• 한국가시화정보학회지
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• 제8권2호
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• pp.51-55
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• 2010

Flow characteristics of a free-horizontal-axis-turbine (FHAT) current power generation system have been investigated by the use of a volumetric PTV. Three types of FHAT system (S50, SE50, S65) have been tested under the current speed 1.35 knot, 1.5 knot and 2 knot. The width of the blade installed around the body is 50 mm. Based upon the power generation characteristics of the FHAT, the flow features of the blade have been investigated. Among the three models it has been verified that the S65 is the most appropriate for power generations.

• 한국의학물리학회지:의학물리
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• 제30권4호
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• pp.94-103
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• 2019

Purpose: To evaluate the clinical feasibility of knowledge-based planning (KBP) for volumetric-modulated arc radiotherapy (VMAT) in spine stereotactic body radiotherapy (SBRT). Methods: Forty-eight VMAT plans for spine SBRT was studied. Two planning target volumes (PTVs) were defined for simultaneous integrated boost: PTV for boost (PTV-B: 27 Gy/3fractions) and PTV elective (PTV-E: 24 Gy/3fractions). The expert VMAT plans were manually generated by experienced planners. Twenty-six plans were used to train the KBP model using Varian RapidPlan. With the trained KBP model each KBP plan was automatically generated by an individual with little experience and compared with the expert plan (closed-loop validation). Twenty-two plans that had not been used for KBP model training were also compared with the KBP results (open-loop validation). Results: Although the minimal dose of PTV-B and PTV-E was lower and the maximal dose was higher than those of the expert plan, the difference was no larger than 0.7 Gy. In the closed-loop validation, D_1.2cc, D_0.35cc, and D_mean of the spinal cord was decreased by 0.9 Gy, 0.6 Gy, and 0.9 Gy, respectively, in the KBP plans (P<0.05). In the open-loop validation, only D_mean of the spinal cord was significantly decreased, by 0.5 Gy (P<0.05). Conclusions: The dose coverage and uniformity for PTV was slightly worse in the KBP for spine SBRT while the dose to the spinal cord was reduced, but the differences were small. Thus, inexperienced planners could easily generate a clinically feasible plan for spine SBRT by using KBP.

• International Journal of Automotive Technology
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• 제7권4호
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• pp.441-448
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• 2006

In-cylinder flows such as tumble and swirl play an important role on the engine combustion efficiencies and emission formations. The tumble flow, which is dominant in current high performance gasoline engines, is able to effect fuel consumptions and emissions under a partial load condition in addition to the volumetric efficiency under a wide open throttle condition. Therefore, it is important to optimize the tumble ratio of a gasoline engine for better fuel economy, lower emissions, and maximum volumetric efficiency. First step for optimizing a tumble ratio is to measure a tumble ratio accurately. For a tumble ratio measurement, many different methods have been developed and used such as steady flow rig, PIV, PTV, and LDV. However, it is not well known about the relations among the measured tumble ratios using different methods. The purpose of this research is to correlate the tumble ratios measured using three different methods and find out merits and demerits of each measurement method. In this research the tumble flow was measured, compared, and correlated using three different measurement methods at the same engine: steady flow rig; 2-dimensional PIV; and 3-dimensional PTV water flow rig.

• 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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• 제27권4호
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• pp.180-188
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• 2016

Acuros XB advanced dose calculation algorithm (AXB, Varian Medical Systems, Palo Alto, CA) has been released recently and provided the advantages of speed and accuracy for dose calculation. For clinical use, it is important to investigate the dosimetric performance of AXB compared to the calculation algorithm of the previous version, Anisotropic Analytical Algorithm (AAA, Varian Medical Systems, Palo Alto, CA). Ten volumetric modulated arc therapy (VMAT) plans for each of the following cases were included: head and neck (H&N), prostate, spine, and lung. The spine and lung cases were treated with stereotactic body radiation therapy (SBRT) technique. For all cases, the dose distributions were calculated using AAA and two dose reporting modes in AXB (dose-to-water, $AXB_w$, and dose-to-medium, $AXB_m$) with same plan parameters. For dosimetric evaluation, the dose-volumetric parameters were calculated for each planning target volume (PTV) and interested normal organs. The differences between AAA and AXB were statistically calculated with paired t-test. As a general trend, $AXB_w$ and $AXB_m$ showed dose underestimation as compared with AAA, which did not exceed within -3.5% and -4.5%, respectively. The maximum dose of PTV calculated by $AXB_w$ and $AXB_m$ was tended to be overestimated with the relative dose difference ranged from 1.6% to 4.6% for all cases. The absolute mean values of the relative dose differences were $1.1{\pm}1.2%$ and $2.0{\pm}1.2%$ when comparing between AAA and $AXB_w$, and AAA and $AXB_m$, respectively. For almost dose-volumetric parameters of PTV, the relative dose differences are statistically significant while there are no statistical significance for normal tissues. Both $AXB_w$ and $AXB_m$ was tended to underestimate dose for PTV and normal tissues compared to AAA. For analyzing two dose reporting modes in AXB, the dose distribution calculated by $AXB_w$ was similar to those of AAA when comparing the dose distributions between AAA and $AXB_m$.

• 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.

• 대한방사선치료학회지
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• 제31권2호
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• pp.33-41
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• 2019

목 적: 용적변조회전 방사선치료(Volumetric Modulated Arc Therapy, VMAT)시, Planning Target Volume(PTV)을 중복 설정하여 손상위험장기(Organ At Risk, OAR)에 인접한 PTV Coverage 감소를 개선하기 위한 연구이다. 대상 및 방법: 본원에서 전뇌(Whole Brain), 담낭(Gall Bladder), 직장(Rectum) 방사선치료를 받은 환자를 대상으로 하였으며, PTV 내 Coverage가 부족한 부분에 PTV를 중복 적용한 치료계획과 적용하지 않은 치료계획으로 구성하여 Coverage 변화와 최대선량, 선량균질지수(Homogeneity Index, H.I.), 처방선량지수(Conformity Index, C.I.)를 비교하였으며, 손상위험장기(Organ At Risk, OAR)의 최대선량과 평균선량의 변화 또한 비교하였다. 결 과: 중복하여 적용한 PTV의 Coverage는 모든 환자에게서 증가하였고, 이에 따른 영향으로 전체 Coverage 또한 4명의 환자에게서 증가하였다. PTV의 최대선량은 5명의 환자에게서 증가하였으며, 모든 환자의 선량균질지수와 처방선량지수는 큰 차이를 나타내지 않았다. 수정체의 최대선량은 최대 1.12배 증가하였으나, 뇌줄기의 경우 2명의 환자에게서 최대선량이 감소하였다. 안구의 평균선량은 최대 1.15배 증가하였으며, 양측 이하선의 경우 큰 차이를 나타내지 않았다. 담낭암 환자의 경우 간과 결장의 평균선량은 각각 0.95배, 0.94배 감소하였으며, 십이지장의 평균선량은 큰 차이가 없었다. 직장암 환자의 경우 OAR로 설정한 양측 대퇴골두와 방광 모두 평균선량은 감소하였으며, 전체 MU는 1명을 제외한 4명의 환자에게서 비슷한 수준으로 나타났다. 결 론: OAR의 선량제한을 고려해가면서 적절하게 사용한다면, PTV의 Coverage 개선에 유용한 방법이라 생각한다.

• Asian Pacific Journal of Cancer Prevention
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• 제15권20호
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• pp.9033-9038
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• 2014

Background: The purpose of this study was to assess the feasibility of deep inspiration breath-hold (DIBH) based volumetric modulated arc therapy (VMAT) for locally advanced left sided breast cancer patients undergoing radical mastectomy. DIBH immobilizes the tumor bed providing dosimetric benefits over free breathing (FB). Materials and Methods: Ten left sided post mastectomy patients were immobilized in a supine position with both the arms lifted above the head on a hemi-body vaclock. Two thermoplastic masks were prepared for each patient, one for normal free breathing and a second made with breath-hold to maintain reproducibility. DIBH CT scans were performed in the prospective mode of the Varian real time position management (RPM) system. The planning target volume (PTV) included the left chest wall and supraclavicular nodes and PTV prescription dose was 5000cGy in 25 fractions. DIBH-3DCRT planning was performed with the single iso-centre technique using a 6MV photon beam and the field-in-field technique. VMAT plans for FB and DIBH contained two partial arcs ($179^{\circ}-300^{\circ}CCW/CW$). Dose volume histograms of PTV and OAR's were analyzed for DIBH-VMAT, FB-VMAT and DIBH-3DCRT. In DIBH mode daily orthogonal ($0^{\circ}$ and $90^{\circ}$) KV images were taken to determine the setup variability and weekly twice CBCT to verify gating threshold level reproducibility. Results: DIBH-VMAT reduced the lung and heart dose compared to FB-VMAT, while maintaining similar PTV coverage. The mean heart $V_{30Gy}$ was $2.3%{\pm}2.7$, $5.1%{\pm}3.2$ and $3.3%{\pm}7.2$ and for left lung $V_{20Gy}$ was $18.57%{\pm}2.9$, $21.7%{\pm}3.9$ and $23.5%{\pm}5.1$ for DIBH-VMAT, FB-VMAT and DIBH-3DCRT respectively. Conclusions: DIBH-VMAT significantly reduced the heart and lung dose for left side chest wall patients compared to FB-VMAT. PTV conformity index, homogeneity index, ipsilateral lung dose and heart dose were better for DIBH-VMAT compared to DIBH-3DCRT. However, contralateral lung and breast volumes exposed to low doses were increased with DIBH-VMAT.

• 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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• 제29권4호
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• pp.157-163
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• 2018

Plans converted using dose-volume-histogram-based plan conversion (DPC) were evaluated by comparing them to the original plans. Changes in the dose volumetric (DV) parameters of five volumetric modulated arc therapy (VMAT) plans for head and neck (HN) cancer and five VMAT plans for prostate cancer were analyzed. For the HN plans, the homogeneity indices (HIs) of the three planning target volumes (PTV) increased by 0.03, 0.02, and 0.03, respectively, after DPC. The maximum doses to the PTVs increased by 1.20, 1.87, and 0.92 Gy, respectively, after DPC. The maximum doses to the optic chiasm, optic nerves, spinal cord, brain stem, lenses, and parotid glands increased after DPC by approximately 4.39, 3.62, 7.55, 7.96, 1.77, and 6.40 Gy, respectively. For the prostate plans after DPC, the HIs for the primary and boost PTVs increased by 0.05 and 0.03, respectively, and the maximum doses to each PTV increased by 1.84 and 0.19 Gy, respectively. After DPC, the mean doses to the rectum and femoral heads increased by approximately 6.19 and 2.79 Gy, respectively, and those to the bladder decreased by 0.20 Gy when summing the primary and boost plans. Because clinically unacceptable changes were sometimes observed after DPC, plans converted by DPC should be carefully reviewed before actual patient treatment.