List of Recent Graduates

Article information

J. Radiat. Prot. Res. 2021;46(1):35-38
Publication date (electronic) : 2021 March 31

KARP

Name of graduate: Choi, Hyun Joon

Affiliation: Department of Radiation Convergence Engineering/Yonsei University/Korea

Graduation date: August. 2020

Degree: Doctor of Philosophy

Name of academic advisor: Min, Chul Hee

Title of thesis: Hybrid Prompt Gamma-Positron Emission Tomography (PG-PET)-based Multi-modality Imaging Method for In vivo Dose Verification in Proton Therapy.

Abstract: In proton therapy, the uncertainty over determining proton range may adversely affect actual dose distribution, owing to the steep dose gradient at the distal edge of the Bragg peak. Accurate prediction for in vivo proton dose distribution is particularly important to improve treatment quality of proton therapy. There are two representative methods, prompt gamma (PG) imaging and positron emission tomography (PET), have been studied for in vivo range verification. This study proposes a PG-PET-based multi-modality imaging method that combines the advantages of these two methods to increase the accuracy in determining the dose distribution in proton therapy. The Monte Carlo (MC) simulation using Geant4.10.00 was performed to optimize the geometry of detector module by obtaining and analyzing 2-D PG distributions with a 150 MeV proton beam. Based on the MC study, we constructed a dual-head PG-PET system. For a proof-of-principle study of the system, we measured PG and positron emitter (PE) distributions emitting from a 3×6×10 cm2 PMMA phantom placed at two different positions for a 45 MeV proton beam. The parallel-hole geometry of tungsten collimator was determined with a 8 mm pitch, 7 mm hole width, and 200 mm thickness, and GAGG scintillator was also determined with a 4 mm pitch and 30 mm thickness. These optimal geometrical parameters informed the manufacture of a detector module with 16×16 arrays of 3.3×3.3×30 mm3 GAGG scintillator and 3×3 mm2 SiPM pixels. In the experimental study, the dual-head PG-PET system was able to successfully obtain PG and PE distributions. In this study, we suggested the integrated PG and PET imaging system to robustly verify the in vivo range in proton therapy. Current results show proof-of-principle, but there should be further study including deep learning algorithms to accurate 3-D dose evaluation.

Name of graduate: Kim, Jiseok

Affiliation: Department of Nuclear Engineering/Hanyang University/Korea

Graduation date: March. 2020

Degree: Doctor of Philosophy

Name of academic advisor: Kim, Yong Kyun

Title of thesis: Neutron Spatial Distribution Measurement Using Activation Foils Fabricated by Printed Electronics Technique.

Abstract: The neutron spatial distribution is an important parameter in the neutron utilization study. Therefore, the distirbution should be accurately determined before or during the experiment. Various detectors can be utilized to measure the neutron spatial distribution, including a position-sensitive He-3 detector and a CCD based on scintillation detector; however, there are difficulties in their uses for the evaluation of neutron fluence in very narrow spaces such as irradiation vials as well as for the evaluation of neutron energy. For this reason, an array-type threshold detector consisting of a combination of multiple two-dimensional (2D) foil arrays with the different elements are extensively utilized to determine the neutron field (energy, spatial distribution). The activation foils are inexpensive, also do not require detector calibration, and exclude background gamma-rays, all while enabling the reconstruction of the neutron energy information using the unfolding method.

Name of graduate: Kim, Jae Hyeon

Affiliation: Department of Nuclear Engineering/Hanyang University/Korea

Graduation date: February. 2021

Degree: Doctor of Philosophy

Name of academic advisor: Kim, Chan Hyeong

Title of thesis: Dual-mode Large-Area Compton Camera For Radioactive Waste Drum Monitoring.

Abstract: To enhance the economic efficiency of NPP decommissioning, it is necessary to reduce disposal cost for radioactive waste drum. For the radioactive waste drum monitoring, this study developed the prof-of-principle Dual-mode Large-Area Compton Camera (DLACC) which is the first Compton imaging system that can provide quantitative information of the hot-spot in the waste drum with the attenuation map and 3-D radiation image obtained by Compton CT mode and Compton imaging mode, respectively. Component detector modules for the prof-of-principle DLACC were developed including large monolithic NaI(Tl) scintillation detectors and a dedicated FPGA-based data acquisition system based on fully digital signal processing. The energy resolution of the developed detector modules was evaluated to be 6.93% for 662 keV. Especially, the energy resolution performance is maintained at the high-count-rate environments with hundreds of kHz, showing that the developed modules can be used for the Compton CT mode which needs to measure 24 mCi gamma-ray source. The performance of the prof-of-principle DLACC was evaluated experimentally for various conditions. The results showed that the DLACC clearly reconstructed the 3-D location of the hot-spot in the radioactive waste drum with the angular resolution of 6.8° FWHM by using the Compton imaging mode. In addition, the DLACC was also able to obtain the attenuation maps of the drum with the Compton CT mode. Finally, for the first time as a Compton imaging system, the results of this study experimentally demonstrated that the DLACC can estimate the activity of the 137Cs hot-spot contamination inside a radioactive waste drum within 1.8 times error by using the 3-D location of hot-spot and the attenuation map in the drum. This study served to verify the potential of the DLACC for radioactive waste drum monitoring.

Name of graduate: Kim, Junwoo

Affiliation: School of Mechanical Engineering/Pusan National University/Korea

Graduation date: August. 2020

Degree: Doctor of Philosophy

Name of academic advisor: Kim, Ho Kyung

Title of thesis: Characterization of Flat-Panel Sandwich Detectors for Dual-Energy Imaging Applications.

Abstract: Conventional dual-energy (DE) chest radiography reconstructs the two images obtained from low-energy and high-energy x-ray into soft-tissue and bone enhancement images to reduce anatomical background noise and improve the conspicuity of the lesion compared to single-energy chest radiography. This method suffers from patient dose and artifacts caused by patient motion between image acquisition and which can be diagnosed with computed tomography or digital tomosynthesis techniques at a high cost. This thesis aims to develop a sandwich detector-based large-area flat-panel detector to prevent the increase of patient dose and motion artifacts in patients by acquiring low-energy (front detector) images and high-energy (rear detector) images simultaneously. The spatial resolution of the two detectors is different because the front detector of the sandwich detector uses a thin scintillator and the rear detector uses a thick scintillator. Log-subtraction techniques are used to reconstruct DE images, resulting in edge-enhancement properties and we modeled them. Also, the unique characteristics of a single-shot DE technique were verified against conventional dual-shot DE images using the same detector. To minimize artifacts such as misalignment between detectors by sandwich structures and the shape of x-ray beams, various registration algorithms were realized to compare DE image quality. The limited area of the sandwich detector produced in the previous study and the low gain of the rear detector motivated the development of the large-area flat-panel sandwich detector, and the performance of the complemented sandwich detector was compared and analyzed by calculating modulation-transfer function, noise-power spectrum, and detective quantum efficiency in the Fourier domain. A theoretical model describing signals and noise from sandwich detectors was designed and experimental verification was performed. To optimize the material and thickness of the energy-separation filter that determines the performance of the DE image in an angiography application, a theoretical model was used to calculate the energy-separation filter material and thickness when the signal-difference-to-noise ratio is maximum using DE signals and noise transmitted by anatomical structures.

Name of graduate: Kim, Jaehyo

Affiliation: Department of Nuclear Engineering/Sejong University/Korea

Graduation date: February. 2021

Degree: Master of Science

Name of academic advisor: Kim, Geehyun

Title of thesis: A Study on the Simulated Spectra Responses of a Scintillation Detector by Tracking Optical Photon Generated from the Gamma-ray Interaction.

Name of graduate: Hong, Wooseong

Affiliation: Department of Nuclear Engineering/Sejong University/Korea

Graduation date: February. 2021

Degree: Master of Science

Name of academic advisor: Kim, Geehyun

Title of thesis: A Simulation Study for Neutron Activation Analysis of Subsurface Contaminants using Nuclear Logging Sonde.

Name of graduate: Jang, Ji won

Affiliation: Department of Radiation Convergence Engineering/Yonsei University/Korea

Graduation date: August. 2020

Degree: Master of Science

Name of academic advisor: Min, Chul Hee

Title of thesis: Development of Accurate Dose Evaluation Technique using the Monte Carlo Simulation in Scanning Proton Therapy.

Name of graduate: Jeong, Areum

Affiliation: Department of Health and Safety Convergence Science/Korea University/Korea

Graduation date: February. 2021

Degree: Master of Science

Name of academic advisor: Lee, Wonho

Title of thesis: Organ Dose Estimation of Radiation Workers in Korea for Risk Assessment of Occupational Exposure.

JHPS

Name of graduate: Jun, Hu

Affiliation: Department of Radiation Science/Hirosaki University/Japan

Graduation date: March. 2020

Degree: Doctor of Philosophy

Name of academic advisor: Tokonami, Shinji

Title of thesis: The health risk assessment of radiation exposure to 222Rn, 220Rn and their progenies.

Abstract: The inhalation doses resulting from the 222Rn, 220Rn, and their progenies are important quantities to estimate the health risk caused by the long-term radiation exposure for epidemiological studies. Nearly the entire lung dose arises from the inhalation of the radon progeny and not from the gas itself as almost all of the gas that is inhaled is subsequently exhaled. Because of the short half-lives of radon progeny, the dose is delivered to the lung tissues before clearance can take place, either by absorption into the blood or by particle transport to the alimentary tract. Therefore, it is necessary to accurately estimate the radiation dose. In practice, the accurate estimation of the radiation dose by inhalation of short-lived progenies from the 222Rn and 220Rn measurements is necessary to focus on the two main procedures: (1) the measurement and estimation of activity concentration of the individual short-lived 222Rn/220Rn decay products and (2) the estimation of dose conversion factor. In order to evaluate the health risk of radiation exposure to 222Rn, 220Rn and their progenies, in this thesis, the researches on the behaviors of 222Rn, 220Rn and their progenies in the indoor environment by using the numerical models were summarized. And then, according to the knowledge of the behaviors of 222Rn and 220Rn progeny, a deposition-based direct radon and thoron progeny passive detector was developed to measure the long-term radon and thoron concentration by using the theoretical model, which can automatically calibrate and optimize the results. And the dose conversion factor of 222Rn and 220Rn progeny based on IMBA Professional® software was calculated based on the reference parameters provided by the ICRP 66 and 137 and was compared with the published value of the other dosimetric software.

Name of graduate: Moriyama, Hitomi

Affiliation: Department of Radiological Sciences/Tokyo Metropolitan University/Japan

Graduation date: March. 2020

Degree: Doctor of Philosophy

Name of academic advisor: Fukushi, Masahiro

Title of thesis: Pathological and molecular biological characteristics of radiation-induced rat mammary carcinoma.

Abstract: Mammary grand is one of the most sensitive organs to radiation-induced carcinogenesis. Neutrons are used as a type of high linear energy transfer (LET) radiation and they have stronger carcinogenic effects compared to low LET radiation. However, the cancer after neutron exposure are not well understood. This study aimed to clarify the characteristics of neutron or γ-ray-induced mammary carcinomas by pathological and molecular biological analysis. Mammary carcinomas from female Sprague-Dawley (SD) rats irradiated at 7 weeks of the age with 0.485 Gy neutron beams or 0.5 Gy γ-rays were compared with carcinomas of non-irradiated rats. Tumors were classified into luminal and non-luminal subtypes based on immunohistochemistry, while their DNA copy-number variants were determined using array comparative genome hybridization (aCGH). Neutrons and γ-rays increased the incidence of luminal carcinomas. The carcinomas in the three groups contained multiple aberrations affecting 46 genes for which mutations have been reported in human breast cancer. Next, to analyze other types of mutations not detected by aCGH such as point mutations, whole exome sequencing (WES) was performed on rat mammary carcinomas. They were obtained from female SD rats irradiated at 7 weeks of the age with 0.97 Gy neutron beams or 4 Gy γ-rays and from non-irradiated rats. The carcinomas also classified into luminal and non-luminal subtypes. Neutrons and γ-rays significantly increased the incidence of luminal subtype over the non-luminal subtype. As the results of WES, focal DNA copy-number losses of chromosome 5 involving cancer genes were detected in carcinomas from the irradiated groups. Surprisingly, the results of DNA copy-number variants using aCGH also showed copy-number losses in this chromosomal region in the carcinoma from irradiated groups. This study suggested that neutrons and γ-rays increased the incidence of luminal subtypes and focal copy-number loss in cancer genes is characteristic for radiation-induced mammary carcinoma.

Name of graduate: Narita, Masato

Affiliation: Department of Radiological Sciences/Tokyo Metropolitan University/Japan

Graduation date: March. 2020

Degree: Master of Science

Name of academic advisor: Fukushi, Masahiro/Inoue, Kazumasa

Title of thesis: Development of Alpha Spectrometers for Radiation Control of Alpha Emitted Radiopharmaceutical.

Name of graduate: Nishiono, Konoko

Affiliation: Graduate school of Science and Engineering/Kindai University/Japan

Graduation date: March. 2019

Degree: Master of Science

Name of academic advisor: Yamanishi, Hirokuni

Title of thesis: Investigation of radioactive cesium accumulation mechanism by mycelium culture experiments and in vitro evaluation of the internal dose by mushroom ingestion.

Name of graduate: Nugrah, Eka Djatnika

Affiliation: Department of Radiation Science/Hirosaki University/Japan

Graduation date: March. 2020

Degree: Master of Science

Name of academic advisor: Tokonami, Shinji

Title of thesis: Natural Radiation and Radioactivity Measurements in Anomalously High Background Radiation Area in Indonesia.

Name of graduate: Saputra, Miki Arian

Affiliation: Department of Radiation Science/Hirosaki University/Japan

Graduation date: March. 2020

Degree: Master of Science

Name of academic advisor: Tokonami, Shinji

Title of thesis: Characteristics of radiation exposure due to radon, thoron, and thoron progeny in extremely high background radiation area named Takandeang, Indonesia.

Name of graduate: Umekawa, Shusuke

Affiliation: Graduate School of Maritime Sciences/Kobe University/Japan

Graduation date: March. 2020

Degree: Master of Science

Name of academic advisor: Oda, Keiji

Title of thesis: Evaluation of the Eye Lens Dose in Non-Uniform Beta and Gamma-Ray Fields.

Name of graduate: Hasan, Md Mahamudul

Affiliation: Department of Environment Systems, Graduate School of Frontier Sciences/The University of Tokyo/Japan

Graduation date: March. 2020

Degree: Master of Science

Name of academic advisor: Iimoto,Takeshi

Title of thesis: Behavior Estimation of Radon in Living Environment and Indoor Radiation Dose.

Name of graduate: Hoshi, Shinichi

Affiliation: Division of Disaster & Radiation Medical Sciences Joint Major, Graduate School of Medicine/Fukushima Medical University/Japan

Graduation date: March. 2020

Degree: Master of Science

Name of academic advisor: Ishikawa, Tetsuo

Title of thesis: INES (International Nuclear and Radiological Event Scale) levels of past nuclear accidents and their relationships with health and social effects.

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