• 한국의학물리학회지:의학물리
• /
• 제31권4호
• /
• pp.135-144
• /
• 2020

Purpose: Gafchromic films for proton dosimetry are dependent on linear energy transfers (LETs), resulting in dose underestimation for high LETs. Despite efforts to resolve this problem for single-energy beams, there remains a need to do so for multi-energy beams. Here, a bimolecular reaction model was applied to correct the under-response of spread-out Bragg peaks (SOBPs). Methods: For depth-dose measurements, a Gafchromic EBT3 film was positioned in water perpendicular to the ground. The gantry was rotated at 15° to avoid disturbances in the beam path. A set of films was exposed to a uniformly scanned 112-MeV pristine proton beam with six different dose intensities, ranging from 0.373 to 4.865 Gy, at a 2-cm depth. Another set of films was irradiated with SOBPs with maximum energies of 110, 150, and 190 MeV having modulation widths of 5.39, 4.27, and 5.34 cm, respectively. The correction function was obtained using 150.8-MeV SOBP data. The LET of the SOBP was then analytically calculated. Finally, the model was validated for a uniform cubic dose distribution and compared with multilayered ionization chamber data. Results: The dose error in the plateau region was within 4% when normalized with the maximum dose. The discrepancy of the range was <1 mm for all measured energies. The highest errors occurred at 70 MeV owing to the steep gradient with the narrowest Bragg peak. Conclusions: With bimolecular model-based correction, an EBT3 film can be used to accurately verify the depth dose of scanned proton beams and could potentially be used to evaluate the depth-dose distribution for patient plans.

• Asian-Australasian Journal of Animal Sciences
• /
• 제32권2호
• /
• pp.274-281
• /
• 2019

Objective: The objective of this study was to estimate the risk of Campylobacter jejuni (C. jejuni) infection from various jerky products in Korea. Methods: For the exposure assessment, the prevalence and predictive models of C. jejuni in the jerky and the temperature and time of the distribution and storage were investigated. In addition, the consumption amounts and frequencies of the products were also investigated. The data for C. jejuni for the prevalence, distribution temperature, distribution time, consumption amount, and consumption frequency were fitted with the @RISK fitting program to obtain appropriate probabilistic distributions. Subsequently, the dose-response models for Campylobacter were researched in the literature. Eventually, the distributions, predictive model, and dose-response model were used to make a simulation model with @RISK to estimate the risk of C. jejuni foodborne illness from the intake of jerky. Results: Among 275 jerky samples, there were no C. jejuni positive samples, and thus, the initial contamination level was statistically predicted with the RiskUniform distribution [RiskUniform (-2, 0.48)]. To describe the changes in the C. jejuni cell counts during distribution and storage, the developed predictive models with the Weibull model (primary model) and polynomial model (secondary model) were utilized. The appropriate probabilistic distribution was the BetaGeneral distribution, and it showed that the average jerky consumption was 51.83 g/d with a frequency of 0.61%. The developed simulation model from this data series and the dose-response model (Beta Poisson model) showed that the risk of C. jejuni foodborne illness per day per person from jerky consumption was $1.56{\times}10^{-12}$. Conclusion: This result suggests that the risk of C. jejuni in jerky could be considered low in Korea.

• 한국의학물리학회지:의학물리
• /
• 제31권2호
• /
• pp.9-19
• /
• 2020

Purpose: This study aims to develop a multi-purpose electron beam irradiation device for preclinical research and material testing using the research electron linear accelerator installed at the Dongnam Institute of Radiological and Medical Sciences. Methods: The fabricated irradiation device comprises a dual scattering foil and collimator. The correct scattering foil thickness, in terms of the energy loss and beam profile uniformity, was determined using Monte Carlo calculations. The ion-chamber and radiochromic films were used to determine the reference dose-rate (Gy/s) and beam profiles as functions of the source to surface distance (SSD) and pulse frequency. Results: The dose-rates for the electron beams were evaluated for the range from 59.16 Gy/s to 5.22 cGy/s at SSDs of 40-120 cm, by controlling the pulse frequency. Furthermore, uniform dose distributions in the electron fields were achieved up to approximately 10 cm in diameter. An empirical formula for the systematic dose-rate calculation for the irradiation system was established using the measured data. Conclusions: A wide dose-rate range electron beam irradiation device was successfully developed in this study. The pre-clinical studies relating to FLASH radiotherapy to the conventional level were made available. Additionally, material studies were made available using a quantified irradiation system. Future studies are required to improve the energy, dose-rate, and field uniformity of the irradiation system.

• Asian Pacific Journal of Cancer Prevention
• /
• 제17권2호
• /
• pp.785-789
• /
• 2016

A key drug for treatment of EGFR mutation-positive non-small cell lung cancer is epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI). While the dosage of many general anti-tumor drugs is adjusted according to the patient body surface area, one uniform dose of most TKIs is recommended regardless of body size. In many cases, dose reduction or drug cessation is necessary due to adverse effects. Disease control, however, is frequently still effective, even after dose reduction. In this study, we retrospectively reviewed the characteristics of 26 patients at Fukuoka University Hospital between January 2004 and January 2015 in whom the EGFR-TKI dose was reduced with respect to progression free survival and overall survival. There were 10 and 16 patients in the gefitinib group and the erlotinib group, respectively. The median progression-free survival in the gefitinib group and the erlotinib group was 22.4 months and 14.1 months, respectively, and the median overall survival was 30.5 months and 32.4 months, respectively. After stratification of patients by body surface area, the overall median progression-free survival was significantly more prolonged in the low body surface area (<1.45 m2) group (25.6 months) compared to the high body surface area (>1.45 m2) group (9.7 months) (p=0.0131). These results indicate that low-dose EGFR-TKI may sufficiently control disease without side effects in lung cancer patients with a small body size.

• Nuclear Engineering and Technology
• /
• 제54권4호
• /
• pp.1414-1420
• /
• 2022

High dose rate (HDR) brachytherapy treatment planning usually involves optimization methods to deliver uniform dose to the target volume and minimize dose to the healthy tissues. Four optimizations were used to evaluate the high-risk clinical target volume (HRCTV) coverage and organ at risk (OAR). Dose-volume histogram (DVH) and dosimetric parameters were analyzed and evaluated. Better coverage was achieved with PGO (mean CI = 0.95), but there were no significant mean CI differences than GrO (p = 0.03322). Mean EQD₂ doses to HRCTV (D₉₀) were also superior for PGO with no significant mean EQD₂ doses than GrO (p = 0.9410). The mean EQD₂ doses to bladder, rectum, and sigmoid were significantly higher for NO plan than PO, GrO, and PGO. PO significantly reduced the mean EQD₂ doses to bladder, rectum, and sigmoid but compromising the conformity index to HRCTV. PGO was superior in conformity index (CI) and mean EQD₂ doses to HRCTV compared with the GrO plan but not statistically significant. The mean EQD₂ doses to the rectum by PGO plan slightly exceeded the limit from ABS recommendation (mean EQD₂ dose = 78.08 Gy EQD₂). However, PGO can shorten the treatment planning process without compromising the CI and keeping the OARs dose below the tolerance limit.

• 한국전기전자재료학회논문지
• /
• 제24권6호
• /
• pp.504-509
• /
• 2011

The conducting current of non-uniform plasma immersed electrode consists of ion current and secondary electron emission current caused by the impinging ion current. The ion current is determined by the ion dose passing through the sheath in front of electrode and the ion distribution in front of the electrode plays an important role in the secondary electron emission. The investigation of the distributed plasma and secondary electron effect on electrode ion current was carried out as the stainless steel electrode plugged with quartz tube was immersed in the inductively coupled Ar plasma using the antenna powered by 1 kw and the density profile was measured. After that, the negative voltage was applied by 1 kV~6 kV to measure the conduction current for the analysis of ion current.

• 대한안전경영과학회지
• /
• 제11권3호
• /
• pp.57-61
• /
• 2009

Garbage cause an environmental pollution, unsightly mess, fouls an odor, and unpleasant feeling. Various measures to solve the problems are studying. And the garbage are collected and treated by the street cleaner. Street cleaner is working for long time in the street from dawn to the night. And many kind of accidents are aroused, like traffic and crushing accident by garbage truck. This kind of accidents is increased every year. To prevent the accident, street cleaner wear a fluorescent light uniform But a count measures for the fallen accident and crushing accident from the garbage truck are insufficient. In addition, a street cleaner dose not like to wear a working uniform because of inconvenience. Therefore this study try to find a safety system of garbage truck for reducing measure of accidents of street cleaner.

• Radiation Oncology Journal
• /
• 제12권2호
• /
• pp.233-241
• /
• 1994

연구목적 : 전신방사선조사시 인체내에 균등한 선량분포를 얻기 위하여 조직보상체를 제작하고 그에따른 선량 분포를 확인하고자 하였다. 대상 및 방법 : 0.8mm두께의 납판을 이용한 조직보상체와, 1mm 및 5mm 두에의 알루미늄판을 이용한 조직보상체를 두경부와 하지 두 부분에 대하여 각각 제작하였다. 좌우 대향전신조사시 각 신체부위에 따른 선량분포의 측정을 위하여 파라핀으로 성인 크기의 인체 모형을 실제 치료시의 체위와 비슷하게 만들어 사용하였다. 방사선은 10MV X-ray(CLIAC 1800. Varian Co., USA)를, 측정기구는 exposure/exposure rate meter(model 192, Capintec, Inc., USA)with ionization chamber(PR 05)를 이용하였고 SAD 360cm에 파라핀 팬텀의 정중선을 맞추고 기하학적 방사선조사야는 $144{\times}144cm^2$으로하여 전신이 포함되도록 하였으며 head, mouth, mid-neck, sternal notch. mid-mediastinum, xiphoid, umbilicus. pelvis. thigh. knee 및 ankle부위에서 midline absorbed dose를 각각 측정하였다. 흉부의 선량 측정에는 조직등가물질로 제작된 상업용 humanoid 팬텀에서 $1{\times}1{\times}6mm^3$부피의 TLD rod(LiF, Harshaw Co.. Netherland)를 이용하였다. 결과 : Umbilicus를 기준으로 하였을때 조직보상체를 적용하지 않은 경우 흡수선량은 $-11.8\%$에서 $21.1\%$까지의 차이를 보였다. 어깨가 포함되는 sternal notch에서의 선량은 $11.8\%$감소하였다. 조직보상체를 적용한 경우의 흡수선량은 0.8mm 납보상체의 경우 mid-neck에서 $-7.9\%$, 그외 다른 부위는 $+1.3\%$에서 $-5.3\%$가지 였다. 그리고 1mm 및 5mm 알루미늄 보상체를 적용한 경우 ankle부위에서 $5.3\%$. 그외 다른 부위는 $-2.6\%$에서 $2.6\%$가지의 흡수선량 차이를 보였다. 결론 : 납과 알루미늄으로 제작한 전신방사선조사용 조직보상체는 선량기준점인 umbilicus선량에 비교하였을 때 두경부와 하지에 있어서 비교적 만족할만한 보상효과를 나타내었다. 어깨가 있는 상흉부에서는 선량이 $11.8\%$ 정도 감소하므로 환자의 lateral thickness 차이에 따라 선량기준점을 sternal notch로 선택하거나 boost irradiation이 고려되어야함을 알 수 있었다.

• 한국의학물리학회지:의학물리
• /
• 제28권1호
• /
• pp.33-38
• /
• 2017

Creating individualized build-up material for superficial photon beam radiation therapy at irregular surface is complex with rice or commonly used flat shape bolus. In this study, we implemented a workflow using 3D printed patient specific bolus and describe our clinical experience. To provide better fitted build-up to irregular surface, the 3D printing technique was used. The PolyLactic Acid (PLA) which processed with nontoxic plant component was used for 3D printer filament material for clinical usage. The 3D printed bolus was designed using virtual bolus structure delineated on patient CT images. Dose distributions were generated from treatment plan for bolus assigned uniform relative electron density and bolus using relative electron density from CT image and compared to evaluate the inhomogeneity effect of bolus material. Pretreatment QA is performed to verify the relative electron density applied to bolus structure by gamma analysis. As an in-vivo dosimetry, Optically Stimulated Luminescent Dosimeters (OSLD) are used to measure the skin dose. The plan comparison result shows that discrepancies between the virtual bolus plan and printed bolus plan are negligible. (0.3% maximum dose difference and 0.2% mean dose difference). The dose distribution is evaluated with gamma method (2%, 2 mm) at the center of GTV and the passing rate was 99.6%. The OSLD measurement shows 0.3% to 2.1% higher than expected dose at patient treatment lesion. In this study, we treated Mycosis fungoides patient with patient specific bolus using 3D printing technique. The accuracy of treatment plan was verified by pretreatment QA and in-vivo dosimetry. The QA results and 4 month follow up result shows the radiation treatment using 3D printing bolus is feasible to treat irregular patient skin.

• 대한방사선치료학회지
• /
• 제23권2호
• /
• pp.91-96
• /
• 2011

목 적: 전신조사방사선치료를 시행한 환자에서 체질량지수와 열형광선량계를 이용한 선량측정 정보를 비교 분석하여 환자에게 보다 균등한 선량을 조사하고자 한다. 대상 및 방법: 2006년부터 2011년 8월까지 전신조사방사선치료를 시행한 환자 28명을 대상으로 하였다. 각 환자는 열형광선량계를 이용하여 두부, 경부, 흉부, 복부, 골반부, 대퇴부, 슬관절부, 족관절부에서 선량을 측정하였다. 각각의 환자에 대하여 처방 중심점인 복부점과 각 측정점에서의 선량측정치를 비교하였고, 선량기준이 되는 복부점의 측정값과 환자의 체질량지수를 비교 분석하였다. 결 과: 28명 환자에서 처방에 기준이 되는 중심점인 복부선량은 평균 $100.6{\pm}5.5%$이었고, 복부점과 다른 7개의 측정점 평균값과의 최대 차이는 두부, 경부, 흉부, 골반부, 대퇴부, 슬관절부, 족관절부에서 각각 $92.8{\pm}4.2%$, $97.6{\pm}6.2%$, $96.4{\pm}5.5%$, $102.6{\pm}5.3%$, $103.4{\pm}7.9%$, $95.8{\pm}5.9%$, $96.1{\pm}5.5%$였다. 각각의 환자에 대하여 복부점의 선량과 환자의 체질량지수와 관계를 산점도(scatter plot)로 나타내고 선형관계를 회귀분석 한 결과, 회귀직선은 선량(y)=-1.009 BMI (x)＋123.3이고 $R^2$값은 0.697로 나타났다. 결 론: 전신방사선치료시 열형광선량계로 측정된 자료를 바탕으로 선량을 평가하였고 분석 결과 처방 선량에 대하여 기준이 되는 복부선량은 평균 $100.6%{\pm}5.5%$로 만족하였다. 본 실험결과 체질량지수와 선량과의 관계 분석을 통하여 얻은 정보에 따라 체질량지수가 높은 환자에 대하여 보정 값을 적용한다면 보다 균등한 선량을 달성할 수 있을 것으로 사료된다.