• Journal of the Korean Society of Radiology
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• v.15 no.4
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• pp.445-453
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• 2021

CT scan is reported to have a high risk of cancer due to a relatively high dose among medical radiological examinations. In particular, exposure to radiation to the breast, which is sensitive to radiation, is inevitable during a chest CT scan for female patient. In this study, the dose reduction effect of wearing a compression band during chest CT scans in women was evaluated, and the lifetime attributable risk due to the effective dose exposed during the CT scan was estimated. As a result, when the compression band was used, the effective tube current decreased as the outer perimeter of the chest became smaller, and it was analyzed that the CT dose index and effective dose were also reduced. In addition, the lifetime attributable risk by chest CT scan was found to reduce the cancer risk by 3.2 per 100,000 for all cancers, 0.2 per 100,000 for solid cancer, and 0.8 per 100,000 for breast cancer, based on women in their 30s when using a compression band. It is judged that the risk of cancer can be reduced through the use of appropriate scan parameters and dose optimization measures such as compression bands for future CT examinations.

• Journal of radiological science and technology
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• v.38 no.4
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• pp.383-387
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• 2015

This study investigated the size specific dose estimates of difference localizer on pediatric CT image. Seventy one cases of pediatric abdomen-pelvic CT (M:F=36:35) were included in this study. Anterior-posterior and lateral diameters were measured in axial CT images. Conversion factors from American Association of Physicists in Medicine (AAPM) report 204 were obtained for effective diameter to determine size specific dose estimate (SSDE) from the CT dose index volume (CTDIvol) recorded from the dose reports. For the localizer of mid-slice SSDE was 107.63% higher than CTDIvol and that of xiphoid-process slices SSDE was higher than 92.91%. The maximum error of iliac crest slices, xiphoid process slices and femur head slices between mid-slices were 7.48%, 17.81% and 14.04%. In conclusion, despite the SSDE of difference localizer has large number of errors, SSDE should be regarded as the primary evaluation tool of the patient radiation in pediatric CT for evaluation.

• Journal of radiological science and technology
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• v.46 no.2
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• pp.99-106
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• 2023

The height of the table should be considered important during computed tomography (CT) examination, but according to previous studies, not all radiology technologists set the table at the patient's center at the examination, which affects the exposure dose and image quality received by the patient. Therefore, this study intends to study the image quality exposure dose according to the height of the table to realize the optimal image quality and dose during the brain CT scan. The head phantom images were acquired using Philips Brilliance iCT 256. When the image was acquired, the table height was adjusted to 815, 865, 915, 965, 1015, and 1030 mm, respectively, and each scan was performed 3 times for each height. For the exposure dose measurement, optically stimulated luminescence dosimeter (OSLD) was attached to the front, side, eye, and thyroid gland of the head phantom. In the signal to noise ratio (SNR) measurement result, The SNR values for each table height were all lower than 915 mm. As a result of exposure dose, the exposure dose on each area increased as the table height decreased. The height of the table has a close relationship with the patient's radiation exposure dose in the CT scan.

• The Journal of the Korea Contents Association
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• v.15 no.6
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• pp.290-296
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• 2015

The purpose of this study was to derive the proposals and to suggest the exposure dose reduction scheme on pediatric head CT scan by analyzing and comparing CT dose index (CTDI) and the national diagnostic reference levels. From January 2014 to December, 231 children under 10years who were requested a pediatric head CT scan with head injury were examined. Research methods were to research and analyze the general characteristics kVp, mA test coverage $CTDI_{vol}$ and DLP referring to dose reports and electronic medical record (EMR). As a result, 7.4%(17 patients) of the total subjects in $CTDI_{vol}$ showed a national diagnostic reference levels exceeding. For DLP 41.6%(96 patients) in excess was relatively higher than $CTDI_{vol}$. DLP was exceeded more than about 60% that is higher than the CT dose index presented by Korea Food & Drug Administration. it is cause of high DLP that scan range increased more than about 30% wider than the standard test coverage presented in Health Insurance Review & Assessment Service. In conclusion, it is able to significantly lower the dose if it is complied with checking the baseline scan range of pediatric head CT scan and appropriately adjusting the protocol.

• Tuberculosis and Respiratory Diseases
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• v.57 no.2
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• pp.118-124
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• 2004

Lung cancer is the leading cause of cancer death for men and women in the industrialized world. It is desirable to detect disease at a stage when it is not causing symptoms and when control or cure is possible. If the screening test detects patients with the disease at an early stage, they can be examined to confirm the diagnosis and intervention can alter the natural history of the disease. The results of screening programs designed to detect early lung cancer using either conventional chest radiograph or sputum cytology are disappointing for a diagnostic screening test. Because of advances in helical CT imaging techniques, screening for lung cancer has been suggested as a possible method of improving outcome. Findings in recent publications suggest that substantial dose reduction is possible in chest CT. The advantages of low-dose CT are more sensitive than chest radiograph for detecting small pulmonary nodules that may be lung cancers, shorter scanning time than conventional chest CT scan without intravenous contrast injection, cheaper cost than standard CT, low radiation dose. However, the true clinical significance of the small tumors found by screening is still unknown, and their effect on mortality awaits future investigation. Furthermore, in addition to detecting an increased number of lung cancers, low-dose CT found at least one indeterminate nodule in many of all screened patients. The majority should be benign but evaluation of all these indeterminate nodules is not a trivial problem in routine practice. In conclusion, lung cancer screening with low-dose CT is a complex subject. The true effectiveness of lung cancer screening (a reduction in mortality from lung cancer) with low-dose CT can be determined through well-designed randomized control trials with enrolment of appropriate subjects.

• Journal of Radiation Protection and Research
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• v.30 no.3
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• pp.113-119
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• 2005

The computed tomogrpahy(CT) provides a high quality in images of human body but contributes to the relatively high patient dose. The frequency of CT examination is increasing and, therefore, the concerns about the patient dose are also increasing. In this study the experimental determination of patient dose was performed by using a physical anthropomorphic phantom and thermoluminescent dosimeter(TLD). The measurements were done for the both axial and spiral scan mode. As a result the effective doses for each scan mode were 17.78mSv and 10.01 mSv respectively and the fact that the degree of the reduction in the patient dose depends on the pitch scan parameter was confirmed. The measurement methods suggested in this study can be applied for the reassessment of the patient dose when the technique in CT equipment is developed or the protocol for CT scanning is changed.

• Journal of Biomedical Engineering Research
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• v.35 no.5
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• pp.151-159
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• 2014

Computed tomography (CT) is one of the most widely used medical imaging modality. However, substantial x-ray dose exposed to the human subject during the CT scan is a great concern. Region-of-interest (ROI) CT is considered to be a possible solution for its potential to reduce the x-ray dose to the human subject. In most of ROI-CT scans, the ROI is set to a circular shape whose diameter is often considerably smaller than the full field-of-view (FOV). However, an arbitrarily shaped ROI is very desirable to reduce the x-ray dose more than the circularly shaped ROI can do. We propose a new method to make a non-circular convex-shaped ROI along with the image reconstruction method. To make a ROI with an arbitrary convex shape, dynamic collimations are necessary to minimize the x-ray dose at each angle of view. In addition to the dynamic collimation, we get the ROI projection data with slightly lower sampling rate in the view direction to further reduce the x-ray dose. We reconstruct images from the ROI projection data in the compressed sensing (CS) framework assisted by the exterior projection data acquired from the pilot scan to set the ROI. To validate the proposed method, we used the experimental micro-CT projection data after truncating them to simulate the dynamic collimation. The reconstructed ROI images showed little errors as compared to the images reconstructed from the full-FOV scan data as well as little artifacts inside the ROI. We expect the proposed method can significantly reduce the x-ray dose in CT scans if the dynamic collimation is realized in real CT machines.

• Journal of radiological science and technology
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• v.42 no.2
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• pp.105-111
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• 2019

A medical personnel could be placed beside a patient together in CT room to do Ambu-bag for a seriously ill patients or emergency patient. At this time, the medical personnel can be exposed indirect radiation unnecessarily. In this case, it is necessary to recognize indirect radiation dose levels and methods to reduce them using actual clinical CT protocols such as Chest, Abdomen, and Brain CT. We researched surface radiation dose with or without radiation protectors such as apron and goggles according to different distances far from gantry using two different CT scanners (Fixed MDCT and mobile CT). As a result, for Chest, Abdomen, and Brain CT with Fixed MDCT, indirect radiation dose on thorax portion were 0.047, 0.089, 0.034 mSv without apron. Also, those with apron were 0.007, 0.012, 0.006 mSv. In case of mobile CT, it was 0.014 mSv without apron and 0.005 mSv with apron. By using protectors and increasing the distance, we could reduce it to 97%. Systematic management is necessary based on the measured data in order to minimize radiation damage due to indirect exposure dose.

• The Journal of the Korea Contents Association
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• v.17 no.6
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• pp.81-85
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• 2017

The aim of this study was to evaluate the usability of applied Low dose Computed Tomography(LDCT) protocol in examining urinary calculus using computed tomography. The subjects of this study were urological patients who visited a medical institution located in Busan from June to December 2016 and the protocol used in this study was Adaptive Statistical Iterative Reconstruction: low-dose CT with 50% Adaptive Statistical Iterative Reconstruction (ASIR). As results of quantitative analysis, the mean pixel value and standard deviation within kidney region of image(ROI)of the axial image were $26.21{\pm}7.08$ in abdomen CT pre scan and $20.03{\pm}8.16$ in low-dose CT. Also the mean pixel value and standard deviation within kidney ROI of the coronal image were $22.07{\pm}7.35$ in abdomen CT pre scan and $21.67{\pm}6.11$ in low dose CT. The results of qualitative analysis showed that four raters' mean values of observed kidney artifacts were $19.14{\pm}0.36$ when using abdomen CT protocol and $19.17{\pm}0.43$ in low-dose CT, and the mean value of resolution and contrast was $19.35{\pm}0.70$ when using abdomen CT protocol and $19.29{\pm}0.58$ in low-dose CT. Also the results of a exposure dose analysis showed that the mean values of CTDIvol and DLP in abdomen CT pre scan were 18.02 mGy and $887.51mGy{\cdot}cm$ respectively and the mean values of CTDIvol and DLP when using low-dose CT protocol were 7.412 mGy and $361.22mGy{\cdot}cm$ respectively. The resulting dose reduction rate was 58.82% and 59.29%, respectively.

• Progress in Medical Physics
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• v.30 no.4
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• pp.160-166
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• 2019

This study examined the clinical use of two newly installed computed tomography (CT) simulators in the Department of Radiation Oncology. The accreditation procedure was performed by the Korean Institute for Accreditation of Medical Imaging. An Xi R/F dosimeter was used to measure the CT dose index for each plug of the CT dose index phantom. Image qualities such as the Hounsfield unit (HU) value of water, noise level, homogeneity, existence of artifacts, spatial resolution, contrast, and slice thickness were evaluated by scanning a CT performance phantom. All test items were evaluated as to whether they were within the required tolerance level. CT calibration curves-the relationship between CT number and relative electron density-were obtained for dose calculations in the treatment planning system. The positional accuracy of the lasers was also evaluated. The volume CT dose indices for the head phantom were 22.26 mGy and 23.70 mGy, and those for body phantom were 12.30 mGy and 12.99 mGy for the first and second CT simulators, respectively. HU accuracy, noise, and homogeneity for the first CT simulator were -0.2 HU, 4.9 HU, and 0.69 HU, respectively, while those for second CT simulator were 1.9 HU, 4.9 HU, and 0.70 HU, respectively. Five air-filled holes with a diameter of 1.00 mm were used for assessment of spatial resolution and a low contrast object with a diameter of 6.4 mm was clearly discernible by both CT scanners. Both CT simulators exhibited comparable performance and are acceptable for clinical use.