• Radiation Oncology Journal
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• v.21 no.1
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• pp.35-43
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• 2003

Purpose :To analyze the survival period, prognostic factors and complications of patients having undergone high-dose-rate intraluminal brachytherapy (HDR-ILB) as a salvage radiation therapy, while having a catheter, for percutaneous transhepatic billary drainage (PTBD), inserted due to biliary obstruction caused by a secondary malignant biliary tumor Methods and Materials : A retrospective study was performed on 24 patients having undergone HDR-ILB, with PTBD catheter Insertion, be)ween December 1992 and August 2001. Their median age was 58.5, ranging from 35 to 82 years. The primary cancer site were the stomach, gallbladder, liver, pancreas and the colon, with 12, 6, 3, 2 and 1 cases, respectively. Eighteen patients were treated with external beam radiation therapy and HDR-lLB, while slx were treated with HDR-lLB only. The 4otal external beam, and brachytherapy radiations dose were 30$\~$61.2 and 9$\~$30 Gy, with median doses of 50 and 15 Gy, respectively. Results : Of the 24 patients analyzed, 22 died during the follow-up period, with a median survival of 7.3 months. The 6 and 12 months survival rates were 54.2 (13 patients) and 20.8$\%$ (5 patients), respectively. The median survivals for stomach and gailbladder cancers were 7.8 and 10.2 months, respectively, According to the unlvariate analysis, a significant factor affecting survival of over one year was the total radiation dose (over 50 Gy) (o=0.0200), with all )he patients surviving more than one year had been Irradiated with more than 50 Gy. The acute side effects during the radiation therapy were managed with conservative treatment. During the follow-up period, 5 patients showed symptoms of cholangltis due to the radiation therapy Conclusion :An extension to the survival of those patients treated with HDR-ILB is suggested compared to the median historical survival of 4hose patients treated with external biliary drainage. A boost radiation dose could be effectively given, by performing HDR-lLB, which is a prognostic factor In addition, the acute complications of radiation therapy were effectively controlled by conservative management, and It could be regarded as a safe treatment.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.1
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• pp.1-10
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• 2012

Purpose: To evaluate dose distribution differences when the dose rates are randomly changed in intensity-modulated radiation therapy using a dynamic multileafcollimator. Materials and Methods: Two IMRT treatment plans including small-field and large-field plans were made using a commercial treatment planning system (Eclipse, Varian, Palo Alto, CA). Each plan had three sub-plans according to various dose rates of 100, 400, and 600 MU/min. A chamber array (2D-Array Seven729, PTW-Freiburg) was positioned between solid water phantom slabs to give measurement depth of 5 cm and backscattering depth of 5 cm. Beam deliveries were performed on the array detector using a 6 MV beam of a linear accelerator (Clinac 21EX, Varian, Palo Alto, CA) equipped with 120-leaf MLC (Millenium 120, Varian). At first, the beam was delivered with same dose rates as planned to obtain reference values. After the standard measurements, dose rates were then changed as follows: 1) for plans with 100 MU/min, dose rate was varied to 200, 300, 400, 500 and 600 MU/min, 2) for plans with 400 MU/min, dose rate was varied to 100, 200, 300, 500 and 600 MU/min, 3) for plans with 600 MU/min, dose rate was varied to 100, 200, 300, 400 and 500 MU/min. Finally, using an analysis software (Verisoft 3.1, PTW-Freiburg), the dose difference and distribution between the reference and dose-rate-varied measurements was evaluated. Results: For the small field plan, the local dose differences were -0.8, -1.1, -1.3, -1.5, and -1.6% for the dose rate of 200, 300, 400, 500, 600 MU/min, respectively (for 100 MU/min reference), +0.9, +0.3, +0.1, -0.2, and -0.2% for the dose rate of 100, 200, 300, 500, 600 MU/min, respectively (for 400 MU/min reference) and +1.4, +0.8, +0.5, +0.3, and +0.2% for the dose rate of 100, 200, 300, 400, 500 MU/min, respectively (for 600 MU/min reference). On the other hand, for the large field plan, the pass-rate differences were -1.3, -1.6, -1.8, -2.0, and -2.4% for the dose rate of 200, 300, 400, 500, 600 MU/min, respectively (for 100 MU/min reference), +2.0, +1.8, +0.5, -1.2, and -1.6% for the dose rate of 100, 200, 300, 500, 600 MU/min, respectively (for 400 MU/min reference) and +1.5, +1.9, +1.7, +1.9, and +1.2% for the dose rate of 100, 200, 300, 400, 500 MU/min, respectively (for 600 MU/min reference). In short, the dose difference of dose-rate variation was measured to the -2.4~+2.0%. Conclusion: Using the Varian linear accelerator with 120 MLC, the IMRT dose distribution is differed a little <(${\pm}3%$) even though the dose-rate is changed.

• Journal of radiological science and technology
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• v.39 no.2
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• pp.237-246
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• 2016

This study is therefore aimed at measuring the surface dose rate and the spatial dose rate in and outside the radionuclide facility in order to ensure safety of the patients, radiation workers and family care-givers in their use of such equipment and to provide a basic framework for further research on radiation protection. The study was conducted at 4 restrooms in and outside the radionuclide facility of a general hospital in Incheon between May 1 and July 31, 2014. During the study period, the spatial contamination dose rate and the surface contamination dose rate before and after radiation use were measured at the 4 places-thyroid therapy room, PET center, gamma camera room, and outpatient department. According to the restroom use survey by hospitals, restrooms in the radionuclide facility were used not only by patients but also by family care-givers and some of radiation workers. The highest cumulative spatial radiation dose rate was 8.86 mSv/hr at camera room restroom, followed by 7.31 mSv/hr at radioactive iodine therapy room restroom, 2.29 mSv/hr at PET center restroom, and 0.26 mSv/hr at outpatient department restroom, respectively. The surface radiation dose rate measured before and after radiation use was the highest at toilets, which are in direct contact with patient's excretion, followed by the center and the entrance of restrooms. Unsealed radioactive sources used in nuclear medicine are relatively safe due to short half lives and low energy. A patient who received those radioactive sources, however, may become a mobile radioactive source and contaminate areas the patient contacts-camera room, sedation room, and restroom-through secretion and excretion. Therefore, patients administered radionuclides should be advised to drink sufficient amounts of water to efficiently minimize radiation exposure to others by reducing the biological half-life, and members of the public-family care-givers, pregnant women, and children-be as far away from the patients until the dose remains below the permitted dose limit.

• Progress in Medical Physics
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• v.9 no.4
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• pp.259-266
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• 1998

To achieve the 2D dose distribution around the designed high dose rate Ir-192 source substitution for Co-60 brachytherapy source, we determined the exposure rate constant and tissue attenuation factors as a large depth as a 20 cm from source center. The exposure rate constant is used for apparent activity in designed source with self-absorption and encapsulation steel wall. The tissue dose delivered from the 4401 segments of 2.5 mm in a diameter and 2.5 mm height of disk-type source layer. In the experiments, the tissue attenuation factors include the tissue attenuation and multiple scattering in a medium surrounding the source. The fitted the polynomial regression with 4th order for the tissue attenuation factors are very closed to the experimental measurement data within ${\pm}$1% discrepancy. The Meisberger's constant showed the large uncertainty in large distance from source. The exposure rate constant 4.69 Rcm$^2$/mCi-hr was currently used for determination of apparent activity of source and air kerma strength was obtained 0.973 for tissue absorbed dose from the energy spectrum of Ir-192 source. In our experiments with designed high dose rate brachytherapy source, the apparent activity of Ir-192 source was delivered from the 54.6 % of actual physical source activity through the self-absorption and encapsulation wall attenuations. This paper provides the 2-dimensional dose tabulation from unit apparent activity in a water medium for dose planning includes the multiple scattering, source anisotropy effect and geometric factors.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.187-190
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• 2000

Effects of gamma ionizing radiation on recombinant Escherichia coli cells containing stress promoters, recA, fabA, grpE, or katG, fused to luxCDABE originated from Vibrio fischeri were characterized by monitoring transcriptional responses reflected by bioluminescent output. Quantification of gamma-ray intensity may be possible using the recA and fabA promoter fusion since a linear enhancement of bioluminescence emission with increasing gamma-ray intensity was observed. Other strains sensitive to either oxidative stress (DPD2511, katG::luxCDABE) or protein-damaging stress (TV1061, grpE::luxCDABE) were also irradiated by gamma-rays, and resulted in no noticeable bioluminescent output while DPD2794 with recA promoter and DPD2540 with fabA promoter irradiated by the same intensities of gamma-rays gave a significant bioluminescent output. This indicates that the main stresses in the recombinant bacteria caused by ionizing radiation are DNA and membrane-damage, not protein- or oxidative-damage. In addition, in this study, to investigate the relationship between the radiation dose rate and bacterial responses, two recombinant Escherichia coli strains, DPD2794 and GC2, containing lac promoter fused to luxCDABE originating from Photorhapdus luminescences, were used for detecting DNA damage and cellular toxicity under various radiation dose rates. Throughout this study, it was found that these bacteria showed quantitative stress responses to DNA damage and general toxicity caused by gamma rays, depending on the radiation dose rates, indicating that the bacterial stress responses and general toxicity were seriously influenced according to radiation dose rates.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3347-3352
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• 2010

It is recommended that the door of control room is closed during radiography to protect a radiologic technologist. However, for those patients such as of emergency or pediatrics, the door must be kept open unavoidably to apply immediate medical administration and treatment on the potential case of emergency which could be happened through the course of radiography. In addition, it could be efficient by reducing patients waiting time when the door is open for a general case. This study was conducted to evaluate practical exposure rate to a radiologic technologist when the door is open during the radiography, and to find out the ways to minimize radiation exposure and to increase the efficiency simultaneously. Measuring practical exposure rate was fulfilled with glass dosimeter, and it was 2.02 mGy/week at the location of radiologic technologist under the condition that the door is open during the radiography, which was about 2.3 times higher than the 100 mR/week. It means that the considerable amount of scattered rays through the door opening, and increase exposure rate at the radiologic technologist. Hence we confirmed that a radiologic technologist probably overexposed if the door is open during the radiography. It was also confirmed by the Monte Carlo simulation that the exposure rate could be reduced up to approximately 1/100 by change only the door opening direction. In conclusion, since the proper door opening direction provides same shielding effect whether it is open or close, the door opening direction need to be considered when it is installed at radiography facilities.

• Radiation Oncology Journal
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• v.17 no.3
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• pp.179-187
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• 1999

Brachytherapy has been proved to be an effective method for the purpose of increasing radiation dose to the tumor and reducing the dose to the surrounding normal tissue. In head and neck cancer, the rationale of brachytherapy is as follows; Firstly, early small lesion is radiocurative and the major cause of failure is local recurrence. Seondly, it can diminish evidently the dose to the normal tissue especially masseteric muscle and salivary gland. Thirdly, the anatomy of head and neck is suitable to various technique of brachytherapy. On background of accumulated experience of LDR iridium brachytherapy of head and neck cancer for the last 15 years, the author reviewed the history of radioisotope therapy, the characteristics of radionuclides, and some important things in the method, clinical technique and treatment planning. The author analyzed the clinical result of 185 cases of head and neck cancer treated in the Korea Cancer Center Hospital. Finally the future prospect of brachytherapy of head and neck cancer is discussed.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2009.06a
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• pp.452-452
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• 2009

• Journal of radiological science and technology
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• v.38 no.3
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• pp.237-244
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• 2015

Health professionals in nuclear medicine were known that they get high radiation exposure. To reduce radiation exposure, using shielding materials is needed. In this study, we analyzed the shielding effect about apron during 18F-FDG treatment by using simulation based on Monte Carlo techniques and actual measurement. As a result, absorbed dose distribution of organ varies with handling position of the source. Dose reduction ratio by lead thickness of apron tended to decease, when handling position of the source come close to organ and away from radiation source for simulation. In the case of actual measurement with the dosimetry device, It showed that mean spatial dose distribution was different due to characteristics of dosimetry device. However, spatial dose rate was exponentially reduced according to distance with increasing lead content.

• Journal of the Korean Society of Radiology
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• v.7 no.3
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• pp.251-257
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• 2013

Spatial dose rates of high dose $^{131}I$ therapy patients were Measured Three dimensional (X, Y, Z) distributions. I have constructed geometrical an aluminum support structure for spatial dose meters placed in 5 different heights, 8 different azimuthal angles, 6 different time interval and distance 100 cm from High dose$^{131}I$ therapy patients. when the height of vertical plane Spatial dose distribution is 100 cm, the Spatial dose rates is max and the error range is low. the vertical plane Spatial dose rates was found to be 71.85 ${\mu}Sv/h$ on the average at a distance of 100 cm, height 100 cm, from the patients 24 hours after $^{131}I$ oral administration. I divided 12 patients into two groups. I have analysed group A (drinking 5 L water) and group B (drinking 3 L water) in order to measure decrease spatial dose rates. I have found the spatial distributions of patient dose rates is $44.9{\pm}7.2$ ${\mu}Sv/h$ in group A and $100.3{\pm}8.1$ ${\mu}Sv/h$ in group B by 24 after $^{131}I$ oral administration. the reduction factor was found to be approximately 54 % through drinking 5 L water during 24 hours.