• Journal of Radiation Protection and Research
• /
• v.28 no.3
• /
• pp.199-206
• /
• 2003

Because the MIRD phantom, the representative mathematical phantom was developed for the calculation of internal radiation dose, and simulated by the simplified mathematical equations for rapid computation, the appropriateness of application to external dose calculation and the closeness to real human body should be justified. This study was intended to modify the MIRD phantom according to the comparison of the organ absorbed doses in the two phantoms exposed to monoenergetic broad parallel photon beams of the energy between 0.05 MeV and 10 MeV. The organ absorbed doses of the MIRD phantom and the Zubal yokel phantom were calculated for AP and PA geometries by MCNP4C, general-purpose Monte Carlo code. The MIRD phantom received higher doses than the Zubal phantom for both AP and PA geometries. Effective dose in PA geometry for 0.05 MeV photon beams showed the difference up to 50%. Anatomical axial views of the two phantoms revealed the thinner trunk thickness of the MIRD phantom than that of the Zubal phantom. To find out the optimal thickness of trunk, the difference of effective doses for 0.5 MeV photon beams for various trunk thickness of the MIRD phantom from 20 cm to 36 cm were compared. The optimal thunk thickness, 24 cm and 28 cm for AP and PA geometries, respectively, showed the minimum difference of effective doses between the two phantoms. The trunk model of the MIRD phantom was modified and the organ doses were recalculated using the modified MIRD phantom. The differences of effective dose for AP and PA geometries reduced to 7.3% and the overestimation of organ doses decreased, too. Because MIRD-type phantoms are easier to be adopted in Monte Carlo calculations and to standardize, the modifications of the MIRD phantom allow us to hold the advantage of MIRD-type phantoms over a voxel phantom and alleviate the anatomical difference and consequent disagreement in dose calculation.

• Journal of radiological science and technology
• /
• v.38 no.3
• /
• pp.187-197
• /
• 2015

This study analysed the effectiveness of aluminium(Al) filter in the added compound filtration for the removal of characteristic radiation by energy spectrum and image evaluation. 0.1, 0.2, 0.3 mm copper with and without 1 mm Al were evaluated. The energy spectrum was measured using the GATE and evaluated separately by each energy. Image quality was evaluated by PSNR, MAE, MSE, CNR, SNR and qualitative analysis was performed by seven items for resolution and contrast from chest x-ray criteria of National Cancer Screening and Cardiovascular evaluation table. In the analysis of the quality of the energy per photon spectrum with the exception of a low energy region, without Al were superior in all area. PSNR MAE, MSE, CNR, SNR and qualitative analysis were the same or slightly better. PSNR was over 30 dB and all significant and the p>0.05 in the T-test of qualitative analysis. The energy spectrum and image quality have little difference between before and after use of Al filter. Therefore, it is effective to use the Al filter for the radiation dose management with the compensation capability of DR system.

• Journal of Radiation Protection and Research
• /
• v.31 no.4
• /
• pp.181-186
• /
• 2006

A radiophotoluminescent glass rod detector (GRD) system has recently become commercially available. We investigate the dosimetric properties of the GRD regarding the reproducibility of signal, dose linearity and energy dependence. The reproducibility of five measurements for 50 GRDs is presented by an average of one standard deviation of each GRD and it is ${\pm}1.2%$. It is found to be linear in response to doses of $^{60}Co$ beam in the range 0.5 to 50 Gy with a coefficient of linearity of 0.9998. The energy dependence of the GRD is determined by comparing the dose obtained using cylindrical chamber to that by using the GRD. The GRD response for each beam is normalized to the response for a $^{60}Co$ beam. The responses for 6 and 15 MV x-ray beams are within ${\pm}1.5%$ (1SD). The energy response of GRD for high-energy photon is almost the same as the energy dependence of LiF:Mg:Ti (TLD-100)and shows little energy dependence unlike p-type silicon diode detector. The GRDs have advantages over other detectors such diode detector, and TLD: linearity, reproducibility and energy dependency. It has been verified to be an effective device for small field dosimetry for stereotactic radiosurgery.

• Journal of Radiation Protection and Research
• /
• v.43 no.2
• /
• pp.75-84
• /
• 2018

Background: Gamma-ray spectrometry helps in radiation shielding problems and different applications of radioisotopes. Experimental arrangements including broad beam geometries are widely used. The aim is to investigate and evaluate the ${\gamma}-ray$ spectra via attenuation by environmental materials. Materials and Methods: The photo peak to nominated parts in the ${\gamma}-ray$ spectra and the attenuation coefficients ${\mu}_b/{\rho}$ from broad beam geometries are measured for the materials water, soil, sand and cement at the energies 0.662, 1.25, and 1.332 MeV with a $3{^{\prime}^{\prime}}{\times}3{^{\prime}^{\prime}}$ NaI(Tl) detector. Results and Discussion: The ${\gamma}-ray$ spectra vary according to changes in the effective atomic number $Z_{eff}$ of the attenuator, the photon energy and the solid angle. The peak to total ratios are the most sensitive parts to variations in the experimental conditions and overturn in the region 0.663 MeV to 1.332 MeV. This is indicated as inversion trend. The results are discussed in view of $Z_{eff}$ and the experimental conditions. The intensity build-up is larger at the lower energy and larger scattering angles in agreement with Klein-Nishina formula and other results. The build-up factor B is$${\sim_=}$$1 at high ${\gamma}-energies$ and small scattering angles. Conclusion: The sensitivity to material characteristics decrease gradually from peak: to total, to Compton valley, to Compton plateau ratios. Rigorous collimation is necessary at small energies. Cement, of the largest $Z_{eff}$, is characterized by the maximum broad beam mass attenuation coefficients ${\mu}_b/{\rho}$. The obtained results provide information to decide for the suitable experimental set-up based on aim of the work.

• Nuclear Engineering and Technology
• /
• v.53 no.1
• /
• pp.282-293
• /
• 2021

This paper examines gamma-ray shielding properties of SBC-Bx glass system with the chemical composition of 40SiO₂-10B₂O₃-xBaO-(45-x)CaO- yZnO- zMgO (where x = 0, 10, 20, 30, and 35 mol% and y = z = 6 mol%). Mass attenuation coefficient (µ/ρ) which is an essential parameter to study gamma-ray shielding properties was obtained in the photon energy range of 0.015-15 MeV using PHITS Monte Carlo code for the proposed glasses. The obtained results were compared with those calculated by WinXCOM program. Both the values of PHITS code and WinXCOM program were observed in very good agreement. The (µ/ρ values were then used to derive mean free path (MFP), electron density (N_eff), effective atomic number (Z_eff), and half value layer (HVL) for all the glasses involved. Additionally, G-P method was employed to estimate exposure buildup factor (EBF) for each glass in the energy range of 0.015-15 MeV up to penetration depths of 40 mfp. The results reveal that gamma-ray shielding effectiveness of the SBC-Bx glasses evolves with increasing BaO content in the glass sample. Such that SBC-B35 glass has superior shielding capacity against gamma-rays among the studied glasses. Gamma-ray shielding properties of SBC-B35 glass were compared with different conventional shielding materials, commercial glasses, and newly developed HMO glasse. Therefore, the investigated glasses have potential uses in gamma shielding applications.

• The Journal of Korean Society for Radiation Therapy
• /
• v.8 no.1
• /
• pp.29-35
• /
• 1996

We are often faced with the clinical situations that is inevitably extended SSD for electron beam therapy due to anatomical restriction or applicator structure. But there are some difficulties in accurately predicting output and properties. In electron beam treatment , unlike photon beam the decrease in output for extended SSD does not follow inverse-square law accurately because of a loss of side scatter equilibrium, which is particularly significant for small cone size and low energies. The purpose of our study is to analyze the output in changing with the energy, cone size, air gap beyond the standard SSD and to compare inverse-square law factor derived from calculated effective SSD, mominal SSD with measured output factor. In addition, we have analyzed the change of PDD for several cones with different SSDs which range from 100cm to 120cm with 5cm step and with different energies(6MeV, 9MeV, 12MeV, 16MeV, 20MeV). In accordance with our study, an extended SSD produces a significant change in beam output, negligible change in depth dose which range from 100cm to 120cm SSDs. In order to deliver the more accurate dose to the neoplastic tissue, first of all we recommend inverse-square law using the table of effective SSDs with cone sizes and energies respectively or simply to create a table of extended SSD air gap correction factor. The second we need to have an insight into some change of dose distribution including PPD, penumbra caused by extended SSD for electron beam therapy.

• Current Optics and Photonics
• /
• v.6 no.5
• /
• pp.497-505
• /
• 2022

Topological photonic nanocavities are considered to possess outstanding optical performance, and provide new platforms for realizing strong interaction between light and matter, due to their robustness to impurities and defects. Here hybrid plasmonic topological photonic nanocavities are proposed, by embedding various plasmon nanoantennas such as gold nanospheres, cylinders, and rectangles in a topological photonic crystal corner-state nanocavity. The maximum quality factor Q and minimum effective mode volume V_eff of these hybrid nanocavities can reach the order of 10⁴ and 10^-4 (𝜆/n)³ respectively, and the high figures of merit Q/V_eff for all of these hybrid nanocavites are stable and on the order of 10⁵ (𝜆/n)^-3. The relative positions of the plasmon nanoantennas will influence the coupling strength between the plasmon structures and the topological nanocavity. The hybrid nanocavity with gold nanospheres possesses much higher Q, but relatively large V_eff. The presence of a gold rectangular structure can confine more electromagnetic energy within a smaller space, since its V_eff is smallest, although Q is lowest among these structures. This work provides an outstanding platform for cavity quantum electrodynamics and has a wide range of applications in topological quantum light sources, such as single-photon sources and nanolasers.

• Nuclear Engineering and Technology
• /
• v.55 no.6
• /
• pp.1949-1958
• /
• 2023

The International Commission on Radiological Protection (ICRP) Publication 116 was released to provide a comprehensive dataset of the dose coefficients (DCs) for external exposures produced with the adult reference voxel phantoms of ICRP Publication 110. Although an advanced skeletal dosimetry method for photons and neutrons using fluence-to-dose response functions (DRFs) was introduced in ICRP Publication 116, the ICRP-116 skeletal DCs were calculated by using the simple method conventionally used (i.e., doses to red bone marrow and endosteum approximated by doses to spongiosa and/or medullary cavities). In the present study, the photon and neutron DRFs were used to produce skeletal DCs of the ICRP-110 reference phantoms, which were then compared with the ICRP-116 DCs. For photons, there were significant differences by up to ~2.8 times especially at energies <0.3 MeV. For neutrons, the differences were generally small over the entire energy region (mostly <20%). The general impact of the DRF-based skeletal DCs on the effective dose calculations was negligibly small, supporting the validity of the ICRP-116 effective DCs despite their skeletal DCs derived from the simple method. Meanwhile, we believe that the DRF-based skeletal DCs could be beneficial in better estimates of skeletal doses of individuals for risk assessments.

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

• Journal of the Korean Society of Radiology
• /
• v.12 no.2
• /
• pp.179-184
• /
• 2018

In this study, we compared the measured values of the effective beam size of standard gamma irradiator with the simulation results to provide a useful means to the effective beam area determination. Results of the simulation and measured using ion chamber was distributed in a relative error of 4.5 ~ 7.3% of the case of air kerma rate. The size of the effective beam area is when the simulation was implemented in the horizontal direction 27cm, 21.6cm vertical direction, the measured result using a film was obtained similar results with the horizontal direction 26.5cm, 21.9cm vertical direction. The relative error in the horizontal direction is 1.85% and 1.38% vertical effective beam area was also similarly distributed around the field gamma rays. As a result of the study, it was confirmed that the effectiveness of the simulation was sufficient for the gamma irradiation system. In particular, it is small relative errors in the effective beam size than the air kerma rate is considered to be due to the size of the beam is determined by geometric factors rather than the capacity of the standard source. A further study is needed to improve the reliability of the photon energy distribution diagram using simulation.