• Journal of radiological science and technology
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• v.39 no.4
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• pp.607-614
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• 2016

The study investigates the necessity of 3 dimensional dose distribution evaluation instead of point dose and 2 dimensional dose distribution evaluation. Treatment plans were generated on the RANDO phantom to measure the precise dose distribution of the treatment site 0.5, 1, 1.5, 2, 2.5, 3 cm with the prescribed dose; 1,200 cGy, 5 fractions. Gamma analysis (3%/3 mm, 2%/2 mm) of dose distribution was evaluated with gafchromic EBT2 film and ArcCHECK phantom. The average error of absolute dose was measured at $0.76{\pm}0.59%$ and $1.37{\pm}0.76%$ in cheese phantom and ArcCHECK phantom respectively. The average passing ratio for 3%/3 mm were $97.72{\pm}0.02%$ and $99.26{\pm}0.01%$ in gafchromic EBT2 film and ArcCHECK phantom respectively. The average passing ratio for 2%/2 mm were $94.21{\pm}0.02%$ and $93.02{\pm}0.01%$ in gafchromic EBT2 film and ArcCHECK phantom respectively. There was a more accurate dose distribution of 3D volume phantom than cheese phantom in patients DQA using tomotherapy. Therefor it should be evaluated simultaneously 3 dimensional dose evaluation on target and peripheral area in rotational radiotherapy such as tomotherapy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2278-2284
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• 2012

Exposure-dose reducing effect was measured by using bolus, a tissue-equivalent material as a shield to obtain useful diagnostic images while minimizing the radiation exposure of thyroid which is highly sensitive to radiation during panoramic radiography. The experiment was performed within the period of 1 June 2001 through 30 June 2011 by measuring entrance surface dose and deep dose at the thyroid-corresponding site of a head and neck phantom. As a result, the entrance surface dose in the thyroid for using no shield was 43.84 ${\mu}Gy$ on the average, and the thyroid shield of bolus 10 mm in thickness reduced the dose by 15.45 ${\mu}Gy$(35.24%) to 28.39 ${\mu}Gy$ on the average. The use of a 20 mm thyroid shield resulted in the dose of 25.38 ${\mu}Gy$ on the average, a 18.46 ${\mu}Gy$(42.10%) drop from 43.84 ${\mu}Gy$ for using no shield. On the site 20 mm below the surface, a thyroid shield 10 mm in thickness had no dose-reducing effect, while a 20 mm thyroid shield reduced the dose by 0.06 mSv(20%).

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.100-104
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• 2009

In this study, the space gamma dose rates in the apartments structured with concrete were measured in accordance with construction year. In addition, the environmental radiation rates coming from the subway platforms and the road tunnels were analyzed in the equivalent dose by multiplying the absorbed dose with the radiation weighting factors. The space gamma dose rates measured in apartments were higher than those of outdoor which was $0.08{\sim}0.11uSv/h$ in the natural conditions. Especially, the older construction year is, the higher becomes space gamma dose rate. The average gamma dose rates in the subway platforms were measured. In the case of Busan and Daegu subway, the earlier the opening year is, the higher becomes dose rate. However, the dose rates of Seoul subway Lines were high overall, regardless of opening year. Seoul subway Line 6 showed the highest value of 0.21uSv/h. The gamma dose rate in road tunnels was higher than one of the outdoor and increased with opening year like as apartment. In dose rate comparison of the concrete structures with the outdoor, therefore, the space gamma dose rate of indoor is higher than one of the outdoor and the older structures have a higher dose rate.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.27 no.3
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• pp.170-179
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• 2017

Objectives: This study aims to investigate the occupational radiation exposures of emergency medical technicians(EMTs) in emergency medical centers in Korea. The results will provide a basis for developing prevention programs to minimize adverse health effects relating to radiation exposure among emergency medical technicians working in this area. Methods: Radiation exposure doses were measured for twenty-two EMTs working in six emergency medical centers. Thermo Luminescent Dosimeters(TLD) were placed on three representative body parts, including chest, neck, and a finger. Measurements were conducted over the entire working hours of the participants for foor weeks. Dosimeters were analyzed according to a standard method by a KFDA-designated lab. Detection rate, annual radiation exposure dose, and relative levels to dose limit were derived based on the measured doses from the dosimeters. SPSS/Win 18.0 software(IBM, US) was used for statistical analysis. Results: Detection rates were 45.5%, 36.4%, and 45.5% for the dosimeters sampled from chest, neck, and a finger, respectively. The average annual doses were $2.39{\pm}3.44mSv/year$(range 0.38-10.0 mSv/year) for the chest, $2.72{\pm}3.05mSv/year$(2.00-11.34) for the neck, and $20.98{\pm}17.57mSv/year$(1.25-53.50) for the hand dose. The average annual eye dose was estimated to $3.61{\pm}2.37mSv/year$(1.50-8.34). The exposure dose levels of EMTs were comparable to those of radiologists, who showed relatively higher radiation dose among health care workers, as reported in another study. Conclusions: EMTs working in emergency medical centers are considered to be at risk of radiation exposure. Although the radiation exposure dose of EMTs does not exceed the dose limit, it is not negligible comparing to other professionals in health care sectors.

• The Journal of Korean Society for Radiation Therapy
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• v.21 no.1
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• pp.1-7
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• 2009

Purpose: The purpose is to evaluate the accuracy of correcting the targeting error through the Target Location System (TLS) for the location change error of the reference point which arises from the movement or motion of patient during the treatment using the CyberKnife. Materials and Methods: In this test, Gafchromic MD-55 film was inserted into the head and neck phantom to analyze the accuracy of the targeting, and then the 6 MV X-ray of CyberKnife (CyberKnife Robotic Radiosurgery System G4, Accuray, US) was irradiated. End to End (E2E) program was used to analyze the accuracy of targeting, which is provided by Accuray Corporation. To compute the error of the targeting, the test was carried out with the films that were irradiated 12 times by maintaining the distance within the rage of $0{\pm}0.2\;mm$ toward x, y, z from the reference point and maintaining the angle within the rage of $0{\pm}0.2^{\circ}$ toward roll, pitch, yaw, and then with the films which were irradiated 6 times by applying intentional movement. And the correlation in the average value of the reference film and the test film were analyzed through independent samples t-test. In addition, the consistency of dose distribution through gamma-index method (dose difference: 3%) was quantified, compared, and analyzed by varying the distance to agreement (DTA) to 1 mm, 1.5 mm, 2 mm, respectively. Results: E2E test result indicated that the average error of the reference film was 0.405 mm and the standard deviation was 0.069 mm. The average error of the test film was 0.413 mm with the standard deviation of 0.121 mm. The result of independent sampling t-test for both averages showed that the significant probability was P=0.836 (confidence level: 95%). Besides, by comparing the consistency of dose distribution of DTA through 1 mm, 1.5 mm, 2 mm, it was found that the average dose distribution of axial film was 95.04%, 97.56%, 98.13%, respectively in 3,314 locations of the reference film, consistent with the average dose distribution of sagittal film that was 95.47%, 97.68%, 98.47%, respectively. By comparing with the test film, it was found that the average dose distribution of axial film was 96.38%, 97.57%, 98.04%, respectively, at 3,323 locations, consistent with the average dose distribution of sagittal film which was 95.50%, 97.87%, 98.36%, respectively. Conclusion: Robotic CyberKnife traces and complements in real time the error in the location change of the reference point caused by the motion or movement of patient during the treatment and provides the accuracy with the consistency of over 95% dose distribution and the targeting error below 1 mm.

• Journal of radiological science and technology
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• v.41 no.1
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• pp.39-45
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• 2018

The purpose of this study is to evaluate the usefulness of a software-based quality assurance system based on Volumetric Modulated Arc Therapy treatment plan. Evaluate treatment plan through the D VH analysis, PTV mean dose ($D_{mean}$) and PTV 95% dose($D_{95}$) compare the MFX based on original treatment plan, Average error rate was $0.9{\pm}0.6%$, $1.0{\pm}0.8%$, respectively. Measuring point dose using phantom and ion chamber, the average error rate between the ionization chamber and MFX was $0.9{\pm}0.7%$, $1.1{\pm}0.7%$ (high dose region), $1.1{\pm}0.9%$, $1.2{\pm}0.7%$ (low dose region). The average gamma though of MFX and $Delta^{4PT}$ is $98.7{\pm}1.2%$, $98.4{\pm}.3%$, respectively. Through this study, A software based QA system that simplifies hardware based QA procedures that involve a lot of time and effort. It can be used as a simple and useful tool in clinical practice.

• Toxicological Research
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• v.33 no.4
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• pp.291-297
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• 2017

This study was performed to investigate the dose-response relationship between average daily cadmium dose (ADCD) from rice and the occurrence of urinary cadmium (U-Cd) in individuals eating that rice. This was a retrospective cohort designed to compare populations from two areas with different levels of cadmium contamination. Five-hundred and sixty-seven participants aged 18 years or older were interviewed to estimate their rice intake, and were assessed for U-Cd. The sources of consumed rice were sampled for cadmium measurement, from which the ADCD was estimated. Binary logistic regression was used to examine the association between ADCD and U-Cd (cut-off point at $2{\mu}g/g$ creatinine), and a correlation between them was established. The lowest estimate was $ADCD=0.5{\mu}g/kg\;bw/day$ [odds ratio (OR) = 1.71; with a 95% confidence interval (CI) 1.02-2.87]. For comparison, the relationship in the contaminated area is expressed by $ADCD=0.7{\mu}g/kg\;bw/day$, OR = 1.84; [95 % CI, 1.06-3.19], while no relationship was found in the non-contaminated area, meaning that the highest level at which this relationship does not exist is $ADCD=0.6{\mu}g/kg\;bw/day$ [95% CI, 0.99-2.95]. Rice, as a main staple food, is the most likely source of dietary cadmium. Abstaining from or limiting rice consumption, therefore, will increase the likelihood of maintaining U-Cd within the normal range. As the recommended maximum ADCD is not to exceed $0.6{\mu}g/kg\;bw/day$, the consumption of rice grown in cadmium-contaminated areas should not be more than 246.8 g/day. However, the exclusion of many edible plants grown in the contaminated area from the analysis might result in an estimated ADCD that does not reflect the true level of cadmium exposure among local people.

• Journal of the Korean Society of Radiology
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• v.12 no.7
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• pp.821-826
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• 2018

This study was performed randomly from all the patients who visited the University Hospital in Gyeonggi-do from January 1, 2018 to June 30, 2018 for the abdominal CT scan. We divided the patients into three groups and evaluated the extent of effective dose and image quality according to the area of the abdominal CT image. As a result, the effective dose was 7.34 mSv in the average area group, 8.39 mSv in the average area and 5.89 mSv in the average area. For the analysis of image quality, ROI was plotted in the same three regions according to the abdominal area. As a result, CT values were significantly different in the abdominal area classified into 3 groups (p <0.05). The results of this study can be used as a basic data for the development of a protocol that can be applied in actual clinical practice. It is thought that it can help to reduce the image quality and the radiation dose.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.958-967
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• 2023

This work studies the defect features in a dilute FeMnNi alloy by an Object Kinetic Monte Carlo (OKMC) model based on the "grey-alloy" method. The dose rate effect is studied at 573 K in a wide range of dose rates from 10^-8 to 10^-4 displacement per atom (dpa)/s and demonstrates that the density of defect clusters rises while the average size of defect clusters decreases with increasing dose rate. However, the dose-rate effect decreases with increasing irradiation dose. The model considered two realistic mechanisms for producing <100>-type self-interstitial atom (SIA) loops and gave reasonable production ratios compared with experimental results. Our simulation shows that the proportion of <100>-type SIA loops could change obviously with the dose rate, influencing hardening prediction for various dose rates irradiation. We also investigated ways to compensate for the dose rate effect. The simulation results verified that about a 100 K temperature shift at a high dose rate of 1×10^-4 dpa/s could produce similar irradiation microstructures to a lower dose rate of 1×10^-7 dpa/s irradiation, including matrix defects and deduced solute migration events. The work brings new insight into the OKMC modeling and the dose rate effect of the Fe-based alloys.

• Journal of radiological science and technology
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• v.38 no.3
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• pp.221-228
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• 2015

Purpose: In digital mammography QC program was used for the purpose of reducing low-dose and high-definition images of the radiation dose. Materials and Methods: In digital mammography using a QC phantom according to the average glandular dose in the exposure method MLO view $0^{\circ}C$, $30^{\circ}C$, $45^{\circ}C$, $50^{\circ}C$, $55^{\circ}C$, $70^{\circ}C$, was measured at $90^{\circ}C$ intervals, an image with Hologic QC program to the SNR and CNR was measured to evaluate. Results: The average dose in the MLO view was wired to $90^{\circ}C$ when the maximum was 1.75 mGy, it decreased approximately 6% was measured at $45^{\circ}C$ 1.65 mGy. In addition, 1.67 mGy, manual record, there were an average wired in accordance with the exposure dose and the dose of 1.52 mGy difference in the way auto filter. Image quality evaluation at every angular section SNR 50 ~ 52, shows a slight difference in CNR 11 ~ 12, it was included in the manufacturer's recommended value. Conclusion: The dose was lowest in MLO view $45^{\circ}C$, the difference between SNR and CNR were insignificant. The method of exposure will need a way to reduce the exposure of the patient's body or unnecessary patient by placing a difference in settings in which the characteristics.