the shorter the exposure time, the stability of radiation output and image quality decrease. In conclusion, it was found that the performance of Digital Radiography can be optimized when stable radiation output and image quality are applied by applying 100 msec ~ 200 msec exposure time.

• Journal of radiological science and technology
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• v.44 no.2
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• pp.101-107
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• 2021

The purpose of this study was to evaluate optimal CT scan parameters to minimize patient dose to the irradiation and maintain satisfactory image quality in low-dose chest computed tomography (CT) scans. In a chest anthropomorphic phantom, chest CT scans were performed at different kVp and mA within reference of 3.4mGy in volume CT Dose Index (CTDI_vol). The following quantitative parameters had been statistically evaluated: image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and figure of merit (FOM). Nine radiographers conducted the blind test to select the optimal kVp-mA combination. Results indicated that the kVp-mA combination of 80kVp-90mA, 100kVp-50mA, 120kVp-30mA and 140kVp-30mA were obtained high SNR and CNR. The 120kVp-30mA combination offered good compromise in the FOM, which showed the quality and dose performance. In the blind test, an image of 80kVp-90mA obtained a high score with 4.7 points, and 120kVp-10mA or 140kVp-10mA with a low tube current were observed severe noise and poor image quality, thus resulting in decreased diagnostic accuracy. On the other hand, in the combination of high kVp and high mA(140kVp-90mA), the image quality was improved, but the radiation dose was also increased. the FOM value of 140kVp-90mA was lower than 120kVp-30mA. The application of appropriate scan parameters in low-dose chest CT scans produced satisfactory results in dose and image quality for the accuracy of the clinical diagnosis.