• The Journal of the Korea Contents Association
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• v.15 no.6
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• pp.297-302
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• 2015

High-energy medical linear accelerator on the dose to the thyroid cancer during radiotherapy were evaluated using optical stimulation luminescence dosimeters(OSLD) using. Scattered's influence in the case of 3D-CRT 25.4 mSv, 28.8 mSv, 31.3 mSv, 26.5 mSv, 27.4 mSv 5 times with an average 27.9 mSv, in the IMRT 46.8 mSv, 43.2 mSv, 42.3 mSv, 41.5 mSv, 44.1 mSv to five times the average of 43.6 was the result of mSv. In the case of light neutron dosimetry results 3D-CRT 3 mSv, 3 mSv, 3.4 mSv, 3.5 mSv, 3.1 mSv to five times the average 3.2 mSv, in the IMRT 5.1 mSv, 4.8 mSv, 4.2 mSv, 4.8 mSv, 4.9 mSv, to five times the average of 4.7 was the result of mSv. Both parties and the light scattered neutrons were significantly appreciated compared to IMRT 3D-CRT. Treatment of cancer using radiation workers, as in this study, and that a significant amount of scattered rays in the adjacent normal tissues during radiation therapy using energy assessment to influence by fully aware of this information is necessary for the exposure reduction efforts the feed.

• 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.

• The Journal of Korean Society for Radiation Therapy
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• v.1 no.1
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• pp.47-51
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• 1985

Authors describe some useful data when constructing tissue-equivalent compensators which would compensate tissue deficit in the treatment field of high energy electromagnetic radiation Tissue equivalent compensator is made of lucite. The ratio of compensator thickness to the thickness of tissue deficit depends on radiation energy, field size and the distance from the compensator to patient skin. When the compensator is separated from skin surface, the thickness ratio is always smaller than 1.0. This means that the larger the separation, the contribution to the total dose by means of scattered radiation from a tissue equivalent compensator is smaller. Authors propose that the thickness of lucite as tissue equivalent compensator is 0.57 times tissue deficit and the separation between compensator and skin is at least 15m for Co-60 gamma ray and 25cm for 10MV X-ray.

• Journal of Radiation Protection and Research
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• v.40 no.1
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• pp.65-72
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• 2015

The basic concepts of radiation-induced skin damage have been established, the biological mechanism has not been studied. In this study, we have examined the effects of gamma rays on skin injury and cyclooxygenase(COX)-2 expression. Gamma irradiation induced clinicopathological changes in a dose- and time-dependent manner in mini-pig skin. The histological changes were consistent with the changes in gross appearance at 12 weeks after irradiation. After three days' irradiation, apoptotic cells in the basal layer were found more frequently in irradiated skin than in normal skin, with the magnitude of the effect being dose-dependent. The thickness of the epidermis transiently increased 3 days after irradiation, and then gradually decreased, although changes in the epithelial thickness of the irradiated field were not observed with irradiation doses over 50 Gy. In the epithelium, there was an initial degenerative phase, during which the rate of basal cell depletion was dependent on the radiation dose (20-70 Gy). One week after irradiation, COX-2 expression was mostly limited to the basal cell layer and was scattered across these cells. High COX-2 expression was detected throughout the full depth of the skin after irradiation. The COX-2 protein is upregulated after irradiation in mini-pig skin. These histological changes associated with radiation exposure dose cause the increased COX-2 expression in a dose-dependent fashion.

• Journal of radiological science and technology
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• v.31 no.4
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• pp.407-413
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• 2008

Measurements of the peripheral dose were performed using a 2D array ion chamber and solid water phantom for a $10{\times}10cm$, source-surface distance (SSD) 90cm, 6 and 15MV photon beam at depths of 0.5cm, 5cm through $d_{max}$. Measurements of peripheral dose at 0.5cm and 5cm depths were performed from 1cm to 5cm outside of fields for the dynamic wedge and physical wedge $15^{\circ}$, $45^{\circ}$. For 6MV photon beam, the average peripheral dose of dynamic wedge were lower by 1.4% and 0.1% than that of physical wedge For 15MV photon beam, the peripheral dose of dynamic wedge were lower by maximum 1.6% that of physical wedge. The results showed that dynamic wedge can reduce scattered dose of clinical organ close to the field edge. The wedge systems produce different peripheral dose that should be considered in properly choosing a wedge system for clinical use.

• Journal of Veterinary Clinics
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• v.40 no.6
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• pp.429-437
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• 2023

In veterinary medicine, most radiographic images are obtained by restraining patients, inevitably exposing the restrainer to secondary scattered radiation. Radiation exposure can result in stochastic reactions such as cancer and genetic effects, as well as deterministic reactions such as skin burns, cataracts, and bone marrow suppression. Radiation-shielding equipment, including aprons, thyroid shields, eyewear, and gloves, can reduce radiation exposure. However, the risk of radiation exposure to the upper arms, face, and back remains, and lead aprons and thyroid shields are heavy, restricting movement. We designed a new radiation-shielding system and compared its shielding ability with those of conventional radiation-shielding systems. We hypothesized that the new shielding system would have a wider radiation-shielding range and similar shielding ability. The radiation exposure dose differed significantly between the conventional and new shielding systems in the forehead, chin, and bilateral upper arm areas (p < 0.001). When both systems were used together, the radiation-shielding ability was better than when only one system was used at all anatomical locations (p < 0.01). This study suggests that the new radiation-shielding system is essential and convenient for veterinary radiation workers because it is a step closer to radiation safety in veterinary radiography.

• Progress in Medical Physics
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• v.27 no.1
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• pp.31-36
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• 2016

The paper discusses radiation dose of dual energy CT on which copper modulation layer, is mounted in order to improve diagnostic performance of the dual energy CT. The radiation dose is estimated using MCNPX and its results are compared with that of the conventional dual energy CT system. CT X-ray spectra of 80 and 120 kVp, which are usually used for thorax, abdominal, head, and neck CT scans, were generated by the SPEC78 code and were used for the source specification 'SDEF' card for MCNPX dose modeling. The copper modulation layer was located 20 cm away from a source covering half of the X-ray window. The radiation dose was measured as changing its thickness from 0.5 to 2.0 mm at intervals of 0.5 mm. Since the MCNPX tally provides only normalized values to a single particle, the dose conversion coefficients of F6 tally for the modulation layer-based dual energy CBCT should be calculated for matching the modeling results into the actual dose. The dose conversion coefficient is $7.2*10^4cGy/output$ that is obtained from dose calibration curve between F6 tally and experimental results in which GAFCHORMIC EBT3 films were exposed by an already known source. Consequently, the dose of the modulation layer-based dual energy cone beam CT is 33~40% less than that of the single energy CT system. On the basis of the results, it is considered that scattered dose produced by the copper modulation layer is very small. It shows that the modulation layer-based dual energy CBCT system can effectively reduce radiation dose, which is the major disadvantage of established dual energy CT.

• Journal of radiological science and technology
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• v.42 no.5
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• pp.365-371
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• 2019

We have developed and applied a diagnostic Multi-Leaf Collimator (MLC) to optimized the X-ray field in medical imaging and the usefulness evaluated through the fusion of infrared image and X-ray image acquired by infrared camera. The hand and skull radiography with multi-leaf collimator(MLC) showed significant area dose reductions of 22.9% and 31.3% compared to ARC and leakage dose was compliant with KS A 4732. Also scattering doses of 50 cm and 100 cm showed a significant decrease to confirm the usefulness of MLC. It was confirmed that the fusion of infrared images with an adjustable degree of transparency was possible in the X-ray images. Therefore, fusion of anatomical information with physiological convergence is expected to contribute and improvement of diagnostic ability. In addition, the feasibility of convergence X-ray imaging and DITI devices and the possibility of driving MLC with infrared images were confirmed.

• Progress in Medical Physics
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• v.18 no.1
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• pp.7-12
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• 2007

In the radiation therapy for breast cancer patients, wedge shaped compensators are essentially used to achieve appropriate dose distribution because of thickness difference according to breast shapes. Tangential Irradiation technique has usually been applied to radiation therapy for breast cancer patients treated with breast conservative surgery. When a primary beam is incident on wedge shaped compensators from medial direction In tangential irradiation technique, low energy scattered radiation is generated and gives additional dose to the breast surface. As a method to reduced additional dose to breast surface, the use of virtual wedge shaped compensator is possible. Eclipse radiation treatment planning (RTP) systems Installed at our institution have virtual wedge shaped compensator for radiation therapy treatment planning. The dose distributions of 15, 30, 45, 60 degree physical wedges and virtual wedges were measured and compared. Results showed that there was no significant differences In symmetry of $10{\times}10$ field among various wedge angles. When the transmission factor was compared, transmission factor Increased linearly as the wedge angle Increased. These results Indicates that the appilcation of virtual wedge in clinical use is appropriate.

• Progress in Medical Physics
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• v.26 no.4
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• pp.208-214
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• 2015

The aim of this study is to investigate the effect of low magnetic field on dose distribution in the partial-breast irradiation (PBI). Eleven patients with an invasive early-stage breast carcinoma were treated prospectively with PBI using 38.5 Gy delivered in 10 fractions using the $ViewRay^{(R)}$ system. For each of the treatment plans, dose distribution was calculated with magnetic field and without magnetic field, and the difference between dose and volume for each organ were evaluated. For planning target volume (PTV), the analysis included the point minimum ($D_{min}$), maximum, mean dose ($D_{mean}$) and volume receiving at least 90% ($V_{90%}$), 95% ($V_{95%}$) and 107% ($V_{107%}$) of the prescribed dose, respectively. For organs at risk (OARs), the ipsilateral lung was analyzed with $D_{mean}$ and the volume receiving 20 Gy ($V_{20\;Gy}$), and the contralateral lung was analyzed with only $D_{mean}$. The heart was analyzed with $D_{mean}$, $D_{max}$, and $V_{20\;Gy}$, and both inner and outer shells were analyzed with the point $D_{min}$, $D_{max}$ and $D_{mean}$, respectively. For PTV, the effect of low magnetic field on dose distribution showed a difference of up to 2% for volume change and 4 Gy for dose. In OARs analysis, the significant effect of the magnetic field was not observed. Despite small deviation values, the average difference of mean dose values showed significant difference (p<0.001), but there was no difference of point minimum dose values in both sehll structures. The largest deviation for the average difference of $D_{max}$ in the outer shell structure was $5.0{\pm}10.5Gy$ (p=0.148). The effect of low magnetic field of 0.35 T on dose deposition by a Co-60 beam was not significantly observed within the body for PBI IMRT plans. The dose deposition was only appreciable outside the body, where a dose build-up due to contaminated electrons generated in the treatment head and scattered electrons formed near the body surface.