• 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.

• 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.

• Progress in Medical Physics
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• v.19 no.1
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• pp.49-55
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• 2008

This study aims to conduct the comparative analysis of the radiation dose according to before and after the calibration of the ionization chamber used for measuring radiation dose in the MDCT, as well as of $CTDI_w$ according to temperature and pressure correction factors in the CT room. A comparative analysis was conducted based on the measured MDCT (GE light speed plus 4 slice, USA) data using head and body CT dosimetric phantom, and Model 2026C electrometer (RADICAL 2026C, USA) calibrated on March 21, 2007. As a result, the $CTDI_w$ value which reflected calibration factors, as well as correction factors of temperature and pressure, was found to be the range of $0.479{\sim}3.162mGy$ in effective radiation dose than the uncorrected values. Also, under the routine abdomen routine CT image acquisition conditions used in reference hospitals, patient effective dose was measured to indicate the difference of the maximum of 0.7 mSv between before and after the application of such factors. These results imply that the calibration of the ion chamber, and the correction of temperature and pressure of the CT room are crucial in measuring and calculating patient effective dose. Thus, to measure patient radiation dose accurately, the detailed information should be made available regarding not only the temperature and pressure of the CT room, but also the humidity and recombination factor, characteristics of X-ray beam quality, exposure conditions, scan region, and so forth.

• Proceedings of the Safety Management and Science Conference
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• 2011.11a
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• pp.563-571
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• 2011

The purpose of the study was to evaluation of the radiation dose reduction using various automatic exposure control (AEC) systems in different manufactures multi-detector computed tomography (MDCT). We used three different manufacturers for the study: General Electric Healthcare, Philips Medical systems and Siemens Medical Solutions. The general scanning protocol was created for the each examination with the same scanning parameters as many as possible. In the various AEC systems, the evaluation of reduced-dose was evaluated by comparing to fixed mAs with using body phantom. Finally, when we applied to AEC for three manufacturers, the radiation dose reduction decreased each 35.3% in the GE, 58.2% in the Philips, and 48.6% in the Siemens. This applies to variety of the AEC systems which will be very useful to reduce the dose and to maintain the high quality.

• Progress in Medical Physics
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• v.18 no.3
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• pp.139-143
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• 2007

The purpose of this study was to measure and evaluate radiation dose for MDCT parameters. Patient dose for various combination of MDCT parameters were experimentally measured, using MDCT (GE light speed plus 4 slice, USA), model 2026C electrometer (RADICAL 2026C, USA), standard Polymethylmethacrylate (PMMA) head and body CT dosimetry phantoms. In clinical situations, for a typical abdominal scan performed with MDCT at 120 kVp, 180 mAs, 20 mm collimation, and a pitch of 0.75 $CTDI_w,\;CTDI_{vol}$ were measured as 20.2 mGy, 26.9 mGy, respectively. When scan length is assumed as 271.3 mm, DLP and measured effective dose of the abdominal would be calculated as $729.1\;mGy{\cdot}cm$, 10.9 mSv, respectively.

• Journal of Radiation Protection and Research
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• v.32 no.3
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• pp.123-133
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• 2007

Z-axis automatic tube current modulation technique automatically adjusts tube current based on size of body region scanned. The purpose of the current study was to compare noise, and radiation dose of multi-detector row CT (MDCT) of lower extremity performed with Z-axis modulation technique of automatic tube current modulation with manual selection fixed tube current. Fifty consecutive underwent MDCT venography of lower extremity with use of a MDCT scanner fixed tube current and Z-axis automatic tube current modulation technique (10, 11 and 12 HU noise index, $70{\sim}450\;mA$). Scanning parameters included 120 kVp, 0.5 second gantry rotation time, 1.35:1 beam pitch, and 1 mm reconstructed section thickness. For each subject, images obtained with Z-axis modulation were compared with previous images obtained with fixed tube current (200, 250, 300 mA) and with other parameters identical. Images were compared for noise at five levels: iliac, femoral, popliteal, tibial, and peroneal vein of lower extremity. Tube current and gantry rotation time used for acquisitions at these levels were recorded. All CT examinations of study and control groups were diagnostically acceptable, though objective noise was significantly more with Z-axis automatic tube current modulation. Compared with fixed tube current, 2-axis modulation resulted in reduction of CTDIvol (range, $-6.5%{\sim}-35.6%$) and DLP (range, $-0.2%{\sim}-20.2%$). Compared with manually selected fixed tube current, 2-axis automatic tube current modulation resulted in reduced radiation dose at MDCT of lower extremity venography.

• Journal of the Korea Convergence Society
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• v.7 no.1
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• pp.89-95
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• 2016

The purpose of this experiment intend to evaluate the quality of the image based on the orbit and basal ganglia with high radiosensitivity for the noise, SNR and dose using the five kinds patient fixing pad in brain phantom MDCT(BrillianceTM CT 64 slice, PHILIPS, Netherward). The noise had a higher values in AP than those of others, but the SNR was lower in AP than those of others. The SNR was higher in UP than those of RP, PP, SP and AP. The UP, RP and PP were no statistically significant(p>0.05), whereas it was significant difference between UP, RP, PP and SP, AP(p<0.05). This is causes of the noise difference is generated due to the differences in the radiation absorption dose in accordance with each the component of the absorbed dose level of the detector according to the reference line and each of SOML when the radiation exposured. The CTDIvol(mGy) and DLP of orbit and basal ganglia were 56.95, 911.50, respectively. There is no difference between both mean dose. In conclusion, it is possible to distinguish among a kind of 5 patient fixing pad by using brain phantom MDCT. Overall, patient fixing pad of UP, RP and PP based on a brain phantom MDCT can provide useful information.

• Journal of radiological science and technology
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• v.34 no.4
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• pp.315-321
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• 2011

The goal of this study is to reduce patient exposure dose by providing image quality and radiation dose according to inspection methods. Volume Computed Tomography Dose Index(CTDIvol) and Dose Length Product(DLP) of prospective and retrospective ECG gating snapshot segment of Coronary CT angiography(CTA) were measured each snapshot segment methods. CT number, noise, uniformity, and resolution were also measured using phantom under the same condition of coronary CTA. The results showed that CT number, noise, uniformity and resolution are similar to each other. In terms of CTDIvol and DLP, however, measurement dose of prospective ECG gating snapshot segment was lower than the retrospective case by 37.5% and 40.3%. Therefore, it is highly recommended that in the coronary CTA, prospective ECG gating scan mode should be chosen to reduce patient dose.

• The Journal of the Korea Contents Association
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• v.14 no.1
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• pp.356-363
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• 2014

Recently pediatric CT has been performed by reduced dose according to tube current modulation이라고, this fact has a possibility more reduce a dose because of strong affect depend on tube current modulation. Almost all MDCT snow show and allow storage of the volume CT dose index (CTDIvol), dose length product (DLP), and effective dose estimations on dose reports, which are essential to assess patient radiation exposure and risks. To decrease these radiation exposure risks, the principles of justification and optimization should be followed. justification means that the examination must be medically indicated and useful. Results is using tube current modulation이라고 tend to the lower kV, the lower effective dose. In case of use a low dose CT protocol, we found a relatively lower effective dose than using tube current modulation. Average effective dose of our studies(brain, chest, abdomen-pelvis) less than 47%, 13.8%, 25.7% of germany reference dose, and 55.7%, 10.2%, 43.6% of UK(United Kingdom) reference dose respectively. when performed examination for reduced dose, we must use tube current modulation and low dose CT protocol including body-weight based tube current adaption.

• Progress in Medical Physics
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• v.21 no.2
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• pp.137-144
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• 2010

The purpose of this study was to evaluate the usefulness of reducing of craniofacial radiation dose using automatic exposure control (AEC) technique in the 64 multi-detector computed tomography (MDCT). We used SOMATOM Definition 64 multi-detector CT, and head of whole body phantom (KUPBU-50, Kyoto Kagaku CO. Ltd). The protocol were helical scan method with 120 kVp, 1 sec of rotation time, 5 mm of slice thickness and increment, 250 mm of FOV, $512{\times}512$ of matrix size, $64{\times}0.625\;mm$ of collimation, and 1 of pitch. The evaluation of dose reducing effect was compared the fixed tube current of 350 with AEC technique. The image quality was measured the noise using standard deviation of CT number. The range of craniofacial bone was to mentum end from calvaria apex, which devided three regions: calvaria~superciliary ridge (1 segment), superciliary ridge~acanthion (2 segment), and acanthion~mentum (3 segment). In the fixed tube current technique, CTDIvol was 57.7 mGy, DLP was $640.2\;mGy{\cdot}cm$ in the all regions. The AEC technique was showed that 1 segment were 30.7 mGy of CTDIvol, 340.7 $mGy{\cdot}cm$ of DLP, 2 segment were 46.5 mGy of CTDIvol, $515.0\;mGy{\cdot}cm$ of DLP, and 3 segment were 30.3 mGy of CTDIvol, $337.0\;mGy{\cdot}cm$ of DLP. The standard deviation of CT number was 2.622 with the fixed tube current technique and 3.023 with the AEC technique in the 1 segment, was 3.118 with the fixed tube current technique and 3.379 with the AEC technique in the 2 segment, was 2.670 with the fixed tube current technique and 3.186 with the AEC technique in the 3 segment. The craniofacial radiation dose using AEC Technique in the 64 MDCT was evaluated the usefulness of reducing for the eye, the parotid and thyroid with high radiation sensitivity particularly.