• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2339-2345
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• 2020

Radiation imaging systems consisting of a large number of channels greatly benefit from multiplexing methods to reduce the number of channels with minimizing the system complexity and development cost. In conventional pixelated radiation detector modules, such as anger logic, is used to reduce a large number of channels that transmit signals to a data acquisition system. However, these methods have limitations of electrical noise and distortion at the detector edge. To solve these problems, a multiplexing concept using a digital signal encoding technique based on a time delay method for signals from detectors was developed in this study. The digital encoding multiplexing (DEM) method was developed based on the time-over-threshold (ToT) method to provide more information including the activation time, position, and energy in one-bit line. This is the major advantage of the DEM method as compared with the traditional ToT method providing only energy information. The energy was measured and calibrated by the ToT method. The energy resolution and coincidence time resolution were observed as 16% and 2.4 ns, respectively, with DEM. The position was successfully distributed on each channel. This study demonstrated the feasibility that DEM was useful to reduce the number of detector channels.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.2
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• pp.463-466
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• 2016

Glioblastoma (GBM) is the most common and aggressive type of primary brain neoplasm. The current standard therapy for GBM consists of maximal surgical resection within safe limits, followed by radiation therapy (RT) and chemotherapy with temozolomide. Despite advances in treatment, the prognosis of GBM remains poor. Epileptic seizure is one of the most common symptoms in patients with GBM. Valproic acid (VPA), a histone deacetylase inhibitor, is often used as an anti-epileptic drug in patients with brain neoplasms due to its effectiveness and low toxicity profile. Several in vivo and in vitro studies have indicated that VPA has radiosensitizing effects for gliomas and radioprotective influence on normal brain tissue or hippocampal neurons. The results of several retrospective studies have also indicated potential benefit to improve survival of patients with GBM. Moreover, the promising treatment results of a phase 2 trial of concurrent radiation therapy, temozolomide, and VPA for patients with GBM have been recently reported. The use of VPA in patients with GBM has thus recently receiving more attention. In this article, we review the role of VPA in radiation therapy for GBM, focusing on the clinical evidence.

• Radiation Oncology Journal
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• v.34 no.3
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• pp.216-222
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• 2016

Purpose: To evaluate the benefit of adjuvant radiation therapy (RT) for retroperitoneal liposarcoma (RPLS) following gross tumor removal. Materials and Methods: We reviewed 77 patients with primary RPLS surgically treated between January 2000 and December 2013. Cases with gross residual disease were excluded. Tumor grade was evaluated according to the French Federation of Cancer Centers Sarcoma Group (FNCLCC) system. Adjuvant RT was delivered to 32 patients (42%) using external beam RT alone. Median follow-up time was 36 months (range, 5 to 169). Results: Among 77 patients, 33 (43%) presented with well-differentiated, 31 (40%) with de-differentiated, 8 (10%) with myxoid/round and 4 (5%) with pleomorphic morphology. The RT group included less well-differentiated subtype than surgery group (28% vs. 53%). During follow up, 34 patients (44%) showed local recurrence. Local recurrence rate was lower in the RT group (38%) compared to the surgery group (49%). The 3-year local control rate (LC) was 55.6%, and the 3-year overall survival (OS) was 82.1%. Tumor histology and FNCLCC grade were significantly associated with local recurrence. There was no statistical significance of adding adjuvant RT in LC (p = 0.312). However, patients with tumor histology other than well-differentiated subtype showed marginally decreased local recurrence rate after adjuvant RT (3-year LC, RT 43.9% vs. no RT 35.3%; p = 0.087). Conclusion: RPLS patients receiving RT experienced less local recurrence. We suggest that the addition of adjuvant RT may be related to improvement of LCs, especially in patients with non-favorable histologic subtypes.

• Radiation Oncology Journal
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• v.11 no.2
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• pp.337-346
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• 1993

This is a retrospective cohort analysis of 58 patients who treated with postoperative radiation therapy following radical hysterectomy and bilateral pelvic adenectomy for early stage carcinoma of uterine cervix between January 1988 and December 1990 at department of radiation oncology, Keimyoung University Hospital. Sixteen percent of patients (9/58) had chemotherapy. Most patients were FIGO I b (47 patients), and FIGO I a and II a were one and ten patients, respectively. The median follow-up periods were 48.5 months. The indications for radiation therapy included pelvic lymph node metastasis, large tumor size, deep stromal invasion, lymphovascular invasion, positive surgical margin, endometrial invasion and parametrial invasion. Eighty five percent of the patients had more than one risk factor. The actuarial overall five year survival rate (5 YSR) and five year disease free survival rate (5 YDFSR) were $89.5\%,\;and\;87.8\%,$ respectively. Their overall recurrence rate was $12.1\%,$(758). Distant metastasis was the most common cause of treatment failure $(71.4\%:5/7).$ The univariate analysis of prognostic factors affecting to five year survival rate disclosed pelvic lymph node status (negative: $95.5\%,\;positive:69.2\%,$ p=0.006) and hemoglobin level $(\le11 :75\%,>11g/dl:93.3\%,p=0.05)$ as significant factor. The age status was marginally significant $(\le40:96.0\%,\;>\;40:84.3\%p=0.15).$ Multivariate analysis clarified three independent prognostic factors: pelvic lymph node metastasis (p=p.006), hemoglobin level (p=0.015) and age (p=0.035). Multivariate analysis of prognostic factor affecting to five year disease free survival rate disclosed pelvic lymph node status (p=0.0078) and status of surgical margin (p=0.008). Complications relating to radiotherapy were $10.3\%,(6/58).$ There were no severe major complication requiring surgical intervention or a long hospital stay. It is our opinion that the benefit of postoperative pelvic radiotherapy may be gained in such a high risk patient population with acceptible morbidity.

• Journal of Radiation Protection and Research
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• v.37 no.1
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• pp.1-9
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• 2012

A year has passed since the nuclear power plant accident in Fukushima on March 11, 2011, and a survey for public perception on radiation by Korean people has been made. The methodological design was based on a quantitative survey and a frequency analysis was done. The analysis objects were survey papers (n=2,754pcs) answered by random ordinary citizens chosen from all over the country. The questionnaires, and study tool, were directly distributed and collected. A total of 40 questionnaires using a coefficient of Cronbach's ${\alpha}$ per each area was 'self perception of radiation' (0.620), 'radiation risk' (0.830), 'benefit from radiation' (0.781), 'radiation controlled' (0.685), 'informative source of radiation' (0.831), 'influence degree from Fukushima accident' (0.763), showing rather high score from all areas. As the result of the questionnaires, the knowledge of radiation concept was 69.50 out of 100 points, which shows a rather significant difference from the result of 'know well about radiation' (53.7%) and 'just know about radiation' (37.40%). According to the survey, one of the main reasons why radiation seems risky was that once exposed to radiation, it may not have negative impacts presently but, the next generation could see negative impacts (66.1%). About 41% of our respondents showed a negative position against the government's report on radiation while 39.5% of respondents said that we should stop running nuclear power in light of Fukushima nuclear power plant accident. This study was done for the first time by Korean people's public perception on radiation after the Fukushima nuclear power plant accident. We expect this might have significant contributions to the establishment of the government's policy on radiation.

• Korean Journal of Head & Neck Oncology
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• v.18 no.1
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• pp.30-35
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• 2002

Objective: To determine the effectiveness and toxicity of chemoradiation therapy in nasopharyngeal carcinoma by comparing with radiation therapy alone. Materials and Methods: Between October 1989 and July 2000, One hundred eleven patients with newly diagnosed and histologically proven nasopharyngeal carcinoma treated in Department of Radiation Oncology, Asan Medical Center were retrospectively reviewed. Forty-five patients were treated with radiation therapy alone (Group I) and 66 patients were treated with radiation therapy and concurrent cisplatin (Group II). Cisplatin was administered once a week, on the first day of each successive week of treatment, starting on day 1 of radiation therapy and given as a intravenous bolus at a dose of $20mg/m^2$ of body-surface area. Radiation therapy was given in doses of 1.8Gy, once a day, 5 days per week with 4MV or 6 MV photons. Initial field was received a total of 60Gy and a primary tumor and enlarged lymph nodes were boosted with an high dose intracavitory brachytherapy and 3D conformal therapy. Results: The complete response rate was 86.7% in Group I, and was 90.9% in Group II. The 5 year overall survival rate for Group I was 60% and for Group II was 45% (p=0.2520). The 5 year disease free survival rate was 52% versus 45%, respectively (p=0.7507). The median follow up was 44 months versus 34 months, respectively. Conclusion: Analysis of the III patients showed no significant difference in disease free survival and overall survival in two treatment group. This retrospective analysis did not demonstrate benefit with concurrent chemoradiation using cisplatin at a dose of $20mg/m^2$ of body-surface area in treatment result than radiation alone.

• Journal of Radiation Protection and Research
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• v.24 no.2
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• pp.65-72
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• 1999

A methodology for determining the optimal durations of the use of contaminated crops as feedstuffs of cattle was designed based on the cost-benefit analysis method. The results of application for pigs, an omnivorous cattle, were discussed for the hypothetical deposition of radionuclides on August 15 when a number of crops are fully developed in Korean agricultural conditions. For investigating the relative cost-effectiveness of the use of contaminated crops as feedstuffs, the net benefit was compared with the case of the direct disposal of contaminated crops. The time-dependent radionuclide concentration in crops after the deposition was predicted using a dynamic food chain model DYNACON. The net benefit from the actions was quantitatively evaluated in terms of cost equivalent of doses and monetary costs of implementing the action. It depended on a number of factors such as radionuclides, variety of crops supplied as feedstuffs and duration of the actions. The use of contaminated crops as feedstuffs was more cost effective for $^{90}Sr\;or\;^{131}I$ deposition than for $^{137}Cs$ deposition.

• Korean Journal of Environmental Biology
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• v.21 no.4
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• pp.384-391
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• 2003

The induction of chromosome aberrations in Hordeum vulgare germs after irradiation is studied for the dose range of 10 to 1,000 mGy. The relationship between the frequency of aberrant cells and the absorbed dose is shown to be non -linear and has a dose-independent plateau within the range of 56-467 mGy where the level of cytogenetic damage is statistically significantly distinguished from the spontaneous level. The comparison of the goodness of the experimental data fitting with mathematical models of different complexities, using the most common quantitative criteria, demonstrates the benefit of the piecewise linear model over the linear and polynomial ones in approximating the cytogenetical disturbance frequency. The results of our study support the conclusion about indirect mechanism of chromosome aberrations induced by low doses or dose rates mutagenesis.

• Journal of Radiation Protection and Research
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• v.18 no.1
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• pp.71-82
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• 1993

It is a fundamental element of the nuclear power plant operation to assess exactly the occupational radiation exposure. And, according to recently published ICRP 60 recommendation, it is needed to reduce individual radiaton exposure limit further. In this paper, an optimization techique was suggested for selection of alternatives for reducing occupational radiation exposure, and used in reviewing alternatives given by a plant utility. After the basic analysis, sensitivity analysis was performed to consider the variabilities of the economic variables. From the result, it was found that an option using steam generator nozzle dam and torquing machine was the best with respect to total benefits, and in case of multi-attribute utility analysis, an option using Co-No seal had the highest utility. Therefore, it was necessary to apply more than one technique togeter in optimization study and to consider qualitative factor, too.

• Radiation Oncology Journal
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• v.31 no.1
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• pp.1-11
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• 2013

Purpose: Compared to conventional radiotherapy (RT), intensity-modulated radiotherapy (IMRT) significantly reduces the rate of treatment-induced late toxicities in head and neck cancer. However, a clear survival benefit of IMRT over conventional RT has not yet been shown. This study is among the first comparative study to compare the survival rates between conventional RT and helical tomotherapy in head and neck cancer. Materials and Methods: From January 2008 to November 2011, 37 patients received conventional RT and 30 patients received helical tomotherapy for management of head and neck cancer. We retrospectively compared the survival rates between patients treated with conventional RT and helical tomotherapy, and analyzed the prognostic factors for survival. Results: The 1- and 2-year locoregional recurrence-free survival rates were 61.2% and 58.1% for the conventional RT group, 89.3% and 80.3% for the helical tomotherapy group, respectively. The locoregional recurrence-free survival rates of the helical tomotherapy group were significantly higher than conventional RT group (p = 0.029). There were no significant differences in the overall and distant metastasis-free survival between the two groups. RT technique, tumor stage, and RT duration were significant prognostic factors for locoregional recurrence-free survival. Conclusion: This study showed the locoregional recurrence-free survival benefits of helical tomotherapy in the treatment of head and neck cancers.