• Progress in Medical Physics
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• v.32 no.4
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• pp.116-121
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• 2021

Purpose: To investigate the effects of dose rate on intensity-modulated radiation therapy (IMRT) quality assurance (QA). Methods: We performed gamma tests using portal dose image prediction and log files of a multileaf collimator. Thirty treatment plans were randomly selected for the IMRT QA plan, and three verification plans for each treatment plan were generated with different dose rates (200, 400, and 600 monitor units [MU]/min). These verification plans were delivered to an electronic portal imager attached to a Varian medical linear accelerator, which recorded and compared with the planned dose. Root-mean-square (RMS) error values of the log files were also compared. Results: With an increase in dose rate, the 2%/2-mm gamma passing rate decreased from 90.9% to 85.5%, indicating that a higher dose rate was associated with lower radiation delivery accuracy. Accordingly, the average RMS error value increased from 0.0170 to 0.0381 cm as dose rate increased. In contrast, the radiation delivery time reduced from 3.83 to 1.49 minutes as the dose rate increased from 200 to 600 MU/min. Conclusions: Our results indicated that radiation delivery accuracy was lower at higher dose rates; however, the accuracy was still clinically acceptable at dose rates of up to 600 MU/min.

• Journal of Radiation Protection and Research
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• v.49 no.2
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• pp.68-77
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• 2024

Background: Cone beam computed tomography (CBCT) is essential for correcting and verifying patient position before radiation therapy. However, it poses additional radiation exposure during CBCT scans. Therefore, this study aimed to evaluate radiological safety for the human body through dose assessment for CBCT. Materials and Methods: For CBCT dose assessment, the depth dose was evaluated using a cheese phantom, and the dose in the orbital area was evaluated using a human body phantom self-fabricated with a three-dimensional printer. Results and Discussion: The evaluation of radiation doses revealed maximum doses of 14.14 mGy and minimum doses of 6.12 mGy for pelvic imaging conditions. For chest imaging conditions, the maximum doses were 4.82 mGy, and the minimum doses were 2.35 mGy. Head imaging conditions showed maximum doses of 1.46 mGy and minimum doses of 0.39 mGy. The eyeball doses using a human body phantom model averaged at 2.11 mGy on the left and 2.19 mGy on the right. The depth dose ranged between 0.39 mGy and 14.14 mGy, depending on the change in depth for each imaging mode, and the average dose in the orbit area using a human body phantom was 2.15 mGy. Conclusion: Based on the experimental results, CBCT did not significantly affect the radiation dose. However, it is important to maintain a minimal radiation dose to optimize radiation protection following the as low as reasonable achievable principle.

• 보존과학연구
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• s.26
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• pp.189-202
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• 2005

This study carried out to understand thermoluminescence dating of ancient tiles at Jinju Janghungri Kilin site. Also radiocarbon dating by the benzene synthesis method and Liquid scintillation counting method were performed for comparison for the agedetermination of charcoal sample at the obtained same site.1st and 2nd glow curve were obtained according to the typical method thermoluminescence. Plateau tests of revealed the proper temperature range to be $300~440^{\circ}C$ Palaeodose average values were formed to the 2.44Gy.Annual dose of ancient tiles was calculated from soil samples and ancient tiles it self by measuring alpha radiation dose, potassium concentrations and water contents respectively. Annual dose average values were calculated to be 7.012mGy/yr.The radiocarbon age(BP year) was converted to calibrated age(AD/BC year) using high precision curve. Radiocarbon ages were calculated to be AD 15~17 .Comparison of samples with their radiocarbon and thermoluminescence ages for revealed the in range the AD 15~17. This result means that the measured absolute ages are in good agreement with each other within the margin of error.

• Journal of radiological science and technology
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• v.23 no.2
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• pp.63-67
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• 2000

The purpose of this study is to survey the present status of portable radiography and the result of free space scattered dose rate when taking a radiography at the general hospital or the university hospital in Taejon city. The results were as follows; 1. The number of cases using portable radiography for three years increased to averages 16.2%, 7.7% per year from January 1st in 1996 to December 31st in 1998. 2. The average of distance of adjacent patients was 219.1 cm at the ward. 3. For portable chest radiography, the free space scattered dose rate was 10.5 mSv/hr at 50 cm distance, 1.8 mSv/hr at 100 cm distance, and 0.2 mSv/hr at 200 cm distance. Therefore, in case of portable chest radiography at the ward, the average of distance of adjacent patients is 219.1 cm, so it does not have influence on the adjacent patients. But during the portable radiography, a guardian who is close to the patient, doctor, nurse and radiologic technologists has to set up the shield to prevent from the unnecessary radiation or the distance should be as great as possible from the mobile X-ray equipment.

• Environmental Analysis Health and Toxicology
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• v.18 no.4
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• pp.255-269
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• 2003

The objective of this study was to estimate human exposure to benzo (a)pyrene through multimedia/multi-pathway exposure scenario. The human exposure scenario for benzo(a)pyrene was consisted of 12 multiple exposure pathways, and the multipathway human exposure model based on this scenario constituted. In this study, the multipathway human exposure model was used to estimate the concentrations in the exposure contact media, human intake factors and lifetime average daily dose (LAD $D_{model}$) of benzo(a)pyrene in the environment. Sensitivity analysis was performed to identify the important parameters and Monte-Carlo simulation was undertaken to examine the uncertainty of the model. The total LAD $D_{model}$ was estimated to be 5.52${\times}$10$^{-7}$ mg/kg-day (2.06${\times}$10$^{-7}$ -8.65${\times}$10$^{-7}$ mg/kg-day) using the multipathway human exposure model. The inhalation dose accounted for 78% of the total LADD, whereas ingestion and dermal contact intake accounted for 20.2% and 1.8% of the total exposure, respectively. Based on the sensitivity analysis, the most significant contributing input parameter was benzo (a)pyrene concentration of ambient air. Consequently, exposure via inhalation in outdoor/indoor air was the highest compared with the exposure via other medium/pathways.

• Journal of Computational Design and Engineering
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• v.2 no.2
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• pp.113-118
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• 2015

An important problem in low-dose CT is the image quality degradation caused by photon starvation. There are a lot of algorithms in sinogram domain or image domain to solve this problem. In view of strong self-similarity contained in the special sinusoid-like strip data in the sinogram space, we propose a novel non-local filtering, whose average weights are related to both the image FBP (filtered backprojection) reconstructed from restored sinogram data and the image directly FBP reconstructed from noisy sinogram data. In the process of sinogram restoration, we apply a non-local method with smoothness parameters adjusted adaptively to the variance of noisy sinogram data, which makes the method much effective for noise reduction in sinogram domain. Simulation experiments show that our proposed method by filtering in both image and projection domains has a better performance in noise reduction and details preservation in reconstructed images.

• Carbon letters
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• v.15 no.4
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• pp.262-267
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• 2014

Pyrolized fuel oil (PFO) was reformed by novel electron beam (E-beam) radiation, and the elemental composition, chemical bonds, average molecular weight, solubility, softening point, yields, and density of the modified patches were characterized. These properties of modified pitch were dependent on the reforming method (heat or E-beam radiation treatment) and absorbed dose. Aromaticity ($F_a$), average molecular weight, solubility, softening point, and density increased in proportion to the absorbed dose of E-beam radiation, with the exception of the highest absorbed dose, due to modification by free radical polymerization and the powerful energy intensity of E-beam treatment. The H/C ratio and yield exhibited the opposite trend for the same reason. These results indicate that novel E-beam radiation reforming is suitable for the preparation of aromatic pitch with a high ${\beta}$-resin content.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.375-383
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• 2020

This study aimed to propose a methodology for quantitatively analyzing problems resulting from the performance and combination of the ionization chamber when using an automatic exposure control (AEC) and to optimize the performance of the digital radiography (DR). In the experimental method, the X-ray quality of the parameters used for the examination of the abdomen and pelvis was evaluated by percentage average error (PAE) and half value layer (HVL). Then, the stability of the radiation output and the image quality were analyzed by calculating the entrance surface dose (ESD) and entropy when the three ionization chambers were combined. As a result, all of the X-ray quality of the digital radiography used in the experiment showed a percentage average error and a half value layer in the normal range. The entrance surface dose increased in proportion to the combination of chambers, and entropy increased in proportion to the combination of ionization chambers except when three chambers were combined. In conclusion, analysis using entrance surface dose and entropy was found to be a useful method for evaluating the performance and combination problems of the ionization chamber, and the optimal performance of the digital radiography can be maintained when two or less ionization chambers are combined.

• Journal of radiological science and technology
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• v.36 no.1
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• pp.31-38
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• 2013

The prostate cancer is the most common malignant tumor in males. Prostate cancer is the most common malignant tumor that occurs in the male in Korea in 2007 to an annual average of 5,292 cases and 3.3% of the total cancer incidence seventh occurred. Our study compared property for tomotherapy and proton therapy in radiotherapy of prostate cancer patients. We analyzed DVH(Dose Volume Histogram) and dose distribution for prostate, bladder and rectum for radiation treatment planning of prostate cancer with 11 patients in Ilsan K cancer hospital from June to November 2011. There was no differences between tomotherapy and proton therapy in the purpose of prostate cancer therapy for PTV. The adjacent organs of bladder and rectum of average dose-volume were 2port proton therapy that it was low dose treatment comparing with tomotherapy and 5port proton therapy. $H{\cdot}I$ of proton therapy was less than $H{\cdot}I$ of tomotherapy. Also, 5port was less than 2port in $H{\cdot}I$ of proton therapy. However, 2port proton therapy has more advantage over 5port proton therapy that the bladder and rectum of average dose-volume and control time of equipment in radiotherapy of prostate cancer.

• Journal of Environmental Health Sciences
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• v.17 no.2
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• pp.48-53
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• 1991

This study was carried out to investigate age, noise intensity, work period, hearing loss at frequencies, hypertension and to examine correlation of the total quantity of noise exposure(Dose) and blood pressure (Response) in the auto industry during May 1987-December 1987. To perform this study 65 workers were tested. Results of this study were as follows: 1. In frequency analysis, the CS-dip phenomenon occurred around 4000 Hz. 2. Between under of ten years group and over of ten years group, average hearing loss value was statitically significant (P < 0.05). 3. The prevalence of hypertension of 65 workers was 7.84% . 4. At 90dB(A) over and 10 years under and workers in the 20's group, the total quantity of noise exposure (Dose) and systolic blood pressure (Response) were statistically significant (P < 0.05). 5. At under 10 years of work period group, the total quantity of noise exposure(Dose) and diastolic blood pressure (Response) were statistically significant(r =0.234, P < 0.1).