• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.227-232
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• 2014

Depolymerization of sodium alginate (SA) was carried out by electron beam irradiation in a hydrogen peroxide atmosphere. E-beam with 1.0 and 2.5 MeV of accelerating voltages were employed in this experiment. For control of molecular weight and the radiation yield of scission ($G_s$), the irradiation dosage of e-beam was managed in a range from 2.5 to 20 kGy while the quantity of hydrogen peroxide was adjusted in a range of 0 to 4.5%. The chemical structure of the depolymerized sodium alginate (DSA) was analyzed to have scission of 1,4-glycoside bond mainly and a few fragmentary formate end groups which may be produced by the cleavage between C2 and C3 in repeating unit of alginate. It turned out to have simple chemical structures at the DSA end groups, produced by e-beam irradiation, similar with those in the polymer SA structure. As a result, the molecular weight of SA decreased as the energy and dosage of applied e-beam increased, and the radiation yield of scission showed the best result at 2w/v% in SA concentration. The highest radiation yield of scission ($7.919{\times}10^4mol/J$) was confirmed when an irradiation dosage of 20 kGy (2 MeV) and 1.5% hydrogen peroxide were used in 2% SA aqueous solution.

• Journal of the Korean Society of Radiology
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• v.13 no.1
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• pp.119-124
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• 2019

Radiation therapy using flattening filter free beam can prevent beam attenuation caused by flattening filter and can improve treatment efficiency. However, accurate dose control is not established for nonuniform iso dose distributions. In this study, curved dosimeter based on photoconductive material $HgI_2$ was fabricated and its reproducibility and linearity were evaluated at 6 MV photon energy to verify its performance. In order to show the usefulness of the curved measurement, the signals measured on the flat substrate and the curved substrate were compared in the flattening filter free beam using the acrylic filter. As a result, the reproducibility of the unit cell dosimeter was evaluated as SE 0.613%, and the linearity was evaluated as R-sq 0.9999. The usability evaluation of the array curve dosimeter demonstrated its usefulness by indicating a curvature error rate of 11.073%p and a reduced error rate.

• The Journal of Korean Society for Radiation Therapy
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• v.13 no.1
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• pp.14-22
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• 2001

Purpose: The aim of this study is to investigate geometrical and volumetrical changes of liver due to breathing and its impact to NTCP. In order to attain better treatment results it should be considered deliberately during planning session. Mehtods and Materials : Seven patients were examined in this study who have done TACE for accurate tumor margin drawing. After contrast media injection, C-T scan data were obtained in supine position during breathing free, inhalation and exhalation, respectively. For all patients C-T scan were done with same scanning parameters- 5 mm index, 5 mm thickness and pitch 1. Based on C-T data we have measured differences of each variables between breathing status such as changes of total and remained liver volumes, GTV, beam path length and superior to inferior shift. NTCP were calculated using Lyman's effective volume DVH reduction scheme and for this NTCP calculation, the V50 was computed from DVH and each m, n value were referred from Burmans data. Results : The measured total tilter volume and the remained liver volume changed between inspiration and expiration about $1.2-7.7\%(mean+2.7\%)$ and $2.5-13.23\%(mean=5.8\%)$ respectively, and these results were statistically significant(p>0.1). The GTV difference in each patient varied widely from $1.17\%\;to\;30.69\%$, but this result was not statistically significant. Depending on the breathing status, the beam path length was changed from 0.5 cm to 1.1 cm with the average of 0.7 cm, and it was statistically significant(p=0.006). The measured superior to inferior shifts were ranged from 0.5 cm to 3.74 cm. The NTCPs were changed relatively small in each patient, but the variation was large between the patients. The mean NTCP difference was $10.5\%$, with the variation ranged from $7\%\;to\;23.5\%$. Conclusion : Variations of liver volume and of beam path length were changed significantly depending on the breathing statues and the range of variation itself was very different between the patients. Since this variance could seriously affect the clinical outcomes of radiation treatments, the breathing of patients need to be accounted when a final treatment planning is derided.

• Journal of Radiation Protection and Research
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• v.23 no.1
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• pp.33-47
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• 1998

Using a combination of an X-ray generator Installed in radiation calibration laboratory of Korea Atomic Energy Research Institute (KAERI) and a series of 8 radiators and filters described in ISO-4037, monoenergetic fluorescent X-rays from 8.6 keV to 75 keV were produced. This fluorescent X-rays generated by primary X-rays from radiator were discriminated $K_{\beta}$ lines with the aid of filter material and the only $K_{\alpha}$ X-rays were analyzed with the high purity Ge detector and portable MCA. The air kerma rates were measured with the 35 co ionization chamber and compared with the calculational results, and the beam uniformity and the scattered effects of radiation fields were also measured. The beam purities were more than 90 % for the energy range of 8.6 keV to 75 keV and the air kerma rates were from 1.91 mGy/h (radiator : Au, filter : W) to 54.2 mGy (radiator : Mo, filter : Zr) at 43 cm from center of the radiator. The effective area of beam at the measurement point of air kerma rates was 12 cm ${\times}$ 12 cm and the influence of scattered radiation was less than 3 %. The fluorescent X-rays established in this study could be used for the determination of energy response of the radiation measurement devices and the personal dosemeters in low photon energy regions.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2006.08a
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• pp.131-131
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• 2006

• The Journal of Korean Society for Radiation Therapy
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• v.5 no.1
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• pp.68-73
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• 1992

If the same weight is used in parallel opposed 6 and 10 MV x-ray beams, the lowest dose is achieved at SAD. Therefore, dose homogeneity in the target volume is decreased when SAD is taken at center of target volume than center of phantom or patient. With Standard deviation of ${\pm}6\%$ that repuesented the dose homogeneity in tarhet volume, we studied the optimized beam weights at which hot spot dose was least in parallel opposed beams. The optimized beam weights that maximally decrease the hot spot dose, wer 1.29, 1.19, 2.71, 3.50, and 4.70 in 6 MV x-ray and 1.25, 1.53, 1.90, 2.36, 3.01, and 3.7 in 10 MV x-ray, reapectively, when center of target volume was changed to 2,4,6,8,10, and 12cm from center plan of phantom along the centeral axis of beams.

• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.2138-2150
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• 2020

We report the status of the cold neutron triple-axis spectrometer (Cold TAS) and thermal neutron triple-axis spectrometer (Thermal TAS) installed at HANARO. Cold TAS, whose specifications are standard across the world, is in the final phase of commissioning. Proper instrument operation was confirmed through a feasibility study of phonon measurements and data analyses with resolution convolution. In contrast, Thermal TAS is in the initial phase of commissioning, and improvement of the monochromator drum is now in progress from the viewpoint of radiation shielding. In addition, we report recent activities in the development of neutron basic elements, that is, film-coated Si-wafer collimators, which are promising for use in triple-axis spectroscopy, particularly in Cold TAS.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1294-1299
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• 2004

Transient radiative heat transfer is analyzed in a one-dimensional slab using finite volume method (FVM). In this study, the step, $2^{nd}$ order upwind, and QUICK schemes are used for incident diffuse radiation and collimated beam, respectively. The results for diffuse radiation show that all schemes applied in this study give good agreements with available published results. In case of collimated beam, however, the results show deviations from the analytical solutions. To successfully describe the propagations of collimated beam, shock capturing schemes such as TVD scheme are need to be developed.

• Korean Journal of Digital Imaging in Medicine
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• v.12 no.1
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• pp.65-69
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• 2010

High energy electron beams were to concentrically dose inside a tumor and more energy is a shape decreased of dose. Therefore, it is useful to radiation therapy of a tumor. Also high energy electron beams ionized into collision with a atom in structure material of tissue and it has big changes to dose distribution by multiple scattering. The study had to establish characteristic of electron beams from interaction of electron beams and materials. Experiment method was to measure dependence of electron beam central axis for depth dose curve, field flatness and symmetry and field size dependence. The results were able to evaluate data for a datum pint of electron beam. Also radiotherapy has to be considered for not only energy pencil of lines but characteristic, electron guide and isodose curves distribution.

• The Journal of Korean Society for Radiation Therapy
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• v.1 no.1
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• pp.79-83
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• 1985

Carcinoma of the breast has been treated by surgery followed by irradiation of the chest wall and regional lymphatics treatment planning of the breast cancer is required that lung must be spared as much as possible. However megavoltage irradiation of the internal mammary chain results in high dose to underlying heart, esophagus and spinal cord. Electron beam can be used for the irradiation of the internal mammary chain instead of megavoltage beam. We studied dose distribution of single anterior electron field, compared with traditional treatment methods. 12 and 15MeV electron beam with bolus has good dose distribution to spare underlying lung tissue and other organs.