• Korean Journal of Environmental Biology
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• v.24 no.4
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• pp.387-391
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• 2006

Computational and experimental dosimetry of Henschke applicator with respect to high dose rate brachytherapy using the MIRD phantom and a remote control afterloader were performed. A comparison of computational dosimetry was made between the simulated Monte Carlo dosimetry and GAMMADOT brachytherapy Planning system's dosimetry. Dose measurements was performed using ion chamber in a water phantom. Dose rates are calculated using Monte Carlo code MCNP4B and the GAMMADOT. Thecomputational models include the detailed geometry of Ir-192 source, tandem tube, and shielded ovoids for accurate estimation. And transit dose delivered during source extension to and retraction from a given dwell position was estimated by Monte Carlo simulations. Point doses at ICRU bladder/rectal pointswhich have been recommened by ICRU 38 was assessed. Calculated and measured dose distribution data agreed within 4% each other. The shielding effect of ovoids leads to 19% and 20% dose reduction at bladder surface and rectal points.

• Radiation Oncology Journal
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• v.2 no.1
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• pp.11-20
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• 1984

The renewed interest in the use of hyperthermia in cancer therapy is bases on radiobiological and clinical evidence indicated that there may be a significant therapeutic advantage with the use of heat alone or combined with radiation or chemotherapy, There are many methods for generating heat for localized tumor as like radiofrequency, microwave, electromagnetic induction and ultrasound. But it is very difficult to be even thermal dose distribution and stable output of power and then the detection of temperature in tumor is difficult to be precise with thermocouples and semiconductor sensors. We designed the microwave heating generator, dipole antenna applicators and autometic temperature controlled thermocouples for localized hyperthermia on skin and in cavities. 1. The microwave generator with 120 W, 2,450MHz magnetron could be heating up to $40^{\circ}C\~50^{\circ}C\;for\;1\~2$ hours in living tissues. 2. The thermal dose distribution in tissue with microwave was described $42^{\circ}C\~44^{\circ}C$ with in 3 cm depth and $2\~6cm$ diameter area. 3. Skin surface heating applicator with spiral 3 times wave length antenna radiated high Power of microwave. 4, Intracavitary heating applicator with dipole antenna with autometic control temperature sensor kept up continuously constant temperature in tissue. 5. For constant thermal distribution, applied two steps power with 10W microwave after $17\~20W$ during first 10 minutes. 6. The cooling rate by blood flew in living tissue was rised as $10\%$ then meats.

• Macromolecular Research
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• v.16 no.2
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• pp.139-148
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• 2008

Biodegradable and elastic poly(L-lactide-co-$\varepsilon$-caprolactone) (PLCL) was electrospun to prepare nanofibers, and N-isopropylacrylamide (NIPAAm) was then grafted onto their surfaces under aqueous conditions using $^{60}Co-{\gamma}$ irradiation. The graft yield increased with increasing irradiation dose from 5 to 10 kGy and the nanofibers showed a greater graft yield compared with the firms. SEM confirmed that the PLCL nanofibers maintained an interconnected pore structure after grafting with NIPAAm. However, overdoses of irradiation led to the excessive formation of homopolymer gels on the surface of thc PLCL nanofibers. The equilibrium swelling and deswelling ratio of the PNIPAAm-g-PLCL nanofibers (prepared with 10 kGy) was the highest among the samples, which was consistent with the graft yield results. The phase-separation characteristics of PNIPAAm in aqueous conditions conferred a unique temperature-responsive swelling behavior of PNIPAAm-g-PLCL nanofibers, showing the ability to absorb a large amount of water at < $32^{\circ}C$, and abrupt collapse when the temperature was increased to $40^{\circ}C$. In accordance with the temperature-dependent changes in swelling behavior, the release rate of indomethacin and FITC-BSA loaded in PNIPAAm-g-PLCL nanofibers by a diffusion-mediated process was regulated by the change in temperature. Both model drugs demonstrated greater release rate at $40^{\circ}C$ relative to that at $25^{\circ}C$. This approach of the temperature-controlled release of drugs from PNIPAAm-g-PLCL nanofibers using gamma-ray irradiation may be used to design drugs and protein delivery carriers in various biomedical applications.

• Radiation Oncology Journal
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• v.21 no.3
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• pp.199-206
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• 2003

Purpose: This study was undertaken to evaluate the efficacy of postoperative radiotherapy, and to investigate the prognostic factors for FIGO stages IB-IIB cervical cancer patients who were treated with simple hysterectomy, or who had high-risk factors following radical hysterectomy and pelvic lymph node dissection. Materials and Methods: Between March 1986 and December 1998, 58 patients, with FIGO stages IB-IIB cervical cancer were included in this study. The indications for postoperative radiation therapy were based on the pathological findings, including lymph node metastasis, positive surgical margin, parametrial extension, lymphovascular invasion, invasion of more than half the cervical stroma, uterine extension and the incidental finding of cervix cancer fellowing simple hysterectomy. All patients received external pelvic radiotherapy, and 5 patients, received an additional intracavitary radiation therapy. The radiation dose from the external beam to the whole pelvis was $40\~50$ Gy. Vagina cuff Irradiation was peformed, after completion of the external beam irradiation, at a low-dose rate of Cs-137, with the total dose of $4488\~4932$ chy (median: 4500 chy) at 5 mm depth from the vagina surface. The median follow-up period was 44 months ($15\~108$ months). Results: The 5-yr actuarial local control rate, distant free survival and disease-free survival rate were $98\%,\;95\%\;and\;94\%$, respectively. A univariate analysis of the clinical and pathological parameters revealed that the clinical stage (p=0.0145), status of vaginal resection margin (p=0.0002) and parametrial extension (p=0.0001) affected the disease-free survival. From a multivariate analysis, only a parametrial extension independently influenced the disease-free survival. Five patients ($9\%$) experienced Grade 2 late treatment-related complications, such as radiation proctitis (1 patient), cystitis (3 patients) and lymphedema of the leg (1 patient). No patient had grade 3 or 4 complications. Conclusion: Our results indicate that postoperative radiation therapy can achieve good local control and survival rates for patients with stages IB-IIB cervical cancer, treated with a simple hysterectomy, as well as for those treated with a radical hysterectomy, and with unfavorable pathological findings. The prognostic factor for disease-free survival was invasion of the parametrium. The prognosic factor identified in this study for treatment failure can be used as a selection criterion for the combined treatment of radiation and che motherapy.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2317-2323
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• 2024

Medical linear accelerators with an energy of 8 MV or higher are radiated owing to photonuclear reactions and neutron capture reactions. It is necessary to quantitatively evaluate the concentration of radioactive isotopes when replacing or disposing them. HPGe detectors are commonly used to identify isotopes and measure radioactivity. However, because the detection efficiency is generally calibrated using a standard material with a density of 1.0 g/cm³, a self-absorption effect occurs if the density of the measured material is high. In this study, self-absorption correction factors were calculated for tungsten, lead, copper, and SUS-303, which are the main materials of medical linear accelerator head parts, for each gamma-ray energy using MCNP 6.2 code. The self-absorption effect was more pronounced as the energy of the emitted gamma rays decreased and the density of the measured materials increased. These correction factors were applied to the radioactivity measurements of the in-built and portable HPGe detectors. Furthermore, compared to the surface dose rate measured by the survey meter, the accuracy of the measurements of radioactivity improved by an average of 124.31 and 100.53 % for inbuilt and portable HPGe detectors, respectively. The results showed a good agreement, with an average difference of 3.70 and 5.24 %.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.755-760
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• 2019

Compound samples based on the mineral-like magnesium potassium phosphate matrix $MgKPO_4{\times}6H_2O$ were synthesized by solidification of high level waste surrogate. Phase composition and structure of synthesized samples were studied by XRD and SEM methods. Compressive strength of the compounds is $12{\pm}3MPa$. Coefficient of thermal expansion of the samples in the range $250-550^{\circ}C$ is $(11.6{\pm}0.3){\times}10^{-6}1/^{\circ}C$, and coefficient of thermal conductivity in the range $20-500^{\circ}C$ is $0.5W/(m{\times}K)$. Differential leaching rate of elements from the compound, $g/(cm^2{\times}day)$: $Mg-6.7{\times}10^{-6}$, $K-3.0{\times}10^{-4}$, $P-1.2{\times}10^{-4}$, $^{137}Cs-4.6{\times}10^{-7}$; $^{90}Sr-9.6{\times}10^{-7}$; $^{239}Pu-3.7{\times}10^{-9}$, $^{241}Am-9.6{\times}10^{-10}$. Leaching mechanism of radionuclides from the samples at the first 1-2 weeks of the leaching test is determined by dissolution ($^{137}Cs$), wash off ($^{90}Sr$) or diffusion ($^{239}Pu$ and $^{241}Am$) from the compound surface, and when the tests continue to 90-91 days - by surface layer depletion of compound. Since the composition and physico-chemical properties of the compound after irradiation with an electron beam (absorbed dose of 1 MGy) are constant the radiation resistance of compound was established.

• Progress in Medical Physics
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• v.8 no.2
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• pp.45-57
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• 1997

It is mandatory to measure accurately the dose distribution and the total absorbed dose of fast neutron for putting it to the clinical use. At present the methods of measurement of fast neutron are proposed largely by American Associations of Physicists in Medicine, European Clinical Neutron Dosimetry Group, and International Commission on Radiation Units and Measurements. The complexity of measurement, however, induces the methodological differences between them. In our study, therefore, we tried to establish a unique technique of measurement by means of measuring the emitted doses and the dose distribution of fast neutron beam from neutron therapy machine, and to invent a standard method of measurement adequate to our situation. For measuring the absorbed doses and the dose distribution of fast neutron beam, we used IC-17 and IC-18 ion chambers manufactured by A-150 plastic(tissue-equivalent material), IC-17M ion chamber manufactured by magnesium, TE gas and Ar gas, and RDM 2A electrometer. The magnitude of gamma-contamination intermingled with fast neutron beam was about 13％ at 5cm depth of standard irradiated field, and increased as the depth was increased. At the central axis the maximum dose depth and 50％ dose depth were 1.32cm and 14.8cm, respectively. The surface dose rate was 41.6-54.1％ throughout the entire irradiated fields and increased as the irradiated fields were increased. Beam profile was that the horn effect of about 7.5％ appeared at 2.5cm depth and the flattest at 10cm depth.

• Journal of Radiation Protection and Research
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• v.24 no.2
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• pp.109-120
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• 1999

Residual radiation and radioactivity level in TRIGA Mark-II, III research reactors and facilities at the KAERI Seoul site, which are to be decommissioned, have been measured, analyzed and evaluated to know the current status of radiation and radioactivity level and to establish and to provide the technical requirements for the safe decommissioning of the facilities which shall be applied in minimizing the radiation exposure for workers and in preventing the release of the radioactive materials to the environment. Radiation dose rate and surface radioactivity contamination level on the experimental equipments, floors, walls of the facilities, and the surface of the activated materials within the reactor pool structure were measured and evaluated. Radioactivity and radionuclides in the pool and cooling water were also analyzed. In case of the activated reactor pool structures which are very difficult to measure the radiation and radioactivity level, a computer code Fispin was additionally used for estimation of the residual radioactivity and radionuclides. The radiation and radioactivity data obtained in this study were effectively used as basic data for decontamination and dismantling plan for safe decommissioning of TRIGA Mark-II, III facilities.

• Journal of radiological science and technology
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• v.44 no.5
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• pp.481-487
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• 2021

This study was conducted for the purpose of efficient radioactive waste disposal and management. Experiment was evaluated the decontamination efficiencies of the four types decontamination materials(Water, Alcohol, Decontamination Water, Decontamination Gel) with radioactive wastes generated during radio-pharmaceutical production process at Korea Institute Radiological and Medical Sciences(KIRAMS). The radioactive waste sample used in experiment is a lead plate of the fume hood that was disposed in April, 2019. In the experimental method, radioactive waste was measured before and after decontamination using a HPGe semiconductor detector and Gamma survey meter. The measured values before and after decontamination were evaluated for decontamination efficiency as a percentage. As a result, it was confirmed that a lot of specific activity and surface dose rate was removed from the radioactive wastes. In particular, when decontamination water was used, most of the radioactivity of radioactive wastes was removed. Considering these results, if decontamination water is used in decontamination of radioactive waste, decontamination efficiency equivalent to the disposition criteria can be expected with just one decontamination treatment. In addition, in the case of water and alcohol, only on decontamination was effective in approximately 75% and 95%. Otherwise, when decontamination gel was used, it was confirmed that the largest deviation occurred among all experimental results.

• The Journal of Korean Society for Radiation Therapy
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• v.31 no.1
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• pp.75-81
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• 2019

Purpose: Helmet type bolus for 3D printer is being manufactured because of the disadvantages of Bolus materials when photon beam is used for the treatment of scalp malignancy. However, PLA, which is a used material, has a higher density than a tissue equivalent material and inconveniences occur when the patient wears PLA. In this study, we try to treat malignant scalp tumors by using M3 wax helmet with 3D printer. Methods and materials: For the modeling of the helmet type M3 wax, the head phantom was photographed by CT, which was acquired with a DICOM file. The part for helmet on the scalp was made with Helmet contour. The M3 Wax helmet was made by dissolving paraffin wax, mixing magnesium oxide and calcium carbonate, solidifying it in a PLA 3D helmet, and then eliminated PLA 3D Helmet of the surface. The treatment plan was based on Intensity-Modulated Radiation Therapy (IMRT) of 10 Portals, and the therapeutic dose was 200 cGy, using Analytical Anisotropic Algorithm (AAA) of Eclipse. Then, the dose was verified by using EBT3 film and Mosfet (Metal Oxide Semiconductor Field Effect Transistor: USA), and the IMRT plan was measured 3 times in 3 parts by reproducing the phantom of the head human model under the same condition with the CT simulation room. Results: The Hounsfield unit (HU) of the bolus measured by CT was $52{\pm}37.1$. The dose of TPS was 186.6 cGy, 193.2 cGy and 190.6 cGy at the M3 Wax bolus measurement points of A, B and C, and the dose measured three times at Mostet was $179.66{\pm}2.62cGy$, $184.33{\pm}1.24cGy$ and $195.33{\pm}1.69cGy$. And the error rates were -3.71 %, -4.59 %, and 2.48 %. The dose measured with EBT3 film was $182.00{\pm}1.63cGy$, $193.66{\pm}2.05cGy$ and $196{\pm}2.16cGy$. The error rates were -2.46 %, 0.23 % and 2.83 %. Conclusions: The thickness of the M3 wax bolus was 2 cm, which could help the treatment plan to be established by easily lowering the dose of the brain part. The maximum error rate of the scalp surface dose was measured within 5 % and generally within 3 %, even in the A, B, C measurements of dosimeters of EBT3 film and Mosfet in the treatment dose verification. The making period of M3 wax bolus is shorter, cheaper than that of 3D printer, can be reused and is very useful for the treatment of scalp malignancies as human tissue equivalent material. Therefore, we think that the use of casting type M3 wax bolus, which will complement the making period and cost of high capacity Bolus and Compensator in 3D printer, will increase later.