• 한국의학물리학회지:의학물리
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• 제35권1호
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• pp.10-15
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• 2024

Purpose: This study aimed to comprehensively investigate the diverse characteristics of a novel commercial bolus, CLEANBOLUS-WHITE (CBW), to ascertain its suitability for clinical application. Methods: The evaluation of CBW encompassed both physical and biological assessments. Physical parameters such as mass density and shore hardness were measured alongside analyses of element composition. Biological evaluations included assessments for skin irritation and cytotoxicity. Dosimetric properties were examined by calculating surface dose and beam quality using a treatment planning system (TPS). Additionally, doses were measured at maximum and reference depths, and the results were compared with those obtained using a solid water phantom. The effect of air gap on dose measurement was also investigated by comparing measured doses on the RANDO phantom, under the bolus, with doses calculated from the TPS. Results: Biological evaluation confirmed that CBW is non-cytotoxic, nonirritant, and non-sensitizing. The bolus exhibited a mass density of 1.02 g/cm³ and 14 shore 00. Dosimetric evaluations revealed that using the 0.5 cm CBW resulted in less than a 1% difference compared to using the solid water phantom. Furthermore, beam quality calculations in the TPS indicated increased surface dose with the bolus. The air gap effect on dose measurement was deemed negligible, with a difference of approximately 1% between calculated and measured doses, aligning with measurement uncertainty. Conclusions: CBW demonstrates outstanding properties for clinical utilization. The dosimetric evaluation underscores a strong agreement between calculated and measured doses, validating its reliability in both planning and clinical settings.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 추계학술발표회요약집
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• pp.356.2-356
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• 2002

• 한국의학물리학회지:의학물리
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• 제31권4호
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• pp.179-188
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• 2020

Purpose: We compared noncoplanar volumetric modulated arc therapy (ncVMAT) plans to coplanar VMAT (cVMAT) plans by evaluating the dosimetric quality of each for esophageal cancer. Methods: Twenty patients treated for esophageal cancer with the cVMAT technique were retrospectively selected. The cVMAT plans consisted of three coplanar full arc beams. The ncVMAT plans consisted of two coplanar full arc beams and one noncoplanar partial arc beam ranging from 45° to 315° with a couch rotation angle of 315°±5°. For dosimetric evaluation, the dose-volumetric (DV) parameters of the planning target volume (PTV) and organs at risk (OARs) were calculated for all VMAT plans. Results: No clinically noticeable differences between the cVMAT and ncVMAT plans were observed in the DV parameters of the PTV. For the lungs, the V_{13 Gy} and mean dose for ncVMAT plans were smaller than those for cVMAT plans, showing statistically significant differences. For the heart, the values of the maximum dose for cVMAT and ncVMAT plans were 53.8±2.9 and 50.9±3.3 Gy, respectively (P=0.004). For the spinal cord, the values of the maximum dose for cVMAT and ncVMAT plans were 37.1±5.1 and 34.7±5.7 Gy, respectively (P<0.001). Conclusions: The use of ncVMAT plans provides better PTV coverage and sparing of OARs compared to that of cVMAT plans for long, tube-like esophageal cancer. For esophageal cancer, the ncVMAT plans showed a more favorable plan quality than the cVMAT plans.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2003년도 추계학술발표대회 요약집
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• pp.393-393
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• 2003

• 한국의학물리학회지:의학물리
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• 제31권1호
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• pp.8-8
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• 2020

• 대한방사선치료학회지
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• 제11권1호
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• pp.73-78
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• 1999

In general, the patients of the head and neck cancer are treated with 4MV photon beam up to prescribed dose, but spinal cord should be excluded in the treatment field. When its absorbed dose is limited at the tolerance dose. In case of the patients who has the positive posterior neck nodes need a boost electron beam treatment to the prescribed dose. In that case, the anatomical structure of the neck and the physical structure of the standard electron cone interrupt to allow proper access to the disease site. Therefore, we extended treatment SSD for the remove of the those hindrances. In this study, we evaluated the dosimetric variation of the standard electron cone for the extended SSD, from 100cm to 120cm, 5 cm increment, and compare to the custom-made electron cone. As a result, the $\%$ depth dose, the point of maximum dose and the range of maximum were changed within the $2\%$. The penumbra width was increased from 1.0cm to 2.0cm. However, the dosimetric characteristics of the custom-made electron cone was very similar to that of the 100cm SSD standard electron cone and due to its characteristic of physical structure, patients didn't need re-positioning after photon beam treatment, therefore accurate treatment was possible, we conclude that the custom-made electron cone was very useful for the clinical practice.

• 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.

• 대한방사선방어학회:학술대회논문집
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• 대한방사선방어학회 2011년도 추계 학술발표회 및 심포지엄
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• pp.206-207
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• 2011

• 한국방사선학회논문지
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• 제16권7호
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• pp.863-870
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• 2022

DLG (Dosimetric Leaf Gap)와 투과계수는 방사선치료계획 시스템에서 MLC 모델링의 중요 매개변수이다. 본 연구에서는 측정 용적이 다른 검출기를 이용하여 HD-MLC의 DLG와 투과계수를 측정하였고, DLG의 최적화를 통해 방사선 치료계획의 정확성을 평가하였다. 용적이 작은 Semiflux3D, MicroDiamond 검출기로 Dynamic Sweeping Gap 방법을 통해 DLG를 측정하였다. 측정된 DLG 값을 최적화할 수 있도록 10개의 방사선치료계획을 생성하고 QA결과와 비교하였다. 6, 8, 10 MV에서 Semiflux3D로 측정한 DLG는 0.76, 0.83, 0.85 mm 였고, MicroDiomond로 측정한 DLG는 0.78. 0.86, 0.9 mm 였다. 방사선치료계획 시스템에서 검출기로 측정한 DLG와 최적화된 DLG 값으로 생성한 10개의 치료계획을 Postal dosimetry로 QA하여 감마분석 하였다. 6 MV 광자선의 감마분석결과 2 mm/2% 기준에서 DLG 0.78 mm는 평균 94.3%였고, DLG 1.15 mm는 평균 98.4%였다. 10 MV 광자선에서도 DLG 0.9 mm는 평균 91.2%, DLG 1.25 mm는 97.6%였다. HD-MLC의 사용은 방사선치료계획 시스템에 정확한 모델링이 완성되어야 한다. DLG 값을 검출기로 측정하여 임상에 사용할 수 있지만, DLG 값의 최적화가 이루어진다면 환자에게 더 유용한 방사선 치료를 전달할 수 있을 것이다.

• 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.