• Journal of Periodontal and Implant Science
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• v.28 no.1
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• pp.161-175
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• 1998

치주상태의 진단은 일반적으로 치주탐침과 같은 임상적 검사와 보조적으로 방사선 검사를 이용한다. 방사선학적인 검사가 치주조직의 파괴정도와 골 흡수를 진단하는데 유용하지만 실제적인 골 흡수를 정확하게 나타나는데는 한계가 있다고 하였다. 그리고 임상적 측정과 방사선 사진을 비교연구하여 이들간의 관계를 알아보고자 하는 노력이 있었다. 방사선이 임상에서 참고사항으로는 중요하지만 절대적 신뢰를 주는데는 문제가 있는 것으로 생각되어왔다. 방사선학적 측정과 임상지수 측정간의 상관관계에대하여 계속적인 연구를 통해 규명하는 것이 중요하다고 생각되어 저자는 연세대학교 치과 대학병원 치주과를 내원한환자중 연령 및 성별에 관계없이 전신질환이 없는 환자 130명을 대상으로 소구치의 원.근심부, 대구치의 원.중.근심부에서 치주낭의 깊이와 (P.D), 부착상실 (A.L)을 측정하였다. 방사선 사진상의 원.근심부에서 백악 법랑질 경계부에서 치조골능 상부까지의 치조골 수준 (Rx.B.L)을 측정하였고 이개부 부위에서는 이개부의 천정으로부터 나타나는 골 흡수의 방사선 투과상을 측정하였다. 이를 기초로 임상지수와 방사선학적 측정간에 상관관계를 연구하여 다음과 같은 결론을 얻었다. 1. 원·근심부의 P.D와 Rx.B.L을 비교 했을 때 상관관계는 모든 치아에서 높게 나타났다(r=0.897$\sim$r=0.725, p<0.01). 2. 원·근심부의 A.L와 Rx.B.L을 비교 했을 때 상관관계는 모든 치아에서 높게 나타났다 (r=0.915$\sim$r=0.732, p<0.01 ). 3. 대구치 769개가 실험 대상인었다. 상악 대구치중(356개) 40%가 이개부 병소를 나타냈고 (146개), 하악 대구치중(413개) 41%가 이개부 병소를 나타냈다(170개). 4. 대구치의 이개부 병소의 중앙부에서 측정한 P.D와 Rx.B.L을 비교 하였을 때 상관관계는 상악 제1대구치를 제외한 모든 치아에서 높게 나타 났다(r=0.811$\sim$r=0.435, p<0.01). 5. 대구치의 이개부 병소의 중앙부에서 측정한 A.L와 Rx.B.L을 비교 하였을 때 상관관계는 상악 제1대구치를 제외한 모든 치아에서 높게 나타 났다(r=0.906$\sim$r=0.479, p<0.01). 이상의 결과를 종합하여 볼 때 임상지수와 방사선학적 측정을 비교한 바, 이들의 상관관계는 모든 치아에서 밀접하게 나타났다. 따라서 방사선학적 측정은 임상지수와 더불어 치주질환의 진단과 치료계획에 크게 기여할 수 있을 것으로 사료된다.

• Progress in Medical Physics
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• v.26 no.3
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• pp.153-159
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• 2015

This study is to evaluate thedosiemtric leaf gap (DLG) at different depths for dynamic intensity-modulated radiation therapy (IMRT) in order to evaluate the absolute dose and dose distribution according to the different positions of tumors and compare the measured and planned the multileaf collimator (MLC) transmission factor (T.F.) and DLG values. We used the 6 MV and 15 MV photon beam from linear accelerator with a Millenium 120 MLC system. After the import the DICOM RT files, we measured the absolute dose at different depths (2 cm, 5 cm, 10 cm, and 15 cm) to calculate the MLC T. F. and DLG. For 6 MV photon beam, the measured both MLC T. F. and DLG were increased with the increase the measured depths. When applying to treatment planning systemas fixed transmission factor with its value measured under the reference condition at depth of 5 cm, although the difference fixed and varied transmission factor is not significant, the dosiemtric effect could be presented according to the depth that the tumor is placed. Therefore, we are planning to investigate the treatment planning system whichthe T. F. and DLG factor according to at the different depths can be applied in the patient-specific treatment plan.

• Radiation Oncology Journal
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• v.9 no.2
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• pp.333-336
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• 1991

High energy Photon beam has a sharp beam margin due to a less side scatter and the other things. But there still remains a penumbra where the dose changes rapidly in the region near the edge of a radiation beam, although it is short in width. It is suggested that the width of the penumbra depends on the source size, distance from source to diaphragm, source to skin distance, and depth in tissue. However, it is also supposed that the other factors influence the penumbra width. In this paper, we investigate changes of the physical penumbra widths according to various field sizes and depths, by using the three dimensional dosimetry system. As a result, we found that as field size and depth increase, the physical penumbra width also increases.

• Journal of the Korean Society of Radiology
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• v.13 no.7
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• pp.925-932
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• 2019

In this paper, we developed optical dosimetry system with a plastic scintillator, a commercial 50 mm, f1.8 lens, and a commercial high-sensitivity CMOS (complementary metal-oxide semiconductor) camera. And, the correction processors of vignetting, geometrical distortion and scaling were established. Using the developed system, we can measured a percent depth dose, a beam profile and a dose linearity for 6 MV medical LINAC (Linear Accelerator). As results, the optically measured percent depth dose was well matched with the measured percent depth dose by ion-chamber within 2% tolerance. And the determined flatness was 2.8%. We concluded that the optical dosimetry system was sufficient for application of absorbed dose monitoring during radiation therapy.

• Radiation Oncology Journal
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• v.12 no.2
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• pp.225-232
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• 1994

Purpose : This study was to obtain the basic dosimetric data using the 10 MV X-ray for the total body irradiation. Materials and Methods : A linear accelerator photon beam is planned to be used as a radiation source for total body irradiation (TBI) in Chonnam University Hospital. The planned distance from the target to the midplane of a patient is 360cm and the maximum geometric field size is 144cm x 144cm. Polystyrene phantom sized $30{\times}30{\times}30.2cm^3$ and consisted of several sheets with various thickness, and a parallel plate ionization chamber were used to measure surface dose and percent depth dose (PDD) at 345cm SSD, and dose profiles. To evaluate whether a beam modifier is necessary for TBI, dosimetry in build up region was made first with no modifier and next with an 1cm thick acryl plate 20cm far from the polystyrene phantom surface. For a fixed sourec-chamber distance, output factors were measured for various depth. Results : As any beam modifier was not on the way of radiation of 10MV X-ray, the $d_{max}$ and surface dose was 1.8cm and $61\%$, respectively, for 345cm SSD. When an 1cm thick acryl plate was put 20cm far from polystyrene phantom for the SSD, the $d_{max}$ and surface dose were 0.8cm and $94\%$, respectively. With acryl as a beam spoiler, the PDD at 10cm depth was $78.4\%$ and exit dose was a little higher than expected dose at interface of exit surface. For two-opposing fields for a 30cm phantom thick phantom, the surface dose and maximum dose relative to mid-depth dose in our experiments were $102.5\%$ and $106.3\%$, respectively. The off-axis distance of that point of $95\%$ of beam axis dose were 70cm on principal axis and 80cm on diagonal axis. Conclusion: 1. To increase surface dose for TBI by 10MV X-ray at 360cm SAD, 1cm thick acrylic spoiler was sufficient when distance from phantom surface to spoiler was 20cm. 2. At 345cm SSD, 10MV X-ray beam of full field produced a satisfiable dose uniformity for TBI within $7\%$ in the phantom of 30cm thickness by two-opposing irradiation technique. 3. The uniform dose distribution region was 67cm on principal axis of the beam and 80cm on diagonal axis from beam axis. 4. The output factors at mid-point of various thickness revealed linear relation with depth, and it could be applicable to practical TBI.

• Journal of the Korean Society of Radiology
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• v.13 no.6
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• pp.889-894
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• 2019

Upper gastrointestinal series is an examination that uses X-rays. It is important to defend against exposure to radiation during upper gastrointestinal examination because the organs, such as thyroid gland, lens, breasts, and gonads, with relatively high biological sensitivity to radiation are distributed on the examination area. We have made a whole body phantom that can change the depth of organs. radiation dose of eye, thyroid gland, breast and gonads were measured by the same procedure as the actual upper gastrointestinal examination. When performed only fluoroscopy the mean dose reduction of lens, thyroid gland, breast and gonads was 62.2%. The mean dose reduction of lens, thyroid gland, breast and gonads was 59.0% when both fluoroscopy and spot shoot were performed. Therefore, when performed upper gastrointestinal examination it was confirmed that shielding of the lens, thyroid gland, breast and gonads was effective in decreasing the exposure dose. The manufactured human phantom can be used in measuring radiation dose for deep organ because it can adjust the height corresponding to the organs located in the human body.

• The Journal of Korean Society for Radiation Therapy
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• v.13 no.1
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• pp.126-129
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• 2001

I. 목적 : Half beam을 이용하여 인접한 조사면 치료시, 경계부위에서 발생할 수 있는 Jaw Position에 의한 기하학적 오차는 정확한 선량전달에 문제를 일으킨다. 이에 본 저자는 QA용 필름을 이용하여 조사면 setting 방법과 조작자간의 오차를 분석하고 이를 최소화할 수 있는 방법을 찾고자 한다. II. 대상 및 방법 : 본 실험은 6MV선(CL2100C, Varian, USA)을 대상으로 하였으며, 폴리스틸렌팬톰($25{\times}25cm2$)을 SSD 100 cm으로 고정한 후, 측정용 필름(X-omat V2, Kodak, USA)을 5 cm 깊이에 위치 시켜 조사면의 중심에서 경계를 이루는 비대칭 조사면 ($0/7.5{\times}15,7.5/0{\times}15 cm$)을 쌍으로 조사하였다. 조사된 필름은 자동현상기를 이용하여 현상한 후 농도계(Densitometer, Multidata, USA)를 이용하여 중심축상에서의 농도분포를 측정하여 인접한 조사면에서의 오차를 분석하였다. 조작방법과 조작자간의 오차를 분석하기 위하여 5명의 방사선사를 대상으로 auto및 manual set-up을 실시하였고 각 방법의 평균 오차를 분석하기 위해 5회 반복하였다. III. 결과 : 필름 농도곡선을 이용하여 두 조사면이 만나는 경계에서의 오차를 분석한 결과, remote console set-up의 경우 주변 조사면에 비해 $-0.16{\pm}3.44\%$, pendant방식에서는 $+5.04{\pm}4.37\%$로 나타났고, 조작자간의 유의성이 관찰되었다. IV. 결론 : 비대칭 조사면을 이용한 근접 조사면의 치료시 pendant 방식보다 remote console 방식에서 오차가 적 게 나타나므로 Auto set-up 기능의 이용은 치료시에 조사면 경계에서의 선량 오차를 최소한으로 줄이는데 도움이 될 것으로 생각된다. 또한 manual 방식으로 set-up 시 오차의 편차가 크게 나타나므로 치료시에 세심한 주의가 필요할 것으로 사료된다.

• Journal of radiological science and technology
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• v.31 no.4
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• pp.401-406
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• 2008

The aim of this study is to evaluate contra-lateral breast (CLB) surface dose in Field-in-Field (FIF) technique for breast conserving surgery patients. For evaluation of surface dose in FIF technique, we have compared with other techniques, which were open fields (Open), metal wedge (MW), and enhanced dynamic wedge (EDW) techniques under same geometrical condition and prescribed dose. The three dimensional treatment planning system was used for dose optimization. For the verification of dose calculation, measurements using MOSFET detectors with Anderson Rando phantom were performed. The measured points for four different techniques were at the depth of 0cm (epidermis) and 0.5cm bolus (dermis), and spacing toward 2cm, 4cm, 6cm, 8cm, 10cm apart from the edge of tangential medial beam. The dose calculations were done in 0.25cm grid resolution by modified Batho method for inhomogeneity correction. In the planning results, the surface doses were differentiated in the range of $19.6{\sim}36.9%$, $33.2{\sim}138.2%$ for MW, $1.0{\sim}7.9%$, $1.6{\sim}37.4%$ for EDW, and for FIF at the depth of epidermis and dermis as compared to Open respectively. In the measurements, the surface doses were differentiated in the range of $11.1{\sim}71%$, $22.9{\sim}161%$ for MW, $4.1{\sim}15.5%$, $8.2{\sim}37.9%$ for EDW, and 4.9% for FIF at the depth of epidermis and dermis as compared to Open respectively. The surface doses were considered as underestimating in the planning calculation as compared to the measurement with MOSFET detectors. Was concluded as the lowest one among the techniques, even if it was compared with Open method. Our conclusion could be stated that the FIF technique could make the optimum dose distribution in Breast target, while effectively reduce the probability of secondary carcinogenesis due to undesirable scattered radiation to contra-lateral breast.

• The Journal of Korean Society for Radiation Therapy
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• v.28 no.1
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• pp.47-55
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• 2016

To evaluate the position accuracy of the MLC. This study analyzed the variations of the dosimetric leaf gap(DLG) and MLC transmission factor to reflect the location of the MLC leaves according to the dose rate variation for dynamic IMRT. We used the 6 MV and 10 MV X-ray beams from linear accelerator with a Millennium 120 MLC system. We measured the variation of DLG and MLC transmission factor at depth of 10 cm for the water phantom by varying the dose rate to 200, 300, 400, 500 and 600 MU/min using the CC13 and FC-65G chambers. For 6 MV X-ray beam, a result of measuring based on a dose rate 400 MU/min by varying the dose rate to 200, 300, 400, 500 and 600 MU/min of the difference rate was respectively -2.59, -1.89, 0.00, -0.58, -2.89%. For 10 MV X-ray beam, the difference rate was respectively ?2.52, -1.69, 0.00, +1.28, -1.98%. The difference rate of MLC transmission factor was in the range of about ${\pm}1%$ of the measured values at the two types of energy and all of the dose rates. This study evaluated the variation of DLG and MLC transmission factor for the dose rate variation for dynamic IMRT. The difference of the MLC transmission factor according to the dose rate variation is negligible, but, the difference of the DLG was found to be large. Therefore, when randomly changing the dose rate dynamic IMRT, it may significantly affect the dose delivered to the tumor. Unless you change the dose rate during dynamic IMRT, it is thought that is to be the more accurate radiation therapy.

• Journal of radiological science and technology
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• v.33 no.1
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• pp.61-66
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• 2010

In this paper we evaluated small field dose characteristics of exclusive cone fields versus square fields for stereotactic radiosugery (SRS) which is based on linear accelerators (LINAC). For this test, we used a small beam detector (stereotactic fields detector : SFD) with a 6 MV photon beam and a water phantom system (IBA, Germany). Percentage depth dose (PDD) was measured for different field sets (cones : ${\Phi}1\;cm$, ${\Phi}2\;cm$, ${\Phi}3\;cm$ ; square fields : $1{\times}1\;cm^2$, $2{\times}2\;cm^2$, $3{\times}3\;cm^2$) at a source skin distance (SSD) of 100 cm. We measured the point depths at 1.5 cm, 5 cm, 10 cm, 20 cm, and 30 cm. The output factors were measured under the same geometrical conditions of the PDD and normalized at the maximum dose depth. To analyze the penumbra, we measured the dose profile with 95 cm of SSD, 5 cm of depth for each field sizes (${\Phi}1\;cm$, ${\Phi}3\;cm$, $1{\times}1\;cm^2$, and $3{\times}3\;cm^2$) using SFD. We obtained the values for every 1 mm interval in the physical field (90%) and 0.5 mm interval in the penumbra region (20 to 80%). The PDD variation of exclusive cones and square fields were 4.3 to 7.9% lesser than the standard field size ($10{\times}10\;cm^2$. The variation of PDD was reduced while the field size was increased. To compare the beam quality, we analyzed the $PDD_{20,10}$ and the results showed under the 1% of variations for all experiments except for ${\Phi}1\;cm$ cone and $1{\times}1\;cm^2$ fields. Output factors of exclusive cone were increased 3.1~4.6% than the square fields, and the penumbra region of exclusive cone was reduced 20% as compared to the square fields. As the previous researches report, it is very important for SRS and SFD that precise dosimetry in small beam fields. In this paper, we showed the effectiveness of exclusive cone, compared to square field. And we will study on the various detector characteristics for small beam fields.