• Advances in biomechanics and applications
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• v.1 no.1
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• pp.15-22
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• 2014

Computed tomography (CT) is being utilized in orthopaedics and related research to estimate bone strength. These applications benefit from calibration of Hounsfield units to mineral density typical of long bone, up to $1750mg/cm^3$. This study describes a method for establishing repeatable calibration of Hounsfield units to density, and determines the effects of imaging medium on calibration accuracy. Four hydroxyapatite standards were imaged in air on 7 occasions over 19 weeks using a helical multi-slice CT scanner. Each standard was scanned 5 times in different media: porcine soft tissue, water, and air. Calibrated densities were highly repeatable (CV<3.5%). No difference in density was observed between water and soft tissue conditions (p>0.08). This work provides a model for determining repeatable scanner-specific density calibration, demonstrates that the linear relationship between Hounsfield units and density extends to values typical of cortical bone, and supports the practice of imaging calibration standards in an environment similar to that of the target bone.

• 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.

• 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 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.

• Clinics in Shoulder and Elbow
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• v.18 no.2
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• pp.86-90
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• 2015

Background: Although there are several methods for evaluating bone quality, Hounsfield units (HU), a standardized computed tomography (CT) attenuation coefficient, provide a useful tool for estimating focal bone mineral density (BMD). The aim of this study is to investigate the HU for evaluating the degree of osteoporosis in greater tuberosity with regard to anchor positioning. Methods: Forty patients diagnosed as normal on shoulder CT were included and categorized according to age and gender. Axially sectioned CT images were processed to 3-dimensional models containing information about bone quality using Mimics (14.11 platform v14.1.1.1 Materialise). Three-dimensional anchors were simulated and positioned according to 6 regions of interest (ROI) in the greater tuberosity classified using Tingart's system. Mean HU of intra-anchor volumes in the 6 regions was measured. Results: A significant decrease in HU was observed with increasing age (p=0.0001) and menopause (p<0.001). A significant difference in HU was found between male and female groups with males showing the higher values (p=0.0001). HU of proximal areas of ROI was higher than those of distal areas (p<0.005). However, although mean HU of distal posterior ROI showed the lowest values, no statistically significant difference was found between anterior, middle, and posterior regions (p=0.087). Conclusions: Mean HU of ROIs provides a tool for preoperative assessment of focal BMD, which is a factor of suture anchor stability and can be used to aid decision-making regarding secure anchor positioning for rotator cuff repair. Our data support that the most secure point is the proximal regions of ROI.

• Journal of radiological science and technology
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• v.40 no.3
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• pp.385-392
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• 2017

The purpose of this study is to investigate the image quality and exposure dose according to kVp and mAs in CT and to confirm improvement in image quality according to None IR and IR(Iterative Reconstruction) levels. Measurement results of image quality using Image J, HU(Hounsfield units) and BN(Background Noise) are decreased, while SNR(Signal to Noise Ratio) and $CTDI_{vol}$(CT dose index volume) are increased as the kVp increases and there was no change of BHU(Background Hounsfield units). BN was reduced due to increased kVp, while SNR and $CTDI_{vol}$ were increased. Also, the higher IR stage, the lower BN, SI(Signal Intensity) and HU while SNR was improved by about 10~60%. Based on this, when applying IR for clinical applications, it is necessary to finely adjust kVp and mA with a phased approach.

• Journal of Biomedical Engineering Research
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• v.30 no.2
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• pp.135-141
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• 2009

Purpose: The aim of present study is to evaluate a possibility of clinical application for the effect of low intensity ultrasound stimulation (LIUS) in mechanical characteristics of bone on osteoporotic fractures prevention. Materials and Methods: Eight virgin ICR mice (14 weeks old, approximate weight 25g) were ovariectomized (OVX) to induce osteoporosis. The right hind limbs were then stimulated with LIDS (US Group), whereas left hind limbs were not stimulated (CON Group). Both hind limbs of all mice were scanned by in-vivo micro-CT to acquire two-dimensional (2D) images at 0 week before stimulation and 3 weeks and 6 weeks after stimulation. Three-dimensional (3D) finite element (FE) models generated by scanned 2D images were used to determine quantitatively the effect of LIUS on strength related to bone structure. Additionally, distributions of Hounsfield units and elastic moduli, which are related to the bone quality, for the bones in the US and CON groups were determined to analyze quantitatively a degree of improvement of bone qualities achieved by LIUS. Results: The result of FE analysis showed that the structural strength in US Group was significantly increased over time (p<0.05), while that in CON Group was statistically constant over time (p>0.05). High values of Hounsfield units obtained from voxels on micro-CT images and high values of elastic moduli converted from the Hounsfield units were dominantly appeared in US Group compared with those in CON Group. Conclusion: These finding indicated that LIUS would improve the mechanical characteristics of osteoporotic bone via the effects of bone structure (bone strength) and quality (Hounsfield unit and elastic modulus). Therefore, the LIUS may decrease effectively the risk of osteoporotic fracture in clinics.

• Journal of Korean Dental Science
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• v.11 no.1
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• pp.1-4
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• 2018

Purpose: The aim of this study was to evaluate the ossification and maturation of the midpalatal suture in young Koreans using cone-beam computed tomography (CBCT). Materials and Methods: The study sample consisted of 40 patients with ages from 8.2 to 23.6 years who visited the Department of Orthodontics, Chung-Ang University Dental Hospital. CBCT images were taken for diagnosis. From the CBCT image, morphological stages and Hounsfield units (HU) of midpalatal suture were obtained to evaluate the midpalatal suture maturation. Spearman's correlation coefficients were calculated to analyze relationships between chronological age, morphological stage, and HU. Result: There was a wide variation in the morphology of the midpalatal suture in each age group. It showed a modest relationship between the chronological age and the degree of morphological stages. Also there was a modest relationship between the chronological age and HU. In contrast, there was a significant relationship between morphological stages and HU of midpalatal suture (P<0.01). Conclusion: CBCT images can be used for the evaluation of midpalatal suture maturation. For the estimation of the prognosis of rapid maxillary expansion, CBCT may be reliable for the assessment of the maturation of the midpalatal suture.

• Journal of Veterinary Clinics
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• v.34 no.3
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• pp.178-184
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• 2017

The aim of this study was to determine whether Hounsfield units (HUs), volume, and various void parameters can predict stone fragility in extracorporeal shock wave lithotripsy (ESWL). HU, volume, porosity, number of voids/stone volume, and void distribution of 30 struvite stones were estimated using helical computed tomography (CT) and micro-CT. The number of shock waves necessary for full fragmentation was accepted as a measure of the stone fragility in ESWL. The correlations between the number of shock waves and the HU, volume, porosity, and number of voids/stone volume were examined. The number of shock waves of the two groups according to the void distribution was also compared. Stone volume correlated with the number of shock waves. Shell-patterned struvite stones were significantly less susceptible to fragmentation in ESWL than non-shell-patterned struvite stones. Stone volume and void distribution may be predictors of the outcome of ESWL treatment.

• 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.