• Progress in Medical Physics
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• v.23 no.1
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• pp.62-69
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• 2012

The dose re-calculation process using Megavoltage cone-beam CT images is inevitable process to perform the Adaptive Radiation Therapy (ART). The purpose of this study is to improve dose re-calculation accuracy using MVCBCT images by applying intensity calibration method and three dimensional rigid body transform and filtering process. The three dimensional rigid body transform and Gaussian smoothing filtering process to MVCBCT Rando phantom images was applied to reduce image orientation error and the noise of the MVCBCT images. Then, to obtain the predefined modification level for intensity calibration, the cheese phantom images from kilo-voltage CT (kV CT), MVCBCT was acquired. From these cheese phantom images, the calibration table for MVCBCT images was defined from the relationship between Hounsfield Units (HUs) of kV CT and MVCBCT images at the same electron density plugs. The intensity of MVCBCT images from Rando phantom was calibrated using the predefined modification level as discussed above to have the intensity of the kV CT images to make the two images have the same intensity range as if they were obtained from the same modality. Finally, the dose calculation using kV CT, MVCBCT with/without intensity calibration was applied using radiation treatment planning system. As a result, the percentage difference of dose distributions between dose calculation based on kVCT and MVCBCT with intensity calibration was reduced comparing to the percentage difference of dose distribution between dose calculation based on kVCT and MVCBCT without intensity calibration. For head and neck, lung images, the percentage difference between kV CT and non-calibrated MVCBCT images was 1.08%, 2.44%, respectively. In summary, our method has quantitatively improved the accuracy of dose calculation and could be a useful solution to enhance the dose calculation accuracy using MVCBCT images.

• Progress in Medical Physics
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• v.20 no.1
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• pp.37-42
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• 2009

Proton therapy facility, which is recently installed at National Cancer Center in Korea, generally produces a large amount of radiation near cyclotron due to the secondary particles and radioisotopes caused by collision between proton and nearby materials during the acceleration. Although the level of radiation by radioisotope decreases in length of time, radiation exposure problem still exists since workers are easily exposed by a low level of radiation for a long time due to their job assignment for maintenance or repair of the proton facility. In this paper, the working environment near cyclotron, where the highest radiation exposure is expected, was studied by measuring the degree of radiation and its duration for an appropriate level of protective action guide. To do this, we measured the radiation change in the graphite based energy degrader, the efficiency of transmitted beam and relative activation degree of the transmission beam line. The results showed that while the level of radiation exposure around cyclotron and beam line during the operation is much higher than the other radiation therapy facilities, the radiation exposure rate per year is under the limit recommended by the law showing 1~3 mSv/year.

• Tuberculosis and Respiratory Diseases
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• v.47 no.2
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• pp.195-208
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• 1999

Background: Pulmonary infiltrate in immunocompromised hosts has many infectious and non-infectios etiologies. To evaluate the diagnostic yield and therapeutic implication of two invasive diagnostic methods, such as bronchoscopy and surgical lung biopsy, we performed retrospective analysis of these patients. Methods: All immunocompromised patients admitted to Samsung Medical Center from October 1995 to August 1998 who underwent bronchoscopy and/or surgical lung biopsy for the diagnosis of pulmonary infiltrates were included in this study. Confirmative diagnostic yield, the rate of changed therapeutic plan and patients' survival were investigated. Results: Seventy-five episodes of pulmonary infiltrates developed in 70 patients(M : F=46 : 24, median age 51). Underlying diseases of patients were hematologic malignancy(n=30), organ transplantation(n=11), solid tumor(n= 12), connective tissue disease(n=6) and others. Confirmative diagnosis was made in total 53 cases (70.7%), of which 70.2% had infectious etiology. Diagnostic yields of bronchoscopy, bronchoalveolar lavage(BAL), transbronchiallung biopsy(TBLB) and surgical lung biopsy were 35.0%(21/60), 31.4%(16/51), 25.0%(9/36) and 80.0%(20/25). Therapeutic plan was changed in 40%(24/60) of patients after bronchoscopy and in 36%(9/25) of patients after surgical lung biopsy. More patients survived (84.4% vs 60.5%, p=0.024) when therapeutic plan was changed after invasive diagnostic study. Conclusion: Bronchoscopy and surgical lung biopsy are helpful for the therapeutic implication of pulmonary infiltrates in immunocompromised hosts. Large-scale prospective case-control study may further clarify their limitation and usefulness.

• Tuberculosis and Respiratory Diseases
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• v.47 no.5
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• pp.650-659
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• 1999

Background/Aims: It is well recognized that all aerobic cells have the protective mechanisms in order to minimize the tissue damage induced by various reactive oxygen species(ROS). Thioredoxin peroxidase(TPX) which has been recently identified and characterized functions to convert peroxide to water. The protein is also found in various subtypes(TPX-A & B, MER5, HS22 and HORF-06) and is known to be ubiquitous in most human cells. Especially, ischemic brain injuries, partial hepatectomy and radiation induced DNA damages. In treating lung cancer, radiation therapy has a major place in the local control and the relief of symptoms, but radiation induced free radical injury and resulting pulmonary fibrosis has been the major drawback of the therapy. However, little is known about the protective mechanisms and biologic modulations against radiation-induced tissue damages. Methods: Eighteen mice were divided into six groups, 3 in each group, and fifteen had received 900cGy of radiation. The mice were sacrificed according to the pre determined time schedule; immediate, 1, 2, 3 and 6 weeks after irradiation. Extracts were made from the lungs of each mice, Western blot analysis of various subtypes of TPX were done after SDS-P AGE. Examination of H & E stained slides from the same irradiated specimens and the control specimens were also performed. Results: No difference in the intensity of the immunoreactive bands in the irradiated lung samples of the mice compared to the unirradiated control was observed regardless of the time intervals, although H & E examination of the sample specimens demonstrated progressive fibrotic changes of the irradiated lung samples. Conclusion: In conclusion, according to our data, it is suggested that various thioredoxin peroxidase subtypes and catalase which are known to be increased in many repair processes may not be involved in the repair of the radiation injury to the lung and subsequent fibrosis.

• Tuberculosis and Respiratory Diseases
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• v.66 no.6
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• pp.444-450
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• 2009

Background: Biomarkers for cancer have several potential clinical uses, including the following: early cancer detection, monitoring for recurrence prognostication, and risk stratification. However, no biomarker has been shown to have adequate sensitivity and specificity. Many investigators have tried to validate biomarkers for the early detection and recurrence of lung cancer. To evaluate plasma G-CSF as such a biomarker, protein levels were measured and were found to correlate with the clinicopathological features of primary lung tumors. Methods: Between December 2006 and May 2008, 100 patients with histologically-validated primary lung cancer were enrolled into this study. To serve as controls, 127 healthy volunteers were enrolled into this study. Plasma G-CSF levels were measured in lung cancer patients using the sandwich ELISA system (R & D inc.) prior to treatment. Results: The mean plasma G-CSF levels were 12.2$\pm$0.3 pg/mL and 46.0$\pm$3.8 pg/mL (mean$\pm$SE) in the normal and in the cancer groups, respectively. In addition, plasma G-CSF levels were higher in patients with early lung cancer than in healthy volunteers (p<.001). Plasma G-CSF levels were higher in patients who were under 65 years old or smokers. Within the cancer group, plasma G-CSF levels were higher in patients with non small cell lung cancer than in patients with small cell lung cancer (p<.05). Overall, plasma G-CSF levels were shown to increase dependent upon the type of lung cancer diagnsosed. In the order from highest to lowest, the levels of plasma G-CSF tended to decrease in the following order: large cell carcinoma, squamous cell carcinoma, adenocarcinoma, and bronchioloalveolar carcinoma. Plasma G-CSF levels tended to be higher in patients with advanced TNM stage than in localized TNM stage (I, II

• Progress in Medical Physics
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• v.20 no.3
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• pp.139-144
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• 2009

Recently, the mathematical analysis of stent simulation has been improved, with the help of development of various tool which measure mechanical property and location of stent in artery. The most crucial part of the stent modeling is how to design ideal stent and to evaluate the interaction between stent and artery. While there has been great deal of researches on the evaluation of the expansion, stress distribution, deformation of the stent in terms of the various parameters, few verification through computer simulation has been performed about deformation and stress distribution of the stent. In this study, we have produced the corresponding results between experimental test using Universal Testing Machine and computer simulation for the ideal model of stent. Also, we have analyzed and compared stress distribution of stent in the cases of that with membrane and that without membrane. The results of this study would provide minimum change of plan and good quality for ideal stent replacing damaged artery through the analysis using computer simulation in the early stage of stent design.

• Progress in Medical Physics
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• v.25 no.1
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• pp.31-36
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• 2014

We aimed to evaluate the dosimetric characteristics of reproducibility, linearity and dose dependence of optical stimulated luminance dosimeter (OSLD) in the Co-60 Gamma-rays and to analyze with a precedent study in field of the diagnostic radiography and radiotherapy. The reproducibility was 0.76% of the coefficient of variation, the homogeneity was within 1.5% of the coefficient of variation and OSLD had supra-linear response more than 3 Gy. So the correlation between dose and count was fitted by quadratic function. The count depletion by repeated reading was 0.04% per reading regardless of the irradiated dose. And the half time of decay curve according to the irradiated dose was 0.68 min. with 1 Gy, 1.04 min. with 5 Gy, and 1.10 min. with 10 Gy, respectively. In case of annealing for 30 min, the removal rate was 88% with 1 Gy, 90% with 5 Gy, and 92% with 10 Gy, respectively and 99% in case of annealing time for 4 hour. It is feasible to use OSLDs for dose evaluation in Co-60 Gamma-rays when considering the uncertainty on the procedure according to the irradiated dose.

• Clinical and Experimental Pediatrics
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• v.49 no.3
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• pp.292-297
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• 2006

Purpose : In medulloblastoma, craniospinal radiation therapy combined with chemotherapy improves the prognosis of tumors but results in significant endocrine morbidities. We studied the endocrine morbidity, especially growth pattern changes. Methods : The medical records of 37 patients with medulloblastoma were reviewed retrospectively for evaluation of endocrine function and growth. We performed the growth hormone stimulation test in 16 patients whose growth velocity was lower than 4 cm/yr. Results : The height loss was progressive in most patients. The height standard deviation score (SDS) decreased from $-0.1{\pm}1.3$ initially to $-0.6{\pm}1.0$ after 1 year(P<0.01). Growth hormone deficiency(GHD) developed in 14 patients. During the 2 years of growth hormone(GH) treatment, the improvements of height gain or progressions of height loss were not observed. Twelve patients(32.4 percent) revealed primary hypothyroidism. One of six patients diagnosed with compensated hypothyroidism progressed to primary hypothyroidism. Primary and hypergonadotropic hypogonadism were observed in two and one patients respectively. There was no proven case of central adrenal insufficiency. Conclusion : Growth impairment developed frequently, irrespective of the presence of GHD in childhood survivors of medulloblastoma. GH treatment may prevent further loss of height. The impairment of the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-thyroidal axis is less common, while central adrenal insufficiency was not observed.

• Clinical and Experimental Pediatrics
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• v.45 no.8
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• pp.1000-1006
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• 2002

Purpose : In the course of treatment, patients with hematological or oncological disorders often develop pulmonary complication. The patients who develop a severe pulmonary complication have a poor outlook. The causes of pulmonary complication are either infectious or non-infectious in origin. We have analyzed the etiology and outcome of these patients admitted to the pediatric intensive care unit of Asan Medical Center. Methods : Medical records of 95 patients on Pediatric oncology service who were admitted to pediatric intensive care unit(PICU) of Asan Medical Center from Jan 1997 to May 2000 were retrospectively reviewed. Results : The mean age of the patients was 8.5 years(2 months-18 years). The underlying malignancies of these 95 patients were as following; acute lymphoblastic leukemia(31 cases), lymphoma (11 cases), acute myeloid leukemia(nine cases), brain tumor(eight cases) and other solid tumors(25 cases). Pulmonary complications included pneumonia, acute respiratory failure, pneumothorax and pleural effusion. The most common cause of pulmonary complication was infection(88%) in etiology. The overall mortality rate was 56.8%. Pulmonary complications in these patients carried high rates of mortality regardless of whether they were immune compromised(76%) or not(69%). Even without pulmonary complications, the hematological or oncological patients admitted to PICU had high mortality rates of 43%. Conclusion : Pulmonary complications are frequent finding in the hematological or oncological patients admitted to Intensive Care Unit. The main etiology of these pulmonary complications was infection, which carried a high mortality rate regardless of their immune status at the time when they were admitted to PICU.

• Clinical and Experimental Pediatrics
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• v.45 no.8
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• pp.1016-1023
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• 2002

Purpose : Brain tumors are the most common solid tumor in children. We retrospectively investigated the clinical characteristics of pediatric brain tumors, such as age, sex, tumor site and survival, as seen in a single institution over the last 15 years. We tried to evaluate the role of chemotherapy on the survival of some brain tumors. Methods : Three hundred fifty four children with primary brain tumor who were treated at Severance Hospital from Jan. 1985 to Sep. 2001 were enrolled. Results : Pediatric brain tumors were found most frequently in 10-15 years of age group(35.3%) and the ratio of male to female was 1.3 : 1. Supratentorial tumors(52%) were more frequent than infratentorial tumors(48%). Medulloblastoma/primitive neuroectodermal tumor(PNET) was the most common type(24.6%), followed by cerebellar astrocytoma(14.1%). Ten year survival rate of medulloblastoma, cerebellar astrocytoma and cerebral astrocytoma were 59.4%, 79.3% and 71%, respectively. The prognosis for brain stem glioma and glioblastoma multiforme were still grim with a 10 year survival rate of 12.7% and 13.3%, respectively. The addition of chemotherapy for high grade medulloblastoma led to an improved 10 year survival rate of 54.5%, compared with 40% without chemotherapy. Conclusion : The combined use of chemotherapy and radiation and surgery improved survival rate of pediatric brain tumors in our study. Chemotherapy for high grade medulloblastoma improved the 10 year survival rate. Further data analysis of the treatment modalities will lead to better comparisons.