• Radiation Oncology Journal
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• v.26 no.2
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• pp.113-117
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• 2008

Purpose: To evaluate the long term results(local control, survival, failure, and complications) after radiation therapy for skin cancer in elderly patients. Material and Methods: The study spanned from January 1990 to October 2002. Fifteen elderly patients with skin cancer were treated by radiotherapy at the Keimyung University Dongsan Medical Center. The age distribution of the patients surveyed was 72 to 95 years, with a median age of 78.8 years. The pathologic classification of the 15 patients included squamous cell carcinoma(10 patients), basal cell carcinoma(3 patients), verrucous carcinoma(1 patient) and skin adnexal origin carcinoma(1 patient). The most common tumor location was the head(13 patients). The mean tumor diameter was 4.9 cm(range 2 to 9 cm). The radiation dose was delivered via an electron beam of 6 to 15 MeV. The dose range was adjusted to the tumor diameter and depth of tumor invasion. The total radiation dose ranged from $50{\sim}80$ Gy(mean: 66 Gy) with a 2 Gy fractional dose prescribed to the 80% isodose line once a day and 5 times a week. One patient with lymph node metastasis was treated with six MV photon beams boosted with electron beams. The length of the follow-up periods ranged from 10 to 120 months with a median follow-up period of 48 months. Results: The local control rates were 100%(15/15). In addition, the five year disease free survival rate(5YDFS) was 80% and twelve patients(80%) had no recurrence and skin cancer recurrence occurred in 3 patients(20%). Three patients have lived an average of 90 months($68{\sim}120$ months) without recurrence or metastasis. A total of 9 patients who died as a result of other causes had a mean survival time of 55.8 months after radiation therapy. No severe acute or chronic complications were observed after radiation therapy. Only minor complications including radiation dermatitis was treated with supportive care. Conclusion: The results suggest that radiation therapy is an effective and safe treatment method for the treatment of skin cancer in elderly patients who achieved a good survival rate and few minor complications.

• Radiation Oncology Journal
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• v.28 no.2
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• pp.79-84
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• 2010

Purpose: We retrospectively analyzed the long-term results of radical surgery and intraoperative radiation therapy (IORT) in patients with stomach cancer. Materials and Methods: From 1988 to 1994, 51 patients were treated with curative surgery and IORT. Postoperative external beam radiotherapy (EBRT) was administered to 30 patients, while adjuvant chemotherapy was administered to 35 patients. A dose of 15 Gy was irradiated with a 9 MeV electron beam as the IORT and a median dose of EBRT was 43.2 Gy (range, 7.2 to 45 Gy). The follow-up period ranged from 1~254 months, with a median follow-up period of 64 months. Results: The median age of all the patients was 58 years (range, 30 to 71 years). The distribution of pathologic stage (American Joint Committee on Cancer [AJCC] 2002 tumor-note-metastasis [TNM]) was as follows: 13 stage I (25.5%), 10 stage II (19.6%), 25 stage III (49.0%), and 3 stage IV (5.9%). Distant metastases occurred in 11 patients (10 in the peritoneum and 1 in bone), including one patient with concurrent local recurrence (anastomosis site). The 5-year locoregional control, disease free survival and overall survival rates were 94.7%, 66.5%, and 51.7%, respectively. For the multivariate analysis, age, TNM stage, and EBRT were significant prognostic factors for overall survival, and only TNM stage for disease free survival. Conclusion: We could have achieved a high loco-regional control rate in patients with locally advanced stomach cancer by adding IORT to radical surgery. However, the benefit of IORT on survival remains to be elucidated.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.261-270
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• 2019

The separation permeation characteristics of $N_2-O_2$ gas in air at cell membrane model of skin which irradiated by high energy electron(linac 6 MeV) were investigated. The cell membrane model of skin used in this experiment was a sulfonated polydimethyl siloxane(PDMS) non-porous membrane. The pressure range of $N_2$ and $O_2$ gas were appeared from $1kg_f/cm^2$ to $6kg_f/cm^2$. In this experiment(temperature $36.5^{\circ}C$), the permeation change of $N_2$ and $O_2$ gas in non-porous membrane by non-irradiation were found to be $1.19{\times}10^{-4}-2.43{\times}10^{-4}$, $1.72{\times}10^{-4}-2.6{\times}10^{-4}cm^3(STP)/cm^2{\cdot}sec{\cdot}cmHg$, respectively. That of $N_2$ and $O_2$ gas in non-porous membrane by irradiation were found to be $0.19{\times}10^{-4}-0.56{\times}10^{-4}$, $0.41{\times}10^{-4}-0.76{\times}10^{-4}cm^3(STP)/cm^2{\cdot}sec{\cdot}cmHg$, respectively. The irradiated membrane was significantly decreased about 4-10 times than membrane which was not irradiated. And ideal separation factor of $N_2$ and $O_2$ gas by non-irradiation was found to be from 1.32 to 0.42 and that of $N_2$ and $O_2$ gas by irradiation was found to be from 0.237 to 0.125. The irradiated membrane was significantly decreased about 4-5 times than membrane which was not irradiated. When the operation change(cut) and pressure ratio(Pr) by non-irradiation were about 0, One was increased to the oxygen enrichment and the other was decreased to the oxygen enrichment. The irradiated membrane was significantly decreased about 4-19 times than membrane which was not irradiated. As the pressure of $N_2$ and $O_2$ gas was increased, the selectivity was decreased. As separation permeation characteristics of $N_2-O_2$ gas in cell membrane model of skin were abnormal, cell damages were appeared at cell.

• Journal of The Korean Astronomical Society
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• v.56 no.2
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• pp.231-252
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• 2023

We present the analysis results of the simultaneous multifrequency observations of the blazar 4C +28.07. The observations were conducted by the Interferometric Monitoring of Gamma-ray Bright Active Galactic Nuclei (iMOGABA) program, which is a key science program of the Korean Very Long Baseline Interferometry (VLBI) Network (KVN). Observations of the iMOGABA program for 4C +28.07 were conducted from 16 January 2013 (MJD 56308) to 13 March 2020 (MJD 58921). We also used γ-ray data from the Fermi Large Array Telescope (Fermi-LAT) Light Curve Repository, covering the energy range from 100 MeV to 100 GeV. We divided the iMOGABA data and the Fermi-LAT data into five periods from 0 to 4, according to the prosody of the 22 GHz data and the presence or absence of the data. In order to investigate the characteristics of each period, the light curves were plotted and compared. However, a peak that formed a hill was observed earlier than the period of a strong γ-ray flare at 43-86 GHz in period 3 (MJD 57400-58100). Therefore, we assumed that the minimum total CLEANed flux density for each frequency was quiescent flux (S_q) in which the core of 4C +28.07 emitted the minimum, with the variable flux (S_var) obtained by subtracting S_q from the values of the total CLEANed flux density. We then compared the variability of the spectral indices (α) between adjacent frequencies through a spectral analysis. Most notably, α_22-43 showed optically thick spectra in the absence of a strong γ-ray flare, and when the flare appeared, α_22-43 became optically thinner. In order to find out the characteristics of the magnetic field in the variable region, the magnetic field strength in the synchrotron self-absorption (B_SSA) and the equipartition magnetic field strength (B_eq) were obtained. We found that B_SSA is largely consistent with B_eq within the uncertainty, implying that the SSA region in the source is not significantly deviated from the equipartition condition in the γ-ray quiescent periods.

• Radiation Oncology Journal
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• v.14 no.2
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• pp.95-103
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• 1996

Purpose : A retrospective analysis for patients with oropharyngeal carcinoma who were treated with radiation was performed to assess the results of treatment and patterns of failure, and to identify the factors that might influence survival. materials and methods : From March 1985 through June 1993, 53 patients with oropharyngeal carcinoma were treated with either radiation therapy alone or combination of neoadjuvant chemotherapy and radiation therapy at the Department of Radiation Oncology, Kyungpook National University Hospital. Patients' ages ranged from 31 to 73 years with a median age of 54 years. There were 47 men and 6 women, Forty-two Patients ($79.2\%$) had squamous cell carcinoma, 10 patients ($18.9\%$) had undifferentiated carcinoma and 1 patient ($19\%$) had adenoid cystic carcinoma. There were 2 patients with stage I, 12 patients with stage II, 12 Patients with stage III and 27 patients with stage IV. According to the TNM classification, patients were distributed as follows: T1 7, T2 28, T3 10, T4 7, TX 1, and N0 17, Nl 13, N2 21, N3 2. The primary tumor sites were tonsillar region in 36 patients ($67.9\%$), base of the tongue in 12 patients ($22.6\%$), and soft palate in 5 patients ($9.4\%$). Twenty-five patients were treated with radiation therapy alone and twenty-eight Patients were treated with one to three courses of chemotherapy followed by radiation therapy. Chemotherapeutic regimens used were either CF (cisplatin and 5-fluorouracil) or CVB (cisplatin, vincristine and bleomycin). Radiation therapy was delivered 180-200 cGy daily, five times a week using 6 MV X-ray with or without 8-10 MeV electron beams A tumor dose ranged from 4500 cGy to 7740 cGy with a median dose of 7100 cGy. The follow-up time ranged from 4 months to 99 months with a median of 21 months. Results : Thirty-seven patients ($69.8\%$) achieved a CR (complete response) and PR (partial response) in 16 patients ($30.2\%$) after radiation therapy. The overall survival rates were $47\%$ at 2 years and $42\%$ at 3 years, respectively. The median survival time was 23 months. Overall stage (p=0.02) and response to radiation therapy (p=0.004) were significant prognostic factors for overall survival. The 2-year disease-free survival rate was $45.5\%$. T-stage (p=0.03), N-stage (p=0.04) and overall stage (P=0.04) were significant prognostic factors for disease-free survival. Age, sex, histology, primary site of the tumor, radiation dose, combination of chemotherapy were not significantly associated with disease-free survival. Among evaluable 32 Patients with CR to radiation therapy, 12 patients were considered to have failed Among these, 8 patients failed locoregionally and 4 Patients failed distantly. Conclusion : T-stage, N-stage and overall stage were significant prognostic factors for disease-free survival in the treatment of oropharyngeal cancer Since locoregional failure was the predominant pattern of relapse, potential methods to improve locoregional control with radiation therapy should be attempted. More controlled clinical, trials should be completed before acceptance of chemotherapy as a part of treatment of oropharyngeal carcinoma.

• Radiation Oncology Journal
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• v.13 no.4
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• pp.339-348
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• 1995

Purpose : Since 1983, authors have conducted a study to evaluate the effect of external radiation therapy and to determine affected factors in management of the patients with malignant obstructive jaundice due to porta hepatis metastasis from stomach cancer. Materials and Methods : Thirty two patients with malignant obstructive jaundice due to porta hepatis metastasis from gastric cancer were presented. We have analysed 23 patients who were treated with external radiation therapy of more than 3000cGy. The radiation dose, disease extent at developement of jaundice, total bilirubin levels before radiation therapy, differentiation of histology, combind treatment, intent of primary surgery, initial stage of gastric cancer were analyzed to determine affected factors in radiation therapy. External radiation therapy was delivered with a daily dose of 180-300cGy, 5 times a week fractionation using 4 MeV linear accelerator. The radiation field included the porta hepatis with tumor mass by the abdominal ultrasonography or CT scan. In twenty three patients received more than 3000cGy, total irradiation dose was ranged from 3000cGy to 5480cGy, median 3770cGy. Among 23 patients, 13 patients were delivered more than equivalant dose of TDF 65(4140cGy/23fx). Results : Among 23 patients, complete, partial and no response were observed in 13, 5, 5 patients, respectively. The median survival for all patients was 5 momths. The significant prolongation of median survival was observed in complete responders(11 months) as compared to partial and no responders(5 months, 5 months respectively) Out of 13 patients with complete response, 6 patients lived more than a year Among 13 patients receiving more than 4140cGy equivalent dose, complete, partial and no response were observed in 10, 2 and 1 patients, respectively. The median survival for all these patients was 9.5 months. The median survival for complete responders(10/13) was 11.5 months. Among 10 patients receiving less than 4140cGy equivalent dose, complete, partial and no response were observed in 3, 3, 4 patients, respetively. The median survival for all these patients was 4.3 months Therefore, the radiation dose affected the results of treatment. For the complete response with prolongation of survival duration, at least 4140cGy equivalant dose should be delivered to porta hepatis. In evaluation of the disease extent, 7 patients of 13 complete responders showed localized disease in porta hepatis or peripancreatic area, but all patients with partial and no response showed wide extensive disease or persistant disease of primary gastric cancer. Therefore. the patients with the localized disease were the higher probability of complete response and long term survival. This study suggested that the radiation dose and the disease extent at developement of jaundice affected in radiation therapy for malignant obstructive jaundice. There were no serious complications related to external radiation therapy. Conclusion : External radiation therapy only could achieve the palliative effect in the patients with malignant obstructive jaundice due to porta hepatis metastasis from stomach cancer. This study suggested that the prolongation of survival duration could be achived in complete responders and radiation dose, extent of disease affected the results of treatment of malignant obstructive jaundice.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.188.1-188.1
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• 2015

For present investigation Fe/MgO/Fe/Co multilayer stack is grown on Si substrate using e-beam evaporation in ultrahigh vacuum. This stack is irradiated perpendicularly by 120 MeV $Ag^{8+}$ at different fluences ranging from $1{\times}10^{11}$ to $1{\times}10^{13}ions/cm^2$ in high vacuum using 15UD Pelletron Accelerator at Inter University Accelerator Centre, New Delhi. Magnetic measurements carried out on pre and post irradiated stacks show significant changes in the shape of perpendicular hysteresis which is relevant with previous observation of re-orientation of magnetic moment along the direction of ion trajectory. However increase in plane squareness may be due to the modification of interface structure of stacks. X-ray reflectivity measurements show onset of interface roughness and interface mixing. X-ray diffraction measurements carried out using synchrotron radiation shows amorphous nature of MgO and Co layer in the stack. Peak corresponding body centered Fe [JCPDS-06-0696] is observed in X-ray diffraction pattern of pre and post irradiated stacks. Peak broadening shows granular nature of Fe layer. Estimated crystallite size is $22{\pm}1nm$ for pre-irradiated stack. Crystallite size first increases with irradiation then decreases. Structural quality of these stacks was further studied using transmission electron microscopic measurements. Thickness from these measurements are 54, 36, 23, 58 and 3 nm respectively for MgO, Fe, MgO, Fe+Co and Au layers in the stack. These measurements envisage poor crystallinity of different layers. Interfaces are not clear which indicate mixing at interface. With increase fluence mixing and diffusion was increased in the stack. X-ray absorption spectroscopic measurements carried out on these stacks show changes of Fe valence state after irradiation along with change of O(2p)-metal (3d) hybridized state. Valence state change predicts oxide formation at interface which causes enhanced in-plane magnetization.

• Journal of Radiation Protection and Research
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• v.45 no.2
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• pp.69-75
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• 2020

Background: Dose conversion coefficients (DCCs) have been commonly used to estimate radiation-dose absorption by human organs based on physical measurements of fluence or kerma. The International Commission on Radiological Protection (ICRP) has reported a library of DCCs, but few studies have been conducted on their applicability to non-Caucasian populations. In the present study, we collected a total of 8 Korean pediatric and adult voxel phantoms to calculate the organ DCCs for idealized external photon-irradiation geometries. Materials and Methods: We adopted one pediatric female phantom (ETRI Child), two adult female phantoms (KORWOMAN and HDRK Female), and five adult male phantoms (KORMAN, ETRI Man, KTMAN1, KTMAN2, and HDRK Man). A general-purpose Monte Carlo radiation transport code, MCNPX2.7 (Monte Carlo N-Particle Transport extended version 2.7), was employed to calculate the DCCs for 13 major radiosensitive organs in six irradiation geometries (anteroposterior, posteroanterior, right lateral, left lateral, rotational, and isotropic) and 33 photon energy bins (0.01-20 MeV). Results and Discussion: The DCCs for major radiosensitive organs (e.g., lungs and colon) in anteroposterior geometry agreed reasonably well across the 8 Korean phantoms, whereas those for deep-seated organs (e.g., gonads) varied significantly. The DCCs of the child phantom were greater than those of the adult phantoms. A comparison with the ICRP Publication 116 data showed reasonable agreements with the Korean phantom-based data. The variations in organ DCCs were well explained using the distribution of organ depths from the phantom surface. Conclusion: A library of dose conversion coefficients for major radiosensitive organs in a series of pediatric and adult Korean voxel phantoms was established and compared with the reference data from the ICRP. This comparison showed that our Korean phantom-based data agrees reasonably with the ICRP reference data.

• Progress in Medical Physics
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• v.13 no.2
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• pp.55-61
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• 2002

In this work, EPM (effective point of measurement) of parallel plate ionization chamber with three different spacing were investigated. If the plate separation is less than 2 mm one generally assumes that the effective point of measurement is just behind the front window of the parallel plate ionization chamber. For chamber with relatively large separation, such as the ones used for very accurate exposure measurements, this assumption breaks down and the EPM depends on plate separation and thickness of the front window. For parallel plate chambers, conventional theoretical analyses suggest that the EPM is the inner front wall and that it shifts towards the geometric centre of the chamber as the plate separation increases. The PP-IC (parallel plate ionization chamber) is fabricated using acrylic plate for the chamber medium and printed circuit board for electrical configuration. The various sizes of the sensitive volumes designed so far are 0.9, 1.9, and 3.1 cc. The gap between two electrodes ranges from 3, 6, and 10mm. Also the charge-to-voltage converter is designed to collect the electrons produced in the ionization chamber cavity. As the result of our experiment, the EPM shift was within 0.6 mm in photon beams and 0.4 mm to 2.5 mm in electron beams for the plate separation of 6 mm and 10 mm. EPM shifts towards the geometric center of the chamber as the plate separation increases.

• Progress in Medical Physics
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• v.27 no.3
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• pp.156-161
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• 2016

When air discharged from a radioisotope production facility is contaminated with radiation, the public may be exposed to radiation. The objective of this study is to manage such radiation exposure. We measured the airborne radioactivity concentration at a 30 MeV cyclotron radioisotope production facility to assess whether the exhaust gas was contaminated. Additionally, we investigted the radioactive contamination of the air filter for efficient air purification and radiation safety control. To measure the airborne radiation concentration, specimens were collected weekly for 4 h after the beginning of the radioisotope production. Regarding the air purifier, five specimens were collected at different positions of each filter-pre-filter, high-efficiency particulate air filter, and charcoal filter-installed in the cyclotron production room. The concentrations of F-18, I-123, I-131, and Tl-201 generated in the radioiodine production room were $13.5Bq/m^3$, $27.0Bq/m^3$, $0.10Bq/m^3$, and $11.5Bq/m^3$, respectively; the concentrations of F-18, I-123, and I-131 produced in the radioisotope production room were $0.05Bq/m^3$, $16.1Bq/m^3$, and $0.45Bq/m^3$, correspondingly; and those of F-18, I-123, I-131, and Tl-201 generated in the accelerator room were $2.07Bq/m^3$, $53.0Bq/m^3$, $0.37Bq/m^3$, and $0.15Bq/m^3$, respectively. The maximum radiation concentration of I-123 generated in the radioiodine production room was 1,820 Bq/g, which can be disposed after 2 days. The maximum radiation concentration of Tl-202 generated in the radioisotope production room was 205 Bq/g, and this isotope must be stored for 53 days. The I-123 generated in the radioiodine production room had a maximum concentration of 1,530 Bq/g and must be stored for 2 days. The maximum radiation concentration of Na-22 generated in the radioisotope production room was 0.18 Bq/g and this isotope must be disposed after 827 days. To manage the exhaust, the efficiency of air purification must be enhanced by selecting an air purifier with a long life and determining the appropriate replacement time by examining the differential pressure through systematic measurements of the airborne radiation contamination level.