• Journal of radiological science and technology
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• v.40 no.1
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• pp.93-99
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• 2017

Dose enhancement effects at megavoltage (MV) X and ${\gamma}-ray$ energies, and the effects of different energy levels on incident energy, dose enhancement agents, and concentrations were analyzed using Monte Carlo simulations. Gold, gadolinium, Iodine, and iron oxide ($Fe_2O_3$) were compared as dose enhancement agents. For incident energy, 4, 6, 10 and 15 MV X-ray spectra produced by a linear accelerator and a Co-60 ${\gamma}-ray$ were used. The dose enhancement factor (DEF) was calculated using an ICRU Slab phantom for concentrations of 7, 18, and 30 mg/g. The DEF was higher at higher concentrations of dose enhancement agents and at lower incident energies. The calculated DEF ranged from 1.035 to 1.079, and dose enhancement effects were highest for iron oxide, followed by iodine, gadolinium, and gold. Thus, this study contributes to improving the therapeutic ratio by delivering larger doses of radiation to tumor volume, and provides data to support further in vivo and in vitro studies.

• The Journal of the Korea Contents Association
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• v.16 no.8
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• pp.477-483
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• 2016

The effect of dose enhancement was evaluated using Snyder head phantom, dependence on size of gold nanoparticle and material concentration in megavoltage X, ${\gamma}$-ray. Monte Carlo simulation using MCNPX was used for 4, 6, 10, 15 MV and Co-60 ${\gamma}$-ray. Described the tumor in Snyder head phantom, gold nanoparticle of 25, 75, 125nm diameter was inserted inside tumor. Concentration of dose enhancement material was used for 5, 15, 25 mg/g and dose enhancement factor was calculated on the basis of the no dose enhancement material. The lower incident energy and the higher concentration of material were that high dose enhancement factor is indicated. The size of gold nanoparticle had relatively high dependence on lower incident energy and higher concentration of material. It will increase dose inside the tumor, and be additional effect of use of gold nanoparticles in radiation therapy.

• Journal of the Korean Society of Radiology
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• v.11 no.2
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• pp.87-94
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• 2017

Monte Carlo simulations were used to assess dose enhancement effects for 60-, 90-, 120-, and 150-kV X-rays, and for 6- and 15-MV X-rays. The MCNPX code was used for a computer simulation of the ICRU slab phantom, and gold, gadolinium, and iron oxide (Fe2O3) were employed as dose enhancement agents. In consideration of the buildup region of the incident energy, agent concentrations of 5, 10, 15, and 20 mg/g were inserted on the surface of the phantom at a depth of 5 cm. Based on baseline values obtained in the absence of dose enhancement agents, a quantitative analysis was performed by evaluating depth-dependent changes in the absorbed energy and the dose enhancement factor (DEF). A higher concentration of dose enhancement agents led to a greater dose enhancement effect with iron oxide, gadolinium, and gold in descending order. For kilovoltage (kV) X-rays, as the incident energy was decreased and as the energy became closer to the ionization potential of the atoms in the enhancement agent, the dose enhancement effect increased. In the megavoltage (MV) X-ray range, dose enhancement was higher at 6 MV compared with 15 MV. However, the overall dose enhancements were significantly lower compared to the results obtained with kV X-rays.

• Radiation Oncology Journal
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• v.7 no.1
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• pp.85-92
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• 1989

Dosimerty based on electron spin resonance (ESR) analysis of radiation induced free radicals in amino acids is relevant to biological dosimetry applications. Alanine detectors are without walls and are tissue equivalent. Therefore, alanine ESR dosimetry looks promising for use in the therapy level. The dose range of the alanine/ESR dosimetry system can be extended down to 1 Gy. In water phantom the absorbed dose of electrons generated by a medical linear accelerator of different initial energies $(6\~21MeV)$ and therapeutic dose levels (1~60 Gy) was measured. Furthermore, depth dose measurements carried out with alanine dosimeters were compared with ionization chamber measurements. As the results, the measured absorbed doses for shallow depth of initial electron energies above 15 MeV were higher by$2\~5\%$ than those calculated by nominal energy $C_E$ factors. This seems to be caused by low energy scattered beams generated from the scattering foil and electron cones of beam projecting device in medical linear accelerator.

• Proceedings of the Korea Contents Association Conference
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• 2014.11a
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• pp.183-184
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• 2014

유방촬영은 날로 증가추세에 있으며 압박을 통해 영상을 얻는 것이 화질을 향상시키고 피폭선량을 줄이는데 필수적이다. 그러나 압박대 자체의 두께로 인해 산란선과 피폭선량을 증가시킬 수 있으므로 압박대 재질에 대한 고찰이 필요하다. 현재 임상에서 쓰이고 있는 재질은 폴리카보네이트이며 플라스틱 계열이다. 환자의 피폭선량을 줄이기 위해 노력한다면 이보다 더 좋은 재질에 대해 고려해볼 필요가 있기에 본 연구에서는 플라스틱 계열 물질과 탄소계열의 카본의 방사선투과성에 대해 비교해 보고자 한다.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.571-576
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• 1998

방사성물질의 수송용기 등에 사용되는 에폭시수지계 중성자 차폐재를 제조하였다 기본물질은 재질(KNS-102) 및 수소 첨가된 비스페놀 A힘(KNS-106) 그리고 패놀-노블락형 에폭시수지 (KNS-611)이며, 첨가제로는 수산화알루미늄 및 탄화붕소이다. 이들 중성자 차폐재들은 유동성이 좋아 수송용기와 같은 복잡한 구조에 사용할 수 있다. 제조된 중성자 차폐재들을 방사선 조사선 량에 대한 영향과 가압경수로 사용후핵연료_ 28다발을 수송할 수 있는 수송용기에 적용하여 차폐능 평가를 수행하였다 0.7 MGy 까지 중성자 차폐재들은 방사선 조사선량의 증가에 따라 중성자 차폐재의 거시적 제거 단면적($\Sigma$$_{R}$)은 약간 증가하는 경향을 나타내었으며, 수송용기에 적용하여 ANISN 전산코드로 차폐능 평가를 수행한 결과 정상수송시 중성자 차폐재의 두께가 12 cm 이상일 때 수송용기 반경방향표면에서 최대 방사선량율은 168 ~ 214 $\mu$Sv/h로 나타났으며, 수송용기 표면에서 100 cm 지점에서의 최대 방사선량율은 74 ~ 93 $\mu$Sv/h로 나타났다. 이들은 모두 관련된 법규들에서 규정된 최대 허용방사선량율을 만족하는 것으로 나타났다.

• Proceedings of the Korea Contents Association Conference
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• 2015.05a
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• pp.187-188
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• 2015

유방촬영은 날로 증가추세에 있으며 압박을통해 영상을 얻는 것이 화질을 향상시키고 피폭선량을 줄이는데 필수적이다. 그러나 압박대 자체의 두께로 인해 산란선과 피폭선량을 증가시킬 수 있으므로 압박대 재질에 대한 고찰이 필요하다. 현재 임상에서 쓰이고 있는 재질은 폴리카보네이트이며 플라스틱 계열이다. 환자의 피폭선량을 줄이기위해 노력한다면 이보다 더 좋은 재질에 대해 고려해볼 필요가 있기에 본 연구에서는 플라스틱 계열 물질 중 비결정 플라스틱에 대한 방사선투과성에 대해 비교해 보고자 한다.

• Radiation Oncology Journal
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• v.14 no.4
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• pp.339-345
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• 1996

Purpose : This study was performed for adequate irradiating tumor area when 6 MV linear accerelator photon was used to treat the head and neck tumor. The skin surface dose and maximum build-up region was measured by using a spoiler which was located between skin surface and collimator. Methods : A spoiler was made of tissue equivalent material and the skin surface dose and maximum build-up region was measured varing with field size, thickness of spoiler and interval between skin and collimator. The results of skin surface dose and maximum build-up dose was represented as a build-up ratio and it was compared with dose distribution by using a bolus. Results : The skin surface dose was increased with appling spoiler and decreased by distance of the skin-spoiler separation. The maxium build-up region was 1.5 cm below the skin surface and it was markedly decreased near the skin surface. By using a 1.0-cm thickness spoiler, Dmax moved to 5, 10.2, 12.3 13.9 and 14.8 mm from the skin surface by separation of the spoiler from the skin 0, 5, 10, 15. 20 cm, respectively. Conclusion : The skin surface dose was increased and maximum build-up region was moved to the surface by using a spoiler. Therefore spoiler was useful in treating by high energy photon in the head and neck tumor.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.253-260
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• 2019

Radiation dose enhancement is a method of increasing the cross section of interaction, thus increasing the deposited dose. This can contribute to linear energy transfer, LET and relative biological effectiveness, RBE. Previous studies on dose enhancement have been mainly focused on X, ${\gamma}-rays$, but in this study, the dose enhancement was analyzed for proton using Monte Carlo simulation using MCNP6. Based on the mathematical modeling method, energy spectrum and relative intensity of spread out Bragg-peak were calculated, and evaluated dose enhancement factor and dose distribution of dose enhancement material, such as aurum and gadolinium. Dose enhancement factor of 1.085-1.120 folds in aurum, 1.047-1.091 folds in gadolinium was shown. In addition, it showed a decrease of 95% modulation range and practical range. This may lead to an uncertain dose in the tumor tissue as well as dose enhancement. Therefore, it is necessary to make appropriate corrections for spread out Bragg-peak and practical range from mass stopping power. It is expected that Monte Carlo simulation for dose enhancement will be used as basic data for in-vivo and in-vitro experiments.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.5
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• pp.588-593
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• 2006

This study was intended to observe possibility of which radiation technique can be used for oligopeptide production from pigskin collagen to reduce environmental pollution in processing and simplify the processing steps. Raw pigskin was ground using chopper, and then defatted in acetone cooled at $-20^{\circ}C$ freezer. Defatted dried pigskin was irradiated at 20, 40, 60, 100, 150, 200, 250, and 300 kGy using Co-60 gamma rays irradiator. With irradiation doses, the amount of soluble proteins increased, and the viscosity and turbidity of soluble proteins decreased, which could be clue of that irradiation degrade high molecular proteins directly. pH of soluble proteins from defatted pigskin increased in the sample above 150 kGy, and low molecular weight components (below 24 kDa) in SDS-PAGE increased. From gel permeation chromatography of the hydrolysates of pigskin irradiated at 300 kGy showed the major peak of 9,000, 8,200, 860, and 170 Da.