Evaluation of the annual effective dose due to the external irradiation induced by using NORM added consumer products.

This study aims to evaluate the annual effective dose from a sleeping mattress containing naturally occurring radioactive material (NORM). In this study, the dose rate was measured using two different portable radiation detectors, namely the Geiger Müller (GM) tube and portable high-purity germanium (HPGe) detector; the annual effective dose was calculated using annualized usage of the products, and the equivalent does was evaluated via Monte Carlo (MC) simulation and using the model of the human body, which is known as a computational human phantom. The dose rate of the product, excluding background radiation at the shielded room, was measured as 0.22 and 0.13 µSv/h in the GM-tube and portable HPGe, respectively. Assuming that the sleeping mattress was used for an average sleeping of 8 h/day, the annual effective dose was calculated as 0.64 and 0.38 mSv/y using the GM-tube and portable HPGe detectors, respectively. Also, the annual effective dose calculated using MC simulation and radioactivity values from the nuclides analysis was 0.13 mSv/y. The annual effective dose calculated using the two different portable detectors and MC simulation is less than the annual effective dose limit for the general public, which is set at 1 mSv/y. This technique could be used not only for the safety regulation for products containing NORM but also for the accurate evaluation of the effective dose for radiation workers in the diverse radiation field.

Development of advanced skin dose evaluation technique using a tetrahedral-mesh phantom in external beam radiotherapy: a Monte Carlo simulation study.

Incorrect prediction of skin dose in external beam radiotherapy (EBR) can have normal tissue complication such as acute skin desquamation and skin necrosis. The absorbed dose of skin should be evaluated within basal layer, placed between the epidermis and dermis layers. However, current treatment planning systems (TPS) cannot correctly define the skin layer because of the limitation of voxel resolution in computed tomography (CT). Recently, a new tetrahedral-mesh (TM) phantom was developed to evaluate radiation dose realistically. This study aims to develop a technique to evaluate realistic skin dose using the TM phantom in EBR. The TM phantom was modeled with thin skin layers, including the epidermis, basal layer, and dermis from CT images. Using the Geant4 toolkit, the simulation was performed to evaluate the skin dose according to the radiation treatment conditions. The skin dose was evaluated at a surface depth of 50 µm and 2000 µm. The difference in average skin dose between depths was up to 37%, depending on the thickness and region of the skin to be measured. The results indicate that the skin dose has been overestimated when the skin is evaluated using commercial TPS. Although it is not possible with traditional TPS, our skin dose evaluation technique can realistically express the absorbed dose at thin skin layers from a patient-specific phantom.

Effective Dose Calculation Program (EDCP) for the usage of NORM-added consumer product.

The aim of this study is to develop the Effective Dose Calculation Program (EDCP) for the usage of Naturally Occurring Radioactive Material (NORM) added consumer products. The EDCP was developed based on a database of effective dose conversion coefficient and the Matrix Laboratory (MATLAB) program to incorporate a Graphic User Interface (GUI) for ease of use. To validate EDCP, the effective dose calculated with EDCP by manually determining the source region by using the GUI and that by using the reference mathematical algorithm were compared for pillow, waist supporter, eye-patch and sleeping mattress. The results show that the annual effective dose calculated with EDCP was almost identical to that calculated using the reference mathematical algorithm in most of the assessment cases. With the assumption of the gamma energy of 1 MeV and activity of 1 MBq, the annual effective doses of pillow, waist supporter, sleeping mattress, and eye-patch determined using the reference algorithm were 3.444 mSv year-1, 2.770 mSv year-1, 4.629 mSv year-1, and 3.567 mSv year-1, respectively, while those calculated using EDCP were 3.561 mSv year-1, 2.630 mSv year-1, 4.740 mSv year-1, and 3.780 mSv year-1, respectively. The differences in the annual effective doses were less than 5%, despite the different calculation methods employed. The EDCP can therefore be effectively used for radiation protection management in the context of the usage of NORM-added consumer products. Additionally, EDCP can be used by members of the public through the GUI for various studies in the field of radiation protection, thus facilitating easy access to the program.

Development of an effective dose coefficient database using a computational human phantom and Monte Carlo simulations to evaluate exposure dose for the usage of NORM-added consumer products.

After the Fukushima accident in Japan, the Korean Government implemented the "Act on Protective Action Guidelines Against Radiation in the Natural Environment" to regulate unnecessary radiation exposure to the public. However, despite the law which came into effect in July 2012, an appropriate method to evaluate the equivalent and effective doses from naturally occurring radioactive material (NORM) in consumer products is not available. The aim of the present study is to develop and validate an effective dose coefficient database enabling the simple and correct evaluation of the effective dose due to the usage of NORM-added consumer products. To construct the database, we used a skin source method with a computational human phantom and Monte Carlo (MC) simulation. For the validation, the effective dose was compared between the database using interpolation method and the original MC method. Our result showed a similar equivalent dose across the 26 organs and a corresponding average dose between the database and the MC calculations of < 5% difference. The differences in the effective doses were even less, and the result generally show that equivalent and effective doses can be quickly calculated with the database with sufficient accuracy.

An effective dose assessment technique with NORM added consumer products using skin-point source on computational human phantom.

The aim of this study is to develop the assessment technique of the effective dose by calculating the organ equivalent dose with a Monte Carlo (MC) simulation and a computational human phantom for the naturally occurring radioactive material (NORM) added consumer products. In this study, we suggests the method determining the MC source term based on the skin-point source enabling the convenient and conservative modeling of the various type of the products. To validate the skin-point source method, the organ equivalent doses were compared with that by the product modeling source of the realistic shape for the pillow, waist supporter, sleeping mattress etc. Our results show that according to the source location, the organ equivalent doses were observed as the similar tendency for both source determining methods, however, it was observed that the annual effective dose with the skin-point source was conservative than that with the modeling source with the maximum 3.3 times higher dose. With the assumption of the gamma energy of 1MeV and product activity of 1Bqg-1, the annual effective doses of the pillow, waist supporter and sleeping mattress with skin-point source was 3.09E-16SvBq-1year-1, 1.45E-15SvBq-1year-1, and 2,82E-16SvBq-1year-1, respectively, while the product modeling source showed 9.22E-17SvBq-1year-1, 9.29E-16SvBq-1year-1, and 8.83E-17SvBq-1year-1, respectively. In conclusion, it was demonstrated in this study that the skin-point source method could be employed to efficiently evaluate the annual effective dose due to the usage of the NORM added consumer products.

Effective dose evaluation of NORM-added consumer products using Monte Carlo simulations and the ICRP computational human phantoms.

The aim of this study is to evaluate the potential hazard of naturally occurring radioactive material (NORM) added consumer products. Using the Monte Carlo method, the radioactive products were simulated with ICRP reference phantom and the organ doses were calculated with the usage scenario. Finally, the annual effective doses were evaluated as lower than the public dose limit of 1mSv y(-1) for 44 products. It was demonstrated that NORM-added consumer products could be quantitatively assessed for the safety regulation.

Feasibility study for the assessment of the exposed dose with TENORM added in consumer products.

Consumer products including naturally occurring radioactive material have been distributed widely in human life. The potential hazard of the excessively added technically enhanced naturally occurring radioactive material (TENORM) in consumer products should be assessed. The aim of this study is to evaluate the organ equivalent dose and the annual effective dose with the usage of the TENORM added in paints. The activities of gammas emitted from natural radionuclides in the five types of paints were measured with the high-purity germanium detector, and the annual effective dose was assessed with the computational human phantom and the Monte Carlo method. The results show that uranium and thorium series were mainly measured over the five paints. Based on the exposure scenario of the paints in the room, the highest effective dose was evaluated as <1 mSv y(-1) of the public dose limit.