• Radiation Oncology Journal
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• v.29 no.2
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• pp.107-114
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• 2011

Purpose: To assess the degree and clinical impact of location error of the dens on the X-axis during radiotherapy to brain and head and neck tumors. Materials and Methods: Twenty-one patients with brain tumors or head and neck tumors who received three-dimensional conformal radiation therapy or intensity-modulated radiation therapy from January 2009 to June 2010 were included in this study. In comparison two-dimensional verification portal images with initial simulation images, location error of the nasal septum and the dens on the X-axis was measured. The effect of set-up errors of the dens was simulated in the planning system and analyzed with physical dose parameters. Results: A total of 402 portal images were reviewed. The mean location error at the nasal septum was 0.16 mm and at the dens was 0.33 mm (absolute value). Location errors of more than 3 mm were recorded in 43 cases (10.7%) at the nasal septum, compared to 133 cases (33.1%) at the dens. There was no case with a location error more than 5 mm at the nasal septum, compared to 11 cases (2.7%) at the dens. In a dosimetric simulation, a location error more than 5 mm at the dens could induce a reduction in the clinical target volume 1 coverage (V95: 100%${\rightarrow}$87.2%) and overdosing to a critical normal organ (Spinal cord V45: <0.1%${\rightarrow}$12.6%). Conclusion: In both brain and head and neck radiotherapy, a relatively larger set-up error was detected at the dens than the nasal septum when using an electronic portal imaging device. Consideration of the location error of the dens is necessary at the time of the precise radiation beam delivery in two-dimensional verification systems.

• Radiation Oncology Journal
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• v.29 no.2
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• pp.115-120
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• 2011

Purpose: To examine the feasibility of the treatment planning for minimizing carotid artery dose in the radiotherapy of early glottic cancer. Materials and Methods: From 2007 to 2010, computed tomography simulation images of 31 patients treated by radiotherapy for early glottic cancer were analyzed. The virtual planning was used to compare the parallel-opposing fields (POF) with the modified oblique fields (MOF) placed at angles to exclude the ipsilateral carotid arteries. Planning target volume (PTV), irradiated volume, carotid artery, and spinal cord were analyzed at a mean dose, $V_{35}$, $V_{40}$, $V_{50}$ and with a percent dose-volume. Results: The beam angles were arranged 25 degrees anteriorly in 23 patients and 30 degrees anteriorly in 8 dose-volume of carotid artery shows the significant difference (p<0.001). The mean doses of carotid artery were 38.5 Gy for POF and 26.3 Gy for MOF and the difference was statistically significant (p=0.012). Similarly, $V_{35}$, $V_{40}$, and $V_{50}$ also showed significant differences between POF and MOF. Conclusion: The modified oblique field was respected to prevent a carotid artery stenosis and reduce the incidence of a stroke based on these results.

• Tuberculosis and Respiratory Diseases
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• v.47 no.1
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• pp.77-89
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• 1999

Background: High-dose chemotherapy is increasingly employed in many refractory malignant diseases. This therapy has been reported to increase response rate and survival benefits but it is also associated with higher treatment-related morbidity and mortality. We evaluated clinical characteristics and course of the pulmonary toxicity following high-dose chemotherapy with peripheral blood stem cell transplantation. Methods: Ninety-seven patients who had received high-dose chemotherapy with peripheral blood stem cell transplantation were evaluated. Five patients who developed lung lesions which were not related to infection nor primary malignant disease underwent transbronchial lung biopsy. The patients' clinical characteristics, treatments, and prognosis were reviewed retrospectively. Results: Five patients(5.1%) developed idiopathic pneumonia syndrome. The high dose chemotherapy regimens employed were cyclophosphamide, BCNU, and cisplatin in 3 cases, one case of BCNU, etoposide, Ara-C, and cyclophosphamide combination, and a regimen consisting of BCNU, etoposide, Ara-C, and melphalan. The total dose of BCNU used was 300-400 mg/$m^2$ and that of cyclophosphsmide was 6,000 mg/$m^2$. All of 5 patients received radiation therapy before this treatment. After an average duration of 14 weeks (4-26 weeks) of high-dose chemotherapy, patients developed cough, dyspnea and fever. The chest X-rays showed bilateral diffuse infiltration in 3 cases and the focal infiltration in the other 2 cases. All the patients received corticosteroid therapy as a treatment for the lung lesions. Two of them progressed to acute respiratory distress syndrome and died. Three patients recovered without residual lung lesion but one of them died of dilated cardiomyopathy. Conclusion: High-dose chemotherapy with peripheral blood stem cell transplantation especially which containing BCNU regimen may develop idiopathic pneumonia syndrome related to pulmonary toxicity and corticosteroid therapy may be bel1eficial in some cases.

• Clinical and Experimental Pediatrics
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• v.52 no.6
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• pp.674-679
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• 2009

Purpose : The authors aimed to analyze the long-term effects of treatments, especially external beam radiotherapy (EBRT), in bilateral retinoblastoma patients. Methods : This retrospective study analyzed the medical records of 22 bilateral retinoblastoma patients who were registered between October, 1987 and October, 1998 and followed-up for more than 10 years. They were treated by enucleation, EBRT, and systemic chemotherapy. Age at diagnosis, sex, delay prior to treatment, Reese-Ellsworth (RE) classification, and the local treatment modalities were analyzed in relation to recurrence-free survival (RFS) and complications. Results : Median age at diagnosis was 7.0 months (range 1.7-31.6 months). Leukocoria was the most common presenting feature. Two patients had a familial history. The RE classifications of the 44 eyes were group II in 4, III in 14, IV in 4, and V in 22. At the end of a median follow-up period of 141 months (range 55-218 months), 20 patients were alive. The 10-year ocular survival rate of the 44 eyes was $56.8{\pm}7.5%$. The 10-year RFS and ocular survival rate of the 29 eyes treated by combined EBRT and chemotherapy were 75.9% and 86.2%, respectively. Treatment delay (>3 months) was found to be related to higher risk of recurrence. Complications after EBRT were cataract, retinal detachment, phthisis bulbi, and facial asymmetry. No patient developed a second malignancy during the follow-up period. Conclusion : Early detection and prompt treatment can increase ocular survival rates. In addition, careful attention should be paid to possible long-term sequelae in these patients.

• Korean Journal of Remote Sensing
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• v.34 no.2_1
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• pp.237-248
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• 2018

The vertical distribution of hydrometeor before precipitation near the cloud base has been analyzed using a scanning lidar, rawinsonde data, and Cloud-Resolving Storm Simulator (CReSS). This study mostly focuses on 13 Desember 2016 only. The typical synoptic pattern of lake-effect snowstorm induced easterly in the Yeongdong region. Clouds generated due to high temperature difference between 850 hPa and sea surface (SST) penentrated in the Yeongdong region along with northerly and northeasterly, which eventually resulted precipitation. The cloud base height before the precipitation changed from 750 m to 1,280 m, which was in agreement with that from ceilometer at Sokcho. However, ceilometer tended to detect the cloud base 50 m ~ 100 m below strong signal of lidar backscattering coefficient. As a result, the depolarization ratio increased vertically while the backscattering coefficient decreased about 1,010 m~1,200 m above the ground. Lidar signal might be interpreted to be attenuated with the penetration depth of the cloud layer with of nonspherical hydrometeor (snow, ice cloud). An increase in backscattering signal and a decrease in depolarization ratio occured in the layer of 800 to 1,010 m, probably being associated with an increase in non-spherical particles. There seemed to be a shallow liquid layer with a low depolarization ratio (<0.1) in the layer of 850~900 m. As the altitude increases in the 680 m~850 m, the backscattering coefficient and depolarization ratio increase at the same time. In this range of height, the maximum value (0.6) is displayed. Such a result can be inferred that the nonspherical hydrometeor are distributed by a low density. At this time, the depolarization ratio and the backscattering coefficient did not increase under observed melting layer of 680 m. The lidar has a disadvantage that it is difficult for its beam to penetrate deep into clouds due to attenuation problem. However it is promising to distinguish hydrometeor morphology by utilizing the depolarization ratio and the backscattering coefficient, since its vertical high resolution (2.5 m) enable us to analyze detailed cloud microphysics. It would contribute to understanding cloud microphysics of cold clouds and snowfall when remote sensings including lidar, radar, and in-situ measurements could be timely utilized altogether.

• Progress in Medical Physics
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• v.9 no.3
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• pp.137-141
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• 1998

The purposes of this report are to evaluate whether lead ball and steel ball could be used as protective material of radiation and to acquire physical data of them for protecting 4-10 MV X-ray beams. Lead balls of diameter 2.0～2.5mm or steel balls of diameter 1.5～2.0 mm were filled in an acrylic box of uniform width. An MV radiograph of metal balls in a box were taken to ascertain uniformity of ball distribution in the box. Average density of metal ball and linear attenuation coefficient of metal balls for 4～10 MV X -rays were measured. At the time of measurement of linear attenuation coefficient, Farmer ionization chamber was used and to minimize the scatter effect, distance between the ball and the ionization chamber was 70 cm and field size was 5.5cm${\times}$5.5cm. For comparison, same parameters of lead and steel plates were measured. The distribution of metal balls was uniform in the box. The density of a mixture of lead-air was 6.93g/cm$^3$, 0.611 times density of lead, and the density of a mixture of steel-air was 4.75g/cm$^3$, 0.604 times density of steel. Half-value layers of a mixture of lead-air were 1.89 cm for 4 MV X-ray, 2.07 cm for 6 MV X-ray and 2.16 cm for 10 MV X-ray, and approximately 1.64 times of HVL of lead plate. Half-value layers of a mixture of steel-air were 3.24 cm for 4 MV X-ray, 3.70 cm for 6 MV X-ray and 4.15 cm for 10 MV X-ray, and approximately 1.65 times of HVL of lead plate. Metal balls can be used because they could be distributed evenly. Average densities of mixtures of lead-air and steel-air were 6.93g/cm$^3$, 4.75g/cm$^3$ respectively and approximately 1.65 times of densities of lead and steel. Product of density and HVL for a mixture of metal-air are same as the metal.

• The Journal of Korean Society for Radiation Therapy
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• v.8 no.1
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• pp.19-27
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• 1996

I. Project Title A Study of Brachytherapy for intraocular tumor II. Objective and Importance of the project The eye enucleation or external-beam radiation therapy that has been commonly used for the treatment of intraocular tumor have demerits of visual loss and in deficiency of effective tumor dose. Recently, brachytherapy using the plaques containing radioisotope-now treatment method that decrease the demerits of the above mentioned treatment methods and increase the treatment effect-is introduced and performed in the countries, Our purpose of this research is to design suitable shape of plaque for the ophthalmic brachytherapy, and to measure absorbed doses of Ir-192 ophthalmic plaque and thereby calculate the exact radiation dose of tumor and it's adjacent normal tissue. III. Scope and Contents of the project In order to brachytherapy for intraocular tumor, 1. to determine the eye model and selected suitable radioisotope 2. to design the suitable shape of plaque 3. to measure transmission factor and dose distribution for custom made plaques 4. to compare with the these data and results of computer dose calculation models IV. Results and Proposal for Applications The result were as followed. 1. Eye model was determined as a 25mm diameter sphere, Ir-192 was considered the most appropriate as radioisotope for brachytherapy, because of the size, half, energy and availability. 2. Considering the biological response with human tissue and protection of exposed dose, we made the plaques with gold, of which size were 15mm, 17mm and 20mm in diameter, and 1.5mm in thickness. 3. Transmission factor of plaques are all 0.71 with TLD and film dosimetry at the surface of plaques and 0.45, 0.49 at 1.5mm distance of surface, respectively. 4. As compared the measured data for the plaque with Ir-192 seeds to results of computer dose calculation model by Gary Luxton et al. and CAP-PLAN (Radiation Treatment Planning System), absorbed doses are within ${\pm}10\%$ and distance deviations are within 0.4mm Maximum error is $-11.3\%$ and 0.8mm, respectively. As a result of it, we can treat the intraocular tumor more effectively by using custom made gold plaque and Ir-192 seeds.

• The Journal of Korean Society for Radiation Therapy
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• v.22 no.1
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• pp.53-60
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• 2010

Purpose: We try to calculate EDW-factor easily with the formula applies essential data of EDW-factor and evaluate the validity through a measurement. Materials and Methods: We used the given value of GSTT (Golden Segmented Treatment Table) for the calculation of the EDW-factor. As to the experimental device, 0.6 cc farmer-type ion-chamber, an electrometer and water- phantom were used. A measurement was made at the maximum dose depth of the photon beam energy 6 MV and 15 MV under the condition that SSD (Source to Surface Distance) was 100 cm. The angle of the EDW (Enhanced Dynamic Wedge) which we use in an experiment was 60 degree, 30 degree, 20 degree in the Y1-OUT direction. We used Eclipse planning system (Varian, USA) as RTP system and the EDW-factor was calculated about all fields and EDW direction. In order to show the EDW-factor feature, a measurement was made at the selected field that verify the influence of the dependability about X, Y jaw and off-axis field. Results: When we change the Y1 field, it influence on the EDW-Factor and measured value. But the error between measured values and calculated values was less than 1%. The experimental result indicated the tendency that the error of the result of calculation and measured value becomes smaller as the EDW angle become smaller whether the calculation point (measurement point) and iso-center are same or not. The influence of the field size and energy did not show up. We simulated with the same condition using the RTP system. And we found that it makes no difference between the MU which is calculated manually by applying the EDW-Factor obtained from the commercial program and the value which is calculated by using RTP system. Conclusion: We excluded fitting value from well-known EDW-Factor formula and calculated EDW-factor with the formula applies essential data of EDW-factor only. As a result, there are no significant difference between the measured value and calculated value and it showed errors less than 1%. Also, we implemented the commercial program to calculate EDW-Factor conveniently without measure a factor on each field.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.2
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• pp.107-114
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• 2012

Purpose: Unlike the existing linear accelerator with photon, proton therapy produces a number of second radiation due to the kinds of nuclide including neutron that is produced from the interaction with matter, and more attention must be paid on the exposure level of radiation workers for this reason. Therefore, thermoluminescence dosimeter (TLD) that is being widely used to measure radiation was utilized to analyze the exposure level of the radiation workers and propose a basic data about the radiation exposure level during the proton therapy. Materials and Methods: The subjects were radiation workers who worked at the proton therapy center of National Cancer Center and TLD Badge was used to compare the measured data of exposure level. In order to check the dispersion of exposure dose on body parts from the second radiation coming out surrounding the beam line of proton, TLD (width and length: 3 mm each) was attached to on the body spots (lateral canthi, neck, nipples, umbilicus, back, wrists) and retained them for 8 working hours, and the average data was obtained after measuring them for 80 hours. Moreover, in order to look into the dispersion of spatial exposure in the treatment room, TLD was attached on the snout, PPS (Patient Positioning System), Pendant, block closet, DIPS (Digital Image Positioning System), Console, doors and measured its exposure dose level during the working hours per day. Results: As a result of measuring exposure level of TLD Badge of radiation workers, quarterly average was 0.174 mSv, yearly average was 0.543 mSv, and after measuring the exposure level of body spots, it showed that the highest exposed body spot was neck and the lowest exposed body spot was back (the middle point of a line connecting both scapula superior angles). Investigation into the spatial exposure according to the workers' movement revealed that the exposure level was highest near the snout and as the distance becomes distant, it went lower. Conclusion: Even a small amount of exposure will eventually increase cumulative dose and exposure dose on a specific body part can bring health risks if one works in a same location for a long period. Therefore, radiation workers must thoroughly manage exposure dose and try their best to minimize it according to ALARA (As Low As Reasonably Achievable) as the International Commission on Radiological Protection (ICRP) recommends.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.2
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• pp.77-84
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• 2012

Purpose: To develop a geometrical quality control real-time analysis program using an electronic portal imaging to replace film evaluation method. Materials and Methods: A geometrical quality control item was established with the Eclipse treatment planning system (Version 8.1, Varian, USA) after the Electronic Portal Imaging Device (EPID) took care of the problems occurring from the fixed substructure of the linear accelerator (CL-iX, Varian, USA). Electronic portal image (single exposure before plan) was created at the treatment room's 4DTC (Version 10.2, Varian, USA) and a beam was irradiated in accordance with each item. The gaining the entire electronic portal imaging at the Off-line review and was evaluated by a self-developed geometrical quality control real-time analysis program. As for evaluation methods, the intra-fraction error was analyzed by executing 5 times in a row under identical conditions and procedures on the same day, and in order to confirm the infer-fraction error, it was executed for 10 days under identical conditions of all procedures and was compared with the film evaluation method using an Iso-align$^{TM}$ quality control device. Measurement and analysis time was measured by sorting the time into from the device setup to data achievement and the time amount after the time until the completion of analysis and the convenience of the users and execution processes were compared. Results: The intra-fraction error values for each average 0.1, 0.2, 0.3, 0.2 mm at light-radiation field coincidence, collimator rotation axis, couch rotation axis and gantry rotation axis. By checking the infer-fraction error through 10 days of continuous quality control, the error values obtained were average 1.7, 1.4, 0.7, 1.1 mm for each item. Also, the measurement times were average 36 minutes, 15 minutes for the film evaluation method and electronic portal imaging system, and the analysis times were average 30 minutes, 22 minutes. Conclusion: When conducting a geometrical quality control using an electronic portal imaging, it was found that it is efficient as a quality control tool. It not only reduces costs through not using films, but also reduces the measurement and analysis time which enhances user convenience and can improve the execution process by leaving out film developing procedures etc. Also, images done with evaluation from the self-developed geometrical quality control real-time analysis program, data processing is capable which supports the storage of information.