• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.32 no.4
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• pp.391-396
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• 2006

The CT number is called Hounsfield unit(HU). Generally HU has a score between +1000 from -1000, and it is standardized usingthe air(-1000), water(0), and compact bone(+1000). Hounsfield Unit to standardize the density in computed tomography using the air and water has been used to analysis of lesion in other medical field. Computed tomography is popular method to analysis of lesion in oral & maxillofacial field but the analysis about density of lesion by Hounsfield unit is still obscure. For this study, computed tomography taken in Dankook University Dental Hospital and Hounsfield unit was measured to compare the difference of jaw bone lesion as cystic lesion, benign tumor, malignant tumor.

• Journal of Internet Computing and Services
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• v.21 no.3
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• pp.103-111
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• 2020

Liver cancer is the most fatal cancer that occurs worldwide. In order to diagnose liver cancer, the patient's physical condition was checked by using a CT technique using radiation. Segmentation was needed to diagnose the liver on the patient's abdominal CT scan, which the radiologists had to do manually, which caused tremendous time and human mistakes. In order to automate, researchers attempted segmentation using image segmentation algorithms in computer vision field, but it was still time-consuming because of the interactive based and the setting value. To reduce time and to get more accurate segmentation, researchers have begun to attempt to segment the liver in CT images using CNNs, which show significant performance in various computer vision fields. The pixel value, or numerical value, of the CT image is called the Hounsfield Unit (HU) value, which is a relative representation of the transmittance of radiation, and usually ranges from about -2000 to 2000. In general, deep learning researchers reduce or limit this range and use it for training to remove noise and focus on the target organ. Here, we observed that the range of HU values was limited in many studies but different in various liver segmentation studies, and assumed that performance could vary depending on the HU range. In this paper, we propose the possibility of considering HU value range as a hyper parameter. U-Net and ResUNet were used to compare and experiment with different HU range limit preprocessing of CHAOS dataset under limited conditions. As a result, it was confirmed that the results are different depending on the HU range. This proves that the range limiting the HU value itself can be a hyper parameter, which means that there are HU ranges that can provide optimal performance for various models.

• Imaging Science in Dentistry
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• v.39 no.3
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• pp.115-120
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• 2009

Purpose : The purpose of this study was to determine a conversion coefficient for Hounsfield Units(HU) to material density ($g\;cm^{-3}$) obtained from cone-beam computed tomography ($CBMercuRay^{TM}$) data and to measure the hard tissue density based on the Hounsfield scale on dental head phantom. Materials and Methods : CT Scanner Phantom (AAPM) equipped with CT Number Insert consists of five cylindrical pins of materials with different densities and teflon ring was scanned by using the $CBMercuRay^{TM}$ (Hitachi, Tokyo, Japan) volume scanner. The raw data were converted into DICOM format and the HU of different areas of CT number insert measured by using $CBWorks^{TM}$. Linear regression analysis and Student t-test were performed statistically. Results : There was no significant difference (P > 0.54) between real densities and measured densities. A linear regression was performed using the density, $\rho$($g\;cm^{-3}$), as the dependent variable in terms of the HU (H). The regression equation obtained was $\rho=0.00072H-0.01588$ with an $R^2$ value of 0.9968. Density values based on the Hounsfield scale was $1697.1{\pm}24.9\;HU$ in cortical bone, $526.5{\pm}44.4\;HU$ in trabecular bone, $2639.1{\pm}48.7\;HU$ in enamel, $1246.1{\pm}39.4\;HU$ in dentin of dental head phantom. Conclusion : CBCT provides an effective option for determination of material density expressed as Hounsfield Units.

• Journal of Korean Neurosurgical Society
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• v.54 no.5
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• pp.384-389
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• 2013

Objective : Use of quantitative computed tomography (CT) to evaluate bone mineral density was suggested in the 1970s. Despite its reliability and accuracy, technical shortcomings restricted its usage, and dual-energy X-ray absorptiometry (DXA) became the gold standard evaluation method. Advances in CT technology have reduced its previous limitations, and CT evaluation of bone quality may now be applicable in clinical practice. The aim of this study was to determine if the Hounsfield unit (HU) values obtained from CT correlate with patient age and bone mineral density. Methods : A total of 128 female patients who underwent lumbar CT for back pain were enrolled in the study. Their mean age was 66.4 years. Among them, 70 patients also underwent DXA. The patients were stratified by decade of life, forming five age groups. Lumbar vertebrae L1-4 were analyzed. The HU value of each vertebra was determined by averaging three measurements of the vertebra's trabecular portion, as shown in consecutive axial CT images. The HU values were compared between age groups, and correlations of HU value with bone mineral density and T-scores were determined. Results : The HU values consistently decreased with increasing age with significant differences between age groups (p<0.001). There were significant positive correlations (p<0.001) of HU value with bone mineral density and T-score. Conclusion : The trabecular area HU value consistently decreases with age. Based on the strong positive correlation between HU value and bone mineral density, CT-based HU values might be useful in detecting bone mineral diseases, such as osteoporosis.

• Imaging Science in Dentistry
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• v.40 no.1
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• pp.1-7
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• 2010

Purpose : The purpose of this study was to examine the significance of increased bone density according to whether bone grafts were applied using demographic data with Cone Beam Computed Tomography (CBCT) and to compare the bone densities between before and after implant prosthesis using the Hounsfield index. Materials and Methods : Thirty-six randomly selected computed tomography (CT) scans were used for the analysis. The same sites were evaluated digitally using the Hounsfield scale with V-Implant $2.0^{TM}$, and the results were compared with maxillary posterior bone graft. Statistical data analysis was carried out to determine the correlation between the recorded Hounsfield unit (HU) of the bone graft and implant prosthesis using a Mann-Whitney U test and Wilcoxon Matched-pairs test. Results : The bone grafted maxillary posterior teeth showed an increase in the mean values from-157 HU to 387 HU, whereas non-grafted maxillary posterior teeth showed an increase from 62 HU to 342 HU. After implantation, the grafted and non-grafted groups showed significantly higher bone density than before implantation. However, the grafted group showed significantly more changes than the non-grafted group. Conclusion : Bone density measurements using CBCT might provide an objective assessment of the bone quality as well as the correlation between bone density (Hounsfield scale) and bone grafts in the maxillary molar area.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.4
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• pp.373-384
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• 2007

The purpose of this study was to analyse the stress distribution on the craniofacial suture and cranium after application of RME. Twelve years and six months old boy and twenty years old adult male were chosen for taking computed-tomography for FEM. From DICOM visual information, it was processed by 3-dimensional image construction program Mimics 10.01. Hounsfield unit(HU) which shows gray scale of CT image is picked for revealing mechanical properties of each model. The models have been accomplished with various range of physical properties. After applying 5.0 mm expansion, the maxillary complex model was obeserved for analyzing displacement and stress distribution of the model. The amount of transverse expansion of child and adult maxilla is different according to its location. It appears that it decreases gradually with the distance from separation site. In child, maximum compressive stress located broad area in zygomatic buttress department and the ends of frontal process of maxilla, pterygoid plate, and bones surrounding orbit. However, in adult maximum compressive stress was located smaller area and the stres was higher than child.

• The korean journal of orthodontics
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• v.36 no.6
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• pp.412-421
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• 2006

Objective: The result of finite element analysis depends on material properties, structural expression, density of element, and boundar or loading conditions. To represent proper elastic behavior, a finite element model was made using Hounsfield unit (HU) values in CT images. Methods: A 13 year 6 month old male was used as the subject. A 3 dimensional visualizing program, Mimics, was used to build a 3D object from the DICOM file which was acquired from the CT images. Model 1 was established by giving 24 material properties according to HU. Model 2 was constructed by the conventional method which provides 2 material properties. Protraction force of 500g was applied at a 45 degree downward angle from Frankfort horizontal (FH) plane. Results: Model 1 showed a more flexible response on the first premolar region which had more forward and downward movement of the maxillary anterior segment. Maxilla was bent on the sagittal plane and frontal plane. Model 2 revealed less movement in all directions. It moved downward on the anterior part and upward on the posterior part, which is clockwise rotation of the maxilla. Conclusion: These results signify that different outcomes of finite element analysis can occur according to the given material properties and it is recommended to use HU values for more accurate results.

• Journal of radiological science and technology
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• v.40 no.2
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• pp.229-235
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• 2017

In abdominal Ultrasonography, the fatty liver is diagnosed through hepatic parenchymal echo increased parenchymal density and unclear blood vessel boundary, and according to many studies, abdominal Ultrasonography has 60~90% of sensitivity and 84~95% of specificity in diagnosis of fatty liver, but the result of Ultrasonography is dependent on operators, so there can be difference among operators, and quantitative measurement of fatty infiltration is impossible. Among examinees who same day received abdominal Ultrasonography and chest computed tomography (CT), patients who were diagnosed with a fatty liver in the Ultrasonography were measured with liver Hounsfield Units (HU) of chest CT imaging to analyze the accuracy of the fatty liver diagnosis. Among 720 subject examinees, those who were diagnosed with a fatty liver through abdominal Ultrasonography by family physicians were 448, which is 62.2%. The result of Liver HU measurement in the chest CT imaging of those who were diagnosed with a fatty liver showed that 175 out of 720 had the measured value of less than 40 HU, which is 24.3%, and 173 were included to the 175 among 448 who were diagnosed through Ultrasonography, so 98.9% corresponded. This indicates that the operators' subjective ability has a great impact on diagnosis of lesion in Ultrasonography diagnosis of a fatty liver, and that in check up chest CT, under 40 HU in the measurement of Liver HU can be used for reference materials in diagnosis of a fatty liver.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.183-189
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• 2014

Purpose : Intravenous contrast medium is a substance used to enhance the contrast of normal tissues or malignant tissues within the body. For this reason, intravenous contrast media have been extensively used form treatment-planning CT. However, when the patient is receiving proton therapy, there is no contrast medium in that moment. In this study, evaluate the influence of intravenous contrast medium on proton range and Spread-Out Bragg peak(SOBP) in Treatment Planning System(TPS). Materials and Methods : Hounsfield Unit(HU) value were measured by 20 liver cancer patients with phase change. and evaluate the proton range and SOBP on 5 liver proton treatment plan. By using the hand made water phantom measure the proton range and SOBP on proton treatment plan with changing HU and Depth. Results : Changing value(Pre contrast, Arterial phase, Portal phase) in liver cancer patient were ($58{\pm}5.7$, $75{\pm}9.5$, $117{\pm}14.6$ for liver tissue) and ($40{\pm}6.1$, $279{\pm}49.0$, $154{\pm}22.8$ for aorta), respectively. The mean difference of range was 2.5mm and SOBP was 1.4mm according to HU change. In phantom study, proton range was shorter and SOBP was narrowed with increasing HU. Conclusion : We verify that HU change lead to range and SOBP change in TPS. Additional study is required to verify that change of HU make range and SOBP be changed in actual substance.

• The Journal of the Korea Contents Association
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• v.12 no.10
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• pp.349-356
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• 2012

In the diagnosis of coronary artery atheromatous plaque, Cardiac computed tomography (Cardiac Computed Tomographic Angiography: CCTA) compared with IVUS(Intravascular Ultrasound: IVUS) investigate the diagnostic accuracy, Interested in CCTA atheromatous plaque in computed tomography values (Hounsfield Unit: HU) try to find out. From April 2006 to August 2008 among coronary artery disease(Coronary Artery Disease: CAD) patients with confirmed or suspicious of CAD by CCTA performed atherosclerotic plaques and found 200 patients who underwent IVUS were enrolled. 200 patients who underwent CCTA and IVUS results from the 476 plaque was found, IVUS results of the soft plaque(n; 84), fibrous plaque(n; 63), mixed plaque (n; 97), calcific plaque(n; 232). The results are classified according to the IVUS plaque in HU in the soft plaque : $53.8{\pm}10.5$, fibrous plaque : $108.1{\pm}20.0$, mixed plaque : $371.2{\pm}113.1$, and calcific plaque : $731.0{\pm}160.4$. CCTA had sensitivity of 97% and confidence interval of 95.0-98.3. This study that is the diagnosis of coronary atheromatous plaque for using CCTA, we confirm the high sensitivity and the confidence interval Based on IVUS results CCTA atheromatous plaque with HU in the analysis could be classified to characterize in the treatment of patients with CAD is expected to help.