• Journal of Digital Convergence
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• v.10 no.2
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• pp.249-254
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• 2012

Assessing the exposure dose and the obtained image during the abdominal radiography with 128-slice MDCT scanner and 4-slice MDCT scanner which are recently being used in clinics using the body tissue-equivalent phantom and the glass dosimeter, the results were as follows. During the CT test for the abdomen, the absorbed dose was $35.8{\pm}0.46mGy$ in 4-MDCT, and $19.03{\pm}0.25mGy$ in 128-MDCT, which indicated that the radiation dose necessary to obtain the image meaningful to diagnosis was required less by 128-MDCT(P<0.05). As a result of analyzing the image obtained from the abdominal test using MDCT with a 5-point Likert scale, 4-MDCT showed the result of 3.52 points, and 128-MDCT showed the result of 4.01 points, that is, the image quality of 128-MDCT was evaluated high, and there was a statistically significant difference. In the results above, it is considered that 128 slice MDCT scanner will be much used later as it can reduce the radiation exposure, and make us obtain the high quality of image.

• Korean Journal of Digital Imaging in Medicine
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• v.9 no.2
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• pp.23-30
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• 2007

This study attempts to propose an appropriate method of using digital medical imaging equipments, by studying the effects of automatic exposure control(AEC), grid ratio and the change of radiography distance on the patient dose and detertor acquisition dose during the procedure of acquiring image through a digital medical imaging detector. The change of dose following the change of grid ratio's exposure and radiography distance was measured, by using an abdominal phantom organized with tissue equivalent materials in an amorphous silicon thin film transistor detecter installed with AWC. The case to use grid ratio 12 : 1, focal distance 180cm to radiography distance 110cm in AEC, the patient dose increased rather when we used grid ration 10 : 1, focal distance 110cm. When AEC was not used,the dose necessary for image acquisition decreased as the grid ratio became higher and the distance became further. but detector acquisition dose was not reduced when in applied AEC. When purchasing digiral medical imaging equipments, optional items such as AEC and grid shall be accurately selected to satisfy the use of the equipments. Radiography error made by radiation technologist and unnenessary patient dose can be reduced by selecting equipments with a radiography distance marker equipment when it did not apply AEC. These equipments can also be helpful in maintaining high imaging quality, one of the merits of digital detectors.

• Journal of the Korean Society of Radiology
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• v.16 no.4
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• pp.395-403
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• 2022

Flat-panel detector (FPD) used in digital radiographic imaging systems was used to perform a quantitative power spectrum evaluation as a result of the thickness change of polymethyl methacrylate (PMMA), a tissue equivalent. As the PMMA thickness increases with the resolution-chart phantom image, the effect of the scattering line increases, indicating that the modulation characteristics decrease, and the image is bright. The results show that the noise of the image increases, and noise-power spectral images are obtained by Fourier transform to confirm by spatial frequency. Thus, it can be verified that the PMMA thickness and noise are proportional through the result of evaluating the change of resolution characteristics and representing the 2D noise-power spectrum as one-dimensional values by evaluating the change of scattering line with MTF as the PMMA thickness increases in the image.

• Journal of radiological science and technology
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• v.40 no.2
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• pp.289-295
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• 2017

The aim of this study was to evaluate the dose comparison using Radon phantom with 5 mm and 10 mm tissue equivalent materials, FIF, Wedge(15, 30 angle) and IMRT, to reduce the skin dose of the contralateral breast during breast cancer radiation therapy(Total dose: 50.4Gy). The dose was measured for each treatment plan by attaching to the 8 point of the contralateral breast of the treated region using a optical-stimulated luminance dosimeter(OSLD) as a comparative dose evaluation method. Of the OSLD used in the study, 10 were used with reproducibility within 3%. As a result, the average reduction rates of 5 mm and 10 mm in the FIF treatment plan were 37.23 cGy and 41.77 cGy, respectively, and the average reduction rates in the treatment plan using Wedge $15^{\circ}$ were 70.69 cGy and 87.57 cGy, respectively. The IMRT showed a reduction of 67.37 cGy and 83.17 cGy, respectively. The results of using bolus showed that as the thickness of the bolus increased in all treatments, the dose reduction increased. We concluded that mastectomy as well as general radiotherapy for breast cancer would be very effective for patients who are more likely to be exposed to scattered radiation due to a more demanding or complex treatment plan.

• Radiation Oncology Journal
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• v.14 no.4
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• pp.323-332
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• 1996

Purpose : The wedge filter is the most commonly used beam modifying device during radiation therapy Recently dynamic wedge technique is available through the computer controlled asymmetric collimator, independent jaw. But dosimetric characteristics of dynamic wedge technique is not well known. Therefore we evaluate dosimetric characteristics of dynamic wedge compared to conventional fixed wedge. Materials and Methods : We evaluated dosimetric characteristics of dynamic wedge and fixed wedge by ion chamber, film dosimetry and TLD in phantoms such as water, polystyrene and average breast phantom. Six MV x-ray was used in $15{\times}15cm$ field with 15,30 and 45 degree wedge of dynamic/liked wedge system, Dosimeric characteristics are interpreted by Wellhofer Dosimetrie system WP700/WP700i and contralateral breast dose (CBD) with tangential technique was confirmed by TLD. Results : 1) Percent depth dose through the dynamic wedge technique in tissue equivalent phantom was similar to open field irradiation and there was no beam hardening effect compared to fixed wedge technique. 2) Isodose line composing wedge angle of dynamic wedge is more straight than hard wedge. And dynamic wedge technique was able to make any wedge angle on any depth and field size. 3) The contralateral breast dose in primary breast irradiation was reduced by dynamic wedge technique compared to fixed wedge. When the dynamic wedge technique was applied, the scatter dose was similar to that of open field irradiation. Conclusion : The dynamic wedge technique was superior to fixed wedge technique in dosimetric characteristics and may be more useful in the future.

• Journal of radiological science and technology
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• v.39 no.3
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• pp.407-414
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• 2016

This study is to minimize the patient dose and maintain the image quality according to change of source to image receptor distance and applying additional filter. In this study, we used the DR system, the tissue-equivalent abdomen phantom and the aluminium filter. The exposure conditions were set to 80 kVp using AEC mode. The collimation size was $16{\times}16inch$. The exposure dose were measured 10 times when the SID was changed with 100, 110, 120 and 130 cm, respectively. The pirana 657 for dosimeter was located on center of radiation irradiation. The acquired images were analyzed by using the image J. In the results, the tube current was increased with increasing the SID but ESD was decreased with increasing the SID. The decrease of ESD attribute to use of filter that remove the photon of lower energy. In the histogram results using image J, there were differences between the ESD and the exposure conditions according to change of SID. However, there were not differences in histogram. Therefore, the exposure dose could reduced when set the longer SID. For pediatric exam, the exposure dose could reduced when used the aluminium filter.

• Journal of Radiation Protection and Research
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• v.7 no.1
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• pp.34-48
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• 1982

The prime purpose of this study is to realize an index quantity, absorbed dose index, defined by the ICRU for the characterization of ambient radiation level at any location for the purpose of radiation protection. The experiment has been designed to be carried out in two phases, namely, preliminary and main experiment. In the primary study a 30cm diameter sphere of polyethylene was used, while in the main experiment that of tissue equivalent material was fabricated and used. Both experiments were performed in the gamma-ray fields of $^{137}Cs\;and\;^{60}Co$, and in a neutron beam of thermal column of the TRIGA MARK-II research reactor. In the measurement of gamma-ray absorbed dose TLD-700 $(^{7}LiF)$ chips were used, and for the neutron dose both Au activation foils and TLD chips (TLD-600 $(^{6}LiF)$ and TLD-700 for the discrimination of gamma-ray contribution) were used. Theoretical assessment of the absorbed dose in the sphere phantom has been carried out in accordance with the Ehrlich's idea that deduced on the basis of Burlin's cavity theory in the case of gamma-ray irradiation. For the analysis of neutron dose fluence-KERMA rate conversion method was used. The explanation on the dose assessment is given in detail. Results obtained were numerically and statistically analyzed and the depth dose distributions are presented in the graphic forms with normalized values. In the concluding remarks, the possibility and difficulty of realizing the index quantity, including questions and problems to be solved are mentioned.

• Journal of the Korean Society of Radiology
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• v.17 no.2
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• pp.243-248
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• 2023

This study aims to analyze the secondary carcinogenesis rate caused by exposure of organs at risk of damage using a glass dosimeter during radiosurgery in vestibular schwannoma disease. Using a pediatric phantom of human tissue equivalent material, the volume of the tumor was set to a total of three volumes: 0.506 cm³, 1.008 cm³, and 2.032 cm³, and a radiosurgery plan was established with an average dose of 18.4 ± 3.4 Gy. After mounting the human body phantom on the table of surgical equipment, glass dosimeters were placed on the right eye, left eye, thyroid gland, thymus, right lung, and left lung to measure the exposure dose, respectively. In this study, the incidence of secondary cancer due to exposure to damaged organs during gamma knife radiosurgery in vestibular schwannoma disease with the largest tumor volume of 2.032 cm³ was measured with a glass dosimeter. This study studies the risk of secondary radiation exposure dose that can occur during stereotactic radiosurgery, and it is considered that it will be used as basic data in the field of radiation damage related to the stochastic effect of radiation in the future.

• Journal of the Korean Society of Radiology
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• v.13 no.5
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• pp.791-799
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• 2019

We evaluated the physical properties that occur to dose enhancement and changes from secondary particle production resulting from the interaction between enhancement material. Geant4 was used to perform a Monte Carlo simulation, and the medical internal radiation dose (MIRD) head phantom were employed. X-rays of 4, 6, 10, 15, 18, and 25 MV were used. Aurum (Au) and gadolinium (Gd) were applied within the tumor volume at 10, 20, and 30 mg/g, and an experiment using soft tissue exclusively was concomitantly performed for comparison. Also, particle fluence and initial kinetic energy of secondary particle of interaction were measured to calculate equivalent doses using the radiation weight factor. The properties of physical interaction by the radiation enhancement material showed the great increased in photoelectric effect as compared to the compton scattering and pair production, occurred with the highest, in aurum and gadolinium it is shown in common. The photonuclear effect frequency increased as the energy increased, thereby increasing secondary particle production, including alpha particles, protons, and neutrons. During dose enhancement using aurum, a maximum 424.25-fold increase in the equivalent dose due to neutrons was observed. This study was Monte Carlo simulation corresponds to the physical process of energy transmission in dose enhancement. Its results may be used as a basis for future in vivo and in vitro experiments aiming to improve effects of dose enhancement.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.225-232
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• 2014

Purpose : The purpose of this study was to evaluate the surface and superficial dose for patients requiring postmastectomy radiation therapy(PMRT) with different treatment techniques. Materials and Methods : Computed tomography images were acquired for the phantom(I'mRT, IBA) consisting of tissue equivalent material. Hypothetical chestwall and lung were outlined and modified. Five treatment techniques(Wedged Tangential; WT, 4-field IMRT, 7-field IMRT, TOMO DIRECT, TOMO HELICAL) were evaluated using only 6MV photon beam. GafChromic EBT3 film was used for dose measurements at the surface and superficial dose. Surface dose profiles around the phantom were obtained for each treatment technique. For superficial dose measurements, film were used inside the phantom and analyzed superficial region for depth from 1-6mm. Results : TOMO DIRECT showed the highest surface dose by 47~70% of prescribed dose, while 7-field IMRT showed the lowest by 35~46% of prescribed dose. For the WT, 4-field IMRT and 7-field IMRT, superficial dose were measured over 60%, 70%, and 80% for 1mm, 2mm, and 5mm depth, respectively. In case of TOMO DIRECT and TOMO HELICAL, over 75%, 80%, and 90% of prescribed dose was measured, respectively. Surface and superficial dose range were uniform in overall chestwall for the 7-field IMRT and TOMO HELICAL. In contrast, Because of the dose enhancement effect with oblique incidence, The dose was gradually increased toward the obliquely tangential angle for the WT and TOMO DIRECT. Conclusion : For PMRT, TOMO DIRECT and TOMO HELICAL deliver the higher surface and superficial doses than treatment techniques based linear accelerator. It showed adequate dose(over 75% of prescribed dose) at 1mm depth in skin region.