• Progress in Medical Physics
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• v.10 no.1
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• pp.17-22
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• 1999

INJ-I, INJ-E, PFN, BMI, and PRF were selected among the various factors which constitute a digital linear accelerator to find effects on the dose distribution by changing current and voltage within the permitted scale which Mevatron automatically maintained. We measured the absorbed dose using an ion chamber, analyzed the waveform of beam output using an oscilloscope, and measured symmetry and flatness using a dosimetry system. An RFA plus (Scanditronix, Sweden) device was used as a dosimetry system. Then an 0.6cc ion chamber (PR06C, USA), an electrometer (Capintec192, USA), and an oscilloscope (Tektronix, USA) were employed to measure the changes on the dose distribution characteristics by changing the beam-tuning parameters. When the currents and the voltages of INJ-I, INJ-E, PFN, BMI, and PRF were modified, we were able to see the notable change on the dose rate by examining the change of the output pulse using the oscilloscope and by measuring them using the ion chamber. However, the results of energy and flatness graph from RF A plus were almost identical. The factors had fine differences: INJ-I, INJ-E, PFN, BMI, and PRF had 0.01∼0.02% differences in D10/D20, 0.1∼0.2 % differences in symmetry, and 0.1∼0.4% differences in flatness. Since Mevatron controlled itself automatically to keep the reference value of the factor, it was not able to see large differences in the dose distribution. There were fine differences on the dose rate distribution when the voltage and the currents of the digitized factors were modified Nonetheless, a basic operational management information was achieved.

• Journal of radiological science and technology
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• v.39 no.4
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• pp.571-575
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• 2016

Monte Carlo simulations are widely used as the most accurate technique for dose calculation in radiation therapy. In this paper, the GATE6(Geant4 Application for Tomographic Emission ver.6) code was employed to calculate the dosimetric performance of the photon beams from a linear accelerator(LINAC). The treatment head of a Varian 21EX Clinac was modeled including the major geometric structures within the beam path such as a target, a primary collimator, a flattening filter, a ion chamber, and jaws. The 6 MV photon spectra were characterized in a standard $10{\times}10cm^2$ field at 100 cm source-to-surface distance(SSD) and subsequent dose estimations were made in a water phantom. The measurements of percentage depth dose and dose profiles were performed with 3D water phantom and the simulated data was compared to measured reference data. The simulated results agreed very well with the measured data. It has been found that the GATE6 code is an effective tool for dose optimization in radiotherapy applications.

• Journal of Korea Water Resources Association
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• v.40 no.9
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• pp.697-707
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• 2007

In this study, we estimated the PMP(Probable Maximum Precipitation) and its transition in case of the typhoon Rusa which happened the biggest damage of all typhoons in the Korea. Specially, we analysed the moisture maximizing rate under the consideration of meteorological condition based on the orographic property when it hits in Gangneung region. The PMP is calculated by the rate of the maximum persisting 12 hours 1000 hPa dew points and representative persisting 12 hours 1000 hPa dew point. The former is influenced by the moisture inflow regions. These regions are determined by the surface wind direction, 850 hPa moisture flux and streamline, which are the critically different aspects compared to that of previous study. The latter is calculated using statistics program (FARD2002) provided by NIDP(National Institute for Disaster Prevention). In this program, the dew point is calculated by reappearance period 50-year frequency analysis from 5% of the level of significant when probability distribution type is applied extreme type I (Gumbel distribution) and parameter estimation method is used the Moment method. So this study indicated for small basin$(3.76km^2)$ the difference the PMP through new method and through existing result of established storm transposition and DAD(Depth-Area-Duration). Consequently, the moisture maximizing rate is calculated in the moisture inflow regions determined by meteorological fields is higher $0.20{\sim}0.40$ range than that of previous study. And the precipitation is increased $16{\sim}31%$ when this rate is applied for calculation.

• Journal of the Korean Society of Radiology
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• v.6 no.6
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• pp.455-464
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• 2012

This study suggested evaluation of approximately exposure to low-dose ionization radiation from medical images using a computed radiography (CR) system in standard X-ray examination and experimental model can compare diagnostic reference level (DRL) will suggest on optimization condition of guard about medical radiation of low dose space. Entrance surface dose (ESD) cross-measuring by standard dosimeter and optically stimulated luminescence dosimeters (OSLDs) in experiment condition about tube voltage and current of X-ray generator. Also, Hounsfield unit (HU) scale measured about each experiment condition in CR system and after character relationship table and graph tabulate about ESD and HU scale, approximately radiation dose about head, neck, thoracic, abdomen, and pelvis draw a measurement. In result measuring head, neck, thoracic, abdomen, and pelvis, average of ESD is 2.10, 2.01, 1.13, 2.97, and 1.95 mGy, respectively. HU scale is $3,276{\pm}3.72$, $3,217{\pm}2.93$, $2,768{\pm}3.13$, $3,782{\pm}5.19$, and $2,318{\pm}4.64$, respectively, in CR image. At this moment, using characteristic relationship table and graph, ESD measured approximately 2.16, 2.06, 1.19, 3.05, and 2.07 mGy, respectively. Average error of measuring value and ESD measured approximately smaller than 3%, this have credibility cover all the bases radiology area of measurement 5%. In its final analysis, this study suggest new experimental model approximately can assess radiation dose of patient in standard X-ray examination and can apply to CR examination, digital radiography and even film-cassette system.

• Progress in Medical Physics
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• v.19 no.4
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• pp.285-290
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• 2008

In this study, we have fabricated a one-dimensional fiber-optic dosimeter for electron beam therapy dosimetry. Each fiber-optic dosimeter has an organic scintillator with a plastic optical fiber and it is embedded and arrayed in the plastic phantom to measure one-dimensional high energy electron beam profile of clinical linear accelerator. The scintillating lights generated from each sensor probe are guided by plastic optical fibers to the multi-channel photodiode amplifier system. We have measured one-dimensional electron beam profiles in a PMMA phantom according to different field sizes and energies of electron beam. Also, the isodose and three-dimensional percent depth dose curves in a PMMA phantom are obtained using a one-dimensional fiber-optic dosimeter with different electron beam energies.

• The Journal of the Korea Contents Association
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• v.15 no.6
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• pp.290-296
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• 2015

The purpose of this study was to derive the proposals and to suggest the exposure dose reduction scheme on pediatric head CT scan by analyzing and comparing CT dose index (CTDI) and the national diagnostic reference levels. From January 2014 to December, 231 children under 10years who were requested a pediatric head CT scan with head injury were examined. Research methods were to research and analyze the general characteristics kVp, mA test coverage $CTDI_{vol}$ and DLP referring to dose reports and electronic medical record (EMR). As a result, 7.4%(17 patients) of the total subjects in $CTDI_{vol}$ showed a national diagnostic reference levels exceeding. For DLP 41.6%(96 patients) in excess was relatively higher than $CTDI_{vol}$. DLP was exceeded more than about 60% that is higher than the CT dose index presented by Korea Food & Drug Administration. it is cause of high DLP that scan range increased more than about 30% wider than the standard test coverage presented in Health Insurance Review & Assessment Service. In conclusion, it is able to significantly lower the dose if it is complied with checking the baseline scan range of pediatric head CT scan and appropriately adjusting the protocol.

• Journal of radiological science and technology
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• v.40 no.3
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• pp.393-400
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• 2017

The purpose of this study is to suggest a method to reduce the dose by Analyzing the dose area product (DAP) and image quality according to the change of tube current using NEMA Phantom. The spatial resolution and low contrast resolution were used as evaluation criteria in addition to signal to noise ratio (SNR) and contrast to noise ratio (CNR), which are important image quality parameters of intervention. Tube voltage was fixed at 80 kVp and the amount of tube current was changed to 20, 30, 40, and 50 mAs, and the dose area product and image quality were compared and analyzed. As a result, the dose area product increased from $1066mGycm^2$ to $6160mGycm^2$ to 6 times as the condition increased, while the spatial resolution and low contrast resolution were higher than 20 mAs and 30 mAs, Spatial resolution and low contrast resolution were observed below the evaluation criteria. In addition, the SNR and CNR increased up to 30 mAs, slightly increased at 40 mAs, but not significantly different from the previous one, and decreased at 50 mAs. As a result, the exposure dose significantly increased due to overexposure of the test conditions and the image quality deteriorated in all areas of spatial resolution, low contrast resolution, SNR and CNR.

• Journal of the Korean Society of Radiology
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• v.14 no.1
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• pp.1-6
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• 2020

In this study, it was intended to replace the existing plane parallel ionization chamber, which requires cross-calibration in electron beam treatment. The semiconductor compounds HgI₂ was fabricated as detector, and the characteristics of HgI₂ detector for the 6, 9 and 12 MeV electron beam was analyzed in the linear accelerator. It was also intended to evaluate the possibility of substitution with existing detectors and their applicability as electron beam dosimetry and to use them as a basic study of the development of electronic beam dosimeter. As a result of reproducibility, RSD was 0.4246%, 0.5054%, and 0.8640% at 6, 9, and 12 MeV energy, respectively, indicating that the output signal was stable. As a result of the linearity, the R² was 0.9999 at 6 MeV, 0.9996 at 9 MeV, and 0.9997 at 12 MeV showed that the output signal is proportional to HgI₂ as the dose is increased. The HgI₂ detector of this study is highly applicable to electron beam measurement, and it may be used as a basic research on electron beam detection.

• Journal of the Korean Society of Radiology
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• v.12 no.2
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• pp.209-216
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• 2018

In the field of angiography and interventional radiology, it is said that the risk of radiation exposure to the eyes is high due to the characteristics of work, but currently divided dose assessment and management are not carried out in reality. Therefore, in this study, in order to evaluate the dose of the operator in the surgical environment and to analyze the shields, firstly, we selected the point where the operator is mainly located, evaluated the exposure dose of the eye after attaching the pocket dosimeter to the lateral angle point of the head and neck phantom, and evaluate shielding effect when wearing lead glasses that is currently commercialized. Secondly, we evaluated the tendency of the exposure dose of the eye and the shielding effect through simulation in the same geometric structure as the actual measurement. As a result, in the case of measurement using a dosimeter, the cumulative dose increased with the increase of the fluoroscopic time, and the tendency was different according to the position of the operator. Simulation results show that the dose distribution of the eye lens in the mathematical phantom is about 1.1 ~ 1.3 times higher than that of the cornea. Also, The protective effect of the lead glasses showed a shielding effect of at least 3.7 ~ 21.4% in each eye.

• Journal of radiological science and technology
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• v.40 no.1
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• pp.57-62
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• 2017

The purpose of this study is to reconstruct the treatment plan by applying CBCT and DIR to dose changes according to the change of the patient's motion and breast shape in the large breast cancer patients and to compare the doses using TWF, FIF and IMRT. CT and CBCT were performed with MIM6 to create DIRCT and each treatment plan was made. The patient underwent computed tomography simulation in both prone and supine position. The homogeneity index (HI), conformity index (CI), coverage index (CVI) to the left breast as planning target volume (PTV) were determined and the doses to the lung, heart, and right breast as organ at risk (OAR) were compared by using dose-volume histogram and the unique property of each organ. The value of HI of the PTV breast increased in all treatment planning methods using DIRCT, and CVI and CI were decreased in the treatment planning methods using DIRCT.