• The Journal of the Korea Contents Association
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• v.13 no.4
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• pp.290-299
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• 2013

This study included 198 patients who underwent prospectively electrocardiogram-triggered high-pitch spiral mode(FLASH mode) in cardiac CT for health check: 123 patients who underwent manual exposure control(Group A) and 75 patients who underwent automatic exposure control(Group B). Patients were classified according to BMI grades: Grade 1, Grade 2, Grade 3, Grade 4. Radiation dose, objective and subjective image quality between two groups were compared. In Group B, tube voltage were significantly decreased in all BMI grades. Both $CTDI_{vol}$ and effective dose were significantly reduced in the BMI Grade 1, 3, and 4 whereas they were slightly reduced in the Grade 2(p>0.05), SNR was significantly decreased in the Grade 1 and increased in the Grade 3(p<0.05), but there was no significant difference in the Grade 2, 4 between the two groups(p>0.05). CNR was significantly decreased in the Grade 1(p<0.05), and there was no significant difference in the Grade 2, 3, 4 between the two groups(p>0.05). The subjective image quality showed no significant difference in all BMI Grades between the two groups(p>0.05). Automatic exposure control can lead to a significant reduction of radiation exposure dose without degradation of subjective image quality.

• Journal of Digital Convergence
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• v.12 no.3
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• pp.353-358
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• 2014

This study was conducted to analyze the patient's exposed dose targeting the patients who had acute ischemic stroke symptoms and CT brain perfusion scan, by comparing fixed time technique and bolus tracking technique which was provided by the manufacturer and to identify the Time graph to implement the usability of contrast medium's tracking technique the best contrast enhancement intervals. $CTDI_{VOL}$ of PCT in patient appeared to be 431.72mGy in fixed scan delay protocol, whereas 323.61mGy in Bolus tracking technique. The value of DLP appeared to be $1243.47mGy{\cdot}cm$ in fixed scan delay protocol, whereas $932mGy{\cdot}cm$ in Bolus tracking technique. Time graph appeared to be various in fixed scan delay protocol, whereas the optimal time graph could be obtained in Bolus tracking. The exposure dose could be reduced by 25% applying Bolus tracking technique when taking brain perfusion CT scan.

• Journal of the Korean Society of Radiology
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• v.10 no.3
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• pp.161-169
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• 2016

In this study, the proposal to seek ways to reduce the amount of radiation is drawn by comparing and analyzing CT Dose Index(CTDI) on the pediatric head CT which was performed at the busan regional hospitals, to the national diagnostic reference levels. As a result, it was appeared to exceed the amount of the dose recommendation in order of hospital, general hospital and senior general hospital in the hospital-specific classification and from 2 to 5 year, from 1 month to 1 year and from 6 to 10 year in the age-specific classification. In addition, the amount of the dose recommendation was exceed in order of helical, axial and volume in the scan-specific classification. As the results of the scan range reset to match the diagnostic reference level, the dose reduction showed 11.68%, 15.79% and 20.66% in senior general hospital, general hospital and hospital respectively. In the results of analysing patient average scan ranges which does not deviate from the guideline of patient dose recommendation, there was age of 1 month to 1 year, 2 to 5 year and 6 to 10 year of $03.2{\pm}11.8mm$, $110.5{\pm}14.5mm$, and $117.8{\pm}17.2mm$ respectively.

• Journal of the Korean Society of Radiology
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• v.15 no.7
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• pp.1065-1072
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• 2021

In Computed Tomography, abdominal examination showed the highest proportion of use, and effort of reducing the radiation dose is required. Recently introduced Iterative Reconstruction(IR) is repetitive reconstruction technique of Computed Tomography. SIEMENS' IR, ADMIRE and GE's IR, ASIR-V, were used in this examination. Noise, % Contrast, and High contrast resolution were measured by using ACR phantom for image quality evaluation. In addition, CTDI_vol and DLP displayed in the CT device were used for dose evaluation. When FBP and IR were compared, stage 2 to stage 5 of ADMIRE and 10, 30, 50, 70, and 90% of ASIR-V were applied, noise could be reduced from a minimum of 0.46 to a maximum of 2.38 in ADMIRE compared to FBP, and noise from a minimum of 0.51 to a maximum of 2.5 in ASIR-V compared to FBP. Also, % Contrast and High contrast resolution of FBP and IR were no statistical difference. When IR was used for abdominal CT examination, the radiation dose of ADMIRE is reduced by 25.39% compared to the radiation dose of FBP. Also, the radiation dose of ASIR-V is reduced by 16.61% compared to the radiation dose of FBP. In conclusion, it is believed that if IR is applied during abdominal CT examination, the radiation dose can be reduced without deteriorating the image quality.

• Korean Journal of Radiology
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• v.22 no.7
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• pp.1172-1184
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• 2021

Objective: The purposes of this study were to analyze the radiation doses for pediatric abdominopelvic and chest CT examinations from university hospitals in Korea and to establish the local diagnostic reference levels (DRLs) based on the body weight and size. Materials and Methods: At seven university hospitals in Korea, 2494 CT examinations of patients aged 15 years or younger (1625 abdominopelvic and 869 chest CT examinations) between January and December 2017 were analyzed in this study. CT scans were transferred to commercial automated dose management software for the analysis after being de-identified. DRLs were calculated after grouping the patients according to the body weight and effective diameter. DRLs were set at the 75th percentile of the distribution of each institution's typical values. Results: For body weights of 5, 15, 30, 50, and 80 kg, DRLs (volume CT dose index [CTDI_vol]) were 1.4, 2.2, 2.7, 4.0, and 4.7 mGy, respectively, for abdominopelvic CT and 1.2, 1.5, 2.3, 3.7, and 5.8 mGy, respectively, for chest CT. For effective diameters of < 13 cm, 14-16 cm, 17-20 cm, 21-24 cm, and > 24 cm, DRLs (size-specific dose estimates [SSDE]) were 4.1, 5.0, 5.7, 7.1, and 7.2 mGy, respectively, for abdominopelvic CT and 2.8, 4.6, 4.3, 5.3, and 7.5 mGy, respectively, for chest CT. SSDE was greater than CTDI_vol in all age groups. Overall, the local DRL was lower than DRLs in previously conducted dose surveys and other countries. Conclusion: Our study set local DRLs in pediatric abdominopelvic and chest CT examinations for the body weight and size. Further research involving more facilities and CT examinations is required to develop national DRLs and update the current DRLs.

• The Journal of the Korea Contents Association
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• v.9 no.3
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• pp.225-231
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• 2009

The purpose of the current study was to compare radiation dose of 64MDCT performed with automatic exposure control (AEC) with manual selection fixed tube current. We evaluated the CT scans of phantom of the chest and abdomen using the fixed tube current and AEC technique. Objective image noise shown as the standard deviation of CT value in Hounsfield units was measured on the obtained images. Compared with fixed tube current, AEC resulted in reduction of the chest and abdomen in the CTDIvol (35.2%, 5.9%) and DLP (49.3%, 3.2%). Compared with manually selected fixed tube current, AEC resulted in reduced radiation dose at MDCT study of chest and abdomen.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.681-688
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• 2022

Dose monitoring in CT patients requires accurate dose estimation but most of the CT dose calculation tools are based on Caucasian computational phantoms. We established a library of organ dose conversion coefficients for Korean adults by using four Korean adult male and two female voxel phantoms combined with Monte Carlo simulation techniques. We calculated organ dose conversion coefficients for head, chest, abdomen and pelvis, and chest-abdomen-pelvis scans, and compared the results with the existing data calculated from Caucasian phantoms. We derived representative organ doses for Korean adults using Korean CT dose surveys combined with the dose conversion coefficients. The organ dose conversion coefficients from the Korean adult phantoms were slightly greater than those of the ICRP reference phantoms: up to 13% for the brain doses in head scans and up to 10% for the dose to the small intestine wall in abdominal scans. We derived Korean representative doses to major organs in head, chest, and AP scans using mean CTDI_vol values extracted from the Korean nationwide surveys conducted in 2008 and 2017. The Korean-specific organ dose conversion coefficients should be useful to readily estimate organ absorbed doses for Korean adult male and female patients undergoing CT scans.

• 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 Radiation Industry
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• v.12 no.4
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• pp.365-372
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• 2018

The use of CT examinations is increasing rapidly and radiation dose from CT examinations is much higher than other diagnostic radiography examinations including general radiography and mammography. DRLs used to optimize the radiation dose of patients by diagnostic radiology in each country. The objective of this study was to investigate and to analyze the status of DRLs from CT examinations in domestic and other countries. In other countries, DRLs were set for each age group and each examination considering the medical situation of each country. In Korea, DRLs were set for adults and children in 2017. For adults, DRLs were set for 13 examinations. Reported DLP values were 1119, 297, $472mGy{\cdot}cm$ for head, chest and abdomen pelvis examination, respectively. For children, DRLs were set for head examinations. Reported DLP values were 298 (0~1 years), 404 (2~5 years), 494 (6~10 years), 1,088 (11~15 years) $mGy{\cdot}cm$. DRLs of Korea were similar to other countries for head examinations. For chest examinations and abdomen pelvis examinations were relatively lower than other countries. As a major reason for relatively low radiation dose, it is considered to contribute the activity and management of medical radiation safety at national level.

• Progress in Medical Physics
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• v.21 no.3
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• pp.246-252
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• 2010

The purpose of this study provides measurements of radiation dose from MDCT of head, chest, abdomen and pelvic examinations. A series of dose quantities that are measured of patient weight to compare the dose received during MDCT examinations. Data collected included: weight together with CT dose descriptors, volume CT dose index (CTDIvol) and dose length product (DLP). The effective dose was also estimated and served as collective dose estimation data. Data from 1,774 adult patients attending for a CT examination of the head (n=520) or chest (n=531) or abdomen (n=724) was obtained from spiral CT units using a same CT protocol. Mean values of CTDIvol was a range of 48.6 mGy for head and 6.9, 10.5 mGy for chest, abdomen examinations, respectively. And mean values of DLP was range of 1,604 $mGy{\cdot}cm$ for head, 250 $mGy{\cdot}cm$ for chest, 575 $mGy{\cdot}cm$ for abdomen examinations, respectively. Mean effective dose values for head, chest, abdominal CT were 3.6, 4.2, and 8.6 mSv, respectively. The degree of CTDIvol and DLP was a positive correlation with weight. And there was a positive correlation for weight versus CTDIvol ($r^2$=0.62), DLP ($r^2$=0.694) in chest. And head was also positive correlation with weight versus CTDIvol ($r^2$=0.691), DLP ($r^2$=0.741). We conclude that CTDIvol and DLP is an important determinant of weight within the CT examinations. The results for this study suggest that CT protocol should be tailored according to patient weight.