• Imaging Science in Dentistry
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• 제42권2호
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• pp.65-70
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• 2012

Purpose : The aim of this study was to compare the effective dose for imaging of mandible between multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT). An MDCT with low dose technique was also compared with them. Materials and Methods : Thermoluminescent dosimeter (TLD) chips were placed at 25 organ sites of an anthropomorphic phantom. The mandible of the phantom was exposed using 2 different types of MDCT units (Somatom Sensation 10 for standard-dose MDCT, Somatom Emotion 6 for low-dose MDCT) and 3 different CBCT units (AZ3000CT, Implagraphy, and Kavo 3D eXaM). The radiation absorbed dose was measured and the effective dose was calculated according to the ICRP 2007 report. Results : The effective dose was the highest for Somatom Sensation 10 (425.84 ${\mu}Sv$), followed by AZ3000CT (332.4 ${\mu}Sv$), Somatom Emotion 6 (199.38 ${\mu}Sv$), and 3D eXaM (111.6 ${\mu}Sv$); it was the lowest for Implagraphy (83.09 ${\mu}Sv$). The CBCT showed significant variation in dose level with different device. Conclusion : The effective doses of MDCTs were not significantly different from those of CBCTs for imaging of mandible. The effective dose of MDCT could be markedly decreased by using the low-dose technique.

• 대한디지털의료영상학회논문지
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• 제14권2호
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• pp.15-22
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• 2012

The purpose of this study was to measure the absorbed dose and calculate the effective dose for cone beam computed tomography (CBCT) and panorama units and to estimate usefulness of x-ray protective. Rando phantom and glass dosimeters were used for dosimetry. The absorbed doses were measured at 15 organs and 14 remainder from correspond to ICRP 2007 recommendations. The absorbed dose was highest in salivary glands as measured CBCT 2.420mGy, panorama 0.307mGy. Absorbed dose in another organs were high in order of thyroid, brain, skin, esophagus. The effective dose was CBCT 0.100mSv, panorama 0.011mSv and effective dose of panorama was higher than that of CBCT by 10 times. In case of wearing x-ray protective, reducing effective dose of CBCT by 0.066mSv (66%) and panorama by 0.008mSv (72%). Effective dose were reduced by radiological shielding but it needs further optimization studies, where dosimetric data are analyzed in combination with image quality with keep the patients' exposure as low as possible.

• 한국콘텐츠학회논문지
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• 제12권6호
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• pp.346-352
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• 2012

성인과 달리 영 유아에게 행해지는 방사선 검사 시 투여되는 방사선량의 평가는 활발하게 이루어지지 않고 있다. 따라서 영 유아의 방사선 검사 시 피폭되는 정도를 나타내는 지표로서 입사피부선량을 측정하고 Geant4를 이용한 몬테카를로 시뮬레이션을 통한 결과값을 비교하여 입사피부선량 측정의 재현성을 높이고 다양한 지오메트리 구현의 가능성을 증명하였다. 몬테카를로 시뮬레이션 결과값은 입사피부선량을 선량보정을 위한 정규인자를 통해 추정하였고 단위 X선 조사영역크기로 표준화한 결과 영 유아에게 있어 일회의 방사선 촬영 당 평균 입사피부선량은 $78.41{\mu}Gy$ 였으며 선량계를 통한 측정값과 몬테카를로 시뮬레이션값의 백분율 오차는 최대 -4.77%로 나타났다. 몬테카를로 시뮬레이션을 통한 입사피부선량 평가 방법은 의료기관에서 실제 진단을 위해 내원한 환아를 대상으로 한 입사피부선량 평가의 어려움을 대체할만한 수단으로서의 가능성을 보여준다.

• 대한방사선기술학회지:방사선기술과학
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• 제45권1호
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• pp.69-76
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• 2022

This study, the method of reducing the exposure dose by changing the geometrical requirements among the preceding studies and the method of directly wearing a protector on the patient were used to expose the patient. A comparative experiment was conducted on the method of reducing the dose and the most effective method for reducing the exposure dose was investigated. Using the phantom, the dose of the lens, thyroid gland, and gonad gland in the 5 views most used in coronary angiography and intervention accumulated 5 times for 10 seconds at 60~70 kV, 200~250 mA as an automatic controller of the angiography system, and measured by Optically Stimulated Luminescent Dosimeter(OSLD). SID 100 cm and Cine 15 f/s as a control group the experiment was conducted by dividing the experimental group into 3 groups: a group lowered to Cine 7.5 f/s, a phantom protector, and a group lowered to 95 cm SID. As a result of the experiment, showing decrease in exposure dose compared to the control group. Lowering the cine frame may be the simplest and most effective method to reduce the exposure dose, but there is a limit that it cannot be applied if the operator judges that the diagnostic value is small or feels uncomfortable with the procedure. Conclusion as fallow reducing the exposure dose by directly wearing protector is the next best solution, and it is hoped that the conclusions obtained through this study will help reduce the exposure dose to unnecessary organ.

• 대한방사선기술학회지:방사선기술과학
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• 제45권4호
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• pp.313-320
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• 2022

Both angiography and interventional procedures accompanied by angiography provide many diagnostic and therapeutic benefits to patients and are rapidly increasing. However, unlike general radiography or computed tomography using the same X-ray, the amount of radiation is quite high, but the dose range can vary considerably for each patient and operator. The high sensitivity of the lens to radiation during cerebral angiography and neurointervention is already well known, and although there are many related studies, it is insufficient to easily reduce radiation in diagnosis and treatment. In this situation, in particular, by adding three-dimensional rotational angiography (3D-RA) to the existing two-dimensional (2D) angiography, it is now possible to make an accurate diagnosis. However, since this 3D-RA acquires images through projection of more radiation than before, the exposure dose of the lens may be higher. Therefore, we tried to analyze whether the radiation dose of the lens can be reduced by moving the lens out of the field range by adjusting the table height and magnification ratio during the examination using 3D-RA. The surface dose was measured using a rando phantom and a radiophotoluminescent glass dosimeter (PLD) and the radiation dose was compared by adjusting the table height and magnification ratio based on the central point. As a result, it was found that the radiation dose of the lens decreased as the table height increased from the central point, that is, as the lens was out of the field of view. In conclusion, in 3D-RA, moving the table position of about 2 cm in height will make a significant contribution to the dose reduction of the lens, and it was confirmed that adjusting the magnification ratio can also reduce the surface dose of the lens.

• Journal of Radiation Protection and Research
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• 제46권2호
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• pp.39-47
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• 2021

Background: The National Institutes for Quantum and Radiological Science and Technology-National Institute of Radiological Sciences (QST-NIRS) has continuously investigated the undesired radiation exposure in ion beam radiotherapy mainly in carbon-ion radiotherapy (CIRT). This review introduces our investigations on the secondary neutron dose in CIRT with the broad and scanning beam methods. Materials and Methods: The neutron ambient dose equivalents in CIRT are evaluated based on rem meter (WENDI-II) measurements. The out-of-field organ doses assuming prostate cancer and pediatric brain tumor treatments are also evaluated through the Monte Carlo simulation. This evaluation of the out-of-field dose includes contributions from secondary neutrons and secondary charged particles. Results and Discussion: The measurements of the neutron ambient dose equivalents at a 90#x00B0; angle to the beam axis in CIRT with the broad beam method show that the neutron dose per treatment dose in CIRT is lower than that in proton radiotherapy (PRT). For the scanning beam with the energy scanning technique, the neutron dose per treatment dose in CIRT is lower than that in PRT. Moreover, the out-of-field organ doses in CIRT decreased with distance to the target and are less than the lower bound in intensity-modulated radiotherapy (IMRT) shown in AAPM TG-158 (American Association of Physicists in Medicine Task Group). Conclusion: The evaluation of the out-of-field doses is important from the viewpoint of secondary cancer risk after radiotherapy. Secondary neutrons are the major source in CIRT, especially in the distant area from the target volume. However, the dose level in CIRT is similar or lower than that in PRT and IMRT, even if the contributions from all radiation species are included in the evaluation.

• 한국의학물리학회지:의학물리
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• 제34권3호
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• pp.33-39
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• 2023

Purpose: FLASH radiotherapy (RT) using ultra-high dose rate (>40 Gy/s) radiation is being studied worldwide. However, experimental studies such as preclinical studies using small animals are difficult to perform due to the limited availability of irradiation devices and methods for generating a FLASH beam. In this paper, we report the initial dosimetry results of a prototype electron linear accelerator (LINAC)-based irradiation system to perform ultra-high dose rate (UHDR) preclinical experiments. Methods: The present study used the prototype electron LINAC developed by the Research Center of Dongnam Institute of Radiological and Medical Sciences (DIRAMS) in Korea. We investigated the beam current dependence of the depth dose to determine the optimal beam current for preclinical experiments. The dose rate in the UHDR region was measured by film dosimetry. Results: Depth dose measurements showed that the optimal beam current for preclinical experiments was approximately 33 mA, corresponding to a mean energy of 4.4 MeV. Additionally, the average dose rates of 80.4 Gy/s and 162.0 Gy/s at a source-to-phantom surface distance of 30 cm were obtained at pulse repetition frequencies of 100 Hz and 200 Hz, respectively. The dose per pulse and instantaneous dose rate were estimated to be approximately 0.80 Gy and 3.8×10⁵ Gy/s, respectively. Conclusions: Film dosimetry verified the appropriate dose rates to perform FLASH RT preclinical studies using the developed electron-beam irradiator. However, further research on the development of innovative beam monitoring systems and stabilization of the accelerator beam is required.

• Toxicological Research
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• 제11권1호
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• pp.157-159
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• 1995

A study on antigenicity of HRccine (formalin inactivated HFRS virus vaccine) was investigated in guinea pigs and mice. As a part of the safety evaluation of the HRccine, antigenicity tests were carried out according to the Estabilish Regulations of National Institute of Safety Research. In active systemic anaphylaxis (ASA) test no sign was detected when sensitized with up to 120 clinical dose and challenged with up to 1200 clinical dose in guinea pigs. In passive systemic anaphylaxis test guinea pigs showed no sign. In passive cutaneous anaphylaxis (PCA) test, HRccine specific IgE antibody was not detected when sensitized and challenged with up to 1200 clinical dose. Conclusively, there was no adverse antigenic potential at the clinical dose of 120 clinical dose alone and 120 clinical dose with Al(OH)3.

• 한국전산유체공학회지
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• 제16권4호
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• pp.84-91
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• 2011

Hemodialysis is essential for patients with end stage renal failure. It is important to improve the patency rate and to minimize occurrence of the stenosis. Also, the blood flow to the artificial kidney can affect the blood flow characteristics through arteriovenous graft. Thus, the delivered dose are important factors for analyzing hemodynamic characteristics during hemodialysis access. In this study, the numerical analysis was performed for the effect of the delivered dose during hemodialysis access on the blood flow through the graft. As a result, The adverse pressure gradient occurred in case of a larger delivered dose through a catheter than standard dose and the flow instability increased. Also the circulation flow appeared largely at anastomotic site of the vein when the delivered dose was exceeded about half blood flow of inlet blood flow.

• 자원환경지질
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• 제32권3호
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• pp.273-280
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• 1999

In order to protect inhabitans' health and to collect data for prediction of the effcts from accidental emission of rasioactive materials from nuclear power plant, exposed dose rate be monitored within the limit dose rate. This research was carried out to investigate the accumulation of environmental radioactivity around Younggwang Nuclear Power Plant, and to infer and in infer and assay the additional exposed dose rate of inhabitants in Younggwang site from the operation of nuclear plant operation. External radiation dose rate, radiation environmental samples, and exposed dose rate of inhabitants in Younggwang site were investigated for estimaing environment activity in the vicinity of the nuclear power plant area. For the external radiation dose rate, the result showed that range of normal variation was found and any artificial radioisotope was not deteted in the analysis of environmental samples. Exposed dose rate of inhabitants was lower than 0.4% of the limit value of ICRP and it may be concluded that there was no effect on inhabitants and environment from the operation of nuclear power plant.