• 한국의학물리학회지:의학물리
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• 제14권1호
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• pp.28-33
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• 2003

본 연구는 무고정틀정위방사선치료의 다중호형 기법과 입체조형기법간의 회전중심점의 오차를 알아보고자 하였다. 1997년부터 2000년 12월까지 무고정틀정위방사선치료를 받은 47명의 환자를 대상으로 하였다. 다양한 종양형태와 크기를 고려하여 다중호형 또는 입체조형정위방사선치료를 선택하였다. 각 치료기법에 따른 회전중심점의 오차를 계산하였다. 다중호형과 입체조형정위방사선치료의 공간적 편차값($\Delta$r)은 각각 0.41 mm와 0.54 mm이었다. 다중호형정위방사선치료에서의 회전중심점의 정확도는 x, y, z 방향에서 각각 0.2 mm (SD 0.2 mm), 0.2 mm (SD 0.2), 0.3 mm (SD 0.2 mm)이었고, 입체조형정위방사선치료에서는 각각 0.2 mm (SD 0.2 mm), 0.3 mm (0.2 mm), 0.4 mm (SD 0.2 mm)이었다. 무고정틀 정위방사선치료를 이용한 회전중심점의 오차는 다중호형기법과 입체조형기법간에 차이가 없었다.

• 한국의학물리학회지:의학물리
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• 제25권4호
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• pp.288-297
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• 2014

Dynamic conformal arc therapy (DCAT) and flattening-filter-free (FFF) beams are commonly adopted for efficient conformal dose delivery in stereotactic body radiation therapy (SBRT). Off-axis geometry (OAG) may be necessary to obtain full gantry rotation without collision, which has been shown to be beneficial for peripheral targets using flattened beams. In this study dose distributions in OAG using FFF were evaluated and the effect of mechanical rotation induced uncertainty was investigated. For the lateral target, OAG evaluation, sphere targets (2, 4, and 6 cm diameter) were placed at three locations (central axis, 3 cm off-axis, and 6 cm off-axis) in a representative patient CT set. For each target, DCAT plans under the same objective were obtained for 6X, 6FFF, 10X, and 10FFF. The parameters used to evaluate the quality of the plans were homogeneity index (HI), conformality indices (CI), and beam on time (BOT). Next, the mechanical rotation induced uncertainty was evaluated using five SBRT patient plans that were randomly selected from a group of patients with laterally located tumors. For each of the five cases, a plan was generated using OAG and CAG with the same prescription and coverage. Each was replanned to account for one degree collimator/couch rotation errors during delivery. Prescription isodose coverage, CI, and lung dose were evaluated. HI and CI values for the lateral target, OAG evaluation were similar for flattened and unflattened beams; however, 6FFF provided slightly better values than 10FFF in OAG. For all plans the HI and CI were acceptable with the maximum difference between flattened and unflattend beams being 0.1. FFF beams showed better conformality than flattened beams for low doses and small targets. Variation due to rotational error for isodose coverage, CI, and lung dose was generally smaller for CAG compared to OAG, with some of these comparisons reaching statistical significance. However, the variations in dose distributions for either treatment technique were small and may not be clinically significant. FFF beams showed acceptable dose distributions in OAG. Although 10FFF provides more dramatic BOT reduction, it generally provides less favorable dosimetric indices compared to 6FFF in OAG. Mechanical uncertainty in collimator and couch rotation had an increased effect for OAG compared to CAG; however, the variations in dose distributions for either treatment technique were minimal.

• 한국광학회지
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• 제10권2호
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• pp.120-127
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• 1999

Head-Up Display(HUP)에 사용되는 홀로그래픽 광결합기의 회절 효율 및 결상 특성을 분석하고 제작하였다. Kogelnik의 결합파이론을 통해 반사형 체적 홀로그램에 대한 각도 및 분광 대역 특성을 수치계산하고 홀로그래픽 광학소자에서의 파장 변화에 의한 색수차의 최소화 방법을 HUD의 재생각 및 초점거리 보정에 응용하였다. 또한 자동차에 사용되는 형태로 등각형(conformal type)과 비등각형(non-conformal type)의 홀로그래픽 광결합기를 비교하고 대역 특성을 실험적으로 분석하였다. 실제적으로 등각형 보다 넓은 각도 대역폭을 보이며 광학적 배율(optical power)을 지니는 홀로그래픽 광결합기를 설계, 제작하였다.

• 한국음향학회지
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• 제40권4호
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• pp.347-358
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• 2021

본 연구의 목적은 곡면배열이 설치된 이중 곡률을 갖는 곡면의 형상을 최적화하는 것이다. 곡면은 4개의 미지수로 결정되는 이중 타원구로 모델링 하였다. 곡면 배열의 빔 패턴 분석을 통해서 4개의 미지수 중에 2개의 설계 파라미터를 결정했다. 빔 설계 인자의 sharp 지수의 합으로 표현되는 가중치 목적 함수를 정의했다. 각각의 sharp 지수는 여러 빔 설계 인자 중에 지향 지수, 고각 해상도, 방위각 해상도로 정의했다. 가중치가 주어졌을 때, 모든 격자에 대한 직접 계산을 통해 가중치 목적 함수를 평가하고 2개의 설계 파라미터의 최적값을 찾았다. 시뮬레이션에는 총 4종류의 가중치를 사용했다. 각각의 가중치에 대한 최적 곡면 형상 및 빔 패턴 분석 결과를 보였다. 특별히 균등 가중치를 사용했을 때, 다른 가중치를 사용했을 때보다 부드러운 표면을 갖는 이중 타원체의 형상이 얻어졌다.

• Radiation Oncology Journal
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• 제36권3호
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• pp.241-247
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• 2018

Purpose: A hybrid-dynamic conformal arc therapy (HDCAT) technique consisting of a single half-rotated dynamic conformal arc beam and static field-in-field beams in two directions was designed and evaluated in terms of dosimetric benefits for radiotherapy of lung cancer. Materials and Methods: This planning study was performed in 20 lung cancer cases treated with the VERO system (BrainLAB AG, Feldkirchen, Germany). Dosimetric parameters of HDCAT plans were compared with those of three-dimensional conformal radiotherapy (3D-CRT) plans in terms of target volume coverage, dose conformity, and sparing of organs at risk. Results: HDCAT showed better dose conformity compared with 3D-CRT (conformity index: 0.74 ± 0.06 vs. 0.62 ± 0.06, p < 0.001). HDCAT significantly reduced the lung volume receiving more than 20 Gy (V₂₀: 21.4% ± 8.2% vs. 24.5% ± 8.8%, p < 0.001; V₃₀: 14.2% ± 6.1% vs. 15.1% ± 6.4%, p = 0.02; V₄₀: 8.8% ± 3.9% vs. 10.3% ± 4.5%, p < 0.001; and V₅₀: 5.7% ± 2.7% vs. 7.1% ± 3.2%, p < 0.001), V₄₀ and V₅₀ of the heart (V₄₀: 5.2 ± 3.9 Gy vs. 7.6 ± 5.5 Gy, p < 0.001; V₅₀: 1.8 ± 1.6 Gy vs. 3.1 ± 2.8 Gy, p = 0.001), and the maximum spinal cord dose (34.8 ± 9.4 Gy vs. 42.5 ± 7.8 Gy, p < 0.001) compared with 3D-CRT. Conclusions: HDCAT could achieve highly conformal target coverage and reduce the doses to critical organs such as the lung, heart, and spinal cord compared to 3D-CRT for the treatment of lung cancer patients.

• Radiation Oncology Journal
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• 제18권1호
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• pp.1-10
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• 2000

목적 : 비인강암에서 방사선치료는 근치적 목적으로 사용되고 있으나 방사선치료 후 이하선 기능 저하에 따른 구강 건조증이 생기는 것이 문제이다. 방사선치료에 의한 구강 건조증의 발생을 감소시키기 위해 방사선조사시 이하선을 보호하는 새로운 치료 기법을 개발하고자 하였다. 대상 및 방법 : 림프절 전이가 없고 종양의 침범 범위가 서로 상이한 비인강암 4례를 대상으로 2가지의 새로운 치료계획을 수립하고 기존의 2차원 통상치료계획과 비교하였다. 치료계획-A는 기존의 2차원 통상치료 방법이며, 치료계획-B는 져 Gy 이후에 축소조사를 3차원 입체 조형치료로 하는 것이며, 치료계획-C는 방사선 치료 처음부터 3차원 입체 조형치료를 이용하여 양측 이하선을 방사선 조사영역에서 제외시키면서 30.6 Gy에서 척수 차폐를 시행하고 져 Gy 이후에 축소조사시 비동일 평면 3차원 입체조형치료를 시행하는 방법이다. 위 3가지 치료계획은 모두 70.2 Gy의 선랸을 계획용 표적체적내 회전중심점에 처방하여 각 치료계획마다 계획용 표적체적과 이하선의 등선량 분포, 선량체적 히스토그람(dose volume histogram, DVH), 선량통계(dose statistics), 정상조직손상확률(normal tissue complication probability, NTCP)을 비교하였다. 결과 : 전 예의 환자에서 치료 표적 부위의 등선량 분포, 선량통계와 선량체적 히스토그람상 치료계획-C에서 치료선량이 표적체적 내에 보다 균일하게 조사되었다. 선량통계분석에서 이하선에 조사되는 평균 방사선량은 치료계획-C에서 가장 적었으며(치료계획-A 58 Gy, 치료계획-B 50 Gy, 치료계획-C 48.5 Gy), 46 Gy가 조사되는 체적도 가장 적었다(치료계획-A 100$\%$, 치료계획-B 98$\%$, 치료계획-C 69$\%$). 선량체적 히스토그람도 치료계획-C에서 가장 우수하였고, 선량체적 히스토그람을 이용하여 계산된 정상조직 부작용 확률도 치료계획-C에서 가장 낮았다. 결론 : 방사선치료 초기부터 3차원 입체조형치료를 적용하여 이하선을 치료 조사영역에서 제외하고, 축소 조사시에 다양한 조사방향을 가능하게 하기 위해 45 Gy 이전에 척수 차폐(spinal cord block)를 적용하는 이 같은 새로운 방사선치료 기법이 림프절 전이가 없는 비인강암의 환자에서 구강 건조증 발생을 감소시키는 방사선치료기법으로 추천될 수 있다고 사료된다.

• Nuclear Engineering and Technology
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• 제54권3호
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• pp.1016-1023
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• 2022

In proton therapy, a highly conformal proton dose can be delivered to the tumor by means of the steep distal dose penumbra at the end of the beam range. The proton beam range, however, is highly sensitive to range uncertainty, which makes accurately locating the proton range in the patient difficult. In-vivo range verification is a method to manage range uncertainty, one of the promising techniques being prompt gamma imaging (PGI). In earlier studies, we proposed gamma electron vertex imaging (GEVI), and constructed a proof-of-principle system. The system successfully demonstrated the GEVI imaging principle for therapeutic proton pencil beams without scanning, but showed some limitations under clinical conditions, particularly for pencil beam scanning proton therapy. In the present study, we upgraded the GEVI system in several aspects and tested the performance improvements such as for range-shift verification in the context of line scanning proton treatment. Specifically, the system showed better performance in obtaining accurate prompt gamma (PG) distributions in the clinical environment. Furthermore, high shift-detection sensitivity and accuracy were shown under various range-shift conditions using line scanning proton beams.

• Radiation Oncology Journal
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• 제35권1호
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• pp.78-89
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• 2017

Purpose: To determine the optimal radiotherapy technique for gastric mucosa-associated lymphoid tissue lymphoma (MALToma), we compared the dosimetric parameters and the risk of solid secondary cancer from scattered doses among anterior-posterior/ posterior-anterior parallel-opposed fields (AP/PA), anterior, posterior, right, and left lateral fields (4_field), 3-dimensional conformal radiotherapy (3D-CRT) using noncoplanar beams, and intensity-modulated radiotherapy composed of 7 coplanar beams (IMRT_co) and 7 coplanar and noncoplanar beams (IMRT_non). Materials and Methods: We retrospectively generated 5 planning techniques for 5 patients with gastric MALToma. Homogeneity index (HI), conformity index (CI), and mean doses of the kidney and liver were calculated from the dose-volume histograms. Applied the Biological Effects of Ionizing Radiation VII report to scattered doses, the lifetime attributable risk (LAR) was calculated to estimate the risk of solid secondary cancer. Results: The best value of CI was obtained with IMRT, although the HI varied among patients. The mean kidney dose was the highest with AP/PA, followed by 4_field, 3D-CRT, IMRT_co, and IMRT_non. On the other hand, the mean liver dose was the highest with 4_field and the lowest with AP/PA. Compared with 4_field, the LAR for 3D-CRT decreased except the lungs, and the LAR for IMRT_co and IMRT_non increased except the lungs. However, the absolute differences were much lower than <1%. Conclusion: Tailored RT techniques seem to be beneficial because it could achieve adjacent organ sparing with very small and clinically irrelevant increase of secondary solid cancer risk compared to the conventional techniques.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3140-3149
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• 2023

In theory, the sharp dose falloff at the distal end of a proton beam allows for high conformal dose to the target. However, conformity has not been fully achieved in practice, primarily due to beam range uncertainty, which is approximately 4% and varies slightly across institutions. To address this issue, we developed a new range verification system prototype: a multi-slit prompt-gamma camera (MSPGC). This system features high prompt-gamma detection sensitivity, an advanced range estimation algorithm, and a precise camera positioning system. We evaluated the range measurement precision of the prototype for single spot beams with varying energies, proton quantities, and positions, as well as for spot-scanning proton beams in a simulated SSPT treatment using a phantom. Our results demonstrated high accuracy (<0.4 mm) in range measurement for the tested beam energies and positions. Measurement precision increased significantly with the number of protons, achieving 1% precision with 5 × 10⁸ protons. For spot-scanning proton beams, the prototype ensured more than 5 × 10⁸ protons per spot with a 7 mm or larger spot aggregation, achieving 1% range measurement precision. Based on these findings, we anticipate that the clinical application of the new prototype will reduce range uncertainty (currently approximately 4%) to 1% or less.

• Radiation Oncology Journal
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• 제37권4호
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• pp.232-248
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• 2019

Proton beams have been used for cancer treatment for more than 28 years, and several technological advancements have been made to achieve improved clinical outcomes by delivering more accurate and conformal doses to the target cancer cells while minimizing the dose to normal tissues. The state-of-the-art intensity modulated proton therapy is now prevailing as a major treatment technique in proton facilities worldwide, but still faces many challenges in being applied to the lung. Thus, in this article, the current status of proton therapy technique is reviewed and issues regarding the relevant uncertainty in proton therapy in the lung are summarized.