• 한국의학물리학회지:의학물리
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• 제31권3호
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• pp.124-134
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• 2020

Here we review the evolutionary history of radiation therapy technology through the festschrift of articles in celebration of the 30th anniversary of Korean Society of Medical Physics (KSMP). Radiation therapy technology used in clinical practice has evolved over a long period of time. Various areas of science, such as medical physics, mechanical engineering, and computer engineering, have contributed to the continual development of new devices and techniques. The scope of this review was restricted to two areas; i.e., output energy production and functional development, because it is not possible to include all development processes of this technology due to space limitations. The former includes the technological transition process from the initial technique applied to the first model to the latest technique currently used in a variety of machines. The latter has had a direct effect on treatment outcomes and safety, which changed the paradigm of radiation therapy, leading to new guidelines on dose prescriptions, innovation of dose verification tools, new measurement methods and calculation systems for radiation doses, changes in the criteria for errors, and medical law changes in all countries. Various complex developments are covered in this review. To the best of our knowledge, there have been few reviews on this topic and we consider it very meaningful to provide a review in the festschrift in celebration of the 30th anniversary of the KSMP.

• 한국의학물리학회지:의학물리
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• 제32권4호
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• pp.122-129
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• 2021

Purpose: This study aimed to design a multipurpose dose verification phantom for external audits to secure safe and optimal radiation therapy. Methods: In this study, we used International Atomic Energy Agency (IAEA) LiF powder thermoluminescence dosimeter (TLD), which is generally used in the therapeutic radiation dose assurance project. The newly designed multipurpose phantom (MPP) consists of a container filled with water, a TLD holder, and two water-pressing covers. The size of the phantom was designed to be sufficient (30×30×30 cm³). The water container was filled with water and pressed with the cover for normal incidence to be fixed. The surface of the MPP was devised to maintain the same distance from the source at all times, even in the case of oblique incidence regardless of the water level. The MPP was irradiated with 6, 10, and 15 MV photon beams from Varian Linear Accelerator and measured by a 1.25 cm³ ionization chamber to get the correction factors. Monte Carlo (MC) simulation was also used to compare the measurements. Results: The result obtained by MC had a relatively high uncertainty of 1% at the dosimetry point, but it showed a correction factor value of 1.3% at the 5 cm point. The energy dependence was large at 6 MV and small at 15 MV. Various dosimetric parameters for external audits can be performed within an hour. Conclusions: The results allow an objective comparison of the quality assurance (QA) of individual hospitals. Therefore, this can be employed for external audits or QA systems in radiation therapy institutions.

• 방사성폐기물학회지
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• 제21권4호
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• pp.531-541
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• 2023

The Wolsong Nuclear Power Plant (NPP) operates an on-site spent fuel dry storage facility using concrete silo and vertical module systems. This facility must be safely maintained until the spent nuclear fuel (SNF) is transferred to an external interim or final disposal facility, aligning with national policies on spent nuclear fuel management. The concrete silo system, operational since 1992, requires an aging management review for its long-term operation and potential license renewal. This involves comparing aging management programs of different dry storage systems against the U.S. NRC's guidelines for license renewal of spent nuclear fuel dry storage facilities and the U.S. DOE's program for long-term storage. Based on this comparison, a specific aging management program for the silo system was developed. Furthermore, the facility's current practices-periodic checks of surface dose rate, contamination, weld integrity, leakage, surface and groundwater, cumulative dose, and concrete structure-were evaluated for their suitability in managing the silo system's aging. Based on this review, several improvements were proposed.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.189-194
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• 2024

This paper presents a radiation-hardened-by-design preamplifier that utilizes a self-compensation technique with a charge-sensitive amplifier (CSA) and replica for total ionizing dose (TID) effects. The CSA consists of an operational amplifier (OPAMP) with a 6-bit binary weighted current source (BWCS) and feedback network. The replica circuit is utilized to compensate for the TID effects of the CSA. Two comparators can detect the operating point of the replica OPAMP and generate appropriate signals to control the switches of the BWCS. The proposed preamplifier was fabricated using a general-purpose complementary metal-oxide-silicon field effect transistor 0.18 ㎛ process and verified through a test up to 230 kGy (SiO₂) at a rate of 10.46 kGy (SiO₂)/h. The code of the BWCS control circuit varied with the total radiation dose. During the verification test, the initial value of the digital code was 39, and a final value of 30 was observed. Furthermore, the preamplifier output exhibited a maximum variation error of 2.39%, while the maximum rise-time error was 1.96%. A minimum signal-to-noise ratio of 49.64 dB was measured.

• 한국의학물리학회지:의학물리
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• 제14권1호
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• pp.8-14
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• 2003

두경부 및 흥부에서 척수 견딤선량은 방사선 치료 제약 조건중의 하나이다. 이 영역에서 척수 견딤 선량을 임상적으로 허용 가능한 수준으로 유지하면서 표적에 임상적으로 유의한 선량을 전달하는 것은 쉽지 않은 문제이다. 기존의 치료 방법을 적용할 때 따르는 문제를 해결하기 위해 동적 다엽콜리메이터(dynamic multi leaf collimator, dMLC)를 사용한 척수의 부분 차폐 기법(spial cord partial block technique)을 개발하였다. 이 기법은 기존의 3차원 방사선 치료 계획 장치를 사용하여 치료계획을 수립한다. 치료 계획 절차는 표적을 잘 포함 할 수 있는 빔 방향 및 빔 개수를 설정한 후, 척수 등 방사선 민감 장기를 보호하기 위한 부분차폐를 적용하여 최적화된 선량분포를 만들어 낸다. 이 기법의 유용성을 평가하기 위해 동일한 환자에 대해 기존의 치료 계획과 PBT 치료 계획을 수립하여 상호 비교 평가하였다. 평균 선량과 DVH를 치료 계획 평가 인자로 사용하였다. 임상 적용 가능성을 위해 일련의 정도관리를 수행하여 평가하였다. 이 정도관리는 선량 분포 검증에 대한 필름 도시메트리와 단일점 측정으로 구성되어 있다. PBT 치료계획이 기존의 치료계획 보다 좋은 결과를 얻을 수 있었으며, 두경부에서 유용한 치료 기법임을 볼 수 있었다.

• 대한방사선치료학회지
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• 제7권1호
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• pp.156-166
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• 1995

방사선 전신조사는 일반적인 방사선 치료와는 달리 환자의 몸 전체를 포함할 수 있는 큰 조사야와 확장된 SAD가 요구되어지기 때문에 치료실이 충분히 커야 하고 전신에 균등한 선량을 주기 위해서는 환자 체표면 윤곽의 불규칙성과 조직 불균질성을 보완해 줄 수 있는 보상체가 필요하며 피부선량을 높여주기 위해서는 적절한 두께의 방사선 산란체를 사용하여야 한다. 또한 치료장치 및 사용 에너지, 총선량, 선량률, 선량분할, 환자의 자세, 정상적인 조직과 장기의 차폐 등도 방사선 전신조사를 위한 중요한 인자들로 알려져 있다. 그리고 방사선 전신조사 치료방법은 환자치료를 위한 준비시간과 실제 치료시간이 길기 때문에 일상 치료환자 일정에 지장을 초래할 수도 있으며 연속되는 치료기간 동안 치료조사야의 정확한 재현이 무엇보다 중요한 것으로 사료된다. 본원에서는 환자의 자세를 굴곡좌위로 함으로써 짧은 거리에서도 환자를 조사야내에 충분히 포함시켰고, 납 보상체를 제작하여 조직결손 부위를 보상하여 전신에 균등한 선량을 줄 수 있었으며 폐 차폐물을 제작하여 폐의 선량을 조절하였다. 치료계획시 환자의 음영을 치료실 벽면에 그려넣음으로써 조사야 재현시 도움이 되도록 하였으며 치료시간을 단축할 수 있었다.

• 대한방사선기술학회지:방사선기술과학
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• 제45권5호
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• pp.449-455
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• 2022

This study is to present a Geant4 code for the simulation of the absorbed dose distribution given by a medical linac for 6 MV photon beam. The dose distribution was verified by comparison with calculated beam data and beam data measured in water phantom. They were performed for percentage depth dose(PDD) and beam profile of cross-plane for two field sizes of 10 × 10 and 15 × 15 cm². Deviations of a percentage and distance were obtained. In energy spectrum, the mean energy was 1.69 MeV. Results were in agreement with PDD and beam profile of the phantom with a tolerance limit. The differences in the central beam axis data 𝜹₁ for PDD had been less than 2% and in the build up region, these differences increased up to 4.40% for 10 cm square field. The maximum differences of 𝜹₂ for beam profile were calculated with a result of 4.35% and 5.32% for 10 cm, 15 cm square fields, respectively. It can be observed that the difference was below 4% in 𝜹₃ and 𝜹₄. For two field sizes of 𝜹_50-90 and RW₅₀, the results agreed to within 2 mm. The results of the t-test showed that no statistically significant differences were found between the data for PDD of 𝜹₁, p>0.05. A significant difference on PDD was observed for field sizes of 10 × 10 cm², p=0.041. No significant differences were found in the beam profile of 𝜹₃, 𝜹₄, RW₅₀, and 𝜹_50-90. Significant differences on beam profile of 𝜹₂ were observed for field sizes of 10 × 10 cm², p=0.025 and for 15 × 15 cm², p=0.037. This work described the development and reproducibility of Geant4 code for verification of dose distribution.

• 한국의학물리학회지:의학물리
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• 제19권1호
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• pp.21-34
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• 2008

환자의 CT자료를 기반으로 만들어진 3차원상의 표적물질에 전자 및 광자의 전달 현상을 계산하는 몬테카를로(MC) 도즈계산용 병렬프로그램 (PMCEPT 코드)을 개발하여 베어울프 PC 클러스터에 탑제하였다. 시뮬레이션에서 오차를 최소화하고 코드를 더욱 발전시키기 위해서는 현재의 MC 코드의 한계를 아는 것이 매우 유익하다. 이러한 관점에서 저자는 PMCEPT코드를 이용하여 이질 혹은 동질의 표적물질에서 표준화된 깊이 도즈를 계산하여 잘 알려진 다른 코드들, MCNP5, EGS4, DPM, GEANT4 및 실험결과와 비교를 하였다. PMCEPT결과는 이질 혹은 동질의 표적에서 다른 코드들과 $1{\sim}3%$ 오차 범위 안에서 잘 일치하였다. 계산시간 비교에 있어서도 PMCEPT 코드가 MCNP5 보다는 약 20배, GEANT4코드보다는 약 3배정도 빨랐다. 이러한 결과를 종합하면, PMCEPT코드는 의학물리분야의 시뮬레이션 코드로 사용하기에 매우 좋은 것으로 사료된다.

• 한국의학물리학회지:의학물리
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• 제30권4호
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• pp.128-138
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• 2019

Purpose: Segmental analysis of volumetric modulated arc therapy (VMAT) is not clinically used for compositional error source evaluation. Instead, dose verification is routinely used for plan-specific quality assurance (QA). While this approach identifies the resultant error, it does not specify which machine parameter was responsible for the error. In this research study, we adopted an approach for the segmental analysis of VMAT as a part of machine QA of linear accelerator (LINAC). Methods: Two portal dose QA plans were generated for VMAT QA: a) for full arc and b) for the arc, which was segmented in 12 subsegments. We investigated the multileaf collimator (MLC) position and dosimetric accuracy in the full and segmented arc delivery schemes. A MATLAB program was used to calculate the MLC position error from the data in the dynalog file. The Gamma passing rate (GPR) and the measured to planned dose difference (DD) in each pixel of the electronic portal imaging device was the measurement for dosimetric accuracy. The eclipse treatment planning system and a MATLAB program were used to calculate the dosimetric accuracy. Results: The maximum root-mean-square error of the MLC positions were <1 mm. The GPR was within the range of 98%-99.7% and was similar in both types of VMAT delivery. In general, the DD was <5 calibration units in both full arcs. A similar DD distribution was found for continuous arc and segmented arcs sums. Exceedingly high DD were not observed in any of the arc segment delivery schemes. The LINAC performance was acceptable regarding the execution of the VMAT QA plan. Conclusions: The segmental analysis proposed in this study is expected to be useful for the prediction of the delivery of the VMAT in relation to the gantry angle. We thus recommend the use of segmental analysis of VMAT as part of the regular QA.

• 한국환경과학회지
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• 제18권3호
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• pp.289-298
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• 2009

The blue-green algae which caused odor problem in the tap water are difficult to precipitate in sedimentation basin and clogged the filter void rapidly. The studies of this paper were not only oxidation, coagulation and sedimentation processes for effectively removing blue-green algae but yellow clay and polyamine for verification as coagulants aids. The results of this research are summarized as follows: Higher ozone dose(C) and longer contact time(T) were needed for a high degree of removing blue-green algae efficiency. the removal rate of blue-green algae was proportional to the $C\times T$ value. The removal percent of chlorophyll-a by sedimentation and filter without pre-ozonation was about 75% but 1 mg/L pre-ozonation could increase the removal percent of chlorophyll-a to 99% and more pre-ozonation could remove completely. Though the removal efficiency of turbidity could increased by high dose of chlorination, the dissolved organic carbon was increased. More chlorine dose from 4 to 10 mg/L dissolved organic carbon was decreased. Using yellow clay as coagulant aids increased density of floc so the settling velocity of floc become rising but polyamine could not increase settling velocity of floc though it could formated large floc.