• Title/Summary/Keyword: 연구 영역

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Feasibility of Deep Learning Algorithms for Binary Classification Problems (이진 분류문제에서의 딥러닝 알고리즘의 활용 가능성 평가)

  • Kim, Kitae;Lee, Bomi;Kim, Jong Woo
    • Journal of Intelligence and Information Systems
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    • v.23 no.1
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    • pp.95-108
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    • 2017
  • Recently, AlphaGo which is Bakuk (Go) artificial intelligence program by Google DeepMind, had a huge victory against Lee Sedol. Many people thought that machines would not be able to win a man in Go games because the number of paths to make a one move is more than the number of atoms in the universe unlike chess, but the result was the opposite to what people predicted. After the match, artificial intelligence technology was focused as a core technology of the fourth industrial revolution and attracted attentions from various application domains. Especially, deep learning technique have been attracted as a core artificial intelligence technology used in the AlphaGo algorithm. The deep learning technique is already being applied to many problems. Especially, it shows good performance in image recognition field. In addition, it shows good performance in high dimensional data area such as voice, image and natural language, which was difficult to get good performance using existing machine learning techniques. However, in contrast, it is difficult to find deep leaning researches on traditional business data and structured data analysis. In this study, we tried to find out whether the deep learning techniques have been studied so far can be used not only for the recognition of high dimensional data but also for the binary classification problem of traditional business data analysis such as customer churn analysis, marketing response prediction, and default prediction. And we compare the performance of the deep learning techniques with that of traditional artificial neural network models. The experimental data in the paper is the telemarketing response data of a bank in Portugal. It has input variables such as age, occupation, loan status, and the number of previous telemarketing and has a binary target variable that records whether the customer intends to open an account or not. In this study, to evaluate the possibility of utilization of deep learning algorithms and techniques in binary classification problem, we compared the performance of various models using CNN, LSTM algorithm and dropout, which are widely used algorithms and techniques in deep learning, with that of MLP models which is a traditional artificial neural network model. However, since all the network design alternatives can not be tested due to the nature of the artificial neural network, the experiment was conducted based on restricted settings on the number of hidden layers, the number of neurons in the hidden layer, the number of output data (filters), and the application conditions of the dropout technique. The F1 Score was used to evaluate the performance of models to show how well the models work to classify the interesting class instead of the overall accuracy. The detail methods for applying each deep learning technique in the experiment is as follows. The CNN algorithm is a method that reads adjacent values from a specific value and recognizes the features, but it does not matter how close the distance of each business data field is because each field is usually independent. In this experiment, we set the filter size of the CNN algorithm as the number of fields to learn the whole characteristics of the data at once, and added a hidden layer to make decision based on the additional features. For the model having two LSTM layers, the input direction of the second layer is put in reversed position with first layer in order to reduce the influence from the position of each field. In the case of the dropout technique, we set the neurons to disappear with a probability of 0.5 for each hidden layer. The experimental results show that the predicted model with the highest F1 score was the CNN model using the dropout technique, and the next best model was the MLP model with two hidden layers using the dropout technique. In this study, we were able to get some findings as the experiment had proceeded. First, models using dropout techniques have a slightly more conservative prediction than those without dropout techniques, and it generally shows better performance in classification. Second, CNN models show better classification performance than MLP models. This is interesting because it has shown good performance in binary classification problems which it rarely have been applied to, as well as in the fields where it's effectiveness has been proven. Third, the LSTM algorithm seems to be unsuitable for binary classification problems because the training time is too long compared to the performance improvement. From these results, we can confirm that some of the deep learning algorithms can be applied to solve business binary classification problems.

Assessment of Cerebral Hemodynamic Changes in Pediatric Patients with Moyamoya Disease Using Probabilistic Maps on Analysis of Basal/Acetazolamide Stress Brain Perfusion SPECT (소아 모야모야병에서 뇌확률지도를 이용한 수술전후 혈역학적 변화 분석)

  • Lee, Ho-Young;Lee, Jae-Sung;Kim, Seung-Ki;Wang, Kyu-Chang;Cho, Byung-Kyu;Chung, June-Key;Lee, Myung-Chul;Lee, Dong-Soo
    • Nuclear Medicine and Molecular Imaging
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    • v.42 no.3
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    • pp.192-200
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    • 2008
  • To evaluate the hemodynamic changes and the predictive factors of the clinical outcome in pediatric patients with moyamoya disease, we analyzed pre/post basal/acetazolamide stress brain perfusion SPECT with automated volume of interest (VOIs) method. Methods: Total fifty six (M:F = 33:24, age $6.7{\pm}3.2$ years) pediatric patients with moyamoya disease, who underwent basal/acetazolamide stress brain perfusion SPECT within 6 before and after revascularization surgery (encephalo-duro-arterio-synangiosis (EDAS) with frontal encephalo-galeo-synangiosis (EGS) and EDAS only followed on contralateral hemisphere), and followed-up more than 6 months after post-operative SPECT, were included. A mean follow-up period after post-operative SPECT was $33{\pm}21$ months. Each patient's SPECT image was spatially normalized to Korean template with the SPM2. For the regional count normalization, the count of pons was used as a reference region. The basal/acetazolamide-stressed cerebral blood flow (CBF), the cerebral vascular reserve index (CVRI), and the extent of area with significantly decreased basal/acetazolamide- stressed rCBF than age-matched normal control were evaluated on both medial frontal, frontal, parietal, occipital lobes, and whole brain in each patient's images. The post-operative clinical outcome was assigned as good, poor according to the presence of transient ischemic attacks and/or fixed neurological deficits by pediatric neurosurgeon. Results: In a paired t-test, basal/acetazolamide-stressed rCBF and the CVRI were significantly improved after revascularization (p<0.05). The significant difference in the pre-operative basal/acetazolamide-stressed rCBF and the CVRI between the hemispheres where EDAS with frontal EGS was performed and their contralateral counterparts where EDAS only was done disappeared after operation (p<0.05). In an independent student t-test, the pre-operative basal rCBF in the medial frontal gyrus, the post-operative CVRI in the frontal lobe and the parietal lobe of the hemispheres with EDAS and frontal EGS, the post-operative CVRI, and ${\Delta}CVRI$ showed a significant difference between patients with a good and poor clinical outcome (p<0.05). In a multivariate logistic regression analysis, the ${\Delta}CVRI$ and the post-operative CVRI of medial frontal gyrus on the hemispheres where EDAS with frontal EGS was performed were the significant predictive factors for the clinical outcome (p =0.002, p =0.015), Conclusion: With probabilistic map, we could objectively evaluate pre/post-operative hemodynamic changes of pediatric patients with moyamoya disease. Specifically the post-operative CVRI and the post-operative CVRI of medial frontal gyrus where EDAS with frontal EGS was done were the significant predictive factors for further clinical outcomes.

Evaluation of Artifacts by Dental Metal Prostheses and Implants on PET/CT Images: Phantom and Clinical Studies (PET/CT 영상에서의 치과재료에 의한 인공물에 관한 연구)

  • Bahn, Young-Kag;Park, Hoon-Hee;NamKoong, Hyuk;Cho, Suk-Won;Lim, Han-Sang;Lee, Chang-Ho
    • The Korean Journal of Nuclear Medicine Technology
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    • v.14 no.2
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    • pp.110-116
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    • 2010
  • Purpose: The X-ray attenuation coefficient based on CT images is used for attenuation correction in PET/CT. The polychromatic X-ray beam can introduce beam-hardening artifact on CT images. The aims of the study were to evaluate the effect of dental metal prostheses in phantom and patients on apparent tracer activity measured with PET/CT when using CT attenuation correction. Materials and Methods: 40 normal patients (mean age $54{\pm}12$) was scanned between Jan and Feb 2010. NEMA(National Electrical Manufactures Association) PET $Phantom^{TM}$ (NU2-1994) was filled with $^{18}F$-FDG injected into the water that insert implant and metal prostheses dental cast. Region of interest were drawn in non-artifact region, bright steak artifact region and dark streak artifact region on the same transaxial CT and PET slices. Patients and phantom with dental metal prostheses and dental implant were evaluated the change rate of CT Number and $SUV_{mean}$ in PET/CT. A paired t-test was performed to compare the ratio and the difference of the calculated values. Results: In patients with dental metal prostheses, $SUV_{mean}$ was reduced 19.64% (p<0.05) in the non-steak artifact region than the brightstreak artifact region whereas was increased 90.1% (p>0.05) in the non-steak artifact region than the dark streak artifact region. In phantom with dental metal prostheses, $SUV_{mean}$ was reduced 18.1% (p<0.05) in the non-steak artifact region than the bright streak artifact region whereas was increased 18.0% (p>0.05) in the non-steak artifact region than the dark streak artifact region. In patients with dental implant, $SUV_{mean}$ was increased 19.1% (p<0.05) in the non-steak artifact region than the bright streak artifact region whereas was increased 96.62% (p>0.05) in the non-steak artifact region than the dark streak artifact region. In phantom with dental implant, $SUV_{mean}$ was increased 14.4% (p<0.05) in the non-steak artifact region than the bright streak artifact region whereas was increased 7.0% (p>0.05) in the non-steak artifact region than the dark streak artifact region. Conclusion: When CT is used for attenuation correction in patients with dental metal prostheses, 19.1% reduced $SUV_{mean}$ is anticipated in the dark streak artifact region on CT images. The dark streak artifacts of CT by dental metal prostheses may cause false negative finding in PET/CT. We recommend that the non-attenuation corrected PET images also be evaluated for clinical use.

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Optimal Scheme of Postoperative Chemoradiotherapy in Rectal Cancer : Phase III Prospective Randomized Trial (직장암의 근치적 수술 후 화학요법과 방사선치료의 순서)

  • Kim Young Seok;Kim Jong Hoon;Choi Eun Kyung;Ahn Seung Do;Lee Sang-Wook;Kim Kyoung-Ju;Lee Je Hwan;Kim Jin Cheon;You Chang Sik;Kim Hee Cheol
    • Radiation Oncology Journal
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    • v.20 no.1
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    • pp.53-61
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    • 2002
  • Purpose : To determine the optimal scheme of postoperative chemoradiotherapy in rectal cancer by comparing survival, Patterns of failure, toxicities in early and late radiotherapy groups using a Phase III randomized prospective clinical trial. Materials and Methods : From January 1996 to March 1999, 307 patients with curatively resected AJCC stage II and III rectal cancer were assigned randomly to an 'early (151 patients, arm 1)' or a 'late (156 patients, arm II)' and were administered combined chemotherapy (5-FU $375\;mg/m^2/day$, leucovorin $20\;mg/m^2$, IV bolus daily, for 3 days with RT, 5 days without RT, 8 cycles with 4 weeks interval) and radiation therapy (whole pelvis with 45 Gy/25 fractions/5 weeks). Patients of arm I received radiation therapy from day 1 of the first cycle of chemotherapy and those of arm II from day 57 with a third cycle of chemotherapy. The median follow-up period of living patients was 40 months. Results : Of the 307 patients enrolled, fifty patients did not receive scheduled radiation therapy or chemotherapy. The overall survival rate and disease free survival rate at 5 years were $78.3\%\;and\;68.7\%$ in arm I, and $78.4\%\;and\;67.5\%$ in arm II. The local recurrence rate was $6.6\%\;and\;6.4\%$ (p=0.46) in arms I and II, respectively, no significant difference was observed between the distant metastasis rates of the two arms ($23.8\%\;and\;29.5\%$, p=0.16). During radiation therapy, grade 3 diarrhea or more, by the NCI common toxicity criteria, was observed in $63.0\%\;and\;58.2\%$ of the respective arms (p=N.S.), but most were controlled with supportive care. Hematologic toxicity (leukopenia) greater than RTOG grade 2 was found in only $1.3\%\;and\;2.6\%$ of patients in each respective arm. Conclusion : There was no significant difference in survival, patterns of failure or toxicities between the early and late radiation therapy arms. Postoperative adjuvant chemoradiation was found to be a relatively safe treatment but higher compliance is needed.

Hepatitis Complicated with Mycoplasma pneumoniae Infection in Children (소아의 Mycoplasma pneumoniae 폐렴에 합병된 간염)

  • Lee, Seung Min;Lee, Sung Moon;Tchah, Hann;Jeon, In Sang;Ryoo, Eell;Cho, Kang Ho;Seon, Yong Han;Son, Dong Woo;Hong, Hee Joo
    • Clinical and Experimental Pediatrics
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    • v.48 no.8
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    • pp.832-838
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    • 2005
  • Purpose : Mycoplasma pneumoniae infection is relatively common in childhood. Its extrapulmonary manifestations have been reported so much, but hepatitis associated with it has been reported rarely in Korea. Methods : A clinical study was performed on 556 patients of M. pneumoniae pneumonia diagnosed serologically at Gil hospital from January 2001 to December 2004. We reviewed 65 cases among these patients, who had elevated level of serum AST and ALT greater than 50 IU/L respectively without evidence of hepatitis A, B, C, Cytomegalovirus and Ebstein-Barr virus infections. Results : Hepatitis occurred in 11.7% of Mycoplasma pneumoniae pneumonia, especially in fall and winter times. Male to female ratio was 1.2 : 1 and the mean age was 4 years and 3 months. Besides hepatitis, cough(95.4%), sputum(52.3%) and dyspnea(12.3%) were common as pulmonary manifestations. And among gastrointestinal manifestations, nausea/vomiting(26.2%) was the most common symptom, followed by poor oral intake(12.3%), diarrhea(12.3%) and abdominal pain(6.2%). In addition to hepatomegaly(4.6%) and splenomegaly(4.6%), coarse breathing sound was the most common physical manifestation, followed by rale(63.1%), pharyngeal injection(26.2%), and rash(10.8%). Anemia was noted in 20.0%, neutrophilia in 10.8%, eosinphilia in 38.5% and thrombocytosis in 6.2%, respectively. Mean level of ESR and CRP was 32.02 mm/hr and 6.69 mg/dL, respectively. Mean level of AST and ALT was 293.80 IU/L and 181.48 IU/L, respectively. Hyperbilirubinemia was noted in 7.7% and hypoalbuminemia was noted in 58.5%. Lobar or lobular pneumonia(78.5%) was the most common finding in chest X-ray and left lower lobe(39.2%) was most commonly affected. Pleural effusion was noted in 26.2%. Mean duration of hospitalization was 9.91 days. Serum AST/ALT level was normalized within 9.94 days and pulmonary consolidation resolved within 14.29 days. Conclusion : The prognosis of M. pneumoniae hepatitis is good. However, liver function should be considerately checked in M. pneumoniae infection because its incidence is not so low.

Characristics and Management Plans of Myeongwoldae and Myeongwol Village Groves Located in, Jeju (제주 팽림월대(彭林月臺)의 경관특성 및 관리방안)

  • Rho, Jae-Hyun;Oh, Hyun-Kyung;Chol, Yung-Hyun;Kahng, Byung-Seon;Kim, Young-Suk
    • Journal of the Korean Institute of Traditional Landscape Architecture
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    • v.32 no.2
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    • pp.68-81
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    • 2014
  • This study was conducted to identify the spacialty, to illuminate the existence and values of Myeongwoldae(明月臺) and Forest Myeongwol, and to suggest the sustainable usage, preservation and management plans with the purpose of ecological and cultural landscaping characteristic and value identification. The result of the study is as follows. Castle Myeongwol and Port Myeongwol shows the status of Hallim-eup Myeongwol District which is the administrative center of western Jeju as well as is the fortress. Building Wolgyejeongsa and School Woohakdang, the head temple of education and culture, located in Myeongwol District represents the spaciality of Myeonwol-ri which was the center of education. Stand Myeongwol is one of the most representative Confucian cultural landscapes in Jeju Island and the field of communion with nature where scholars enjoy poetries, nature, changgi(Korean chess), and go in the Joseon Dynasty period. It was found that the current relics of Myeongwoldae was recovered through the maintenance project conducted by Youth Group Myeongwol composed with Hongjong-si(洪鍾時) as the center during the Japanese colonial era in 1931. It seems that the stonework of Myeongwoldae composed of three levels in the order of square, octagon, and circle based on the heaven-man unity theory of Confucianism and the octagon in the middle is the messenger of Cheonwonjibang(天圓地方), in other words, between the square-shaped earth and the circle-shaped sky. It is assumed that both Grand Bridge Myeongwol and Bridge Myeongwol were constructed as arched bridges in early days. Bridge Myeongwol is the only arched bridge remaining in Jeju Island now, which has the modern cultural heritage value. In Forest Myeongwol, 97 taxa of plants were confirmed and in accordance with 'Taxonomic Group and Class Criteria of Floristic Specific Plants', eight taxa were found; Arachniodes aristata of FD IV and Ilex cornuta, Piper kadsura, Litsea japonica, Melia azedarach, Xylosma congestum, Richosanthes kirilowii var. japonica, Dichondra repens, Viburnum odoratissimum var. awabuki of FD III. Otherwise, 14 taxa of naturalized plants including Apium leptophylihum which is imported to Jeju Island only were confirmed. In Forest Myeongwol, 77 trees including 41 Celtis sinensis, 30 Aphananthe aspera, two Wylosma congestum, a Pinus densiflora, a Camellia japonica, a Melia azedarach, and an Ilex cornuta form a colony. Based on the researched data, the preservation and plans of Myeongwoldae and Forest Myeongwol is suggested as follows. Myeongwoldae, Bridge Myeongwol, and Forest Myeongwol should be managed as one integrated division. Bridge Myeongwol, an arched bridge which is hard to be found in Jeju Island is a high-standard stonework requiring long-term preservation plans. Otherwise, Grand Bridge Myeongwol that is exposed to accident risks because of deterioration and needs safety diagnosis requires measures according to the result of precise safety diagnosis. It is desirable to restore it to a two-sluice arched bridge as its initial shape and to preserve and use it as a representative local landmark with Stand Myeongwol. In addition, considering the topophsis based on the analysis result, the current name of Jeju Special Self-Governing Province Monument No. 19 'Myoengwol Hackberry Colony' should change to 'Myeongwol Hackberry-Muku Tree Colony'. In addition, the serial number system which is composed without distinction of hackberry and muku tree should be improved and the regular monitoring of big and old trees, specific plants, and naturalized species is required.

A Study on the Construction and Landscape Characteristics of Munam Pavilion in Changnyeong(聞巖亭) (창녕 문암정(聞巖亭)의 조영 및 경관특성에 관한 연구)

  • Lee, Won-Ho;Kim, Dong-Hyun;Kim, Jae-Ung;Ahn, Gye-Bog
    • Journal of the Korean Institute of Traditional Landscape Architecture
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    • v.32 no.2
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    • pp.27-41
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    • 2014
  • This study aims to investigate the history, cultural values prototype through literature analysis, characteristics of construction, location, space structure and landscape characteristics by Arc-GIS on the Munam pavilion(聞巖亭) in Changnyeong. The results were as follows. First, Shin-cho((辛礎, 1549~1618) is the builder of the Munam pavilion and builder's view of nature is to go back to nature. The period of formation of Munam pavilion is between 1608-1618 as referred from document of retire from politics and build a pavilion. Secondly, Munam pavilion is surrounded by mountains and located at the top of steep slope. Pavilion was known as scenic site of the area. But damaged in a past landscape is caused by near the bridge, agricultural facilities, town, the Kye-sung stream of masonry and beams. Thirdly, Munam pavilion is divided into the main space, which is located on the pavilion, space in located on the pavilion east and west and the orient space, which is located on the Youngjeonggak. Of these, original form of Munam pavilion is a simple structure composed of pavilion and Munam rock, thus at the time of the composition seems to be a direct entry is possible, unlike the current entrance. Fourth, Spatial composition of Munam pavilion is divided into vegetation such as Lagerstroemia indica trees in Sa-ri in Changnyeong, ornament such as letters carved on the rocks and pavilion containing structure. The vegetation around the building is classified as precincts and outside of the premises. Planting of precincts was limited. Outside of area consists of front on the pavilion, which is covered with Lagerstroemia Indica forest and Pinus densiflora forest at the back of the pavilion. Ofthese,LargeLagerstroemiaIndicaforestcorrespondstothenaturalheritageasHistoricalrecordsofrarespeciesresourcesthatareassociated withbuilder. Letterscarvedontherocksrepresenttheboundaryof space, which is close to the location of the Munam pavilion and those associated with the builder as ornaments. Letters carved on the rocks front on the pavilion are rare cases that are made sequentially with a constant direction and rules as act of record for families to honor the achievements. Fifth, 'The eight famous spots of Munam' is divided into landscape elements that have nothing to do with bearing 4 places and landscape elements that have to do with bearing 4 places. Unrelated bearings of landscape elements are Lagerstroemia indica trees in Sa-ri in Changnyeong, Pinus densiflora forest at the back of the pavilion, Okcheon valley, Gwanryongsa temple and Daeheungsa temple. Bearing that related element of absolute orientation, which is corresponding to the elements are Daeheungsa temple, Hwawangsan mountain, Kye-sung stream and Yeongchwisan mountain. Relative bearing is Gwanryongsa temple, Yeongchwisan mountain and Kye-sung stream Gongjigi hill. At Lagerstroemia indica trees in Sa-ri in Changnyeong, Pinus densiflora forest at the back of the pavilion, Kye-sung stream and Okcheon valley, elements are exsting. Currently, it is difficult to confirm the rest of the landscape elements. Because, it is a generic element that reliable estimate of the target and locations are impossible for element. Munam pavilion is made for turn to nature by Shin-cho(辛礎). That was remained a record such as Munamzip(聞巖集) and Munamchungueirok(聞巖忠義錄) that is relating to construction of pavilion. Munam pavilion located in a unique form, archival culture through the letters carved on the rocks and Large Lagerstroemia indica forest and through eight famous spots, cultural landscape elements can be assumed that those elements are remained.

Relationship between Stress and Eating Habits of Adults in Ulsan (울산지역 성인 남녀의 스트레스와 식습관)

  • Kim, Hye-Kyung;Kim, Jin-Hee
    • Journal of Nutrition and Health
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    • v.42 no.6
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    • pp.536-546
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    • 2009
  • This study was done to investigate the effect of stress on appetite and eating habits, and other health-related behaviors. The subjects of this study consisted of 188 males and 224 females in Ulsan area. The results were as follows: When stressed, 56% (n = 231) of the subjects experienced a change in appetite and of these, 32% (n = 132) experienced an increased appetite. Stress-induced eating may be one factor contributing to the development of obesity. There was a gender-specific response to stress in which women are more likely to use food to deal with stress, whereas men are more likely to use alcohol consumption or smoking. It was found that types of stressors were individual (52.9%), social (50.7%), family relations (34.5%), work demands (34.2%) and physical environment (32.3%). Stress-induced symptoms of the subjects were anxiety (38.3%), headache (36.7%) and neck or shoulder aches (36.2%), and females experienced those symptoms more than males. Those older than 50 years had a higher eating habit score and lower stress score compared with younger subjects. There were significant differences between sex, age, occupation, family type, BMI, exercise, sleeping hours and eating habits or stress level. This study may be helpful in advancing findings in this area to better provide health professionals with appropriate counseling tools to improve the health of all individuals.

The Effect of PET/CT Images on SUV with the Correction of CT Image by Using Contrast Media (PET/CT 영상에서 조영제를 이용한 CT 영상의 보정(Correction)에 따른 표준화섭취계수(SUV)의 영향)

  • Ahn, Sha-Ron;Park, Hoon-Hee;Park, Min-Soo;Lee, Seung-Jae;Oh, Shin-Hyun;Lim, Han-Sang;Kim, Jae-Sam;Lee, Chang-Ho
    • The Korean Journal of Nuclear Medicine Technology
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    • v.13 no.1
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    • pp.77-81
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    • 2009
  • Purpose: The PET of the PET/CT (Positron Emission Tomography/Computed Tomography) quantitatively shows the biological and chemical information of the body, but has limitation of presenting the clear anatomic structure. Thus combining the PET with CT, it is not only possible to offer the higher resolution but also effectively shorten the scanning time and reduce the noises by using CT data in attenuation correction. And because, at the CT scanning, the contrast media makes it easy to determine a exact range of the lesion and distinguish the normal organs, there is a certain increase in the use of it. However, in the case of using the contrast media, it affects semi-quantitative measures of the PET/CT images. In this study, therefore, we will be to establish the reliability of the SUV (Standardized Uptake Value) with CT data correction so that it can help more accurate diagnosis. Materials and Methods: In this experiment, a total of 30 people are targeted - age range: from 27 to 72, average age : 49.6 - and DSTe (General Electric Healthcare, Milwaukee, MI, USA) is used for equipment. $^{18}F$- FDG 370~555 MBq is injected into the subjects depending on their weight and, after about 60 minutes of their stable position, a whole-body scan is taken. The CT scan is set to 140 kV and 210 mA, and the injected amount of the contrast media is 2 cc per 1 kg of the patients' weight. With the raw data from the scan, we obtain a image showing the effect of the contrast media through the attenuation correction by both of the corrected and uncorrected CT data. Then we mark out ROI (Region of Interest) in each area to measure SUV and analyze the difference. Results: According to the analysis, the SUV is decreased in the liver and heart which have more bloodstream than the others, because of the contrast media correction. On the other hand, there is no difference in the lungs. Conclusions: Whereas the CT scan images with the contrast media from the PET/CT increase the contrast of the targeted region for the test so that it can improve efficiency of diagnosis, there occurred an increase of SUV, a semi-quantitative analytical method. In this research, we measure the variation of SUV through the correction of the influence of contrast media and compare the differences. As we revise the SUV which is increasing in the image with attenuation correction by using contrast media, we can expect anatomical images of high-resolution. Furthermore, it is considered that through this trusted semi-quantitative method, it will definitely enhance the diagnostic value.

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Air Cavity Effects on the Absorbed Dose for 4-, 6- and 10-MV X-ray Beams : Larynx Model (4-, 6-, 10-MV X-선원에서 공기동이 흡수선량에 미치는 효과 : 후두모형)

  • Kim Chang-Seon;Yang Dae-Sik;Kim Chul-Yong;Choi Myung-Sun
    • Radiation Oncology Journal
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    • v.15 no.4
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    • pp.393-402
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    • 1997
  • Purpose : When an x-ray beam of small field size is irradiated to target area containing an air cavity, such as larynx, the underdosing effect is observed in the region near the interfaces of air and soft tissue. With a larynx model, air cavity embedded in tissue-equivalent material, this study is intonded for examining Parameters, such as beam quality, field size, and cavity size, to affect the dose distribution near the air cavity. Materials and Methods : Three x-rar beams, 4-, 6- and 10-MV, were employed to Perform a measurement using a 2cm $(width){\times}L$ (length in cm, one side of x-ray field used 2cm (height) air cavity in the simulated larynx. A thin window parallel-plate chamber connected to an electrometer was used for a dosimetry system. A ratio of the dose at various distances from the cavity-tissue interface to the dose at the same points in a homogeneous Phantom (ebservedlexpected ratio, O/E) normalized buildup curves, and ratio of distal surface dose to dose at the maximum buildup depth were examined for various field sizes. Measurement for cavity size effect was performed by varying the height (Z) of the air cavity with the width kept constant for several field sizes. Results : No underdosing effect for 4-MV beam for fields larger than $5cm\times5cm$ was found For both 6- and 10-MV beams, the underdosing portion of the larynx at the distal surface was seen to occur for small fields, $4cm\times4cm\;and\;5cm\times5cm$. The underdosed tissue was increased in its volume with beam energy even for similar surface doses. The relative distal surface dose to maximum dose was changed to 0.99 from 0.95, 0.92, and 0.91 for 4-, 6-, and 10-MV, respectively, with increasing field size, $4cm\times4cm\;to\;8cm\times8cm$, For 6- and 10-MV beams, the dose at the surface of the cavity is measured less than the predicted by about two and three percent. respectively. but decrease was found for 4-MV beam for $5cm\times5cm$ field. For the $4cm\timesL\timesZ$ (height in cm). varying depth from 0.0 to 4.8cm, cavity, O/E> 1.0 was observed regardless of the cavity size for any field larger than about $8cm\times8cm$. Conclusion : The magnitude of underdosing depends on beam energy, field size. and cavity size for the larynx model. Based on the result of the study. caution must be used when a small field of a high quality x-ray beam is irradiated to regions including air cavities. and especially the region where the tumor extends to the surface. Low quality beam. such as. 4-MV x-ray, and larger fields can be used preferably to reduce the risk of underdosing, local failure. In the case of high quality beams such as 6- and 10-MV x-rays, however. an additional boost field is recommended to add for the compensation of the underdosing region when a typically used treatment field. $8cm\times8cm$, is employed.

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