• Nuclear Engineering and Technology
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• v.56 no.8
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• pp.3123-3128
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• 2024

The dicentric chromosome assay is a gold standard method to estimate radiation exposure by calculating the ratio of dicentric chromosomes existing in cells. The objective of this study was to propose an automatic dicentric chromosome discrimination method based on deep convolutional neural networks using radiation exposure patient data. From 45 patients with radiation exposure, conventional Giemsa-stained images of 116,258 normal and 2800 dicentric chromosomes were confirmed. ImageNet was used to pre-train VGG19, which was modified and fine-tuned. The proposed modified VGG19 demonstrated dicentric chromosome discrimination performance, with a true positive rate of 0.927, a true negative rate of 0.997, a positive predictive value of 0.882, a negative predictive value of 0.998, and an area under the receiver operating characteristic curve of 0.997.

• Journal of Biomedical Engineering Research
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• v.20 no.2
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• pp.199-204
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• 1999

As the correct measuring of the light dosimetry in biological tissues give the important affection to the effect of PDT treatment we used Monte Carlo simulation to measure the light dosimetry on this study. The parameters using in experiments are the optical properties of the real biological tissue, and we used Henyey-Greenstein phase function among the phase functions. As we results, we displayed the result the change of Fluence rate and the difference against the previous theory was at least 0.35%. Biological tissues using in experiment were Human tissue, pig tissue, rat liver tissue and rabbit muscle tissue. The most of biological tissue have big scattering coefficient in visible wavelength which influences penetration depth. The penetration depth of human tissue in visible region is 1.5~2cm. We showed that it is possible to measure fluence rate and penetration depth within the biological tissues by Monte Carlo simulation very well.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.5
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• pp.499-505
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• 2015

The coupling effect of electric fields incident on the biological object is investigated in regards to dosimetry for a wireless power transfer(WPT) system using electromagnetic resonance phenomenon. The internal electric fields induced a biological sphere model exposed to a magnetic dipole are calculated with the finite-difference time-domain(FDTD) method considering both incident electric and magnetic fields, the impedance method considering only incident magnetic fields, and theoretical analysis. The results represent that the electric coupling effect on a biological object nearby the WPT system should be considered to conduct exact dosimetry.

• Journal of Radiation Protection and Research
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• v.32 no.3
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• pp.111-115
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• 2007

A deuterium oxide leakage accident occurred on October 4, 1999, at nuclear power plant in Korea. The concentration of tritium in air increased and 22 workers were exposed by tritium at that time. It is well known that tritium causes internal exposure. Therefore, we examined complete blood cell count, physical and biological dosimetry fur 13 workers among whole 22 workers to check the health effect and to evaluate the dose estimation of tritium exposure. The leukocyte count test, one of general blood test, was normal. The estimated doses were 0 - 4.44 mSv by physical dosimetry and 0-37 mGy by biological dosimetry. This dose does not exceed radiation dose limit, and the clinical symptoms of the exposed workers were not shown. The consistency between clinical sign and estimated dose means that physical and biological dosimetry were very useful especially in accident evaluation.

• Environmental Analysis Health and Toxicology
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• v.22 no.1 s.56
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• pp.1-8
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• 2007

Biological monitoring, analyses of internal dose for exposure to toxicants, has been thought as one of the belt approaches for risk assessment. As the amount detected in human samples is generally very low, typically in the parts-per-bilion (ppb) or parts-per-trillion (ppt) range, analytic technologies such at HPLC, GC/MS, LC/MS, and LC/MS/MS have been continuously developed. In addition, route specific and sensitive exposure biomarkers have been developed for proper biological monitoring. PBPK modeling, particularly reverse dosimetry, has been emphasized as an useful method via interpretation of biological monitoring results for regulation of toxicants. Thus, this review is focused on the use of PBPK dosimetry models for toxicology research and risk assessment in Korea.

• 대한핵의학회:학술대회논문집
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• 1997.11a
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• pp.469-470
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• 1997

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.270-277
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• 2023

Exposure to ionizing radiation induces free radicals in human nails. These free radicals generate a radiation-induced signal (RIS) in electron paramagnetic resonance (EPR) spectroscopy. Compared with the RIS of tooth enamel samples, that in human nails is more affected by moisture and heat, but has the advantages of being sensitive to radiation and easy to collect. The fingernail as a biological sample is applicable in retrospective dosimetry in cases of localized hand exposure accidents. In this study, the dosimetric characteristics of fingernails were analyzed in fingernail clippings collected from Korean donors. The dose response, fading of radiation-induced and mechanically induced signals, treatment method for evaluation of background signal, minimum detectable dose, and minimum detectable mass were investigated to propose a fingernail-EPR dosimetry protocol. In addition, to validate the practicality of the protocol, blind and field experiments were performed in the laboratory and a non-destructive testing facility. The relative biases in the dose assessment result of the blind and field experiments were 8.43% and 21.68% on average between the reference and reconstructed doses. The results of this study suggest that fingernail-EPR dosimetry can be a useful method for the application of retrospective dosimetry in cases of radiological accidents.

• The Korean Journal of Nuclear Medicine
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• v.29 no.1
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• pp.125-132
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• 1995

The purpose of this study was to establish mononuclear cell cultures such as lymphocytes or buffy coat for the biological dosimetry of in vitro Irradiation of the radionuclide Tc-99m in order to exclude the effect of residual doses seen in the cultures of whole blood. Biological do simetry of Tc-99m on cultured mononuclear cells at doses ranging from 0.05 to 6.00 Gy, by scoring unstable chromosomal aberrations(Ydr) observed in cultured lymphocytes, were performed using peripheral venous blood of healthy normal person. The results showed that; (1) In vitro irradiation of radioisotope in separated lymphocyte or buffy coat showed trace amount of residual doses of isotope after washing. Residual doses of isotopes are increased in proportion to exposed time and irradiated dose without difference between I-131 and Tc-99m. (2) We obtained these linear-quadratic dose response equations in lymphocyte and buffy coat culture after in vitro irradiation of Tc-99m, respectively (Ydr = 0.001949 $D^2$ +0.006279D + 0.000185; Ydr= 0.002531 $D^2$-0.003274 D+0.003488). In conclusion, the linear quadratic dose-response equation from in vitro irradiation of Tc-99m with lymphocyte and buffy coat culture was thought to be useful for assessing Tc-99m induced biological effects. And mono-nuclear cell cultures seem to be the most appropriate experimental model for the assessment of biological dosimetry of internal irradiation of radionuclides.

• Journal of Radiation Protection and Research
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• v.49 no.3
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• pp.102-113
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• 2024

Diffusing alpha-emitters radiation therapy (DaRT) represents a groundbreaking development in cancer therapy, offering a solution to the limitations of conventional radiation therapy. By deploying ²²⁴Ra embedded seeds, DaRT achieves targeted delivery of high-dose alpha particles directly to tumor sites, showing considerable efficacy in tumor control and minimal damage to adjacent healthy tissues. This comprehensive review analyzes the published literature regarding mechanisms, seed production, dose calculation, measurement, and biological experiments related to DaRT. It includes in-depth discussions on mathematical models, Monte Carlo simulations for dose distribution, real-time in vivo dosimetry developments, and biological experiments both in vitro and in vivo. Clinical trial outcomes are also examined to evaluate the therapy's effectiveness in various cancer types. DaRT utilizes ²²⁴Ra-labeled seeds, using the decay chain of ²²⁴Ra to deliver alpha particles effectively within a tumor. Several asymptotic diffusion-leakage models were developed to calculate the alpha dose distribution of DaRT. In vivo dosimetry techniques have been developed for real-time monitoring. Biological experiments demonstrated the cytotoxic effects of DaRT across various cancer cells, with varying radiosensitivity. Additionally, the enhanced effects of combined therapy with chemotherapy and immunotherapy were suggested by many in vivo studies. Clinical trials have shown high complete response rate in squamous cell carcinoma, with minimal side effects, suggesting DaRT's feasibility and safety. DaRT emerges as a highly localized cancer treatment method with minimal side effects compared to traditional radiation therapy. It directly ablates tumors and potentially enhances immune responses, indicating a significant advance in cancer therapy. Future research and ongoing clinical trials will further elucidate its efficacy across different cancer types and in combination with other treatments.

• Proceedings of the KOSOMBE Conference
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• v.1992 no.05
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• pp.148-151
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• 1992

There is a definite requirement to continuously monitor the operating characteristics of radiation therapy machines. It is advisable to monitor the symmetry, flatness, and energy stability of x-ray beams. The semiconductor system was developed using commercially available rectifier diode for th assessment of quality assurance In radiation therapy, which is capable of the above measurements. The beam characteristics of 6MV, 10MV and 21MV photon of Microtron electron accelerator were measured using seven-diodes as detectors and the results were compared with that of using a film results dosimetry with a X-Y plotter. The seven-diode detetor is versatile enough to be used for checking beam profile, flatness, symmetry and energy.