• 대한방사선치료학회지
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• 제24권1호
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• pp.11-14
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• 2012

목 적: Anisotropic Analytical Algorithm (AAA)는 Pencil Beam Convolution (PBC) 알고리즘에 비하여 2차선과 조직 불 균질에 대한 영향에 보다 더 정확한 선량계산을 제공한다. 본 연구는 유방암 접선조사 치료계획에서 PBC 알고리즘과 AAA의 선량계산 알고리즘에 따른 선량분포의 차이를 분석하고자 한다. 대상 및 방법: 선형가속기(CL-6EX, VARIAN, USA)의 6 MV 에너지를 이용한 유방암 환자 10명을 대상으로 Eclipse treatment planning system (Version 8.9, VARIAN, USA)을 사용하여 전산화 치료계획을 수립하였다. Conventional Radiation Therapy plan(Conventional plan)과 Field-in-Field Intensity Modulated Radiation Therapy plan (FiF plan)을 PBC 알고리즘을 이용하여 치료계획을 수립한 후 Monitor Unit (MU)를 고정시키고 AAA로 변경하여 선량계산하고, Dose Volume Histogram (DVH)을 이용하여 치료계획을 비교 분석하였다. 결 과: 첫 번째, Conventional plan의 PBC 알고리즘과 AAA에 따른 차이를 평가한 결과 치료용적에 대한 평균 Conformity Index (CI) 값의 차이는 PBC 알고리즘에서 0.295 높게 평가 되었다. 동측 폐에 대한 선량을 평가한 결과 $V_{47Gy}$과 $V_{45Gy}$는 PBC알고리즘에서 각각 5.83%, 4.04% 높게 평가되었고, Mean dose, $V_{20Gy}$, $V_{5Gy}$, $V_{3Gy}$는 AAA에서 각각 0.6%, 0.29%, 6.35%, 10.23%높게 평가되었다. 두 번째, FiF plan의 경우 치료용적에 대한 평균 CI 값의 차이는 PBC 알고리즘에서 0.165 높게 평가 되었고, 동측 폐에 대한 선량은 $V_{47Gy}$, $V_{45Gy}$, Mean dose는 PBC 알고리즘에서 각각 6.17%, 3.80%, 0.15% 높게 평가되었고, $V_{20Gy}$, $V_{5Gy}$, $V_{3Gy}$는 AAA에서 각각 0.14%, 4.07%, 4.35% 높게 평가되었다. 결 론: 유방암 접선조사에서 AAA로 계산했을 때, PBC 알고리즘에 비해 치료용적에 대한 Conformity가 Conventional plan, FiF plan 각각 0.295, 0.165 낮게 평가 되며, 동측 폐의 고 선량 영역의 선량은 적게 나타나며, 저 선량 영역의 선량은 많게 나타므로 폐에 대한 선량을 평가하는 데 선량계산 알고리즘에 따른 특징을 고려해야 할 것으로 사료된다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.536-540
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• 2003

A new concept of adaptive focusing, using a Rotman lens, is presented in this paper. A Rotman lens is a microwave lens which is able to focus microwave power on its focal arc or generate multiple beams. By adding the array of phase shifters between a Rotman lens and antenna elements, the wavefront can be adaptively modulated to focus objects distributed in short range rather than far-field zone. From the optical point of view, the propagations of the lens have been simplified from the Fresnel diffraction integral to the Fourier transform. Using Fourier Transform, a beam propagation method has been developed to show improvement of the resolution by controlling wavefront of wave propagating from an aperture-type antenna array. The beam width(or spot size) and intensity have been calculated for a focused beam propagating from an array having $10{\lambda}$ of its size. For the beam with $20{\lambda},\;30{\lambda}$, and $50{\lambda}$ of geometrical focal length, the half-power beamwidth (spot size) is about $1.1{\lambda},\;1.3{\lambda}$, and $1.9{\lambda}$, respectively.

• Radiation Oncology Journal
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• 제38권2호
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• pp.138-147
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• 2020

Purpose: To evaluate the dosimetric variations in patients of head and neck cancer treated with definitive or adjuvant radiotherapy using optimized non-coplanar (ncVMAT) beams with coplanar (cVMAT) beams using volumetric arc therapy. Materials and Methods: Twenty-two patients of head and neck cancer that had received radiotherapy using VMAT in our department were retrospectively analyzed. Each of the patients was planned using coplanar and non-coplanar orientations using an optimized couch angle and fluences. We analyzed the Conformity Index (C_IRTOG), Dose Homogeneity Index (DHI), Heterogeneity Index (HI_RTOG), low dose volume, target and organs-at-risk coverage in both the plans without changing planning optimization parameters. Results: The prescription dose ranged from 60 Gy to 70 Gy. Using ncVMAT, C_IRTOG, DHI and HI_RTOG, and tumor coverage (ID_95%) had improved, low dose spillage volume in the body V_5Gy was increased and V_10Gy was reduced. Integral dose and intensity-modulated radiation therapy factor had increased in ncVMAT. In the case of non-coplanar beam arrangements, maximum dose (D_max) of right and left humeral head were reduced significantly whereas apex of the right and left lung mean dose were increased. Conclusion: The use of ncVMAT produced better target coverage and sparing of the shoulder and soft tissue of the neck as well as the critical organ compared with the cVMAT in patients of head and neck malignancy.

• Asian Pacific Journal of Cancer Prevention
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• 제16권8호
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• pp.3257-3265
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• 2015

Background: Radiotherapy is an important treatment of choice for breast cancer patients after breast-conserving surgery, and we compare the feasibility of using dual arc volumetric modulated arc therapy (VMAT2), single arc volumetric modulated arc therapy (VMAT1) and Multi-beam Intensity Modulated Radiotherapy (M-IMRT) on patients after breast-conserving surgery. Materials and Methods: Thirty patients with breast cancer (half right-sided and half left-sided) treated by conservative lumpectomy and requiring whole breast radiotherapy with tumor bed boost were planned with three different radiotherapy techniques: 1) VMAT1; 2) VMAT2; 3) M-IMRT. The distributions for the planning target volume (PTV) and organs at risk (OARs) were compared. Dosimetries for all the techniques were compared. Results: All three techniques satisfied the dose constraint well. VMAT2 showed no obvious difference in the homogeneity index (HI) and conformity index (CI) of the PTV with respect to M-IMRT and VMAT1. VMAT2 clearly improved the treatment efficiency and can also decrease the mean dose and V5Gy of the contralateral lung. The mean dose and maximum dose of the spinal cord and contralateral breast were lower for VMAT2 than the other two techniques. The very low dose distribution (V1Gy) of the contralateral breast also showed great reduction in VMAT2 compared with the other two techniques. For the ipsilateral lung of right-sided breast cancer, the mean dose was decreased significantly in VMAT2 compared with VMAT1 and M-IMRT. The V20Gy and V30Gy of the ipsilateral lung of the left-sided breast cancer for VMAT2 showed obvious reduction compared with the other two techniques. The heart statistics of VMAT2 also decreased considerably compared to VMAT1 and M-IMRT. Conclusions: Compared to the other two techniques, the dual arc volumetric modulated arc therapy technique reduced radiation dose exposure to the organs at risk and maintained a reasonable target dose distribution.

• 대한방사선치료학회지
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• 제26권1호
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• pp.21-28
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• 2014

목 적 : 비소세포 폐암의 치료용적의 크기가 크거나 폐 용적이 작고, 몸의 정중선(Mid line)에 위치한 경우 척수의 허용선량을 고려한 방사선치료계획에서 폐 선량이 많아지게 되는데, 본 연구는 비소세포 폐암 환자의 3차원입체조형치료(Three dimensional conformal radiotherapy, 3D CRT), 제한된 각도를 이용한 세기변조방사선치료(Intensity modulated radiotherapy, IMRT)와 용적변조회전치료(Volumetric Modulated Arc therapy, VMAT) 치료계획을 각각 적용하여 전체 폐 선량을 비교 및 평가하고자 한다. 대상 및 방법 : TrueBeam STx($Varian^{TM}$, USA) 10 MV 에너지를 이용하여 4명의 환자에 대하여 3D CRT, 제한된 각도를 이용한 IMRT와 VMAT 치료계획을 세우고, 총 선량 66 Gy/30 Fx 처방하였을 때, 선량용적히스토그램(Dose Volume Histogram, DVH)을 이용하여 치료계획용적(Planning Target Volume, PTV), 전체 폐 그리고 척수에 들어가는 선량을 평가하였다. PTV에 대한 처방선량지수(Conformity Index, CI), 선량균질지수(Homogeneity index, HI), 처방선량포함지수(Paddick's Conformity Index, PCI)를 구하고, 폐의 30 Gy 용적($V_{30}$), $V_{20}$, $V_{10}$, $V_5$, 평균선량(Mean dose)을 평가하고, 척수의 최대선량 값을 평가하였다. 결 과 : PTV에 대한 CI, HI, PCI의 평균값은 각각 $0.944{\pm}0.009$, $1.106{\pm}0.027$, $1.084{\pm}0.016$으로 평가되었다. 전체 폐에 대한 첫 번째 환자의 $V_{20}$은 3D CRT, IMRT, VMAT 각각 30.7%, 20.2%. 21.2%, 두 번째 환자의 $V_{20}$은 33.0%, 29.2%. 31.5%, 세 번째 환자의 $V_{20}$은 51.3%, 34.3%. 36.9%, 네 번째 환자의 $V_{20}$은 56.9%, 33.7%. 40%로 제한된 각도를 이용한 IMRT 치료계획에서 가장 낮게 평가되었다. 척수에 대한 최대선량 값은 모두 허용선량 미만으로 평가되었다. 결 론 : 비소세포 폐암의 방사선치료계획에서 3D CRT와 비교했을 때, 제한된 각도를 이용한 IMRT나 VAMT을 이용하면 척수의 허용선량을 넘지 않으면서 폐 선량을 줄여줄 수 있는 치료계획을 세울 수 있었다. IMRT와 VAMT을 비교해보면 PTV의 선량포함과 척수선량을 고려했을 때 IMRT 치료계획에서 보다 좁은 각도를 이용한 치료계획이 가능하였고, 이는 폐 선량을 좀 더 줄여줄 수 있는 결과를 얻을 수 있었다.

• 한국의학물리학회지:의학물리
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• 제29권2호
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• pp.66-72
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• 2018

The proper position of a multi-leaf collimator (MLC) is essential for the quality of intensity-modulated radiation therapy (IMRT) and volumetric modulated arc radiotherapy (VMAT) dose delivery. Task Group (TG) 142 provides a quality assurance (QA) procedure for MLC position. Our study investigated the QA validation of the mechanical leaf gap measurement and the maintenance procedure. Two $VitalBeam^{TM}$ systems were evaluated to validate the acceptance of an MLC position. The dosimetric leaf gaps (DLGs) were measured for 6 MV, 6 MVFFF, 10 MV, and 15 MV photon beams. A solid water phantom was irradiated using $10{\times}10cm^2$ field size at source-to-surface distance (SSD) of 90 cm and depth of 10 cm. The portal dose image prediction (PDIP) calculation was implemented on a treatment planning system (TPS) called $Eclipse^{TM}$. A total of 20 VMAT plans were used to confirm the accuracy of dose distribution measured by an electronic portal imaging device (EPID) and those predicted by VMAT plans. The measured leaf gaps were 0.30 mm and 0.35 mm for VitalBeam 1 and 2, respectively. The DLG values decreased by an average of 6.9% and 5.9% after mechanical MLC adjustment. Although the passing rates increased slightly, by 1.5% (relative) and 1.2% (absolute) in arc 1, the average passing rates were still within the good dose delivery level (>95%). Our study shows the existence of a mechanical leaf gap error caused by a degenerated MLC motor. This can be recovered by reinitialization of MLC position on the machine control panel. Consequently, the QA procedure should be performed regularly to protect the MLC system.

• 한국의학물리학회지:의학물리
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• 제32권2호
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• pp.25-39
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• 2021

Brachytherapy, along with external beam radiation therapy (EBRT), is an essential and effective radiation treatment process. In brachytherapy, in contrast to EBRT, the radiation source is radioisotopes. Because these isotopes can be positioned inside or near the tumor, it is possible to protect other organs around the tumor while delivering an extremely high-dose of treatment to the tumor. Brachytherapy has a long history of more than 100 years. In the early 1900s, the radioisotopes used for brachytherapy were only radium or radon isotopes extracted from nature. Over time, however, various radioisotopes have been artificially produced. As radioisotopes have high radioactivity and miniature size, the application of brachytherapy has expanded to high-dose-rate brachytherapy. Recently, advanced treatment techniques used in EBRT, such as image guidance and intensity modulation techniques, have been applied to brachytherapy. Three-dimensional images, such as ultrasound, computed tomography, magnetic resonance imaging, and positron emission tomography are used for accurate delineation of treatment targets and normal organs. Intensity-modulated brachytherapy is anticipated to be performed in the near future, and it is anticipated that the treatment outcomes of applicable cancers will be greatly improved by this treatment's excellent dose delivery characteristics.

• 한국의학물리학회지:의학물리
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• 제29권1호
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• pp.8-15
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• 2018

This work reports the acceptance testing and commissioning experience of the Robotic Intensity-Modulated Radiation Therapy (IMRT) M6 system with a newly released $InCise^{TM}2$ Multileaf Collimator (MLC) installed at the Yonsei Cancer Center. Acceptance testing included a mechanical interdigitation test, leaf positional accuracy, leakage check, and End-to-End (E2E) tests. Beam data measurements included tissue-phantom ratios (TPRs), off-center ratios (OCRs), output factors collected at 11 field sizes (the smallest field size was $7.6mm{\times}7.7mm$ and largest field size was $115.0mm{\times}100.1mm$ at 800 mm source-to-axis distance), and open beam profiles. The beam model was verified by checking patient-specific quality assurance (QA) in four fiducial-inserted phantoms, using 10 intracranial and extracranial patient plans. All measurements for acceptance testing satisfied manufacturing specifications. Mean leaf position offsets using the Garden Fence test were found to be $0.01{\pm}0.06mm$ and $0.07{\pm}0.05mm$ for X1 and X2 leaf banks, respectively. Maximum and average leaf leakages were 0.20% and 0.18%, respectively. E2E tests for five tracking modes showed 0.26 mm (6D Skull), 0.3 mm (Fiducial), 0.26 mm (Xsight Spine), 0.62 mm (Xsight Lung), and 0.6 mm (Synchrony). TPRs, OCRs, output factors, and open beams measured under various conditions agreed with composite data provided from the manufacturer to within 2%. Patient-specific QA results were evaluated in two ways. Point dose measurements with an ion chamber were all within the 5% absolute-dose agreement, and relative-dose measurements using an array ion chamber detector all satisfied the 3%/3 mm gamma criterion for more than 90% of the measurement points. The Robotic IMRT M6 system equipped with the $InCise^{TM}2$ MLC was proven to be accurate and reliable.

• Radiation Oncology Journal
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• 제19권3호
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• pp.275-286
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• 2001

목적 : 세기조절방사선치료의 임상적용을 위한 정도보증 절차를 확립하고, 실제 치료환자 1례에 대한 적용 과정을 보고하고자 한다. 대상 및 방법 : 본원에서는 세기조절방사선치료를 시행하기 위해 역방향 치료계획(inverse planning) 시스템으로 $P^3IMRT$ (ADAC, 미국)와 다엽콜리메이터(Multileaf collimator, MLC)가 부착된 방사선치료용 선형가속기 Primus (Siemens, 미국)를 사용하였다. 먼저 다엽콜리메이터에 대한 위치의 정확성, 재현성, leaf transmission factor를 측정하였다. 또한 소조사면에 대한 치료계획시스템의 commissioning을 실시하였다. 이를 이용하여 C자 형태의 가상 PTV (Planning Target Volume)에 대해 9개의 빔을 사용하여 세기변조 조사빔을 설계하여, 이를 팬톰 내에서 절대선량 및 상대선량을 측정하여 비교, 분석하였다. 실제 6개의 세기변조 조사빔을 사용하여 치료를 시행한 전립선암 환자를 대상으로, 팬톰내에서 재 계산된 선량계산 결과를 0.015 cc 미소전리함, 다이오드선량계(Scanditronix, 스웨덴), 필름 선량계, 그리고 선형배열다중검출기(array detector) 등을 사용하여 절대선량 및 상대선량을 평가하였다. 결과 : MLC 위치 정확도는 1 mm 이내이었으며, 재현성은 0.5 mm 내외로 평가되었고, leaf transmission 인자는 10MV 광자선에 대해서 interleaf leakage의 경우, $1.9\%$, midleaf leakage의 경우, $0.9\%$로 측정되었다. 필름, 다이오드선량계, 미소전리함, 물팬톰용 전리함(0.125 cc) 등의 반음영을 측정해 본 결과, 물팬톰용 전리함으로 측정된 반음영 영역$(80\~20\%)$은 필름에 비해 2 mm 가량 크며, 최소 beamlet 크기가 5 mm 임을 감안할 때 부적합한 것으로 판명되었다. RTP commissioning 후 계산 선량은 $1\times1\;cm^2$ 크기 소조사면에서의 측정치와 $2\%$ 범위 내에서 일치하였다. C자 형태의 PTV에 대한 9개의 세기변조된 조사빔에 대한 2회에 걸친 치료중심점에서의 절대선량 측정결과 개별 조사빔에 대하여는 $10\%$ 이상 차이를 보였으나 총 선량은 $2\%$ 이내에서 일치하였다. 필름을 이용한 선량분포도도 계산치와 비교적 잘 일치하였다. 실제 치료환자의 팬톰 내에서의 절대선량 측정 결과 총 선량은 $1.5\%$ 차이를 보였다. 각 조사빔에 대해 중심 leaf의 측방선량분포도를 필름 및 선형배열다중검출기를 사용하여 측정하였으며, 조사면 밖에서 계산선량이 $2\%$ 내외로 작게 나타났으나, 특정 위치를 제외하고는 $3\%$ 이내로 잘 일치함을 확인하였다. 결론 : 세기조절방사선치료를 위해서는 다엽콜리메이터의 위치에 대한 보다 정밀한 정도관리 절차가 개발되어야 될 것으로 판단되며, 조사빔내 세기패턴을 효율적으로 확인할 수 있는 정도보증 절차가 필요할 것으로 사료된다. 본원에서는 팬톰 내에서의 치료중심점과 같이 특정 지점에서의 절대선량 확인 및 필름 혹은 선형배열다중검출기를 사용한 세기분포 패턴의 확인 과정을 통하여, 이를 적절히 병행하여 사용함으로써 세기조절방사선치료에 적합한 정도관리를 시행할 수 있었다.

• 한국의학물리학회지:의학물리
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• 제27권4호
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• pp.189-195
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• 2016

This paper aims to verify the clinical feasibility of a custom-made film created by a laser cutting tool for End-to-End (E2E) quality assurance in robotic intensity modulated radiation therapy system. The custom-made film was fabricated from the Gafchromic EBT3 film with the size of $8^{{\prime}{\prime}}{\times}10^{{\prime}{\prime}}$ using a drawing that is identical to the shape and scale of the original E2E film. The drawing was created by using a computer aided design program with the image file, which is obtained by scanning original E2E film. Beam delivery and evaluations were respectively performed with the original film and the custom-made film using fixed-cone collimator on three tracking modes: 6D skull (6DS), Xsight spine (XS), and Xsight lung (XL). The differences between total targeting errors of the original and custom-made films were recorded as 0.17 mm, 0.3 mm, and 0.17 mm at 6DS, XS, and XL tracking modes, respectively. This indicates that the custom-made film could yield nearly equivalent results to those of the original E2E film, given the uncertainties caused by distortions during film scanning and vibrations associated with film cutting. By confirming the clinical feasibility of a custom-made film for E2E testing, it can be expected that economic efficiency of the testing will increase accordingly.