• The Journal of Korean Society for Radiation Therapy
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• v.14 no.1
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• pp.175-186
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• 2002

The purpose of this study is directly measure and evaluate about absorbed dose change according to nominal energy and electron cone or medical accelerator on isodose curve, percentage depth dose, contaminated X-ray, inhomogeneous tissue, oblique surface and irradiation on intracavitary that electron beam with high energy distributed in tissue, and it settled standard data of hish energy electron beam treatment, and offer to exactly data for new dote distribution modeling study based on experimental resuls and theory. Electron beam with hish energy of $6{\sim}20$ MeV is used that generated from medical linear accelerator (Clinac 2100C/D, Varian) for the experiment, andwater phantom and Farmer chamber md Markus chamber und for absorbe d dose measurement of electron beam, and standard absorbed dose is calculated by standard measurements of International Atomic Energy Agency(IAEA) TRS 277. Dose analyzer (700i dose distribution analyzer, Wellhofer), film (X-OmatV, Kodak), external cone, intracavitary cone, cork, animal compact bone and air were used for don distribution measurement. As the results of absorbed dose ratio increased while irradiation field was increased, it appeared maximum at some irradiation field size and decreased though irradiation field size was more increased, and it decreased greatly while energy of electron beam was increased, and scattered dose on wall of electron cone was the cause. In percentage depth dose curve of electron beam, Effective depth dose(R80) for nominal energy of 6, 9, 12, 16 and 20 MeV are 1.85, 2.93, 4.07, 5.37 and 6.53 cm respectively, which seems to be one third of electron beam energy (MeV). Contaminated X-ray was generated from interaction between electron beam with high energy and material, and it was about $0.3{\sim}2.3\%$ of maximum dose and increased with increasing energy. Change of depth dose ratio of electron beam was compared with theory by Monte Carlo simulation, and calculation and measured value by Pencil beam model reciprocally, and percentage depth dose and measured value by Pencil beam were agreed almost, however, there were a little lack on build up area and error increased in pendulum and multi treatment since there was no contaminated X-ray part. Percentage depth dose calculated by Monte Carlo simulation appeared to be less from all part except maximum dose area from the curve. The change of percentage depth dose by inhomogeneous tissue, maximum range after penetration the 1 cm bone was moved 1 cm toward to surface then polystyrene phantom. In case of 1 cm and 2 cm cork, it was moved 0.5 cm and 1 cm toward to depth, respectively. In case of air, practical range was extended toward depth without energy loss. Irradiation on intracavitary is using straight and beveled type cones of 2.5, 3.0, 3.5 $cm{\phi}$, and maximum and effective $80\%$ dose depth increases while electron beam energy and size of electron cone increase. In case of contaminated X-ray, as the energy increase, straight type cones were more highly appeared then beveled type. The output factor of intracavitary small field electron cone was $15{\sim}86\%$ of standard external electron cone($15{\times}15cm^2$) and straight type was slightly higher then beveled type.

• Journal of radiological science and technology
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• v.37 no.3
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• pp.187-193
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• 2014

The purpose of this study was to analyze the effect on the selectivity on of high-voltage rectification device that measured the performance of the grid, and the contrast improvement ability (K factor) by measuring the scattered radiation content of the transmitted X-rays. The scattered radiation generated when the X-ray flux comes from the diagnostic X-ray generator that passes through an object. Targeting four different rectifications of X-ray generators, the mean value of the tube voltage and the tube current was measured in order to maximize the accuracy of the generating power dose within the same exposure condition. Using fluorescence meter, the content of the scattered rays that are transmitted through the acrylic was measured depending on the grid usage. When grid is not used, the content of the scattered rays was the lowest (34.158%) with the single-phase rectifier, was increased with the inverter rectifier (37.043%) and the three-phase 24-peak rectification method (37.447%). The difference of the scattered radiation content of each device was significant from the lowest 0.404% to the highest 3.289% while using 8:1 grid, the content of the scattered ray was the lowest with the single content of the scattered ray was the lowest with the single-phase rectifier (18.258%), was increased with the rectifier (25.502%) and the 24-peaks rectification (24.217%). Furthermore, there was difference up to content 7.244% to the lowest content 1.285% within three-phase 24-peaks rectification, inverter rectifications, and single-phase rectifier depending on the selectivity of the grid. Drawn from the statistical analysis, there was a similar relationship between the contrast improvement factor and the K factor. As a result, the grid selectivity and the contrast were increased within the single-phase rectifier rather than the constant voltage rectifier.

• 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.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.147-151
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• 2019

In chest and abdomen CT scans, the radiation exposure doses by scattering lines were measured at the eyeball and thyroid. Radiation exposure was investigated by using shielding devices. The chest and abdomen CT scan protocols used in the real examination were applied to measure and compare radiation doses before and after the use of shielding devices at the eyeball and the thyroid. The radiaton doses were measured with OSLD dosimeters. Barium, tungsten sheets, goggles and neck shields were used to protect the scattered X-ray. The chest CT scans showed respectively 3.01 mSv and 6.21 mSv at the eyeball and the thyroid by the scattered X-ray. The abdomen CT scans showed 0.55 mSv and 3.22 mSv for the eyeball and the thyroid respectively. Barium and tungsten sheets had 11% to 13% protection rates at the eyeball and the thyroid for chest CT scan, and 34% to 49% reduction in radiation dose for the abdomen CT scan. Because of the significant radiation dose, which causes cataracts and thyroid cancer by the repeated and continuous radiation exposure, for the chest and the abdomen CT scans, it is required to use shielding devices to reduce radiation dose for examinations.

• Journal of radiological science and technology
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• v.3 no.1
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• pp.57-66
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• 1980

X-ray grid is the most important means to reduce the scattered ray from patients, but alternative way is air gap technique that is another name of Groedel technique. This technique is mainly used in chest radiography. Authors performed an experimental study on the air gap technique for chest radiography and obtained the results as follows; 1. In using the high voltage air technique, scattered ray could be reduced effectively, while the percentage of scattered ray was slightly increased than conventional grid technique. 2. In film contrast, 30cm air gap technique was inferior to 12:1 grid technique and contrast improvement was increased when the object was thicker and higher voltage was used. 3. The patient exposure dose was reduced about $25{\sim}45%$ compared with conventional grid technique by air gap technique used.

• Journal of radiological science and technology
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• v.43 no.3
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• pp.169-176
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• 2020

Interventional radiology is performed under real-time fluoroscopy, and patients are exposed to a wide range of exposures for a long period of time depending on the examination and procedure. However, studies on radiation protection for patients during an intervention are insufficient. This study aims to evaluate the doses exposed during the intervention and the applicability of 3D printing materials. The organ dose for each intervention site was evaluated using a monte carlo simulatio. Also, the dose reduction effect of the critical organs was calculated when using a shielding device using 3D printing materials. As a result, the organ dose distribution for each intervention site showed a lower dose distribution for organs located far from the x-ray tube. It was analyzed that the influence of scattered rays was higher in the superficial organs of the back of the human body where x-rays were incident. The dose reduction effect on the critical organ using the 3D printing shield showed the highest testis among the gonads, and in the case of other organs, the dose reduction effect gradually decreased in the order of the eye, thyroid, breast, and ovary. Accordingly, it is judged that the 3D printed shield will be sufficiently usable as a shielding device for the radiation protection of critical organs.

• Journal of the Korean Society of Radiology
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• v.6 no.4
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• pp.313-320
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• 2012

Current medical institutions with the development of medical technology to the increased demand for health use of radiation equipment is increasing rapidly. Direct radiation from the patient receives the aim of reducing exposure as much as possible is important and the spatial dose of scattered radiation with in the space to engage in reducing healthcare physician, radiation workers and carers need to reduce indirect exposure. X-ray radiation workers and caregivers in the X-ray room to wearing of protective clothing is advised. However Radiation worker sand caregivers of patients with secondary is done, by wearing protective clothing to wear protective clothing because of the weight and discomfort have been neglected. In this study, based on the presence or absence of clothing scattered radiation from space to measure distances, depending on the horizontal and height by measuring the angle of the importance of wearing protective clothing were investigated.

• Journal of the Korean Society of Radiology
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• v.13 no.5
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• pp.757-763
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• 2019

Recently, Following the recent development of flat panel detector with wide dynamic ranges, increasing numbers of healthcare providers have begun to use digital radiography. As a result, filter thickness standards should be reestablished, as current clinical practice requires the use of thicknesses recommended by the National Council on Radiation Protection and Measurements, which are based on information, acquired using conventional analog systems. Here we investigated the possibility of minimizing dose creep and optimizing patient dose using Al filters in digital radiography. The use of thicker Al filters resulted in a maximum 19.3% reduction in the entrance skin exposure dose when medical images with similar sharpness values were compared. However, resolution, which is a critical factor in imaging, had a significant change of 1.01 lp/mm. This change in resolution is thought to be due to the increased amount of scattered rays generated from the object due to the X-ray beam hardening effect. The increase in the number of scattered rays was verified using the scattering degradation factor. However, the FPD, which has recently been developed and is widely used in various areas, has greater response to radiation than analog devices and has a wide dynamic range. Therefore, the FPD is expected to maintain an appropriate level of resolution corresponding to the increase in the scattered-ray content ratio, which depends on filter thickness. Use of the FPD is also expected to minimize dose creep by reducing the exposure dose.

• Journal of radiological science and technology
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• v.37 no.3
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• pp.195-201
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• 2014

The study examined the changes in the decreased facial exposure dose for radiological technologists depending on increased distance between the workers and the X-ray tube head during intraoral radiography. First, the facial phantom similar to the human tissues was manufactured. The shooting examination was configured to the maxillary molars for adults (60kVp, 10mA, 50msec) and for children (60kVp, 10mA, 20msec), and the chamber was fixed where the facial part of the radiation worker would be placed using the intraoral radiography equipment. The distances between the X-ray tube head and the phantom were set to 10cm, 15cm, 20cm, 25cm, 30cm, 35cm, and 40cm. The phantom was radiated 20 times with each examination condition and the average scattered doses were examined. The rate at the distance of 40cm decreased by about 92.6% to 7.43% based on the scattered rays radiated at the distance of 10cm under the adult conditions. The rate at the distance of 40cm decreased by about 97.6% to 2.58% based on the scattered rays radiated at the distance of 10cm under the children conditions. Protection from the radiation exposure was required during the dental radiographic examination.

• Journal of radiological science and technology
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• v.28 no.3
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• pp.249-254
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• 2005

This study investigated the structural changes of folliculus ovarii according to the dose of the X-rays when mice were exposed to X-rays from 6MeV LINAC. The minute structural changes of folliculus ovarii were observed through an electron microscope with high magnification. Nuclei and protoplasm of granular cells in growing folliculus ovarii abruptly underwent minute structural changes according to the increase of dose of X-rays. Cell residue, by-product of cell decease, neutrophil and macrophage around follicular antrum were observed. The minute structural changes in granular cells showed typical characteristics of apoptosis: the increase of electronic density due to nuclear condensation, fragmentation of nuclei, and atrophy of protoplasm. Necrosis of cells was identified, but it was not so remarkable. Macrophage scattered with apoptotic bodies.