• Journal of the Korean Society of Radiology
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• v.14 no.2
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• pp.105-109
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• 2020

Intensity-modulated radiotherapy(IMRT) has disadvantages such as increasing the low doses of irradiation to normal tissues and accumulated dose for the whole volume by leakage and transmission of the Multi Leaf Collimator (MLC). The accumulated dose and low dose may increase the occurrence of secondary malignant neoplasms. For this reasons, the jaw tracking function of the TrueBeam (Varian Medical Systems, Palo Alto, CA) was developed to reduce the leakage and transmission dose of the MLC with existing linear accelerators. But quantitative analysis of the dose reduction has not been verified. Therefore, in the present study, we intended to verify the clinical possibility of utilizing the jaw tracking function in brain tumor with comparison of treatment plans. To accomplish this, 3 types of original treatment plans were made using Eclipse11 (Varian Medical Systems, Palo Alto, CA): 1) beyond 2 cm distance from the Organs At Risk (OARs); 2) within 2 cm distance from the OARs; and 3) intersecting with the OARs. Jaw tracking treatment plans were also made with copies of the original treatment planning using Smart LMC Version 11.0.31 (Varian Medical Systems, Palo Alto, CA). A comparison between the 2 types of treatment planning methods was performed using the difference of the mean dose and maximum dose to the OARs in cumulative Dose Volume Histogram (DVH). In the DVH comparison, the maximum difference of 0.5 % was observed between the planning methods in the case of over 2 cm distance, and the maximum of 0.6 % was obtained for within the 2 cm distance. For the case intersecting with the OAR, the maximum difference of 2 % was achieved. According to these results, it could be realized that the differences of mean dose and maximum dose to the OARs was larger when the OARs and PTV were closer. Therefore, treatment plans with the jaw tracking function consistently affected the dose reduction and the clinical possibility could be verified.

• Korean Journal of Environmental Agriculture
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• v.22 no.3
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• pp.215-219
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• 2003

To investigate the effects of low dose gamma radiation and seed moisture content (SMC) on germination and early growth of vegetable crops, seeds of chinese cabbage (Brassica campestris L.), radish (Raphanus sativus L.), red pepper (Capcicum annuum L.), figleaf gourd (Cucurbita ficifolia Bouche) and bottle gourd (Lagenaria siceraria Standl), with different SMC were irradiated with different doses ($0{\sim}20\;Gy$) of gamma-ray by irradiator ($^{60}Co$, ca.150 TBq of capacity, AECL). Vegetable crops in which low dose gamma radiation was irradiated in seeds with different moisture content showed different response in seed germination and early growth to low dose gamma radiation. The germination rate of chinese cabbage, figleaf ground and bottle gourd irradiated with $2{\sim}8\;Gy$ showed interactive responses against relative SMC. Also, significant interactions occurred for the early growth between those factors. The stimulating effects of gamma radiation were more pronounced for hydrated seeds of chinese cabbage, radish, figleaf gourd and bottle gourd showing prominent responses with $2{\sim}10\;Gy$ irradiation, particularly for chinese cabbage and bottle gourd. These results suggest that radiation may promote germination and early growth of vegetable crops through interaction with SMC.

• Biomolecules & Therapeutics
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• v.6 no.1
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• pp.37-44
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• 1998

This study was performed to examine the effects of DA-9601, a novel antiulcer agent extracted from Artemisiae Herba, on radiation colitis in the rat. Female Wistar rats received a 30 Gy dose of irradiation to the 2 cm of distal colon in length using an intrarectal applicator system. 30 mg/tg or 100 mg/kg of DA- 9601 was administered orally 30 min before and 4 h after radiation on day 1. And the same dose of DA-9601 was given to the animals twice a day from day 2 to 14. As a reference control, sucralfate suspension (100 or 300 mg/head) was given as an enema based on the same treatment schedule of DA-9601. Body weight change and the frequency of diarrhea were recorded during the observation period as markers of radiationinduced injury, All animals were sacrificed on day 15 for evaluation of macro- and microscopic findings and mucosal myeloperoxidase (MPO) activity. Radiated animals showed diarrhea, mucosal redness and histologic changes characterized by edema and eosinophilic infiltration of the periglandular lamina propria with loss of colonic epithelium. Radiation also significantly increased mucosal MfO activity of affected colon f\\\\\\\\`<0.05). However, most of these changes were completely protected by oral administration with DA-9601. DA-9601 reduced radiation-induced histologic alteration significantly in a dose-related manner (P<0.05). In addition, mucosal MPO activity in rats receiving high dose of DA-9601 decreased significantly when compared with that in radiated control. High dose of sucralfate (300 mg/head) alleviated radiation-induced histologic lesion, but failed to reach statistical significance. The results of this study suggest that DA-9601 can be useful for the prevention of acute clinical symptoms of radiation proctocolitis and that decrease of mucosal MPO by DA-9601 plays a role in its protective mechanism(s), at least in part.

• Journal of radiological science and technology
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• v.30 no.2
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• pp.139-145
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• 2007

Dose evaluation for small field such as stereotactic radiosurgery was performed using $Gafchromic^{(R)}$ EBT film. Every film which irradiated 6MV photon beam was scanned and obtained the optical density(OD) by flat bed scanner after 24 hours of irradiation. This study compared dose from diode in water and Gafchromic $EBT^{(R)}$ film in acrylic phantom to verify the reliability of the film, and to evaluate the SRS in clinical dose distributions from calculation and measurement in the region of virtual target in humanoid and cylindrical phantoms were compared. The Gafchromic $EBT^{(R)}$ film was found to be linear up to 9Gy. The $D_{max}$ for 6 MV was measured at 1.5 cm from the surface by both of diode and the film. As the depth is deeper, the error was measured within $2{\sim}3%$ at $10{\sim}20\;cm$ depth. Comparing between distribution from calculation and measurement, we found that there is 5% error at 90% isodose line. We found that given dose could be measured accurately by using the phantoms. It was feasible to use the Gafchromic $EBT^{(R)}$ film in quality assurance of SRS.

• The Journal of Korean Society for Radiation Therapy
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• v.11 no.1
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• pp.53-59
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• 1999

The aim of this study is to improve the accuracy of field placement and junction between adjacent fields and block shielding through the use of a computed tomography(CT) simulator and virtual simulation. The information was acquired by assessment of Alderson Rando phantom image using CT simulator (I.Q. Xtra - Picker), determination of each field by virtual fluoroscopy of voxel IQ workstation AcQsim and colored critical structures that were obtained by contouring in virtual simulation. And also using a coronal, sagittal and axial view can determine the field and adjacent field gap correctly without calculation during the procedure. With the treatment planning by using the Helax TMS 4.0, the dose in the junction among the adjacent fields and the spinal cord and cribriform plate of the critical structure was evaluated by the dose volume histogram. The pilot image of coronal and sagittal view took about 2minutes and 26minutes to get 100 images. Image translation to the virtual simulation workstation took about 6minutes. Contouring a critical structure such as cribriform plate, spinal cord using a virtual fluoroscopy were eligible to determine a correct field and shielding. The process took about 20 minutes. As the result of the Helax planning, the dose distribution in adjacent field junction was ideal, and the dose level shows almost 100 percentage in the dose volume histogram of the spinal cord and cribriform plate CT simulation can get a correct therapy area due to enhancement of critical structures such as spinal cord and cribriform plate. In addition, using a Spiral CT scanner can be saved a lot of time to plan a simulation therefore this function can reduce difficulties to keep the patient position without any movements to the patient, physician and radiotherapy technician.

• Progress in Medical Physics
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• v.23 no.1
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• pp.54-61
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• 2012

A polymer gel dosimeter was fabricated. A 3-dimensional dosimetry experiment was performed in the small field of the photon of the cyberknife. The dosimeter was installed in a head and neck phantom. It was manufactured from the acrylic and it was used in dosimetry. By using the head and neck CT protocol of the CyberKnife system, CT images of the head and neck phantom were obtained and delivered to the treatment planning system. The irradiation to the dosimeter in the treatment planning was performed, and then, the image was obtained by using 3.0T magnetic resonance imaging (MRI) after 24 hours. The dose distribution of the phantom was analyzed by using MATLAB. The results of this measurement were compared to the results of calculation in the treatment planning. In the isodose curve on the axial direction, the dose distribution coincided with the high dose area, 0.76mm difference on 80%, rather than the low dose area, 1.29 mm difference on 40%. In this research, the fact that the polymer gel dosimeter and MRI can be applied for analyzing a small field in a 3 dimensional dosimetry was confirmed. Moreover, the feasibility of using these for the therapeutic radiation quality control was also confirmed.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.129-132
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• 2002

The practical virtual compensator, which uses a dynamic multi-leaf collimator (dMLC) and three-dimensional radiation therapy planning (3D RTP) system, was designed. And the feasibility study of the virtual compensator was done to verify that the virtual compensator acts a role as the replacement of the physical compensator. Design procedure consists of three steps. The first step is to generate the isodose distributions from the 3D RTP system (Render Plan, Elekta). Then isodose line pattern was used as the compensator pattern. Pre-determined compensating ratio was applied to generate the fluence map for the compensator design. The second step is to generate the leaf sequence file with Ma's algorithm in the respect of optimum MU-efficiency. All the procedure was done with home-made software. The last step is the QA procedure which performs the comparison of the dose distributions which are produced from the irradiation with the virtual compensator and from the calculation by 3D RTP. In this study, a phantom was fabricated for the verification of properness of the designed compensator. It is consisted of the styrofoam part which mimics irregular shaped contour or the missing tissues and the mini water phantom. Inhomogeneous dose distribution due to the styrofoam missing tissue could be calculated with the RTP system. The film dosimetry in the phantom with and without the compensator showed significant improvement of the dose distributions. The virtual compensator designed in this study was proved to be a replacement of the physical compensator in the practical point of view.

• Progress in Medical Physics
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• v.29 no.2
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• pp.59-65
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• 2018

This paper describes the clinical use of the dose verification of multileaf collimator (MLC)-based CyberKnife plans by combining the Octavius 1000SRS detector and water-equivalent RW3 slab phantom. The slab phantom consists of 14 plates, each with a thickness of 10 mm. One plate was modified to support tracking by inserting 14 custom-made fiducials on surface holes positioned at the outer region of $10{\times}10cm^2$. The fiducial-inserted plate was placed on the 1000SRS detector and three plates were additionally stacked up to build the reference depth. Below the detector, 10 plates were placed to avoid longer delivery times caused by proximity detection program alerts. The cross-calibration factor prior to phantom delivery was obtained by performing with 200 monitor units (MU) on the field size of $95{\times}92.5mm^2$. After irradiation, the measured dose distribution of the coronal plane was compared with the dose distribution calculated by the MultiPlan treatment planning system. The results were assessed by comparing the absolute dose at the center point of 1000SRS and the 3-D Gamma (${\gamma}$) index using 220 patient-specific quality assurance (QA). The discrepancy between measured and calculated doses at the center point of 1000SRS detector ranged from -3.9% to 8.2%. In the dosimetric comparison using 3-D ${\gamma}$-function (3%/3 mm criteria), the mean passing rates with ${\gamma}$-parameter ${\leq}1$ were $97.4%{\pm}2.4%$. The combination of the 1000SRS detector and RW3 slab phantom can be utilized for dosimetry validation of patient-specific QA in the CyberKnife MLC system, which made it possible to measure absolute dose distributions regardless of tracking mode.

• Journal of Radiation Protection and Research
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• v.28 no.1
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• pp.35-42
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• 2003

Methodology for calculating the organ equivalent doses and the effective doses of pediatric and adult patients undergoing medical X-ray examinations were established. The MIRD-type mathematical phantoms of 4 age groups were constructed with addition of the esophagus to the same phantoms. Two typical examination procedures, chest PA and abdomen AP, were simulated for the pediatric patients as well as the adult as illustrative examples. The results confirmed that patients pick up approximate 0.03 mSv of effective dose from a single chest PA examination, and 0.4 to 1.7 mSv from an abdomen AP examination depending on the ages. For dose calculations where irradiation is made with a limited field, the details of the position, size and shape of the organs and the organ depth from the entrance surface considerably affect the resulting doses. Therefore, it is important to optimize radiation protection by control of X-ray properties and beam examination field. The calculation result, provided in this study, can be used to implement optimization for medical radiation protection.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.393-400
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• 2020

Unlike conventional radiographic examinations, angiointerventional procedures have a high risk of radiation exposure to patients or operators due to prolonged radiation exposure time. This study was undertaken to examine effects of reducing the radiation risk by applying dose reduction fiber (DRF) shielding cloth during angiography. To investigate the properties of DRF shielding cloth, we measured the scattered radiation below and above a human phantom using a glass dosimeter, at site distances 10 cm away from the irradiated field. The results obtained reveal a 15 ~ 31% reduction of scattered radiation in the irradiation field, and 53 ~ 70% reduced radiation measured after phantom transmission. Taken together, our data indicate that application of DRF shielding cloth for radiation reduction at non-procedural sites during interventional procedure results in reduction of scattered doses to patients and operators, without affecting the medical examinations. We propose the use of DRF shielding during angiointerventional procedures, in order to reduce the risk of radiation exposure of patients and operators.