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Toward a novel dosimetry system using acrylic disk radiation sensor for proton pencil beam scanning
Cho, Shinhaeng,Lee, Nuri,Song, Sanghyeon,Son, Jaeman,Kim, Haksoo,Jeong, Jong Hwi,Lee, Se Byeong,Lim, Youngkyung,Moon, Sunyoung,Yoon, Myonggeun,Shin, Dongho Published for the American Association of Physicis 2018 Medical physics Vol.45 No.11
Cho Shinhaeng,Cho Ick Joon,Kim Yong Hyub,Jeong Jae-Uk,Yoon Mee Sun,Ahn Sung-Ja,Nam Taek-Keun,Song Ju-Young 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.5
The internal target volume (ITV)-based IMRT method can be used to reduce the effect of respiratory tumor motion. In this study, the effect of tumor motion on the dosimetric accuracy during ITV-based IMRT was investigated. ITV-based IMRT plans for a total of ten cases of liver cancer were prepared in TomoTherapy (Tomo) and volumetric modulated arc therapy (VMAT). Delivery quality assurance (DQA) plans were created using Delta4 phantom for the verification of dosimetric accuracy of the established Tomo and VMAT plans. DQA measurements were performed in both the static mode and the Hexa-Motion mode by using the Delta4 Hexa-Motion system in Tomo and VMAT. In the static mode, the average gamma passing rate (GPR) using a 3% dose difference/3 mm distance-to-agreement criteria was 99.61% in Tomo and 99.35% in VMAT, which confirmed sufficient dosimetric accuracy in both IMRT methods. For the Hexa-Motion measurement, the average GRP result of 90.93% in Tomo was higher than the result of 82.58% obtained in VMAT. In addition, the difference in the GPR results between the static and the Hexa-motion modes in Tomo was 8.68%, which is approximately 8% less than the 16.77% difference in VMAT. This study verifies that the dosimetric error of ITV-based IMRT due to the tumor motion was larger in VMAT than in Tomo. Also, Tomo can be considered to be more suitable than the conventional LINAC-based VMAT method in terms of the dosimetric accuracy of ITV-based IMRT for the treatment of a moving tumor.
Cho Shinhaeng,Cho Ick Joon,Kim Yong Hyub,Jeong Jea-Uk,Yoon Mee Sun,Nam Taek Keun,Ahn Sung Ja,Song Ju-Young 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.2
The Halcyon, closed-bore and O-ring type linear accelerator, is unable to use the specialized device which can reduce respiratory tumor-motion efect such as a gating system, and the internal target volume (ITV)-based IMRT method should be applied to the treatment of moving tumor target. In this study, the tumor-motion efect on the dosimetric accuracy of the ITV-based IMRT using the Halcyon. ITV-based volumetric modulated arc therapy (VMAT) plans using the Halcyon were prepared for ten cases of liver cancer while changing the number of arcs (1-arc, 3-arc, and 5-arc) in the plan. Delivery quality assurance (DQA) plans were created using the Delta4 Phantom+diode array to verify the dosimetric accuracy of the VMAT plans. DQA measurements were performed in both the static and the Hexa-Motion mode using the Delta4 HexaMotion system to evaluate the motion efect on the dosimetric accuracy. In the static mode, the average gamma pass rate (GPR) value was 99.98% for the 3%/3 mm criterion and 99.02% for the 2%/2 mm criterion, which can verify the sufcient dosimetric accuracy of the VMAT plans in this study. The average GPR values calculated with a 3%/3 mm criterion in the Hexa-Motion mode were 68.25%, 69.17%, and 75.52% for the 1-arc, 3-arc, and 5-arc VMAT plans, respectively. When the 2%/2 mm criterion was used, the average GPR values in the Hexa-Motion mode were 50.76%, 50.33%, and 56.21% for the 1-arc, 3-arc, and 5-arc VMAT plans. These signifcantly lower GPR values show that the dosimetric accuracy in the Halcyon is more afected by tumor motion compared to the conventional linear accelerator. This study verifes that it is advantageous to use a large number of arcs in the ITV-based VMAT plan implemented using the Halcyon to reduce dosimetric error due to tumor motion
Dosimetric Impact of Ti Mesh on Proton Beam Therapy
Cho, Shinhaeng,Goh, Youngmoon,Kim, Chankyu,Kim, Haksoo,Jeong, Jong Hwi,Lim, Young Kyung,Lee, Se Byeong,Shin, Dongho Korean Society of Medical Physics 2017 의학물리 Vol.28 No.4
When a high density metallic implant is placed in the path of the proton beam, spatial heterogeneity can be caused due to artifacts in three dimensional (3D) computed tomography (CT) scans. These artifacts result in range uncertainty in dose calculation in treatment planning system (TPS). And this uncertainty may cause significant underdosing to the target volume or overdosing to normal tissue beyond the target. In clinical cases, metal implants must be placed in the beam path in order to preserve organ at risk (OARs) and increase target coverage for tumors. So we should introduce Ti-mesh. In this paper, we measured the lateral dose profile for proton beam using an EBT3 film to confirm dosimetric impact of Ti-mesh when the Ti-mesh plate was placed in the proton beam pathway. The effect of Ti-mesh on the proton beam was investigated by comparing the lateral dose profile calculated from TPS with the film-measured value under the same conditions.
Investigation of Optical Properties of Ceramic Ce:GAGG by High Temperature Annealing
박찬선,Muhammad Nasir Ullah,김찬호,Shinhaeng Cho,염정열 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.12
An as-fabricated cerium-doped ceramic scintillator Gd$_3$Al$_2$Ga$_3$O$_{12}$ (Ce:GAGG) was thermally annealed at different temperatures. The light output and energy resolution of the scintillators were measured before and after thermal treatment. The effect of thermal annealing in the air at high temperature (at 1000 $^\circ$C for 5 hours) deforms the microstructure by mitigating oxygen vacancies of the ceramic scintillator. This has been proven by XPS study that showed the existence of oxygen vacancies and subsequent decrease of oxygen deficiency amid annealing treatment that led to an output signal increase. The diffusion ability of oxygen atoms by annealing played a key role in compensating for defect sites. In this study, by controlling thermodynamic conditions, the light output was enhanced by $\sim$30.4\% and the energy resolution improved by $\sim$2.4\% after annealing at 1000 $^\circ$C in the air.