• Nuclear Engineering and Technology
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• 제54권2호
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• pp.507-513
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• 2022

When X-ray energy above 8 MV is used, photoneutrons are generated by the photonuclear reaction, which activates the components of linear accelerator (linac). Safely managing the radioactive material, when disposing linac or replacing components, is difficult, as the standards for the radioactive material management are not clear in Korea. We surveyed the management status of radioactive components occurred from medical linacs in Korea. And we also measured the activation of each part of the discarded Elekta linac using a survey meter and portable High Purity Germanium (HPGe) detector. We found that most medical institutions did not perform radiation measurements when disposing of radioactive components. The radioactive material was either stored within the institution or collected by the manufacturer. The surface dose rate measurements showed that the parts with high surface dose rates were target, primary collimator, and multileaf collimator (MLC). ⁶⁰Co nuclide was detected in most parts, whereas for the target, ⁶⁰Co and ¹⁸⁴Re nuclides were detected. Results suggest that most institutions in Korea did not have the regulations for disposing radioactive waste from linac or the management procedures and standards were unclear. Further studies are underway to evaluate short-lived radionuclides and to lay the foundation for radioactive waste management from medical linacs.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(1)
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• pp.149-154
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• 1998

A subcritical reactor driven by a linear proton accelerator has been considered as a nuclear waste incinerator at Korea Atomic Energy Research Institute(KAERI). Since the multiplication factor of a subcritical reactor is less than unity, to compensate exponentially decreasing fission neutrons from spallation reactions are essentially required for operating the reactor in its steady state. furthermore, the profile of accelerator beam currents is very important in controlling a subcritical reactor, because the reactor power varies in accordance of the profile of external neutrons. We have developed a code system to find numerical solutions of reactor kinetics equations, which are the simplest dynamic model for controlling reactors. In a due course of our previous numerical study of point kinetics equations for critical reactors, however, we learned that the same code system can be used in studying dynamic behavior of the subcritical reactor. Our major motivation of this paper is to investigate responses of subcritical reactors for small changes in thermal hydraulic parameters. Building a thermal hydraulic model for the subcritical reactor dynamics, we performed numerical simulations for dynamic responses of the reactor based on point kinetics equations with a source term. Linearizing a set of coupled differential equations for reactor responses, we focus our research interest on dynamic responses of the reactor to variations of the thermal hydraulic parameters in transient phases.

• 대한의용생체공학회:의공학회지
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• 제13권1호
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• pp.19-24
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• 1992

Lineacgrams are diagnostic films taken using X-ray from the linear accelerator with the patient in the treatment position to assure that the treatment is being delivered in accordance with the treatment prescription. But the image quality of the lineacgram is so bad because of the high X-ray energy. This paper presents a new algorithm that enhances the image of lineacgram. Thls algorithm calculates optimal threshold value which is used for segmentation of lineacgram using co-occurrence matrix and enhances the image Inside and outside treatment area preserving treatments boundary.

• 한국의학물리학회지:의학물리
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• 제22권2호
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• pp.79-84
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• 2011

본 연구에서는 GEANT4 toolkit을 이용하여 의료용 선형가속기에 대한 몬테칼로(Monte Carlo) 전산모사를 하였다. Medical Linac2 예제를 수정해서 사용하였다. 에너지스펙트럼, 최빈에너지, 평균에너지를 EGS4 결과와 비교 하였고 선속의 중심에서부터 반경에 따른 단위면적당 광자수, 단위면적당 에너지, 평균에너지를 분석하였다. 그 결과 EGS4 결과와 큰 차이를 보이지 않기 때문에 Medical Linac2 예제의 선속특성에 관한 전산모사에 큰 문제점은 없는 것으로 판단된다. 같은 헤드구조에서도 Physics List의 모델에 따라서는 결과에 차이가 발생하므로 연구 환경에 알맞은 Physics List 모델을 선택하는 것이 중요하다고 판단된다. 본 연구는 처음 몬테칼로 전산모사를 접하는 사용자가 선속특성에 대한 전산모사를 수행하고 6 MV 광자선속의 특성을 분석하는 과정에 많은 도움이 될 것으로 사료된다.

• 대한방사성의약품학회지
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• 제7권2호
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• pp.119-125
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• 2021

⁸²Sr for ⁸²Rb generator was produced through the irradiation of the proton beam on the ^nat.RbCI target at the target irradiation facility installed at the end of the Rl-dedicated beamline of the 100 MeV proton linear accelerator of KOMAC (Korea Multi-purpose Accelerator Complex). The average current of the proton beam was 1.2 µA for irradiation time of 150 min. For the separation and purification of the ⁸²Sr from ^nat.RbCI irradiated, Chelex-100 resin was used. The activities of ⁸²Sr in the irradiated ^nat.RbCI target solution and after purification were 45.29 µCi and 43.4 µCi, respectively. The separation and purification yield was 95.8%. As an adsorbent to be filled in the generator for ⁸²Sr adsorption hydrous tin oxide was selected. The adsorption yield of ⁸²Sr into the generator adsorbent was > 99 %, and the total amount of ⁸²Sr adsorbed to the generator was 21.6 µCi as of the day of the ⁸²Rb elution experiment. When the elution amount was 22 mL, the maximum⁸²Rb elution yield was 93.3%, and the elution yield increased as the flow rate increased. After the eluted ⁸²Rb was filled in the correction phantom of the small PET for animals, a PET image was taken. The image scan time was set to 5 min, and the phantom PET image was successfully obtained. As results of impurity analysis on eluted ⁸²Rb using ICP-MS, ^nat.Rb stable isotopes that compete in vivo of ⁸²Rb were identified as undetected levels and were determined to be No-Carrier-Added (NCA).

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.411-414
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• 2002

The CdTe semiconductor detector has a higher detection efficiency for x-rays and $\square$amma rays and a wider energy band gap compared with Si and Ge semiconductor detectors. Therefore, the size of the detector element can be made small, and can be operated at room temperature. The interaction between a CdTe detector and incident x-rays is mainly photoelectric absorption in the photon energy range of up to 100 keV. In this energy range, Compton effects are almost negligible. We have developed a 256 channel CdTe array detector system for monochromatic x-ray CT using synchrotron radiation. The CdTe array detector system, the element size of which is 1.98 mm (h) x 1.98 mm (w) x 0.5 mm (t), was operated in photon counting mode. In order to improve the spatial resolution, we tilted the CdTe array detector against the incident parallel monochromatic x-ray beam. The experiments were performed at the BL20B2 experimental hutch in SPring-8. The energy of incident monochromatic x-rays was set at 55 keV. Phantom measurements were performed at the detector angle of 0, 30 and 45 degrees against the incident parallel monochromatic x-rays. The linear attenuation coefficients were calculated from the reconstructed CT images. By increasing the detector angle, the spatial resolutions were improved. There was no significant difference between the linear attenuation coefficients which were corrected by the detector angle. It was found that this method was useful for improving the spatial resolution in a parallel monochromatic x-ray CT system.

• Journal of Radiation Protection and Research
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• 제11권1호
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• pp.51-56
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• 1986

방사선(放射線)의 의학적(醫學的) 진단치료(診斷治療) 이용률(利用率)이 증가(增加)함에 따라 의료인(醫療人)과 환자(患者)들에 대한 방사선(放射線) 피폭확률(被曝確率)이 비예적(比例的)으로 증가(增加)되어 정량적(定量的)인 분석(分析)과 피폭관리(被曝管理)의 필요성(必要性)이 요구(要求)되고 있다. 연세(延世) 암센터는 암치료(癌治療)를 위하여 설치사용(設置使用)되고 있는 의료용(醫療用) 고(高)에너지 선형가속기(線型加速器)에 대한 누출(漏出) 및 산난선(散亂線)의 방어벽(防禦壁)과 방어계획(防禦計劃)이 이미 준비(準備)되어 있다. 그러나 장치(裝置)의 사용빈도(使用頻度)가 증가(增加)됨에 따라 치료실내(治療室內)의 공간(空間) 선량분포(線量分布)와 광핵반응(光核反應)으로 인한 유도방사능(誘導放射能)의 위험성(危險性)을 인식(認識)하고 이들에 대한 노출량(露出量)을 전리함(電離函), 열형광측정기(熱螢光測程器) 및 에너지 분석기등(分析器等)을 이용(利用)하여 측정(測定)하였다. 18 MeV 전자선(電子線)에 의한 실중선량(室中線量)은 1 m 지점(地點)에서 종양선량(腫瘍線量)의 0.02%였고 X-선(線)에 의한 실중선량(室中線量)은 약(約) 0.12%였다. 선형가속기(線型加速器)에서 10 MV X-선(線)을 30 Gy 조사(照射)한 직후 광핵반응(光核反應)에 의한 유도방사능(誘導放射能)을 측정(測定)한 결과(結果) 0.65 mR/hr 였으며 광핵반응(光核反應)에 의한 중성자(中性子) 방사화(放射化)는 주로 Cu-64, W-185, Mo-94, Ta-182등(等)의 원소(元宵)로 추정(推定)할 수 있었다.

• 한국의학물리학회지:의학물리
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• 제21권2호
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• pp.223-231
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• 2010

국내 개설된 방사선종양학과 중 선형가속기 및 근접치료기기가 설치되어 환자치료를 시행하고 있는 총 72개 기관에 대해 설문을 수행하였다. 설문은 선형가속기, 근접치료기기 등의 품질관리 효율성을 파악하기 위해 주기별 품질관리 수행여부, 수행인력 및 주체, 수행 시간을 조사하였다. 선형가속기 및 근접치료기기에 대한 각각의 품질관리 검사 항목에 대한 주기별 수행 여부를 조사하였다. 조사결과 품질관리 검사항목 수에서 미국 및 유럽의 품질관리 지침서와 비교하여 일일 및 주간점검 항목수의 경우는 8~10로서 유사한 결과를 보였으나, 월간과 연간점검 항목 수는 미국 및 유럽의 경우 17~21 항목이었고, 국내의 경우는 15.5로 낮게 나타났다. 또한 국내의 여건은 품질관리를 수행 할 인력 및 시간의 부족과 제한으로 인해 미국 및 유럽의 품질관리 지침서에서 권고하는 소요인력 및 시간과 비교하여 대략 50% 수준의 낮은 수치를 보였다. 따라서 본 연구에서 수집한 국내 방사선종양학과의 품질관리 검사항목 및 실행 주기, 수행 인력 및 수행시간에 관한 현황 조사 결과와 기존에 발표된 미국의학물리학회 TG-40 보고서 및 유럽의 품질관리 지침서를 활용한다면 국내 실정 및 각 기관에 적합한 품질관리 지침서를 수립하는데 유용할 것으로 기대된다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2004년도 추계학술발표회 발표논문집
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• pp.683-684
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• 2004

The RF system for PEFP 20MeV proton linear accelerator is described. The RF system for 3MeV RFQ was already installed and operated to drive the RFQ. The klystron was tested up to 600kW itself and operated up to 350kW routinely. The HPRF dummy load was stabilized with the change of the coolant. Preparation of 20MeV DTL HPRF test has been completed. LCP and PLC system for klystron power supply was already prepared. Voltage fluctuation was measured during klystron test. Voltage control feedback loop seems to be re-adjusted.

• 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.