• Progress in Medical Physics
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• v.3 no.1
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• pp.45-52
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• 1992

Authors started IORT for stomach cancer patient on 1988 and rectal cancer on 1991. We devloped various sized. shaped IORT cones for better clinical application and homogeneous surface and depth dose distribution. Authors obtained results as following. 1. The acryl cover fixed on the end for rectal IORT cone not only improvement of surface dose but also flattness of dose distribution. 2. Dose distribution of elliptical cone were shown almost 100% at inner field. 3. The output with acryl cone size were similar output of made electron cone.

• Progress in Medical Physics
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• v.25 no.1
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• pp.23-30
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• 2014

The purpose of this study is to evaluate the developed dose verification program for in vivo dosimetry based on transit dose in radiotherapy. Five intensity modulated radiotherapy (IMRT) plans of lung cancer patients were used in the irradiation of a homogeneous solid water phantom and anthropomorphic phantom. Transit dose distribution was measured using electronic portal imaging device (EPID) and used for the calculation of in vivo dose in patient. The average passing rate compared with treatment planning system based on a gamma index with a 3% dose and a 3 mm distance-to-dose agreement tolerance limit was 95% for the in vivo dose with the homogeneous phantom, but was reduced to 81.8% for the in vivo dose with the anthropomorphic phantom. This feasibility study suggested that transit dose-based in vivo dosimetry can provide information about the actual dose delivery to patients in the treatment room.

• Progress in Medical Physics
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• v.4 no.1
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• pp.17-21
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• 1993

근접방사선치료는 방사성동위원소를 종양에 밀착시키거나 또는 종양내에 직접 삽입하여 치료하는 방법으로서 종양에는 일시에 많은 선량을 주는 반면 주위 정상조직에는 선량을 최소화시킬 수 있는 장점이 있다. 따라서 근래에 들어 종양치료에 있어서 외부방사선치료와 병행하여 근접방사선치료를 시행하는 병원이 증가하고 있다. 그러나 근접방사선치료는 방출 방사선의 에너지가 낮고, 대부분 짧은 반감기를 가지며, 소형의, 수 mCi에서 수Ci 정도의 방사능을 가진 방사성동위원소들을 인체에 직접 삽입하는 것으로 정확한 선량 분포를 위해서는 방사성동위원소의 방사능량, 위치, 분포 등의 정확성 확보가 절실히 요구된다. 따라서 이 논문은 근접방사선치료시스템의 QA프로그램 개발을 위하여 작성하였다.

• Progress in Medical Physics
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• v.9 no.4
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• pp.247-257
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• 1998

For effective radiotherapy, it should always be considered that calculation of different dose distribution in heterogenous tissue is important particularly on lung which has low density and large volume. To take precise dose distribution of 6MV X-ray in the thoracic cage, the authors had made a tissue equivalent phantom for thorax, measured dose distribution by thermoluminescent dosimeter and mm dosimeter, and derived methmetical equation coincided with provided theoretical formula. In comparision with isodose curve on case of homogeneous soft tissue, dose of heterogeneous lung tissue had been shown increase about 4% per cm depth on one and multiportal field, less than 15% difference on rotation field for esophagus, and around 20% difference on rotation field for lung according to the degree of rotation angle that must be corrected by dose compensation.

• 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.

• Progress in Medical Physics
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• v.2 no.2
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• pp.141-148
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• 1991

A since authors started IORT for stomach cancer patient on 198, we developed various sized, shaped IORT cones for better clinical application and homogeneous surface and depth dose distribution. Authors concluded as following. 1. The shaping block should be fixed on the tray, not under the tray for homogeneous dose distribution. 2. The straight cone was showed better dose distribution than divergence cone. 3. The acryl cone was superior than the stainless-steel cone. 4. The acryl cover fixed on the end for IORT cone not only improvement of surface dose, but also homogenity of depth dose.

• Journal of the Korean Society of Radiology
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• v.11 no.6
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• pp.423-428
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• 2017

In this study, the calculation of the effective spatial dose distribution of the diagnostic imaging laboratory of K university was performed by the Monte Carlo simulation. The radiation generator has a maximum tube voltage of 150 kVp and a maximum current of 700 mA. Using the results, we compared the spatial effective dose distributions of diagnostic imaging laboratory when the shielding door was closed and opened. In conclusion, it was found that the effective dose in the operating room of the diagnostic imaging laboratory does not exceed the annual dose limit (6 mSv/y) of the student (occasional visitor) even when the door is opened. However, since the effective dose when the door is open is about 16 times higher in front of the lead glass window and about 3,000 times higher in front of the doorway than the case when the door is closed, closing the shielding door at the time of the practical exercising reduces unnecessary radiation exposure by great extent.

• 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.

• Journal of the Korean Society of Radiology
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• v.18 no.5
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• pp.391-402
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• 2024

In this study, an indicator for setting dose constraints was presented using the frequency distribution of the annual exposure dose per radiation worker. To this end, from January 2017 to December 2019, we surveyed personal dosimeter reading values per month for 13 radiography inspection offices that had reported the establishment of a workplace to move and use radioisotopes, etc. for the purpose of radiographic testing (RT) in Korea, and performed a frequency analysis of the annual exposure dose per radiation worker. In this study, the indicator for setting dose constraints was based on the 95th percentile according to the recommendations of international organizations related to radiation protection. As a result, the dose constraints in the field of RT was set at an average of 5.15 mSv over the three-year investigation period. The nuclear energy-related business operator, if was set its own dose constraints proposed in this study and was operated successfully, were able to manage the exposure dose inequality of 52 people, equivalent to 5% of registered radiation workers, and could expect a reduction in collective dose of 760 man-mSv. Therefore, the nuclear energy-related business operator set its own dose constraints using the indicator for setting dose constraints proposed in this study, will be able to achieve optimization of protection by excluding exposure situations in which a dose level higher than the set dose constraint is expected from the process of establishing a protection plan.

• Progress in Medical Physics
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• v.9 no.4
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• pp.207-215
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• 1998

There have been many radiation measurement methods so far among which film dosimetry, TLD, and ion chamber are the most frequently used methods. But this study describes a new radiation measurement method which uses polymer gel and magnetic resonance imaging(MRI). The objective of this study is to fabricate a polymer gel sensitive to radiation and to generate a dose to MRI contrast relationship, and to apply this results to the radiation measurement for the brachytherapy. To do this, 12 cm diameter cylindrical gel phantom was made, and the phantom was irradiated using the 30 mm diameter circular collimator which was used for radiosurgery. And this irradiated phantom was scanned with MRI. To find out the relationship between the radiation dose and the transversal relaxation time, an image processing software(IDL) was used. From this study it is found out that the radiation dose showed linear relationship to the transversal relaxation time of the gel up to 17 Gy($R^2$=0.993) and they had a different relationship above 17 Gy. The dose distributions were calculated using these results for the Ir-192 sources, one for the HDR afterloading system and the other for a 2 mCi seed source. And these calculated dose distributions were compared to the ones from the treatment planning computers. From this study the dose to the irradiated gel's transversal relaxation time relationship was examined, and this result was tried for the measurement of the brachytherapy.