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Yoon, Myonggeun,Shin, Dongho,Kwak, Jungwon,Park, Soah,Lim, Young Kyung,Kim, Dongwook,Park, Sung Yong,Lee, Se Byeong,Shin, Kyung Hwan,Kim, Tae Hyun,Cho, Kwan Ho Elsevier 2009 Medical dosimetry Vol.34 No.3
<P><B>Abstract</B></P><P>We compared the main characteristics of movement-induced dose reduction during photon and proton beam treatment, based on an analysis of dose-volume histograms. To simulate target movement, a target contour was delineated in a scanned phantom and displaced by 3 to 20 mm. Although the dose reductions to the target in the 2 treatment systems were similar for transverse (perpendicular to beam direction) target motion, they were completely different for longitudinal (parallel to beam direction) target motion. While both modalities showed a relationship between the degree of target shift and the reduction in dose coverage, dose reduction showed a strong directional dependence in proton beam treatment. Clinical simulation of target movement for a prostate cancer patient showed that, although coverage and conformity indices for a 6-mm lateral movement of the prostate were reduced by 9% and 16%, respectively, for proton beam treatment, they were reduced by only 1% and 7%, respectively, for photon treatment. This difference was greater for a 15-mm target movement in the lateral direction, which lowered the coverage and conformity indices by 34% and 54%, respectively, for proton beam treatment, but changed little during photon treatment. In addition, we found that the equivalent uniform dose (EUD) and homogeneity index show similar characteristics during target movement. These results suggest that movement-induced dose reduction differs significantly between photon and proton beam treatment. Attention should be paid to the target margin in proton beam treatment due to the distinct characteristics of heavy ion beams.</P>
Risk of a second cancer from scattered radiation in acoustic neuroma treatment
Yoon, Myonggeun,Lee, Hyunho,Sung, Jiwon,Shin, Dongoh,Park, Sungho,Chung, Weon Kuu,Jahng, Geon-Ho,Kim, Dong Wook Korean Physical Society 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.12
The present study aimed to compare the risk of a secondary cancer from scattered and leakage doses in patients receiving intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), and stereotactic radiosurgery (SRS). Four acoustic neuroma patients were treated with IMRT, VMAT, or SRS. Their excess relative risk (ERR), excess absolute risk (EAR), and lifetime attributable risk (LAR) of a secondary cancer were estimated using the corresponding secondary doses measured at various organs by using radio-photoluminescence glass dosimeters (RPLGD) placed inside a humanoid phantom. When a prescription dose was delivered in the planning target volume of the 4 patients, the average organ equivalent doses (OED) at the thyroid, lung, liver, bowel, bladder, prostate (or ovary), and rectum were 14.6, 1.7, 0.9, 0.8, 0.6, 0.6, and 0.6 cGy, respectively, for IMRT whereas they were 19.1, 1.8, 2.0, 0.6, 0.4, 0.4, and 0.4 cGy, respectively, for VMAT, and 22.8, 4.6, 1.4, 0.7, 0.5, 0.5, and 0.5 cGy, respectively, for SRS. The OED decreased as the distance from the primary beam increased. The thyroid received the highest OED compared to other organs. A lifetime attributable risk evaluation estimated that more than 0.03% of acoustic neuroma (AN) patients would get radiation-induced cancer within 20 years of receiving radiation therapy. The organ with the highest radiation-induced cancer risk after radiation treatment for AN was the thyroid. We found that the LAR could be increased by the transmitted dose from the primary beam. No modality-specific difference in radiation-induced cancer risk was observed in our study.
Yoon, Myonggeun,Kim, Jin-Sung,Shin, Dongho,Park, Sung Yong,Lee, Se Byeong,Kim, Dae Yong,Kim, Taehyun,Shin, Kyung Hwan,Cho, Kwan Ho Wiley (John WileySons) 2008 Medical physics Vol.35 No.8
<P>The authors have developed an automatic quality assurance method based on computerized tomography (CT) data for physically manufactured proton range compensators. Eight range compensators used for proton therapy at their institution were scanned using CT and their depth distributions were compared with data provided by a proton treatment planning system (TPS). The depth difference (DD), distance to agreement (DTA), and a composite analysis (CA) indicating regions that passed either of the tests were used for depth verification. When the tolerance limits were set at 3 mm for DD and 1 mm for DTA, the average percentages of points exceeding the acceptance criteria for DD, DTA, and CA for the eight compensators were 9.0%, 5.3% and 3.2%, respectively. In general, the percentages of points exceeding the acceptance criteria were much higher in DD than in DTA analysis and mismatch of depth was greater in regions with high depth gradients. This is considered to arise mainly because of systematic errors such as the physical size of the drill, slight bending or slipping of the drill bit near high gradient regions, the limit of CT resolution, and the uncertainty in CT number. When the tolerance limit of DTA was increased from 1 to 2 mm, the average percentage of points exceeding the acceptance criteria for DTA was reduced from 5.3% to 0.9%. Their results show that depth comparison of proton range compensators based on CT images can provide more systematic data than does the current method, in which a representative group of drill points is measured manually.</P>
A new homogeneity index based on statistical analysis of the dose–volume histogram
Yoon, Myonggeun,Park, Sung Yong,Shin, Dongho,Lee, Se Byeong,Pyo, Hong Ryull,Kim, Dae Yong,Cho, Kwan Ho unknown 2007 Journal of applied clinical medical physics Vol.8 No.2
<P>The goal of the present study was to develop a new dose–volume histogram (DVH)– based homogeneity index for effectively evaluating the dose homogeneity of intensity‐modulated radiotherapy plans. The new index, called the sigma‐index (“<I>S</I>‐index”) is defined as the standard deviation of the normalized differential DVH curve. In a study of 16 patients with brain tumors at our institution, the <I>S</I>‐index was found to vary from 0.80 to 3.15. Our results showed that the <I>S</I>‐index provides a more reliable and accurate measure of dose homogeneity than that given by conventional methods. A guideline for evaluating the dose homogeneity of treatment plans based on the <I>S</I>‐index and its relation to equivalent uniform dose is discussed.</P><P>PACS numbers: 87.53.Xd, 87.53.Tf</P>
Effect of radiation scattering on dose uniformity in open and closed cell culture vessels
Yoon, Myonggeun,Park, Sung Yong,Shin, Jungwook,Kwak, Jungwon,Park, Junghun,Shin, Dongho,Park, Soah,Lee, Se Byeong,Lee, Doo Hyun,Shin, Kyung Hwan,Pyo, Hong Ryull,Kim, Joo-Young,Cho, Kwan Ho Informa Healthcare 2007 International Journal of Radiation Biology Vol.83 No.8
<P> Purpose: Dose uniformity in cell culture vessels such as Petri dishes and anoxic irradiation chambers is very important in radiobiological work as dose uniformity affects cell survival probabilities. In this study, we investigated X-ray dose inhomogeneity, caused by scattering, in typical culture vessels. Materials and methods: Three different cubic cell culture vessels, with side lengths of 10 cm, 15 cm and 20 cm, were designed and irradiated by X-rays of 6 MV and 15 MV at a source-to-surface distance (SSD) of 100 cm using a Varian 2100CD linear accelerator. Results: The relative X-ray dose distribution in a cell culture vessel depended strongly on whether the vessel had a lid. The percentage of the cell culture surface with the dose differing by more than 10% from the mean value of the dose was 43.4% in lidless vessels and 9.7% in lidded vessels. Conclusions: In radiobiological work, X-ray dose inhomogeneity within a cell culture vessel is not negligible and the placement of cells in the vessel should be carefully considered.</P>
Chung, Kwangzoo,Yoon, Myonggeun,Son, Jaeman,Yong Park, Sung,Lee, Kiho,Shin, Dongho,Kyung Lim, Young,Byeong Lee, Se The American Association of Physicists in Medicine 2013 Medical physics Vol.40 No.2
<P>To evaluate the transit dose based patient specific quality assurance (QA) of intensity modulated radiation therapy (IMRT) for verification of the accuracy of dose delivered to the patient.</P>
Biophysical Model Including a Potentially Lethal Damage Repair Parameter in Fractionated Carbon Beam
Choi Eunae,Yoon Myonggeun,Suzuki Masao,Matsufuji Naruhiro,Jung Wonguyn 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.2
The amount of potentially lethal damage repair (PLDR) is a significant factor in the process of modeling the survival curves of cells irradiated with fractionated carbon beams. Because the amount of PLDR generally depends on the features of the cells and the linear energy transfer (LET), the amount of PLDR of cells irradiated with fractionated carbon beams shows distinct differences from that of cells irradiated with X-rays. This study considered a new parameter dependent on the correlation between the PLDR trait (T) of the cells over a time interval (Δ) at the fractionated carbon beam irradiation. The survival curves of the cells irradiated with fractionated carbon beams n times were predicted using the ζ and the Ψ values from the delay assay. This study aims to overcome the barriers of traditional methods by developing a new survival curve model with new parameters based on an analysis of the PLDR traits of cells over time interval in fractionated carbon beam irradiation and to suggest a model that produces results significantly closer to the experimental data.
Shim Jina,Yoon Myonggeun,Lee Youngjin 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.11
This study aimed to quantitatively analyze the efciency of the fast non-local means (FNLM) flter in increasing the nodule detection sensitivity in pediatric chest computed tomography (CT) using 3D-printed lung nodules. For that purpose, we compared fltered back projection (FBP) with FNLM flter with iterative reconstruction (IR) method. The performance of the proposed FNLM flter was compared through various quantitative evaluations by modeling the previously used noise reduction methods. When the FNLM flter was applied to the acquired FBP reconstruction method-based CT image, the coefcient of variation and contrast-to-noise ratio values in the lung nodule region showed similar values to those of the IR method. In addition, it was demonstrated that the point spread function value that can evaluate sharpness can be improved by using the FNLM flter. In conclusion, the results of this study are expected to maximize the image quality and reduce the dose by fusing the CT image reconstructed by the FBP method and the FNLM flter with excellent characteristics.