• Progress in Medical Physics
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• v.20 no.2
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• pp.97-105
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• 2009

Absorbed dose to water based protocols recommended that plane-parallel chambers be calibrated against calibrated cylindrical chambers in a high energy electron beam with $R_{50}$>7 $g/cm^2$ (E${\gtrsim}$16 MeV). However, such high-energy electron beams are not available at all radiotherapy centers. In this study, we are compared the absorbed dose to water determined according to cross-calibration method in a high energy electron beam of 16 MeV and in electron beam energies of 12 MeV below the cross-calibration quality remark. Absorbed dose were performed for PTW 30013, Wellhofer FC65G Farmer type cylindrical chamber and for PTW 34001, Wellhofer PPC40 Roos type plane-parallel chamber. The cylindrical and the plane-parallel chamber to be calibrated are compared by alternately positioning each at reference depth, $Z_{ret}=0.6R_{50}-0.1$ in water phantom. The $D_W$ of plane-parallel chamber are derived using across-calibration method at high-energy electron beams of 16, 20 MeV. Then a good agreement is obtained the $D_W$ of plane-parallel chamber in 12 MeV. The agreement between 20 MeV and 12 MeV are within 0.2% for IAEA TRS-398.

• The Journal of Korean Society for Radiation Therapy
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• v.22 no.2
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• pp.135-144
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• 2010

Purpose: The purpose of this study is that through production of phantom for respiration gated radiotherapy, assessing appropriacy of exposure dose for the therapy using RPM (Real-time Position Management). Materials and Methods: We located measurement object on the phantom for respiration gated radiotherapy made of 2 linear actuator, acrylic panel, stanchion, iron plate ets. to drive (up, down, front, back). Using 4D CT scan, we analyzed patient's respiration and reproduced the movement by computer. On the phantom, we located a 2D-Array (PTW) and an White water phantom (4.5 cm) and used DMLC (interval 2 cm) in the field size $10{\times}10\;cm$, then exposed 21EX X-ray 100 MU, in the case of phantom was (1) static (2) moving (3) gated using RPM respectively gantry $0^{\circ}$ and $90^{\circ}$ We measured with a 0.125 CC ionization chamber (PTW) on the phantom (7.5 cm) in the same condition. Results: Ionization chamber: There were within 0.3% of error with gating respiration and approximately 2% of error without gating in the same condition. 2D-Array: Gantry $90^{\circ}$, field size $10{\times}10\;cm$, using DMLC. There were within 3% of error with gating respiration and approximately 16% of error without gating. Conclusion: The phantom for respiration gated radiotherapy makes plans considering patient's movement, quantitative analysis of exposure dose and proper assessment therapy for IMRT patients using RPM possible.

• Honam Mathematical Journal
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• v.29 no.2
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• pp.119-192
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• 2007

A very important Hopf algebra is the graded Hopf algebra Symm of symmetric functions. It can be characterized as the unique graded positive selfdual Hopf algebra with orthonormal graded distinguished basis and just one primitive element from the distinguished basis. This result is due to Andrei Zelevinsky. A noncommutative graded Hopf algebra of this type cannot exist. But there is a most important positive graded Hopf algebra with distinguished basis that is noncommutative and that is twisted selfdual, the Malvenuto-Poirier-Reutenauer Hopf algebra of permutations. Thus the question arises whether there is a corresponding uniqueness theorem for MPR. This prepreprint records initial investigations in this direction and proves that uniquenees holds up to and including the degree 4 which has rank 24.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.311-312
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• 2008

장거리 배전선로를 이용하여 대용량의 모터펌프를 기동할 경우 상대적으로 큰 임피던스 전압강하에 따른 모터의 기동불능 및 기동지연 등의 현상이 발생할 가능성이 있다. 본 논문에서는 K-water D 취수장에서 운영중인 2200kW 모터 기동시 발생하는 이상 현상에 대한 원인을 분석하고 이에 대한 해결책을 제시하였다. 특히 장거리 배전선로 환경하에서의 모터 기동시 문제점에 대한 해결책을 제시하기 위해 PTW를 이용하여 시뮬레이션하였다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2230-2231
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• 2008

최근에 국제유가의 급상승과 코토의정서 발의에 따른 대외적인 환경여건 변화로 인해 국내에서는 재생에너지 보급사업 및 에너지절감기술 관련 정책과 신기술이 활발히 추진되고 있다. 본 논문에서는 전기설비간의 주 동맥인 케이블 선정에 있어 케이블 굵기를 달리 하는 조건에 따라 전력손실량 변화의 실험값을 모의시험장치를 이용하여 취득하였고 이를 비교분석함으로 써 케이블 부문에서 에너지절감의 이론적 근거를 실증하였다. 또한, 수자원공사 수도사업장 중 취수장 전력시스템을 모델로 전력계통해석프로그램(PTW)을 이용하여 케이블 굵기 변화에 따른 전력손실량 변화를 모의하고 경제성분석을 통해 기존 케이블의 굵기 선정 방법을 재 고찰하고자 한다.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2005.04a
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• pp.96-99
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• 2005

본 연구에서는 식품의약품안전청의 도움을 받아 1998년부터 2003년까지 장기간에 걸친 교정정수의 분석을 통한 원통형이온함의 모델별 안정성을 확인하여 보다 효율적인 이온함의 선택으로 방사선치료기관의 선량측정체계의 정확도 향상에 기여하고자 한다. 방사선치료기관에서 사용하고 있는 Farmer형의 원통형이온함에 대한 에어커마 교정정수(NK)를 분석한 결과 Wellhofer FC65G (IC70)와 PTW 30001, 30013 (30006) 그리고 NE 2571 이온함 모델에 대한 교정정수는 모두 0.3%이내에서 잘 일치하였다. 또한 에어커마 교정정수를 이용하여 계산된 물 흡수선량 교정정수(Cal. ND,W)와 실제 측정에 의해 결정된 물 흡수선량 교정정수(Mea. ND,W)를 비교한 결과는 약 1.0% 정도 측정에 의한 교정정수가 높게 나타났으며 에어커마 교정정수를 분석한 결과와 마찬가지로 위 동일한 모델의 이온함에 대해서 측정의 표준편차가 0.14～0.17%로 나타나 장기적인 안정성이 입증되었다.

• The Journal of Korean Society for Radiation Therapy
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• v.7 no.1
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• pp.176-184
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• 1995

It is very useful benefits to use the megavoltage photon beams in deep site tumor radiotherapy for skin sparing effects. But, In some cases of head and mock tumors, it is often necessary to use spoiler for rapid buildup on skin region. A spoiler with tissue equivalent material to be moved between the patients and the collimator can increase or control the skin dose and buildup region due to position and thickness of the spoiler was measured. Then, the effect of spoiler on skin dose and build up region in protruded tumor of head and neck was evaluated quantitatively. The measurements were abtained with PTW 2334 chamber (Markus type) on a polystylene phantom for 6MV x-ray from an accelerator.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.1
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• pp.1-10
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• 2012

Purpose: To evaluate dose distribution differences when the dose rates are randomly changed in intensity-modulated radiation therapy using a dynamic multileafcollimator. Materials and Methods: Two IMRT treatment plans including small-field and large-field plans were made using a commercial treatment planning system (Eclipse, Varian, Palo Alto, CA). Each plan had three sub-plans according to various dose rates of 100, 400, and 600 MU/min. A chamber array (2D-Array Seven729, PTW-Freiburg) was positioned between solid water phantom slabs to give measurement depth of 5 cm and backscattering depth of 5 cm. Beam deliveries were performed on the array detector using a 6 MV beam of a linear accelerator (Clinac 21EX, Varian, Palo Alto, CA) equipped with 120-leaf MLC (Millenium 120, Varian). At first, the beam was delivered with same dose rates as planned to obtain reference values. After the standard measurements, dose rates were then changed as follows: 1) for plans with 100 MU/min, dose rate was varied to 200, 300, 400, 500 and 600 MU/min, 2) for plans with 400 MU/min, dose rate was varied to 100, 200, 300, 500 and 600 MU/min, 3) for plans with 600 MU/min, dose rate was varied to 100, 200, 300, 400 and 500 MU/min. Finally, using an analysis software (Verisoft 3.1, PTW-Freiburg), the dose difference and distribution between the reference and dose-rate-varied measurements was evaluated. Results: For the small field plan, the local dose differences were -0.8, -1.1, -1.3, -1.5, and -1.6% for the dose rate of 200, 300, 400, 500, 600 MU/min, respectively (for 100 MU/min reference), +0.9, +0.3, +0.1, -0.2, and -0.2% for the dose rate of 100, 200, 300, 500, 600 MU/min, respectively (for 400 MU/min reference) and +1.4, +0.8, +0.5, +0.3, and +0.2% for the dose rate of 100, 200, 300, 400, 500 MU/min, respectively (for 600 MU/min reference). On the other hand, for the large field plan, the pass-rate differences were -1.3, -1.6, -1.8, -2.0, and -2.4% for the dose rate of 200, 300, 400, 500, 600 MU/min, respectively (for 100 MU/min reference), +2.0, +1.8, +0.5, -1.2, and -1.6% for the dose rate of 100, 200, 300, 500, 600 MU/min, respectively (for 400 MU/min reference) and +1.5, +1.9, +1.7, +1.9, and +1.2% for the dose rate of 100, 200, 300, 400, 500 MU/min, respectively (for 600 MU/min reference). In short, the dose difference of dose-rate variation was measured to the -2.4~+2.0%. Conclusion: Using the Varian linear accelerator with 120 MLC, the IMRT dose distribution is differed a little <(${\pm}3%$) even though the dose-rate is changed.

• The Journal of Korean Society for Radiation Therapy
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• v.30 no.1_2
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• pp.191-199
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• 2018

Purpose : In this study, we evaluated the usefulness of colloid gel(slime) as a compensator for irregular patient surfaces in radiation therapy. Materials and Methods : For this study, colloid gel suitable for treatment was made and four experiments were conducted to evaluate the applicability of radiation therapy. Trilogy(Varian) and CT(SOMATOM, Siemens) were used as treatment equipment and CT equipment. First, the homogeneity according to the composition of colloid gel was measured using EBT3 Film(RIT). Second, the Hounsfield Unit(HU) value of colloid gel was measured and confirmed by CRIS phantom, Eclipse RTP(Eclipse 13.1, Varian) and CT. Third, to measure the deformation and degeneration of colloid gel during the treatment period, it was measured 3 times daily for 2 weeks using an ion chamber(PTW-30013, PTW). The fourth experiment was compared the treatment plan and measured dose distributions using bolus, rice, colloid gel and additional, dose profiles in an environment similar to actual treatment using our own acrylic phantom. Result : First experiment, density of the colloid gel cases 1, 2 and 3 was $1.02g/cm^3$, $0.99g/cm^3$ and $0.96g/cm^3$. When the homogeneity was measured at 6 MV and 9 MeV, case 1 was more homogeneous than the other cases, as 1.55 and 1.98. In the second experiment, the HU values of case 1, 2, 3 were 15 and when the treatment plan was compared with the measured doses, the difference was within 1 % at all 9, 12 MeV and a difference of -1.53 % and -1.56 % within the whole 2 % at 6 MV. In the third experiment, the dose change of colloid gel was measured to be about 1 % for 2 weeks. In the fourth experiment, the dose difference between the treatment plan and EBT3 film was similar for both colloid gel and bolus, rice at 6 MV. But colloid gel showed less dose difference than bolus and rice at 9 MeV. Also, dose profile of colloid gel showed a more uniform dose distribution than the bolus and rice. Conclusion : In this study, the density of colloid gel prepared for radiation therapy was $1.02g/cm^3$ similar to the density of water, and alteration or deformation was not observed during the radiotherapy process. Although we pay attention to the density when manufacturing colloid gel, it is sufficient in that it can deliver the dose uniformly through the compensation of the patient's body surface more than the bolus and rice, and can be manufactured at low cost. Further studies and studies for clinical applications are expected to be applicable to radiation therapy.

• The Journal of Korean Society for Radiation Therapy
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• v.14 no.1
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• pp.41-47
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• 2002

1.목적 두경부암(head and neck Ca)과 쇄골상부(Supraclavicular)에 6MV 광자선으로 치료 시 치료부위(Target volume)가 피부에서 대략 $1^{\sim}2mm$정도 깊이에 위치할 경우, 6MV 광자선의 선량분포는 표면선량이 낮아서 치료에 적합하지 않기 때문에 Bolus와 같이 사용하지만 Skin Sparing(피부보호)효과의 손실로 피부의 손상이 발생할 수 있다. 이러한 이유로 피부의 보호와 치료 시 표면선량의 증가를 위해 Spoiler(산란판)를 제작하여 측정 후 그 특성을 이해하고 선량의 분포를 통하여 Bolus와 비교한 후에 Spoiler의 유용성에 대해 평가하고자 하였다. 2.방법 Siemens사 선형가속기(PRIMUS)의 6MV 광자선을 사용하여 Spoiler의 사용여부 및 Spoiler의 사용 시에는 조사면의 크기를 $5{\times}5,\;7{\times}7,\;10{\times}10,\;15{\times}15,\;20{\times}20cm^2$로 하고 Spoiler와 표면과의 거리는 6, 10, 15cm로 바꾸어 가면서 물팬톰(PTW. 독일)을 이용해 깊이와 측방에 따른 선량분포를 Markus 전리함(PTW. 독일)으로 측정하였으며 전리함의 방수를 위해 씌어진 방수 캡 때문에 표면선량을 별도의 고형 팬톰으로 측정하였다. 표면의 측정선량은 전리함의 측면 벽 등에 의한 선량 측정치의 증가 현상으로 과 반응을 보였으며 이를 교정하였다. 그리고 측정된 데이터를 치료계획 시스템(Pinnacle 6.0m)으로 비교, 분석하였다. 3.결과 Spoiler의 사용 시 3cm깊이 측정선량 백분율과 Spoiler를 사용하지 않은 해당 치료 조사면의 3cm깊이 선량의 백분율에 일치하도록 하여 가상의 치료 깊이인 2mm에서 측정값을 비교하여 본 결과 조사면 $5{\times}5,\;10{\times}10,\;20{\times}20cm^2$에서 OPEN시 62, 64, $70\%$, Bolus는 97, 97, $99\%$로 Spoiler의 사용 시 표면과의 거리가 6cm에서 82, 98, $103\%$, 10cm에는 72, 89, $101\%$, 15m에 65, 79, $96\%$로 나타났으며 표면에서의 측정값을 비교하여 본 결과 OPEN시 11, 17, $27\%$, Bolus는 84, 84, $86\%$, Spoiler의 사용 시 6cm에서 40, 71, $93\%$, 10cm에는 25, 50, $81\%$, 15cm에 18, 36, $67\%$를 나타내었다. 또한 3m깊이에서의 측방 선량분포에서 Spoiler의 거리변화(6, 10cm)는 심부선량의 변화에 영향을 주지 않는 것으로 확인할 수 있었다. 그리고 위의 실험측정치를 치료계획 시스템에 입력하여 선량분포를 확인한 결과 Spoiler를 사용하는 경우 OPEN에 비해 선량분포 영역을 표면으로 끌어 올릴 수 있으며 Bolus 보다 피부 보호효과는 어느 정도 유지가 되는 것을 보여주었다. 4.결론 이와 같이 Spoiler는 Bolus와 비교하여 6MV 광자선의 build up 영역을 표면으로 증가시키는 동시에 Skin Sparing(피부보호)효과를 유지할 수 있으며 두경부암의 치료에서 Spoiler의 사용이 가능한 조건으로는 조사면이 $5{\times}5cm^2$에서 Spoiler와 표면과의 거리가 6cm일 때, $7{\times}7cm^2$에서 6cm, 10cm였고 $10{\times}10cm^2$는 10cm, 15cm로, $15{\times}15cm^2$는 15cm의 간격으로 평가되었다. 또한 $20{\times}20cm^2$의 조사면, Spoiler가 6cm 간격 인 경우 Bolus를 사용한 것 보다 더욱 높은 표면선량을 나타내었다. 그러나 Spoiler와 표면간의 거리를 다르게 함으로써 깊이에 따라 선량분포를 다양하게 나타낼 수 있기 때문에 표면선량의 증가와 피부의 보호를 위해 환자의 피부 두께, 실제 치료 부위의 깊이 등을 고려한다면 Spoiler를 사용하는 것이 bolus를 사용하는 것보다 더 유용하게 적용할 수 있을 것으로 사료된다.