• Nuclear Engineering and Technology
• /
• 제56권8호
• /
• pp.3123-3128
• /
• 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.

• 대한의용생체공학회:의공학회지
• /
• 제20권2호
• /
• pp.199-204
• /
• 1999

생체조직내의 정확한 광선량 측정이 PDT 치료의 효과에 중요한 영향을 주므로 본 연구에서는 광선량 측정을 위해서 Monte Carlo 시뮬레이션을 이용하였다. 실험에 사용한 계수는 실제 생체조직의 광학계수이고 위상함수는 Henyey-Greenstein 위상함수를 사용하였다. 결과는 깊이에 따른 Fluency rate의 변화로 나타내었으며 기존 이론과의 차이는 0.35%에 지나지 않았다. 실험에 사용한 생체조직은 인체조직, 돼지조직, 쥐간조직, 토기근육조직이다. 대부분의 생체조직은 가시광선영역에서 큰 산란계수를 가지고 있으며 이것은 투과도에 큰 영향을 미치는 것으로 밝혀졌다. 가시광선 영역에서 인체조직의 투과 깊이는 1.5~2cm이었다. Monte Carlo 시뮬레이션을 이용하여 생체조직내의 광전파(light propagation), 광선량(light dosimetry), 에너지율(fluence rate), 투과깊이(penetration depth)를 효과적으로 측정할 수 있음을 보여주었다.

• 한국전자파학회논문지
• /
• 제26권5호
• /
• pp.499-505
• /
• 2015

전자기 공진 현상을 이용한 무선전력전송 시스템에 대한 조사량 평가 시 전기장의 고려 여부를 검토하였다. 인체로 인가되는 전기장과 자기장의 상대적인 크기가 조사량 평가 시에 중요한 지표가 되기 때문에, 이를 검토하기 위해 자기 다이폴 인근의 다양한 전자기장의 크기를 갖는 곳에 구형의 간이 인체 모델을 위치시키고, 구 모델 내부로 유도되는 전기장의 값을 이론과 수치해석을 통하여 구하고 비교하였다. 그 결과, 전기장을 무시할 수 없는 영역이 존재함을 확인하였으며, 이는 무선전력전송의 조사량 평가 시 외부 전기장에 대한 고려가 필요함을 알 수 있었다.

• Journal of Radiation Protection and Research
• /
• 제32권3호
• /
• pp.111-115
• /
• 2007

원자력 발전소의 중수누출에 따른 삼중수소 농도증가에 의한 방사선 내부피폭과 이에 대한건강영향평가를 실시하였다. 전체 22명 가운데 13명에 대하여 검사를 실시하였으며, 이들의 내부피폭량은 $0{\sim}4.44\;mSv$ 였다. 일반혈액검사 중 백혈구수치의 변화를 이용하여 평가한 결과에서 결정적 영향에 대한 특이사항은 나타나지 않았으며, 생물학적 선량평가 방법을 이용한 체내피폭량은 $0{\sim}37\;mGy$로 확인되었다. 결론적으로 방사선 피폭은 허용한도를 초과하지 않았으며, 결정적 영향인 임상적 증상이 보이지 않았다. 이와 같이 의학적 징후와 선량평가 추정치와의 일치성은 사고시 특히 물리적 생물학적 선량평가가 유용함을 보여 준다.

• Environmental Analysis Health and Toxicology
• /
• 제22권1호
• /
• pp.1-8
• /
• 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
• /
• 대한핵의학회 1997년도 제36차 추계학술대회
• /
• pp.469-470
• /
• 1997

• Nuclear Engineering and Technology
• /
• 제55권1호
• /
• pp.270-277
• /
• 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.

• 대한핵의학회지
• /
• 제29권1호
• /
• pp.125-132
• /
• 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
• /
• 제49권3호
• /
• pp.102-113
• /
• 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.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1992년도 춘계학술대회
• /
• pp.148-151
• /
• 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.