• Radiation Oncology Journal
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• 제35권1호
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• pp.90-100
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• 2017

Purpose: To Study the dosimetric advantage of the Jaw tracking technique in intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) for Head and Neck Cancers. Materials and Methods: We retrospectively selected 10 previously treated head and neck cancer patients stage (T1/T2, N1, M0) in this study. All the patients were planned for IMRT and VMAT with simultaneous integrated boost technique. IMRT and VMAT plans were performed with jaw tracking (JT) and with static jaw (SJ) technique by keeping the same constraints and priorities for a particular patient. Target conformity, dose to the critical structures and low dose volumes were recorded and analyzed for IMRT and VMAT plans with and without JT for all the patients. Results: The conformity index average of all patients followed by standard deviation (${\bar{x}}{\pm}{\sigma}_{\bar{x}}$) of the JT-IMRT, SJ-IMRT, JT-VMAT, and SJ-VMAT were $1.72{\pm}0.56$, $1.67{\pm}0.57$, $1.83{\pm}0.65$, and $1.85{\pm}0.64$, and homogeneity index were $0.059{\pm}0.05$, $0.064{\pm}0.05$, $0.064{\pm}0.04$, and $0.064{\pm}0.05$. JT-IMRT shows significant mean reduction in right parotid and left parotid shows of 7.64% (p < 0.001) and 7.45% (p < 0.001) compare to SJ-IMRT. JT-IMRT plans also shows considerable dose reduction to thyroid, inferior constrictors, spinal cord and brainstem compared to the SJ-IMRT plans. Conclusion: Significant dose reductions were observed for critical structure in the JT-IMRT compared to SJ-IMRT technique. In JT-VMAT plans dose reduction to the critical structure were not significant compared to the SJ-IMRT due to relatively lesser monitor units.

• 한국전자파학회논문지
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• 제14권12호
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• pp.1311-1320
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• 2003

본 논문에서는 RF 전자기장을 사용한 동물 및 세포 실험에서 전자기장 노출량의 정확성을 평가할 수 있는 방법을 제안하였다. 이를 위해 전자파 흡수율(SAR)을 전자기장 노출량의 단위로 사용한 동물 및 세포 연구 논문과 휴대폰 및 PDA에 대한 전자파 흡수율 시험 성적서를 대상으로 출력 전력, 전력 밀도 등과 SAR의 상관 관계 및 회귀 관계를 분석하였다. 동물 실험의 경우 전력 밀도와 SAR이, 세포 실험의 경우 출력 전력이 duty factor를 고려한 SAR과 통계적으로 유의한 상관 관계를 보였다. 회귀분석에서의 노출 불확실성을 평가하기 위해 결정계수값을 분석하였다. 각각의 실험장치 및 방법에 대한 해석 또는 측정 기법의 분석 이전에 본 연구 방법을 실시하여 대상 연구군의 특성을 고찰한다면 보다 효율적인 전자기장노출신뢰성 평가를 실시할 수 있을 것으로 판단된다.

• Radiation Oncology Journal
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• 제36권4호
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• pp.332-340
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• 2018

Purpose: To retrospectively analyze dosimetric parameters of volumetric-modulated arc therapy (VMAT) and three-dimensional conformal radiotherapy (3D-CRT) delivered to extranodal marginal zone B-cell lymphomas of mucosa-associated lymphoid tissue in the stomach (gastric MALT lymphoma) to find out advantages of VMAT and conditions for definite benefits of VMAT. Materials and Methods: Fifty patients with stage I-II gastric MALT lymphoma received VMAT (n = 14) or 3D-CRT (n = 36) between December 2005 and April 2018. Twenty-seven patients were categorized according to whether the planning target volume (PTV) overlaps kidney(s). Dosimetric parameters were analyzed by dose-volume histogram. Results: Radiation dose to the liver was definitely lower with VMAT in terms of mean dose (p = 0.026) and V₁₅ (p = 0.008). The V₁₅ of the left kidney was lower with VMAT (p = 0.065). For those with PTV overlapping kidney(s), the left kidney V₁₅ was significantly lower with VMAT. Furthermore, the closer the distance between the PTV and kidneys, the less the left kidney V₁₅ with VMAT (p = 0.037). Delineation of kidney(s) by integrating all respiratory phases had no additional benefit. Conclusions: VMAT significantly increased monitor units, reduced treatment time and radiation dose to the liver and kidneys. The benefit of VMAT was definite in reducing the left kidney V₁₅, especially in geometrically challenging conditions of overlap or close separation between PTV and kidney(s).

• 한국의학물리학회지:의학물리
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• 제9권2호
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• pp.105-113
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• 1998

고에너지 광자선을 발생시키는 의료용선형가속기의 선질은 경우에 따라 변이를 가져오게 된다. 이러한 변이를 정확하게 판정하여 줄 수 있는 방사선측정법의 활용은 매우 중요하다. 보편적으로 광자선의 측정에 있어서 전리함의 사용이 아주 빈번하였으나 전자포탈영상장치(EPID)의 등장은 새로운 방사선측정법에 대한 가능성의 시작을 예견해준다. 실험은 6MV 광자선의 대칭성, Light/Radiation congruence, 그리고 Wedge filter를 통한 간편한 에너지의 변화에측과 위치의 정확도에 대하여 측정을 시행하였다. 사실 방사선측정의 대표적인 방법은 물팬톰-전리함응 이용한 모델인데 본 실험에서는 영상의 화소가 지니는 디지탈 값을 적절한 소프트웨어로 읽어내어서 데이터를 환산하여 결과를 얻었다. 선행실험에서 얻은 상대선량률을 적용하여 대칭성에서는 조사야영역이 l0$\times$10$cm^2$ 일 때 횡축과 종축에서 1.2%, 1.2%로 비교적 오차가 적었다. 그리고 Light/Radiation field congruence 여부는 횡축이 0.3%, 그리고 종축이 0.2%로서 예상한 기대값에 접근하였다. 다음으로 wedge filter를 활용한 에너지의 변이와 위치의 정확도에 대한 움직임을 알 수 있었다.

• Journal of Radiation Protection and Research
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• 제44권1호
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• pp.43-52
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• 2019

Background: The mid-term performance of clinical linear accelerator (LINAC) during volumetric modulated arc therapy (VMAT) treatment period is not performed in clinical practice and usually replaced with one-time plan quality assurance (QA). In this research we aim to monitor daily reproducibility of VMAT delivery from tracking individual leaf movement error and dosimetric error to evaluate the mid-term quality of the machine used. Materials and Methods: First, multileaf collimator (MLC) information was imported into MATLAB program to determine which of the MLC leaves in the leaf bank had the maximum RMS position error (maxRMS). We estimated where the maximum positional errors (maxPE) of the chosen leaf occur along its path length and tracked its daily variations over the entire treatment period. Secondly, picture information of dosimetric error from portal dosimetry was imported into MATLAB where representative high gamma index region (HGR) was determined as HGR with length of > 1 cm and their centers were daily tracked. Results and Discussion: The maxPEs in the brain and tongue cases were distributed broader than in other cases, but all data were found located within ${\pm}0.5mm$. From first day to last day all of five cases show the similar visual pattern of HGRs and Centers of the longest HGRs remained within ${\pm}1mm$ of that in first day. These findings prove excellent mid-term performance of the LINAC used in VMAT treatments over a full course of treatment. Conclusion: Tracking the daily location changes of leaf movement and dosimetric error can be a good indicator of predicting the daily quality like stability and reproducibility of beam delivering in VMAT treatment.

• 한국의학물리학회지:의학물리
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• 제34권4호
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• pp.48-54
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• 2023

Purpose: In this study, the dosimetric characteristics of lung stereotactic body radiotherapy (SBRT) plans using the new Halcyon system were analyzed to assess its suitability. Methods: We compared the key dosimetric parameters calculated for the Halcyon SBRT plans with those of a conventional C-arm linear accelerator (LINAC) equipped with a high-definition multileaf collimator (HD-MLC)-Trilogy Tx. A total of 10 patients with non-small-cell lung cancer were selected, and all SBRT plans were generated using the RapidArc technique. Results: Trilogy Tx exhibited significant superiority over Halcyon in terms of target dose coverage (conformity index, homogeneity index, D_{0.1 cc}, and D_95%) and dose spillage (gradient). Trilogy Tx was more efficient than Halcyon in the lung SBRT beam delivery process in terms of the total number of monitor units, modulation factor, and beam-on time. However, it was feasible to achieve a dose distribution that met SBRT plan requirements using Halcyon, with no significant differences in satisfying organs at risk dose constraints between both plans. Conclusions: Results confirm that Halcyon is a viable alternative for performing lung SBRT in the absence of a LINAC equipped with HD-MLC. However, extra consideration should be taken in determining whether to use Halcyon when the planning target volume setting is enormous, as in the case of significant tumor motions.

• 한국의학물리학회지:의학물리
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• 제25권4호
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• pp.199-204
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• 2014

유방암 환자들에 대한 방사선치료에서 순치료계획 세기변조방사선치료법을 쐐기접선조사기법과 선량측정면에서 비교분석하고자 이 연구를 수행했다. 우측 유방암 환자 20명과 좌측 유방암 환자 10명에 대해 후향적으로 연구를 시행했다. 각 환자에 대해 쐐기접선조사기법과 순치료계획 세기변조방사선치료법을 이용한 방사선치료 계획을 수립한 후에 선량학적 분석을 시도했다. 방사선치료계획용 표적체적에 대한 선량학적 비교 분석을 위해 homogeneity index, conformity index, uniformity index를 사용했다. 또한 폐와 심장에 대한 선량학적 분석을 위해서 평균선량값과 10, 20, 30 Gy 이상을 조사받는 체적의 백분율을 비교했다. 순치료계획 세기변조방사선치료법은 쐐기접선조사기법에 비해 계획표적체적에 대해 선량측정면에서 통계적으로 의미있게 더 나은 결과를 보였다. 폐에 대한 방사선량도 순치료계획 세기변조방사선치료법을 사용했을 때 10 Gy, 30 Gy 이상 조사받는 체적의 백분율이 통계적으로 의미있게 낮았다. 좌측 유방암 환자들에서 심장에 대한 방사선량을 측정했을 때에도 순치료계획 세기변조방사선치료법을 사용했을 때 평균선량값, 20 Gy, 30 Gy이상 조사받는 체적의 백분율이 더 낮은 것을 알 수 있었다. 순치료계획 세기변조방사선치료법은 쐐기접선조사기법에 비해 유방의 표적체적에 대한 선량균일성, 적합성 등에서 더 나은 결과를 보였다. 또한 순치료계획 세기변조방사선치료법을 사용했을 때 폐와 심장에 대한 방사선량도 더 낮출 수 있었다.

• Radiation Oncology Journal
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• 제29권3호
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• pp.206-213
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• 2011

Purpose: Intensity modulated radiation therapy (IMRT) is a high precision therapy technique that can achieve a conformal dose distribution on a given target. However, organ motion induced by respiration can result in significant dosimetric error. Therefore, this study explores the dosimetric error that result from various patterns of respiration. Materials and Methods: Experiments were designed to deliver a treatment plan made for a real patient to an in-house developed motion phantom. The motion pattern; the amplitude and period as well as inhale-exhale period, could be controlled by in-house developed software. Dose distribution was measured using EDR2 film and analysis was performed by RIT113 software. Three respiratory patterns were generated for the purpose of this study; first the 'even inhale-exhale pattern', second the slightly long exhale pattern (0.35 seconds longer than inhale period) named 'general signal pattern', and third a 'long exhale pattern' (0.7 seconds longer than inhale period). One dimensional dose profile comparisons and gamma index analysis on 2 dimensions were performed. Results: In one-dimensional dose profile comparisons, 5% in the target and 30% dose difference at the boundary were observed in the long exhale pattern. The center of high dose region in the profile was shifted 1 mm to inhale (caudal) direction for the 'even inhale-exhale pattern', 2 mm and 5 mm shifts to exhale (cranial) direction were observed for 'slightly long exhale pattern' and 'long exhale pattern', respectively. The areas of gamma index >1 were 11.88 %, 15.11%, and 24.33% for 'even inhale-exhale pattern', 'general pattern', and 'long exhale pattern', respectively. The long exhale pattern showed largest errors. Conclusion: To reduce the dosimetric error due to respiratory motions, controlling patient's breathing to be closer to even inhaleexhale period is helpful with minimizing the motion amplitude.

• 한국의학물리학회지:의학물리
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• 제26권4호
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• pp.223-228
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• 2015

이중으로 집중된 미세 다엽콜리메이터(Double-focused micro Multileaf Collimator: ${\mu}MLC$)는 보통의 다엽콜리메이터(Multileaf Collimator: MLC)에 비하여 조사면 가장자리 부분의 선량을 급격하게 줄여준다. 이러한 특성 때문에, 미세 다엽 콜리메이터는 정위적 방사선 수술과 치료(Stereotactic Radio-Surgery/RadioTtherapy, SRS/SRT)에 사용되어 왔다. 우리는 Elekta Synergy 선형가속기에 이중으로 집중된 동적 미세 다엽콜리메이터(Double-focused Dynamic micro-Multileaf Collimator: DMLC)를 부착하여 선량학적 특성을 평가하였다. 본 연구에서는, 필름(GafChromic EBT2 film), EDGE 다이오드 검출기, 3차원 물 팬텀을 이용하였다. 깊이선량백분율(Percent Depth Dose, PDD), 엽 투과도(leaf leakage), 반그림자(Penumbra)를 측정하였고, 모든 데이터들은 6MV 광자선으로 측정하였다. 그 결과, DMLC가 1% 이내의 투과도를 갖는것을 확인할 수 있었다. DMLC는 이중으로 집중 되는 구조를 가졌기 때문에 반 그림자가 조사야 크기에 대하여 독립적인 것을 확인하였다. 본 연구에서는 DMLC의 선량학적 특성을 바탕으로, Elekta Synergy에 부착된 DMLC의 적용 가능성을 증명하였다.

• Asian Pacific Journal of Cancer Prevention
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• 제14권7호
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• pp.4223-4228
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• 2013

Background: The purpose of this study was to determine the clinical and dosimetric factors associated with acute esophagitis (AE) in lung cancer patients treated with conformal radiotherapy (RT) in Turkey. Materials and Methods: In this retrospective review 104 lung cancer patients were examined. Esophagitis grades were verified weekly during treatment, and at 1 week, and 1 and 2 months afterwards. The clinical parameters included patient age, gender, tumor pathology, number of chemotherapy treatments before RT, concurrent chemotherapy, radiation dose, tumor response to RT, tumor localization, interruption of RT, weight loss, tumor and nodal stage and tumor volume. The following dosimetric parameters were analyzed for correlation of AE: The maximum ($D_{max}$) and mean ($D_{mean}$) doses delivered to the esophagus, the percentage of esophagus volume receiving ${\geq}10$ Gy ($V_{10}$), ${\geq}20$ Gy ($V_{20}$), ${\geq}30$ Gy ($V_{30}$), ${\geq}35$ Gy ($V_{35}$), ${\geq}40$ Gy ($V_{40}$), ${\geq}45$ Gy ($V_{45}$), ${\geq}50$ Gy ($V_{50}$) and ${\geq}60$ Gy ($V_{60}$). Results: Fifty-five patients (52.9%) developed AE. Maximum grades of AE were recorded: Grade 1 in 51 patients (49%), and Grade 2 in 4 patients (3.8%). Clinical factors had no statistically significant influence on the incidence of AE. In terms of dosimetric findings, correlation analyses demonstrated a significant association between AE and $D_{max}$ (>5117 cGy), $D_{mean}$ (>1487 cGy) and $V_{10-60}$ (percentage of volume receiving >10 to 60 Gy). The most significant relationship between RT and esophagitis were in $D_{max}$ (>5117 cGy) (p=0.002) and percentage of esophageal volume receiving >30 Gy ($V_{30}$ >31%) (p=0.008) in the logistic regression analysis. Conclusions: The maximum dose esophagus greater than 5117 cGy and approximately one third (31%) of the esophageal volume receiving >30 Gy was the most statistically significant predictive factor associated with esophagitis due to RT.