• Journal of the Korean Society of Radiology
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• v.16 no.6
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• pp.681-686
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• 2022

In this study, a scintillation resin for 3D printing was fabricated with 1.0 wt% of PPO organic scintillator, 5.0 wt% of MMA, and commercial acrylic resin. Using the scintillation resin, 3D-shaped plastic scintillator radiation sensors were successfully fabricated quickly and inexpensively with a commercial 3D DLP printer. The 3D printed plastic scintillator has a good dose-output linearity of R-square 0.998 was obtained in the range of 1 to 10 nA of beam current of the 45 MeV proton beam. The developed 3D plastic scintillator has low light output, so there is a limit to its use in low-dose-rate gamma-ray or X-ray dosimetry. However, it was confirmed that the tissue equivalent material could be usefully used for measuring high energy or high dose rates radiation, such as proton beams and ultra-high dose rate beams.

• Nuclear Engineering and Technology
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• v.9 no.2
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• pp.65-74
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• 1977

The radiation-induced graft polymerization of acrylic acid onto polyester fabric was investigated with accelerated electron beams as ratiation source at high dose rates. Homopolymerization was suppressed by addition of cations which is known as homopolymerization inhibitor, but this practical advantage was obtained at the expense of grafting efficiency. The rate of grafting (%/sec) was proportional to the 0.82th power of dose rates over the range from 1.6$\times$10$^{6}$ to 10$\times$10$^{6}$ rad/sec. The grafted polyester fabric showed considerable improvement in moisture regain and antistatic properties.

• Radiation Oncology Journal
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• v.37 no.3
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• pp.193-200
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• 2019

Purpose: To explore the role of salvage radiotherapy (RT) for recurrent thymoma as an alternative to surgery. Materials and Methods: Between 2007 and 2015, 47 patients who received salvage RT for recurrent thymoma at Yonsei Cancer Center were included in this study. Recurrent sites included initial tumor bed (n = 4), pleura (n = 19), lung parenchyma (n = 10), distant (n = 9), and multiple regions (n = 5). Three-dimensional conformal and intensity-modulated RT were used in 29 and 18 patients, respectively. Median prescribed dose to gross tumor was 52 Gy (range, 30 to 70 Gy), with equivalent doses in 2-Gy fractions (EQD₂). We investigated overall survival (OS), progression-free survival (PFS), and patterns of failure. Local failure after salvage RT was defined as recurrence at the target volume receiving >50% of the prescription dose. Results: Median follow-up time was 83 months (range, 8 to 299 months). Five-year OS and PFS were 70% and 22%, respectively. The overall response rate was 97.9%; complete response, 34%; partial response, 44.7%; and stable disease, 19.1%. In multivariate analysis, histologic type and salvage RT dose (≥52 Gy, EQD₂) were significantly associated with OS. The high dose group (≥52 Gy, EQD₂) had significantly better outcomes than the low dose group (5-year OS: 80% vs. 59%, p = 0.046; 5-year PFS: 30% vs. 14%, p=0.002). Treatment failure occurred in 34 patients; out-of-field failure was dominant (intra-thoracic recurrence 35.3%; extrathoracic recurrence 11.8%), while local failure rate was 5.8%. Conclusion: Salvage RT for recurrent thymoma using high doses and advanced precision techniques produced favorable outcomes, providing evidence that recurrent thymoma is radiosensitive.

• Journal of radiological science and technology
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• v.43 no.5
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• pp.375-382
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• 2020

PET/CT is a medical equipment that detects 0.511 MeV of gamma rays. The radiation workers are inevitably exposed to ionizing radiation in the process of handling the isotope. Accordingly, PET/CT workers use syringe shields made of lead and tungsten to protect their hands. However, lead and tungsten are known to generate very high scattering particles by interacting with gamma rays. Therefore, in this study, we tried to find out the effect on the scattering particles emitted from the syringe shield. In the experiment, first, the exposure dose to the hand (Rod phantom) was evaluated according to the metal material (lead, tungsten, iron, stainless steel) using Monte Carlo simulation. The exposure dose was compared according to whether or not plastic is attached. Second, the exposure dose of scattering particles was measured using a dosimeter and lead. As a result of the experiment, the shielding rate of plastics using the Monte Carlo simulation showed the largest difference in dose of about 40 % in lead, and the lowest in iron, about 15 %. As a result of the dosimeter test, when the plastic tape was wound on lead, it was found that the reduction rate was about 15 %, 28 %, and 39 % depending on the thickness. Based on the above results, it was found that 0.511 MeV of gamma ray interacts with the shielding tool to emit scattered rays and has a very large effect on radiation exposure. However, it was considered that the scattering particles could be sufficiently removed with plastics with a low atomic number. From now on, when using high-energy radiation, the shielding tool and the skin should not be in direct contact, and should be covered with a material with a low atomic number.

• Development and Reproduction
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• v.22 no.1
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• pp.85-94
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• 2018

Endocrine disruptors have been concerned in toxicology but now challenged as physiological point especially concerned with exposing dose and period. In this study the low-dose chronic administration of di(2-ethylhexyl) phthaltae (DEHP) during reproductive period was examined to evaluate the possible roles. Adult male and female CD-1 mice were exposed to DEHP with drinking water containing $133{\mu}g/L$ and $1,330{\mu}g/L$ DEHP in water according to OECD 433 guide line and sacrificed just after weaning. The weights of uterus and ovary were decreased by drinking of $1,330{\mu}g/L$ DEHP water. There was not adverse effects on either accumulated mating rate and mating rate depend on estrus stage, pregnancy duration, and sex ration at birth. However, the accumulated rate of successful delivery and litter size were significantly high at $1,330{\mu}g/L$ DEHP water. The number of epididymal sperm was significantly increased by drinking of $1,330{\mu}g/L$ DEHP water. In addition, the number of follicles (primary, secondary, tertiary) were more many than control at $1,330{\mu}g/L$ DEHP water drunk mother. Though further studies are needed to identify what are the mechanism of DEHP in folliculogenesis and spermatogenesis. From this study we firstly report the effect of low-dose chronic administration of DEHP with drinking could change the ovarian follicle population size and spermatogenesis rate. Put together, those finding is different from previous high-dose effects and suggest the physiological role of DEHP in gonads and uterus.

• Journal of the Korean Society of Radiology
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• v.7 no.3
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• pp.251-257
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• 2013

Spatial dose rates of high dose $^{131}I$ therapy patients were Measured Three dimensional (X, Y, Z) distributions. I have constructed geometrical an aluminum support structure for spatial dose meters placed in 5 different heights, 8 different azimuthal angles, 6 different time interval and distance 100 cm from High dose$^{131}I$ therapy patients. when the height of vertical plane Spatial dose distribution is 100 cm, the Spatial dose rates is max and the error range is low. the vertical plane Spatial dose rates was found to be 71.85 ${\mu}Sv/h$ on the average at a distance of 100 cm, height 100 cm, from the patients 24 hours after $^{131}I$ oral administration. I divided 12 patients into two groups. I have analysed group A (drinking 5 L water) and group B (drinking 3 L water) in order to measure decrease spatial dose rates. I have found the spatial distributions of patient dose rates is $44.9{\pm}7.2$ ${\mu}Sv/h$ in group A and $100.3{\pm}8.1$ ${\mu}Sv/h$ in group B by 24 after $^{131}I$ oral administration. the reduction factor was found to be approximately 54 % through drinking 5 L water during 24 hours.

• Radiation Oncology Journal
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• v.7 no.2
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• pp.213-225
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• 1989

An analysis has been made of two hundred seven patients who were treated at the department of Radiation Oncology of Korea University Hospital for lung cancer from January 1981 through December 1986. There were 137 patients of nonsmall cell carcinoma (137/207, 66%), 26 patients of small cell carcinoma (26/207, 12.5%) and 44 patients of unproven histology. By aims of treatment, there were 104 patients (104/207, 50%) treated for cure, 89 patients (89/207, 42.9%) for palliation and 14 patients treated postoperatively. In 22 out of 207 patients, chemotherapy was done with radiotherapy, 12 of which were patients with small cell carcinoma. Stage II patients were 49 (49/207, 23.6%), stage III patients were 157 (157/207, 75.8%) and one patient had an occult cancer The tumor was initial Iy measured by CAT scan and chest X-rays in the 165 (165/207, 79.7%) patients, among which 117 patients had tumor diameter more than 5cm and 48 patients less than 5cm. Radiation therapy was given with Cobalt 60 teletherapy unit and the treatment volume encompassed primary tumor and the mediastinum. For curative aim, daily tumor dose of 180 cGy was given up to the range of 5,400~6,120cGy/30~34F/6~7 week period and for palliative aim, daily tumor dose of 300 cGy was given up to the range of 3,600~4,500 cGy/12~15F/2~3 week period. Postoperatively, mediastinum was treated for total dose of 5,040 cGy/28F/5.5 week period. 123 patients (123/207, 59%) were followed up after completion of radiotherapy for 14 months to 7 years. Local tumor response to the irradiation was measured by chest X-ray taken at one month follow up and was evaluated for response rate, if they were regressed more than 50% or less than 50% of the initial tumor size. The treatment results were as follows; 1. The median survival time was 8.5 months and survival rates for 1 year, 2 year and 5 year was 25%, 3.5% and 1% of nonsmall cell lung ca of 74 evaluable patients. 2. More than 50% of local tumor response rate was obtained in about half of overall cases; 90.5% for small cell ca, 50% for squamous cell ca, 25% for adenoca and 57% for large cell ca. 3. Response rate more than 50% was seen in the 50% of the patient group with tumor diameter more than 5cm and in the 55% of those with tumor diameter less than 5cm. 4. By total raidation dose given, patient group which was given 5,400~6,120 cGy equivalent dose or higher showed tumor response rate more than 50% in 53% of the patients, whereas the group with dose less than 5,400cGy equivalent, in 25% of the patients. 5. Survival rate for 6 month, 1 year and 2 year was compared between the group of local tumor response rate more than 50% vs. group with response rate less than 50%; 74% vs. 43%, 33% vs, 23%, 10% vs. 1%, respectively. 6. Local failure was seen in 21%(44/207) of the patients, which occured mostly within 15 months after completion of radiation therapy. Distant metastases were seen in 49.7%(103/207) of the patients, of which 43 cases were found before initiation of radiotherapy. The most common metastatic sites were bone and brain. In this sutdy, 1 year,2 year and S year survival rates were somewhat poor compared to the other studies. It mainly seems to be due to the poor general status of the patients and the far-advanced stage of the disease. In nonsmall cell cancer patients who had limited local disease and had small primary tumor size, we observed better local response. In addition, dose higher than 6,000 cGy group showed better tumor control than lower dose group. Survival rate was better for the local control group. For imporvement of local control of the lung cancer and hence, the survival of the patients with lung cancer, proper radical radiotherapy with high dose for localized disease is needed. New modality of treatment such as high LET beam in radiation therapy or drugs for the advanced disease as well as early diagnosis is also needed.

• Journal of Radiation Protection and Research
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• v.28 no.2
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• pp.145-154
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• 2003

By optimizing the radiation protection the collective dose and individual dose could be reduced during YGN #4 $5^{th}$ outage in 2001. The collective doses for the two high radiation jobs decreased to 85% and 65% of expected doses. The proportion of workers with low dose (below 1mSv) exposure increased 4% while the proportion of workers with over 3mSv and 5mSv exposure are decreased to 2%, 1% respectively. But none is exposed over 8mSv for the annual dose. To aid decision of utilizing the robot, cost- benefit analysis was performed and reasonable point was proposed to use the robot. For the first time job, repeated ALARA meeting and mock up training were implemented to set up working procedure by identifying the trouble. To easily set up standard procedure, mockup process was videotaped and reviewed during ALARA meeting. Monitoring is a good approach to chase radiological working condition such as working time, dose rate. behavior of workers, especially for high radiation work. Those data were estimated and adjusted from the stage of work planning to mock up. At the stage of actual work the monitoring data were compared to the estimation and recorded to database. This database will not only be used as a powerful tool for dose optimization at the following outage but also as a guideline to dose constraint set up for optimization for each specific situation.

• Radiation Oncology Journal
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• v.10 no.2
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• pp.267-275
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• 1992

Remote afterloading high dose rate brachytherapy (HDRB) is a new technology and needs new biological principle for time and dose schedule. Here, authors attempt to evaluate the technique and clinical outcome in 116 patients, 590 procedures peformed at Asan Medical Center for 3 years. From Sep. 1989 to Aug 1992, 471 procedures of intracavitary radiation in 58 patients of cervical cancer and 26 of nasopharyngeal cancer,79 intraluminal radiation in 12 of esophageal cancer, 11 of endobronchial cancer and 1 Klatskin tumor and 40 interstitial brachytherapy in 4 of breast cancer, 1 sarcoma and 1 urethral cancer were performed. Median follow-up was 7 months with range $1\~31$ months. All procedures except interstitial were performed under the local anesthesia and they were all well tolerated and completed the planned therapy except 6 patients. 53/58 patients with cervical cancer and 22/26 patients with nasopharynx cancer achieved CR. Among 15 patients with palliative therapy, $80{\%}$ achieved palliation. We will describe the details of the technique and results in the text. To evaluate biologic effects of HDRB and optimal time/dose/fractionation schedule, we need longer follow-up. But authors feel that HDRB with proper fractionation schedule may yield superior results compared to the low dose rate brachytherapy considering the advantages of HDRB in safety factor for operator, better control of radiation dose and volume and patients comfort over the low dose brachytherapy.

• Progress in Medical Physics
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• v.12 no.1
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• pp.19-29
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• 2001

In dose modeling, the shape of actual source and sealed capsule are important parameter to determine the physical dose computation. The author investigated the effect of filter of source self-absorption and sealed capsule to designed the high dose rate Ir-192 source for Ralstron(Japan) unit. The size of source designed to 1.5 mm $\Phi$ x 1.5mm length of actual source sealed with stainless steel which is 3.0mm $\Phi$ x 12.0mm length connected to driving cable. The dose attenuation was derived 66.3 % from 2655 segmented source at reference point of 10mm lateral distance of source. The output dose rate factor in tissue for designed source showed 0.0013511 cGy/mCi-sec in reference point at 1cm lateral distance of source center. The dose distribution at inferior of source showed the 52% of that of source tip region, however, the filtering effect was small as 4% at 45degrees of source axis. The dose attenuation within 20 degrees of source axis at near source-cable connector showed large filtering effect as 40% over, but the small effect was revealed isotropic dose distribution at large angle.