• Progress in Medical Physics
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• v.20 no.4
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• pp.191-198
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• 2009

In this study, we evaluated an edge detector for small-beam dosimetry. We measured the dose linearity, dose rate dependence, output factor, beam profiles, and percentage depth dose using an edge detector (Model 1118 Edge) for 6-MV photon beams at different field sizes and depths. The obtained values were compared with those obtained using a standard volume ionization chamber (CC13) and photon diode detector (PFD). The dose linearity results for the three detectors showed good agreement within 1%. The edge detector had the best linearity of ${\pm}0.08%$. The edge detector and PFD showed little dose rate dependency throughout the range of 100~600 MU/min, while CC13 showed a significant discrepancy of approximately -5% at 100 MU/min. The output factors of the three detectors showed good agreement within 1% for the tested field sizes. However, the output factor of CC13 compared to the other two detectors had a maximum difference of 21% for small field sizes (${\sim}4{\times}4\;cm^2$). When analyzing the 20~80% penumbra, the penumbra measured using CC13 was approximately two times wider than that using the edge detector for all field sizes. The width measured using PFD was approximately 30% wider for all field sizes. Compared to the edge detector, the 10~90% penumbras measured using the CC13 and PFD were approximately 55% and 19% wider, respectively. The full width at half maximum (FWHM) of the edge detector was close to the real field size, while the other two detectors measured values that were 8~10% greater for all field sizes. Percentage depth doses measured by the three detectors corresponded to each other for small beams. Based on the results, we consider the edge detector as an appropriate small-beam detector, while CC13 and PFD can lead to some errors when used for small beam fields under $4{\times}4\;cm^2$.

• Progress in Medical Physics
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• v.21 no.1
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• pp.113-119
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• 2010

Software for GafChromic EBT2 film dosimetry was developed in this study. The software provides film calibration functions based on color channels, which are categorized depending on the colors red, green, blue, and gray. Evaluations of the correction effects for light scattering of a flat-bed scanner and thickness differences of the active layer are available. Dosimetric results from EBT2 films can be compared with those from the treatment planning system ECLIPSE or the two-dimensional ionization chamber array MatriXX. Dose verification using EBT2 films is implemented by carrying out the following procedures: file import, noise filtering, background correction and active layer correction, dose calculation, and evaluation. The relative and absolute background corrections are selectively applied. The calibration results and fitting equation for the sensitometric curve are exported to files. After two different types of dose matrixes are aligned through the interpolation of spatial pixel spacing, interactive translation, and rotation, profiles and isodose curves are compared. In addition, the gamma index and gamma histogram are analyzed according to the determined criteria of distance-to-agreement and dose difference. The performance evaluations were achieved by dose verification in the $60^{\circ}$-enhanced dynamic wedged field and intensity-modulated (IM) beams for prostate cancer. All pass ratios for the two types of tests showed more than 99% in the evaluation, and a gamma histogram with 3 mm and 3% criteria was used. The software was developed for use in routine periodic quality assurance and complex IM beam verification. It can also be used as a dedicated radiochromic film software tool for analyzing dose distribution.

• Progress in Medical Physics
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• v.3 no.2
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• pp.1-12
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• 1992

For intraoperative radiation therapy using electron beams, a cone system to deliver a large dose to the tumor during surgical operation and to save the surrounding normal tissue should be developed and dosimetry for the cone system is necessary to find proper X-ray collimator setting as well as to get useful data for clinical use. We developed a docking type of a cone system consisting of two parts made of aluminum: holder and cone. The cones which range from 4cm to 9cm with 1cm step at 100cm SSD of photon beam are 28cm long circular tubular cylinders. The system has two 26cm long holders: one for the cones larger than or equal to 7cm diamter and another for the smaller ones than 7cm. On the side of the holder is an aperture for insertion of a lamp and mirror to observe treatment field. Depth dose curve. dose profile and output factor at dept of dose maximum. and dose distribution in water for each cone size were measured with a p-type silicone detector controlled by a linear scanner for several extra opening of X-ray collimators. For a combination of electron energy and cone size, the opening of the X-ray collimator was caused to the surface dose, depths of dose maximum and 80%, dose profile and output factor. The variation of the output factor was the most remarkable. The output factors of 9MeV electron, as an example, range from 0.637 to 1.549. The opening of X-ray collimators would cause the quantity of scattered electrons coming to the IORT cone system. which in turn would change the dose distribution as well as the output factor. Dosimetry for an IORT cone system is inevitable to minimize uncertainty in the clinical use.

• The Journal of Korean Society for Radiation Therapy
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• v.34
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• pp.21-30
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• 2022

Purpose: The purpose of this study is to evaluate the effectiveness of oral positioning stent, the BinkieRT^TM in radiation treatment for head and neck cancer patients in terms of tongue positions reproducibility, tongue doses and material properties. Materials and Methods: 24 cases using BinkieRT^TM during radiation treatments were enrolled. The tongue was contoured on planning CT and CBCT images taken every 3 days during treatment, and then the DSC and center of tongue shift values were analyzed to evaluate the reproducibility of the tongue. The tongue dose was compared in terms of dose distribution when using BinkieRT^TM and different type of oral stents (mouthpiece, paraffin wax). Randomly selected respective 10 patients were measured tongue doses of initial treatment plan for nasal cavity and unilateral parotid cancer. Finally, In terms of material evaluation, HU and relative electron density were identified in RTPS. Results: As a result of DSC analysis, it was 0.8 ± 0.07, skewness -0.8, kurtosis 0.61, and 95% CI was 0.79~0.82. To analyze the deviation of the central tongue shift during the treatment period, a 95% confidence interval for shift in the LR, SI, and AP directions were indicated, and a one-sample t-test for 0, which is an ideal value in the deviation(n=144). As a result of the t-test, the mean and SD in the LR and SI directions were 0.01 ± 0.14 cm (p→.05), 0.03 ± 0.25 cm (p→.05), and -0.08 ± 0.25 cm (p ←.05) in the AP direction. In the case of unilateral parotid cancer patients, the Dmean to the tongue of patients using BinkieRT^TM was 16.92% ± 3.58% compared to the prescribed dose, and 23.99% ± 10.86% of patients with Paraffin Wax, indicating that the tongue dose was relatively lower when using BinkieRT^TM (p←.05). On the other hand, among nasal cavity cancer patients, the Dmean of tongue dose for patients who used BinkieRT^TM was 4.4% ± 5.6%, and for those who used mouthpiece, 5.9% ± 6.8%, but it was not statistically significant (p→.05). The relative electron density of Paraffin Wax, BinkieRT^TM and Putty is 0.94, 0.99, 1.26 and the mass density is 0.95, 0.99 and 1.32 (g/cc), Transmission Factor is 0.99, 0.98, 0.96 respectively. Conclusion: The result of the tongue DSC analysis over the treatment period was about 0.8 and Deviation of the center of tongue shifts were within 0.2 cm, the reproducibility was more likely excellent. In the case of unilateral head and neck cancer patients, it was found that the use of BinkieRT^TM rather than Paraffin Wax or Putty can reduce the unnecessary dose irradiated to the tongue. This study might be useful to understand of BinkieRT^TM's properties and advantages. And also it could be another considered option as oral stent to keep the reproducibility of tongue and reducing dose during head and neck radiation treatments.

• Journal of Radiation Protection and Research
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• v.23 no.3
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• pp.139-147
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• 1998

Purpose: Tissue inhomogeneity such as lung affects tumor dose as well as transmission dose in new concept of on-line dosimetry which estimates tumor dose from transmission dose using the new algorithm. This study was carried out to confirm accuracy of correction by tissue density in tumor dose estimation utilizing transmission dose. Methods: Cork phantom (CP, density $0.202\;gm/cm^3$) having similar density with lung parenchyme and polystyrene phantom (PP, density $1.040\;gm/cm^3$) having similar density with soft tissue were used. Dose measurement was carried out under condition simulating human chest. On simulating AP-PA irradiation, PPs with 3 cm thickness were placed above and below CP, which had thickness of 5, 10, and 20 cm. On simulating lateral irradiation, 6 cm thickness of PP was placed between two 10 cm thickness CPs additional 3 cm thick PP was placed to both lateral sides. 4, 6, and 10 MV x-ray were used. Field size was in the range of $3{\times}3$ cm through $20{\times}20$ cm, and phantom-chamber distance (PCD) was 10 to 50 cm. Above result was compared with another sets of data with equivalent thickness of PP which was corrected by density. Result: When transmission dose of PP was compared with equivalent thickness of CP which was corrected with density, the average error was 0.18 (${\pm}0.27$) % for 4 MV, 0.10 (${\pm}0.43$) % for 6 MV, and 0.33 (${\pm}0.30$) % for 10 MV with CP having thickness of 5 cm. When CP was 10 cm thick, the error was 0.23 (${\pm}0.73$) %, 0.05 (${\pm}0.57$) %, and 0.04 (${\pm}0.40$) %, while for 20 cm, error was 0.55 (${\pm}0.36$) %, 0.34 (${\pm}0.27$) %, and 0.34 (${\pm}0.18$) % for corresponding energy. With lateral irradiation model, difference was 1.15 (${\pm}1.86$) %, 0.90 (${\pm}1.43$) %, and 0.86 (${\pm}1.01$) % for corresponding energy. Relatively large difference was found in case of PCD having value of 10 cm. Omitting PCD with 10 cm, the difference was reduced to 0.47 (${\pm}$1.17) %, 0.42 (${\pm}$0.96) %, and 0.55 (${\pm}$0.77) % for corresponding energy. Conclusion When tissue inhomogeneity such as lung is in tract of x-ray beam, tumor dose could be calculated from transmission dose after correction utilizing tissue density.

• Journal of the Korean Society of Radiology
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• v.11 no.2
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• pp.139-144
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• 2017

Percutaneous vertebroplasty (PVP) is increasingly used to treat osteoporotic vertebral fractures, myeloma and osteolytic vertebral metastases. The purpose of this study was to measure the absorbed radiation exposure dose and time during PVP and to assess the possibility of deterministic radiation effects to the operator and patient. The radiation dose and time measure by three pain physicians performed consecutive procedures using the twenty case PVP. Patient's dosimeter placed at the anteroposterior(AP) side was treatment of the vertebra body located in the upper level 2-3 and lateral(LAT) side was flank proximal to C-arm tube of back. Operator's dosimeter placed at the apron outside of upper sternum (thyroid), left chest, lower extremity and apron inside of left chest. Results: Radiation exposure times were $3.6{\pm}0.71min$. Measurements on the Patient radiation dose were AP $121.4{\pm}48.1{\mu}Sv$, LAT side $614.7{\pm}177.1{\mu}Sv$. Operator radiation dose were outside of the lead apron upper sternum $33.7{\pm}7.3{\mu}Sv$, outside of the lead apron chest $49.2{\pm}15.0{\mu}Sv$, outside of the lead apron lower extremity $12.8{\pm}3.8{\mu}Sv$ and inside of the lead apron chest $4.2{\pm}1.4{\mu}Sv$. To escape from the danger of radiation first long distance from the c-arm tube second exposure time reduced second lead apron used fluoroscopy during PVP is more safety patient and operation from the radiation exposure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.442-448
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• 2016

This study was conducted to determine the appropriateness of systemic radiation exposure control for students in clinical practice by comparing radiation exposure in radiography employees at different stations of a hospital with that of students conducting clinical practice using identical stations. Overall, 121 students who conducted clinical practice in the department of radiology area of C university hospital from July 2014 to August 2014 and 62 workers working in the same medical facility (47 in the department of radiology, 8 in the department of radiation oncology, 7 in the department of nuclear medicine) were investigated. The radiation exposure experienced by students was measured for 8 weeks, which is the duration of the clinical practice. Additionally, radiation exposure of workers were classified into 4 groups, department of radiology, department of radiation oncology, and department of nuclear medicine was compared. Dose was measured with OSLD and differences among groups were identified by ANOVA followed by Duncan's multiple range test. Among employees, those in the department of radiology, oncology and nuclear medicine were exposed depth doses of $0.127{\pm}0.331mSv$, $0.01{\pm}0.003mSv$, and $0.431{\pm}0.205mSv$, respectively, while students were exposed to $0.143{\pm}0.136mSv$. Additionally, workers in the department of radiology, oncology and nuclear medicine were exposed to surface doses of $0.131{\pm}0.331mSv$, $0.009{\pm}0.003mSv$, and $0.445{\pm}0.198mSv$, respectively, while students were exposed to $0.151{\pm}0.14mSv$, which was significantly different in both doses (p < 0.01). The average dose that students received is higher than that of the other groups (except for nuclear medicine workers), indicating that further improvements must be made in systemic controls for individual radiation exposure by including the students as subjects of management for protection from radiation.

• Nuclear Engineering and Technology
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• v.25 no.4
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• pp.561-569
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• 1993

DOT4.2-QAD-CG coupling method was used to analyze the dose rates outside the side and the bottom shield system of CANDU 6 plant. The average dose rates at the main airlock and the new fuel loading area are approximately 6 $\mu$Sv/h as it is required. The calculated dose rates have a good agreement with the measurements at the operating CANDU 6 plant. The method used in this paper can be applied to the radiation shielding analysis of Wolsong 2, 3, and 4 CANDU 6 type plants which will be constructed in the near future.

• Radiation Oncology Journal
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• v.9 no.2
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• pp.319-324
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• 1991

In our institution, a 76-year-old woman with primary urethral carcinoma was treated with remote afterloading high dose rate (HDR) interstitial brachytherapy using micro selectron Ir-192. In this paper, authors described the technical aspect of remote afterloading HDR interstitial brachytherapy for female urethal cancer.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.3
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• pp.582-586
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• 2004

Cooked rice for immunosuppressed patients was irradiated at 0, 5 and 10 kGy, and investigated on the irradiation effect on color, texture, and shelf-life during storage at 3$0^{\circ}C$. Yellowness was significantly increased in cooked rice with the increase of storage period and irradiation dose (p<0.05) and the ratio of adhesiveness/hardness of cooked rice was decreased by irradiation at 10 kGy. The result of total plate count of non-irradiated cooked rice was 7 log CFU/g and that of 5 kGy irradiated cooked rice on 7 day storage was 4 log CFU/g, while that of 10 kGy irradiated sample was not detected even at the end of storage. Irradiation with 5 kGy on cooked rice is proper to prolong the shelf-life considering color, texture, and it was extended to over a month. Further research is necessary to apply the high-dose irradiation for long-term preservation to inhibit color and texture change.