• The Journal of Korean Medicine
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• v.31 no.3
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• pp.1-7
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• 2010

Objectives: To introduce to TKM scientific dose conversion methods of human to animal or animal to human for new drug investigations. Methods: We searched guidelines of the FDA and KFDA, and compared them with references for drug-dose conversion from various databases such as PubMed and Google. Then, we analyzed the potential issues and problems related to dose conversion in safety documentation of new herbal drugs based on our experiences during Investigational New Drug (IND) applications of TKM. Results: Dose conversion from human to animal or animal to human must be appropriately translated during new drug development. From time to time, investigators have some difficulty in determining the appropriate dose, because of misunderstandings of dose conversion, especially when they estimate starting dose in clinical or animal studies to investigate efficacy, toxicology and mechanisms. Therefore, education of appropriate dose calculation is crucial for investigators. The animal dose should not be extrapolated to humans by a simple conversion method based only on body weight, because many studies suggest the normalization method is based mainly on body surface area (BSA). In general, the body surface area seems to have good correlation among species with several parameters including oxygen utilization, caloric expenditure, basal metabolism, blood volume and circulating plasma protein. Likewise, a safety factor should be taken into consideration when deciding high dose in animal toxicology study. Conclusion: Herein, we explain the significance of dose conversion based on body surface area and starting dose estimation for clinical trials with safety factor.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.681-688
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• 2022

Dose monitoring in CT patients requires accurate dose estimation but most of the CT dose calculation tools are based on Caucasian computational phantoms. We established a library of organ dose conversion coefficients for Korean adults by using four Korean adult male and two female voxel phantoms combined with Monte Carlo simulation techniques. We calculated organ dose conversion coefficients for head, chest, abdomen and pelvis, and chest-abdomen-pelvis scans, and compared the results with the existing data calculated from Caucasian phantoms. We derived representative organ doses for Korean adults using Korean CT dose surveys combined with the dose conversion coefficients. The organ dose conversion coefficients from the Korean adult phantoms were slightly greater than those of the ICRP reference phantoms: up to 13% for the brain doses in head scans and up to 10% for the dose to the small intestine wall in abdominal scans. We derived Korean representative doses to major organs in head, chest, and AP scans using mean CTDI_vol values extracted from the Korean nationwide surveys conducted in 2008 and 2017. The Korean-specific organ dose conversion coefficients should be useful to readily estimate organ absorbed doses for Korean adult male and female patients undergoing CT scans.

• Nuclear Engineering and Technology
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• v.42 no.1
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• pp.89-96
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• 2010

This paper describes the methodology of calculating the internal dose conversion coefficient in order to assess the radiological impact on non-human species. This paper also presents the internal dose conversion coefficients of 25 radionuclides ($^3H,\;^7Be,\;^{14}C,\;^{40}K,\;^{51}Cr,\;^{54}Mn,\;^{59}Fe,\;^{58}Co,\;^{60}Co,\;^{65}Zn,\;^{90}Sr,\;^{95}Nb,\;^{99}Tc,\;^{106}Ru,\;^{129}I,\;^{131}I,\;^{136}Cs,\;^{137}Cs,\;^{140}Ba,\;^{140}La,\;^{144}Ce,\;^{238}U,\;^{239}Pu,\;^{240}Pu$) for domestic seven reference animals (roe deer, rat, frog, snake, Chinese minnow, bee, and earthworm) and one reference plant (pine tree). The uniform isotropic model was applied in order to calculate the internal dose conversion coefficients. The calculated internal dose conversion coefficient (${\mu}Gyd^{-1}$ per $Bqkg^{-1}$) ranged from $10^{-6}$ to $10^{-2}$ according to the type of radionuclides and organisms studied. It turns out that the internal does conversion coefficient was higher for alpha radionuclides, such as $^{238}U,\;^{239}Pu$, and $^{240}Pu$, and for large organisms, such as roe deer and pine tree. The internal dose conversion coefficients of $^{239}U,\;^{240}Pu,\;^{238}U,\;^{14}C,\;^3H$, and $^{99}Tc$ were independent of the organism.

• Journal of Radiation Protection and Research
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• v.46 no.3
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• pp.98-105
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• 2021

Background: In recent events of the coronavirus disease 2019 (COVID-19) pandemic, computed tomography (CT) scans are being globally used as a complement to the reverse-transcription polymerase chain reaction (RT-PCR) tests. It will be important to be aware of major organ dose levels, which are more relevant quantity to derive potential long-term adverse effect, for Korean pediatric and adult patients undergoing CT for COVID-19. Materials and Methods: We calculated organ dose conversion coefficients for Korean pediatric and adult CT patients directly from Korean pediatric and adult computational phantoms combined with Monte Carlo radiation transport techniques. We then estimated major organ doses delivered to the Korean child and adult patients undergoing CT for COVID-19 combining the dose conversion coefficients and the international survey data. We also compared our Korean dose conversion coefficients with those from Caucasian reference pediatric and adult phantoms. Results and Discussion: Based on the dose conversion coefficients we established in this study and the international survey data of COVID-19-related CT scans, we found that Korean 7-year-old child and adult males may receive about 4-32 mGy and 3-21 mGy of lung dose, respectively. We learned that the lung dose conversion coefficient for the Korean child phantom was up to 1.5-fold greater than that for the Korean adult phantom. We also found no substantial difference in dose conversion coefficients between Korean and Caucasian phantoms. Conclusion: We estimated radiation dose delivered to the Korean child and adult phantoms undergoing COVID-19-related CT examinations. The dose conversion coefficients derived for different CT scan types can be also used universally for other dosimetry studies concerning Korean CT scans. We also confirmed that the Caucasian-based CT organ dose calculation tools may be used for the Korean population with reasonable accuracy.

• Journal of Biomedical Engineering Research
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• v.39 no.6
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• pp.243-249
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• 2018

The indoor radon concentration was measured in the lecture room of the university and the radon concentration was converted to the amount related to the radon exposure using the dose conversion convention and compared with the reference levels for the radon concentration control. The effect of indoor radon inhalation was evaluated by estimating the life effective dose and the risk of exposure. To measure the radon concentration, measurements were made with a radon meter and a dedicated analysis Capture Ver. 5.5 program in a university lecture room from January to February 2018. The radon concentration measurement was carried out for 5 consecutive hours for 24 hours after keeping the airtight condition for 12 hours before the measurement. Radon exposure risk was calculated using the radon dose and dose conversion factor. Indoor radon concentration, radon exposure risk, and annual effective dose were found within the 95% confidence interval as the minimum and maximum boundary ranges. The radon concentration in the lecture room was $43.1-79.1Bq/m^3$, and the maximum boundary range within the 95% confidence interval was $77.7Bq/m^3$. The annual effective dose was estimated to be 0.20-0.36 mSv/y (mean 0.28 mSv/y). The life-time effective dose was estimated to be 0.66-1.18 mSv (mean $0.93{\pm}0.08mSv$). Life effective doses were estimated to be 0.88-0.99 mSv and radon exposure risk was estimated to be 12.4 out of 10.9 per 100,000. Radon concentration was measured, dose effective dose was evaluated using dose conversion convention, and degree of health hazard by indoor radon exposure was evaluated by predicting radon exposure risk using nominal hazard coefficient. It was concluded that indoor living environment could be applied to other specific exposure situations.

• Journal of Radiation Protection and Research
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• v.6 no.1
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• pp.8-24
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• 1981

This paper presents flux-to-dose-rate conversion factors for neutrons and gamma rays based on the American National Standard Institute(ANSI) N666. These data are used to calculated the dose rate distribution of neutron and gamma ray in radiation fields. Neutron flux-to-dose-rate conversion factors for energies from $2.5{\times}10^{-8}$ to 20 MeV are presented; the corresponding energy range for gamma rays is 0.01 to 15 MeV. Flux-to-dose-rate conversion factors were calculated, under the assumption that radiation energy distribution has nonlinearity in the phantom, have different meaning from those values obtained by monoetiergetic radiation. Especially, these values were determined with the cross section library. The flux-to-dose-rate conversion factors obtained in this work were in a good agreement to the values presented by ANSI. Those data will be a useful for the radiation shielding analysis and the radiation dosimetry in the case of continuous energy distributions.

• Journal of Radiation Protection and Research
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• v.41 no.4
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• pp.424-435
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• 2016

Background: The International Commission on Radiological Protection (ICRP) recommendations and the Federal Guidance Report (FGR) published by the U.S. Environmental Protection Agency (EPA) have been widely applied worldwide in the fields of radiation protection and dose assessment. The dose conversion coefficients of the ICRP and FGR are widely used for assessing exposure doses. However, before the coefficients are used, the user must thoroughly understand the derivation process of the coefficients to ensure that they are used appropriately in the evaluation. Materials and Methods: The ICRP provides recommendations to regulatory and advisory agencies, mainly in the form of guidance on the fundamental principles on which appropriate radiological protection can be based. The FGR provides federal and state agencies with technical information to assist their implementation of radiation protection programs for the U.S. population. The system of radiation dose assessment and dose conversion coefficients in the ICRP and FGR is reviewed in this study. Results and Discussion: A thorough understanding of their background is essential for the proper use of dose conversion coefficients. The FGR dose assessment system was strongly influenced by the ICRP and the U.S. National Council on Radiation Protection and Measurements (NCRP), and is hence consistent with those recommendations. Moreover, the ICRP and FGR both used the scientific data reported by Biological Effects of Ionizing Radiation (BEIR) and United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) as their primary source of information. The difference between the ICRP and FGR lies in the fact that the ICRP utilized information regarding a population of diverse races, whereas the FGR utilized data on the American population, as its goal was to provide guidelines for radiological protection in the US. Conclusion: The contents of this study are expected to be utilized as basic research material in the areas of radiation protection and dose assessment.

• Nuclear Engineering and Technology
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• v.12 no.3
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• pp.171-179
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• 1980

This paper presentss flux-to-dose conversion factors for neutrons and gamma-rays based on the concept of the maximum absorbed dose. Neutron flux-to-does-rate conversion factors for energies from 2.5$\times$10$^{-8}$ to 20 MeV are presented while the conversion factors for gamma-rays are given in the energy range of 0.01 to 15MeV. Flux-to-does-rate conversion factors, which were calculated under the assumption that the radiation energy distribution has nonlinearity in phantom, are different from those values obtained by monoenergetic radiation. Especially, these values obtained here were determined for the cross section libray such as DLC-23, DLC-27, and DLC-31. The flux-to-dose-rate conversion factors obtained in this work are in a good agreement with the values presented by American National Standard Institute (ANSI) N666. These results are used to calculate the dose rate distribution of neutron and gamma-ray in any radiation fields, and will be useful for the radiation shielding analysis, radiation protection and radiation dosimetry concerned with problems of continuous energy distribution.

• Journal of Radiation Protection and Research
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• v.47 no.2
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• pp.77-85
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• 2022

Background: After the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, a model was developed to estimate the external exposure doses for residents who were expected to return to their homes after evacuation orders were lifted. However, the model's accuracy and uncertainties in parameters used to estimate external doses have not been evaluated. Materials and Methods: The model estimates effective doses based on the integrated ambient dose equivalent (H^*(10)) and life patterns, considering a dose reduction factor to estimate the indoor H^*(10) and a conversion factor from H^*(10) to the effective dose. Because personal dose equivalent (H_p(10)) has been reported to agree well with the effective dose after the FDNPS accident, this study validates the model's accuracy by comparing the estimated effective doses with H_p(10). The H_p(10) and life pattern data were collected for 36 adult participants who lived or worked near the FDNPS in 2019. Results and Discussion: The estimated effective doses correlated significantly with H_p(10); however, the estimated effective doses were lower than H_p(10) for indoor sites. A comparison with the measured indoor H^*(10) showed that the estimated indoor H^*(10) was not underestimated. However, the H_p(10) to H^*(10) ratio indoors, which corresponds to the practical conversion factor from H^*(10) to the effective dose, was significantly larger than the same ratio outdoors, meaning that the conversion factor of 0.6 is not appropriate for indoors due to the changes in irradiation geometry and gamma spectra. This could have led to a lower effective dose than H_p(10). Conclusion: The estimated effective doses correlated significantly with H_p(10), demonstrating the model's applicability for effective dose estimation. However, the lower value of the effective dose indoors could be because the conversion factor did not reflect the actual environment.

• Journal of Radiation Protection and Research
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• v.47 no.3
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• pp.158-166
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• 2022

Background: The effects of radiation on the health of radiation workers who are constantly susceptible to occupational exposure must be assessed based on an accurate and reliable reconstruction of organ-absorbed doses that can be calculated using personal dosimeter readings measured as H_p(10) and dose conversion coefficients. However, the data used in the dose reconstruction contain significant biases arising from the lack of reality and could result in an inaccurate measure of organ-absorbed doses. Therefore, this study quantified the biases involved in organ dose reconstruction and calculated the bias-corrected H_p(10)-to-organ-absorbed dose coefficients for the use in epidemiological studies of Korean radiation workers. Materials and Methods: Two major biases were considered: (a) the bias in H_p(10) arising from the difference between the dosimeter calibration geometry and the actual exposure geometry, and (b) the bias in air kerma-to-H_p(10) conversion coefficients resulting from geometric differences between the human body and slab phantom. The biases were quantified by implementing personal dosimeters on the slab and human phantoms coupled with a Monte Carlo method and considered to calculate the bias-corrected H_p(10)-to-organ-absorbed dose conversion coefficients. Results and Discussion: The bias in H_p(10) was significant for large incident angles and low energies (e.g., 0.32 for right lateral at 218 keV), whereas the bias in dose coefficients was significant for the posteroanterior (PA) geometry only (e.g., 0.79 at 218 keV). The bias-corrected H_p(10)-to-organ-absorbed dose conversion coefficients derived in this study were up to 3.09- fold greater than those from the International Commission on Radiological Protection publications without considering the biases. Conclusion: The obtained results will aid future studies in assessing the health effects of occupational exposure of Korean radiation workers. The bias-corrected dose coefficients of this study can be used to calculate organ doses for Korean radiation workers based on personal dose records.