• Proceedings of the Korean Information Science Society Conference
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• 1998.10c
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• pp.438-440
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• 1998

본 논문에서는 복부의 전산화 단층촬영 영상으로부터 체지방의 양을 측정하기 위한 영상처리에서 사용되는 문턱치의 자동 설정 방법을 제안한다. 체지방의 정량적 측정은 비만과 관련된 진단 및 치료에 있어서 중요하다. 기존의 비만도 측정은 체중과 신장의 비, 허리와 둔부 둘레의 비, 손으로 잡히는 복부의 두께 등 단순한 측정방법을 사용하여 실제 지방의 양을 제대로 반영하지 못하는 단점이 있다. 이러한 단점을 보완하기 위하여 최근에 전산화 단층촬영 영상으로부터 영상처리를 통하여 직접 지방의 양을 측정하려는 시도가 있다. 전산화 단층촬영 영상을 이용하면 지방의 양을 정량적으로 측정할 수 있고 피하지방과 복강내지방 등 특정부위의 체지방의 양을 측정할 수 있다. 전산화 단층촬영은 밀도에 비례하는 하운스필드 단위 값으로 구성된 영상을 제공한다. 일반적으로 체지방은 하운스필드 단위 값이 -150에서 -50사이인 것으로 알려져 있다. 그러나, 체지방의 문턱치는 사람에 따라 다르고, 또한 같은 사람에 대해서도 촬영 부위에 따라 다르다. 본 논문에서는 이러한 차이를 히스토그램을 통하여 보이고 히스토그램의 가우시안 함수 근사로부터 체지방의 문턱치를 자동으로 설정하는 방법을 제안한다.

• Progress in Medical Physics
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• v.20 no.3
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• pp.145-151
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• 2009

This study aims to evaluate CT (Computed Tomography) characteristics through the estimation of HU (Hounsfield Unit) and the corresponding variations using coefficient of variation values for various materials as a function of physical factor. HU values for various materials with varying densities as a function of physical factor were measured using MDCT (Siemens SOMATOM Sensation 4, Germany). The results showed that the HU values were decreased and increased as a function of kVp and material density, respectively. Especially, the HU values for bone and iodine at 140 kVp were 32% and 42% smaller than those at 80 kVp, respectively. In case of iodine, the HU values also decreased and increased as a function of kVp and concentration, respectively. While the HU values were fixed as a function of mAs. The decreased ratio of HU values between 80 keV and 140 keV was different at various concentration and maximum difference was shown as 1.73 at 3% concentration. These results indicated that it may be possible to separate composition of materials, e.g. iodine and bone, using single source CT. The results showed that dual energy techniques using single source CT can be applied to material separation and expand CT imaging techniques to other practical applications.

• Journal of radiological science and technology
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• v.38 no.4
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• pp.421-427
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• 2015

In this study, we have observed the change of the Hounsfield (HU) in the alteration of by changing in size of physical area and setting size of region of interest (ROI) at focus on kVp and mAs. Four-channel multi-detector computed tomography was used to get transverse axial scanning images and HU. Three dimensional printer which is type of fused deposition modeling (FDM) was used to produce the Phantom. The structure of the phantom was designed to be a type of cylinder that contains 33 mm, 24 mm, 19 mm, 16 mm, 9 mm size of circle holes that are symmetrically located. It was charged with mixing iodine contrast agent and distilled water in the holes. The images were gained with changing by 90 kVp, 120 kVp, 140 kVp and 50 mAs, 100 mAs, 150 mAs, respectively. The 'image J' was used to get the HU measurement of gained images of ROI. As a result, it was confirmed that kVp affects to HU more than mAs. And it is suggested that the smaller size of physical area, the more decreasing HU even in material of a uniform density and the smaller setting size of ROI, the more increasing HU. Therefore, it is reason that to set maximum ROI within 5 HU is the best way to minimize in the alteration of by changing in size of physical area and setting size of region of interest.

• Journal of the Korean Society of Radiology
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• v.16 no.6
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• pp.709-718
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• 2022

We evaluated the effect of high-density aluminum, titanium, and steel metal inserts on computed tomography (CT) numbers and radiation treatment plans for Tomotherapy. CT images were obtained using a cylindrical TomoPhantom comprising cylindrical rods of various densities and metal inserts. Three CT image sets were evaluated for image quality as the mean CT number and standard deviation. Dose evaluation also performed. The reference values did not significantly differ between the CT image sets with the corrected metal inserts. The higher-density material exhibited the largest difference in the mean CT number and standard deviation. The conformity index at Iterative-Metal Artifact Reduction (iMAR) was approximately 20% better than that of non-iMAR. No significant target or organ at risk dose difference was observed between non-iMAR and iMAR. Therefore, iMAR is helpful for target or organ at risk delineation and for reducing uncertainty for three-dimensional conformal radiation therapy in Tomotherapy.

• Journal of Veterinary Clinics
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• v.31 no.6
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• pp.495-501
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• 2014

The objective of this study was to evaluate the differences and reproducibility of Hounsfield unit (HU) value and volume measurements on different computed tomography (CT) scanner types and different collimations by using a gelatin phantom. The phantom consisting of five synthetic simulated calculus spanning diameters from 3.0 mm to 12.0 mm with 100 HU was scanned using a two-channel multi-detector row CT (MDCT) scanner, a four-channel MDCT scanner, and two 64-channel MDCT scanners. For all different scanner types, the thinnest possible collimation and the second thinnest collimation was used. The HU values and volumes of the synthetic simulated calculus were independently measured three times with minimum intervals of 2 weeks and by three experienced veterinary radiologists. ANOVA and Scheff$\acute{e}$ test for the multiple comparison were performed for statistical comparison of the HU values and volumes of the synthetic simulated calculus according to different CT scanner types and different collimations. The reproducibility of the HU value and volume measurements was determined by calculating Cohen's k. The reproducibility of HU value and volume measurements was very good. HU value varied between different CT scanner types, among different beam collimations. However, there was not statistically significant difference. The percent error (PE) decreased as the collimation thickness decreased, but the decrease was statistically insignificant. In addition, no statistically significant difference in the PEs of the different CT scanner types was found. It can be concluded that the CT scanner type insignificantly affects HU value and the volumetric measurement, but that a thinner collimation tends to be more useful for accurate volumetric measurement.

• 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.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.185-192
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• 2019

DXA is the most commonly used BMD examination equipment with the best performance on reflecting the biological alteration with tiny change of bone density. In spite of the importance of the quality control to maintain the accuracy and precision of the examination, considerable number of hospitals are not conducting QC due to the difficulty and high cost of the phantom product. This study develops the cross revision phantom with 3D printer and the change of the degree of infilling filaments which can be readily secured, and provides the usefulness assessment of the developed phantom by comparing with existing products. The Hounsfield Units of ABS, TPU, PLA, 30% Cu-PLA, and 30% Al-PLA are assessed. The Hounsfield Units result at infilling rate 100% was $-149.74{\pm}2.36$, $-55.62{\pm}7.14$, $-7.68{\pm}3.82$, $87.53{\pm}1.07$, and $1795.20{\pm}16.15$. The L1, L2, L3 BMD of 3D printing phantom with linear regression model were $0.620{\pm}0.010g/cm^2$, $1.092{\pm}0.025g/cm^2$, $1.554{\pm}0.026g/cm^2$ which are statistically relevant to the existing phantom products. This result provides the base line data for various medical phantom produce and capability of proper quality control of DXA equipment.

• Journal of the Korean Society of Radiology
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• v.6 no.6
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• pp.455-464
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• 2012

This study suggested evaluation of approximately exposure to low-dose ionization radiation from medical images using a computed radiography (CR) system in standard X-ray examination and experimental model can compare diagnostic reference level (DRL) will suggest on optimization condition of guard about medical radiation of low dose space. Entrance surface dose (ESD) cross-measuring by standard dosimeter and optically stimulated luminescence dosimeters (OSLDs) in experiment condition about tube voltage and current of X-ray generator. Also, Hounsfield unit (HU) scale measured about each experiment condition in CR system and after character relationship table and graph tabulate about ESD and HU scale, approximately radiation dose about head, neck, thoracic, abdomen, and pelvis draw a measurement. In result measuring head, neck, thoracic, abdomen, and pelvis, average of ESD is 2.10, 2.01, 1.13, 2.97, and 1.95 mGy, respectively. HU scale is $3,276{\pm}3.72$, $3,217{\pm}2.93$, $2,768{\pm}3.13$, $3,782{\pm}5.19$, and $2,318{\pm}4.64$, respectively, in CR image. At this moment, using characteristic relationship table and graph, ESD measured approximately 2.16, 2.06, 1.19, 3.05, and 2.07 mGy, respectively. Average error of measuring value and ESD measured approximately smaller than 3%, this have credibility cover all the bases radiology area of measurement 5%. In its final analysis, this study suggest new experimental model approximately can assess radiation dose of patient in standard X-ray examination and can apply to CR examination, digital radiography and even film-cassette system.

• The Journal of the Korea Contents Association
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• v.12 no.9
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• pp.270-279
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• 2012

This paper explores CT findings of a rabbit brain infection model injected with Escherichia coli and investigates the changes in Hounsfield unit (HU) of arterial blood over time. The brain infection model was produced by injecting E. coli $1{\times}10^7$ CFU/ml, 0.1 ml through the burr hole in the calvarium; 2~3 mm in depth from the dura mater, and contrast-enhanced CT, dynamic CT and arterial blood CT images were gained. It was found that various brain infections such as brain abscess, ventriculitis and meningitis. The CT image of brain abscess showed a typical pattern which the peripheral area was strongly contrast-enhanced while the center was weakly contrast-enhanced. The CT image of ventriculitis showed a strong contrast-enhancement along the lateral ventricle wall, and the CT image of meningitis showed a strong contrast-enhancement in the area between the telencephalon and the diencephalon. In dynamic CT images, the HU value of the infection core before injecting contrast medium was $31.01{\pm}3.55$. By 10 minutes after the injection, the value increased gradually to $40.36{\pm}3.76$. The HU value in the areas of the marginal rim where was hyper-enhanced showed $47.23{\pm}3.12$ before contrast injection, and it increased to $63.59{\pm}3.31$ about 45 seconds after the injection. In addition, the HU value of the normal brain tissue opposite to the E. coli. injected brain was $39.01{\pm}3.24$ before the injection, but after the contrast injection, the value increased to $49.01{\pm}4.29$ in about 30 seconds, and then it showed a gradual decline. In the arterial blood CT, the HU value before the contrast injection was $87.78{\pm}6.88$, and it increased dramatically between 10 to 30 seconds until it reached a maximum value of $749.13{\pm}98.48$. Then it fell sharply to $467.85{\pm}62.98$ between 30 seconds to 45 seconds and reached a plateau by 60 seconds. Later, the value showed a steady decrease and indicated $188.28{\pm}25.03$ at 20 minutes. Through this experiment, it was demonstrated that the brain infection model can be produced by injecting E. coli., and the characteristic of the infection model can be well observed with contrast-enhanced CT scan. The dynamic CT scan showed that the center of the infection was gradually contrast-enhanced, whereases the peripheral area was rapidly contrast-enhanced and then slowly decreased. As for arterial blood, it increased significantly between 10 seconds to 30 seconds after the contrast medium injection and decreased gradually after reaching a plateau.