• Proceedings of the Korea Contents Association Conference
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• 2014.11a
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• pp.211-212
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• 2014

단일에너지 복부 검사에서 사용했던 조영제 양 대비 30%, 40%, 50%, 60%, 70%로 각각 설정하여 영상을 획득한 후 대동맥, 하대정맥, 간문맥, 간실질에 관심영역을 설정하여 조영증강정도(houns -field unit; HU)를 구하여 단일에너지에서 측정된 부위와의 값을 비교 분석하였다. 그 결과 기존대비 60%로 조영제를 설정한 군에서는 대동맥 HU : $210.80{\pm}13.609$, 하대정맥 HU : $190.40{\pm}25.215$, 간문맥 $198.40{\pm}21.232$, 간실질 HU : $119.20{\pm}7.98$로 각각 측정되었으며. 단일에너지 복부 CT 검사는 대동맥 HU : $205.40{\pm}16.426$, 하대정맥 HU : $188.20{\pm}21.476$, 간문맥 HU : $195.40{\pm}22.744$, 간실질 HU : $121.00{\pm}6.595$ 이었다. 따라서 이중에너지를 이용하여 복부 조영 CT검사를 시행할 때 조영제의 양을 60%로 설정한 후 검사하는 것이 각 장기에서의 단일에너지 조영검사시와 비슷한 조영증강정도를 획득할 수 있다.

• Radiation Oncology Journal
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• v.15 no.2
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• pp.153-158
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• 1997

Purpose : The Dual-Energy Quantitative Computed Tomography(DEQCT) was compared with bone equivalent $K_2HPO_4$ standard solution and ash weight of animal cadaveric trabecular bone in the measurement of bone mineral contents(BMC). Method and Materials : The attenuation coefficient of tissues highly depends on the radiation energy density and effective atomic number of composition, The bone mineral content of DEQCT in this experiments was determined from empirical constants and mass attenuation coefficients of bone,fat and soft tissue equivalent solution in two photon spectra. In this experiments, the BMC of DEQCT with 80 and $120kV_p$ X rays was compared to ash weight of animal trabecular bone. Results : We obtained the mass attenuation coefficient of 0.2409 0.5608 and 0.2206 in $80kV_p$, and 0.2046, 0.3273 and $0.1971cm^2/g$ in $120kV_p$ X-ray spectra for water bone and fat equivalent materials, respectively. The BMC with DEQCT was acomplished with empirical constants $K_1=0.3232,\;K_2$=0.2450 and mass attenuation coefficients has very closed to ash weight of animal trabecular bone The BMC of empirical DEQCT and that of manufacturing DEQCT were correlated with ash weight as a correlation r= 0.998 and r= 0.996, respectively. Conclusion : The BMC of empirical DEQCT using the experimental mass attenuation coefficients and that of manufacture have showed very close to ash weight of animal trabecular bone.

• Journal of the Korean Society of Radiology
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• v.82 no.6
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• pp.1477-1492
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• 2021

Purpose Dedicated breast CT is an emerging volumetric X-ray imaging modality for diagnosis that does not require any painful breast compression. To improve the detection rate of weakly enhanced lesions, an adaptive image rescaling (AIR) technique was proposed. Materials and Methods Two disks containing five identical holes and five holes of different diameters were scanned using 60/100 kVp to obtain single-energy CT (SECT), dual-energy CT (DECT), and AIR images. A piece of pork was also scanned as a subclinical trial. The image quality was evaluated using image contrast and contrast-to-noise ratio (CNR). The difference of imaging performances was confirmed using student's t test. Results Total mean image contrast of AIR (0.70) reached 74.5% of that of DECT (0.94) and was higher than that of SECT (0.22) by 318.2%. Total mean CNR of AIR (5.08) was 35.5% of that of SECT (14.30) and was higher than that of DECT (2.28) by 222.8%. A similar trend was observed in the subclinical study. Conclusion The results demonstrated superior image contrast of AIR over SECT, and its higher overall image quality compared to DECT with half the exposure. Therefore, AIR seems to have the potential to improve the detectability of lesions with dedicated breast CT.

• Journal of the Korean Society of Radiology
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• v.16 no.5
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• pp.553-558
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• 2022

The purpose of this work was a simulation study to evaluate the virtual monochromatic (VM) image quality of blood vessels compared to the monochromatic image. Dual-energy images were obtained based on the linear attenuation coefficients of five materials at 50 keV and 80 keV at low- and high-energies, respectively. A weighting factor is required to synthesize the VM image, and the liver and bone were used as basis materials to obtain the weighting factor. VM images were synthesized at energies ranging from 30 keV to 100 keV. Image quality was evaluated by Contrast to noise ratio (CNR) and noise by setting calcium and contrast medium as signals and blood as background. According to the results, the energies with the maximum CNR were 50 keV and 60 keV for calcium and contrast medium, respectively. The energies showing the minimum noise were 70 keV, 70 keV, and 60 keV in calcium, iodine contrast medium, and blood, respectively. The VM image can contribute to the improvement of diagnostic performance in CT examination because it can implement an image at the optimal energy that minimize noise and maximize CNR.

• Imaging Science in Dentistry
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• v.41 no.3
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• pp.101-106
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• 2011

Purpose : This study evaluated the potential use of the computed tomography indices (CTI) on cone beam CT (CBCT) images for an assessment of the bone mineral density (BMD) in postmenopausal osteoporotic women. Materials and Methods : Twenty-one postmenopausal osteoporotic women and 21 postmenopausal healthy women were enrolled as the subjects. The BMD of the lumbar vertebrae and femur were calculated by dual energy X-ray absorptiometry (DXA) using a DXA scanner. The CBCT images were obtained from the unilateral mental foramen region using a PSR-$9000N^{TM}$ Dental CT system. The axial, sagittal, and coronal images were reconstructed from the block images using $OnDemend3D^{TM}$. The new term "CTI" on CBCT images was proposed. The relationship between the CT measurements and BMDs were assessed and the intra-observer agreement was determined. Results : There were significant differences between the normal and osteoporotic groups in the computed tomography mandibular index superior (CTI(S)), computed tomography mandibular index inferior (CTI(I)), and computed tomography cortical index (CTCI). On the other hand, there was no difference between the groups in the computed tomography mental index (CTMI: inferior cortical width). Conclusion : CTI(S), CTI(I), and CTCI on the CBCT images can be used to assess the osteoporotic women.

• Journal of the Korean Society of Radiology
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• v.82 no.1
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• pp.173-181
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• 2021

Purpose To evaluate the ability of the Hounsfield unit (HU) measurement of the femoral neck during multidetector computed tomography (MDCT) for assessing osteoporosis compared with dual-energy X-ray absorptiometry (DXA). Materials and Methods Forty-two patients with femoral neck fractures who underwent MDCT and DXA from July to December 2016 were included in this study. HU measurements were made of the cancellous portions of the normal contralateral femoral neck on MDCT. Bone mineral density (BMD) and T-scores were obtained at the femur DXA. Correlations of HU values with BMD and T-scores were analyzed using Spearman's correlation test. Results The mean BMD and T-score of the femoral neck were 0.650 g/cm² and -2.4, respectively. The mean HU values for the normal, osteopenia, and osteoporosis groups were 131.9, 98.9, and 41.3, respectively. HU values at the femoral neck were positively correlated with BMD (r² = 0.670; p < 0.001) and T-scores (r² = 0.676; p < 0.001). Conclusion The HU values of the femoral neck on MDCT are significantly correlated with BMD and T-scores of femur DXA. The HU values may serve as a diagnostic tool for the screening of regional bone quality when MDCT is performed for other reasons.

• Nutrition Research and Practice
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• v.4 no.2
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• pp.128-135
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• 2010

Obesity was characterized in Korean elementary students using different obesity assessment tests on 103 overweight elementary students from three schools of Jeonbuk Province. The body mass index (BMI) and obesity index (OI) were compared, and the data using DEXA and CT were compared with the data using BIA and a tape measure. The results of this study are as follows: first, 27 students who were classified as obese by OI were classified as overweight by BMI, and 3 students who were classified as standard weight by BMI were classified as overweight by OI. Secondly, by DEXA and BIA measurements, there was 1.51% difference in body fat percentage (boys 1.66%, girls 1.17%) and the difference in body fat mass between boys and girls was 0.77 kg (boys 0.85 kg, girls 0.59 kg), but those differences in body fat percentage and mass were not statistically significant. Thirdly, the average total abdominal fat (TAF) measured by CT scans of obese children was more significantly related with subcutaneous fat (r = 0.983, P < 0.01) than visceral fat (r = 0.640, P < 0.01). Also, TAF were highest significant with waist circumference by a tape measure (r = 0.744, P < 0.01). In summary, as there are some differences of assessment results between two obesity test methods (BMI, OI), we need more definite standards to determine the degree of obesity. The BIA seems to be the most simple and effective way to measure body fat mass, whereas waist/hip ratio (WHR) using a tape measurer is considered to be the most effective method for assessing abdominal fat in elementary students.

• Journal of the Korean Society of Radiology
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• v.16 no.1
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• pp.53-59
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• 2022

DEXA, as the standard areal bone mineral density (aBMD) measurement method, often shows an insuficient correlation between aBMDs of the measured bones and referring bones and is inaccurate due to the mass effect. In contrast, quantitative computer tomography (QCT), as a volumetric BMD (vBMD) measurement method, is being advanced so that it uses less radiation before, owing to improved CT device and computer imaging technology. Because dual-energy CTs can modulate the image signals showing tumor or specific chemicals as well as the ability to measure vBMD, they are expanding their application. For pre-checking vBMD of surgeon-specific bone volume at implantation candidate sites, a finite element creation-based local vBMD measurement technique was developed. The local vBMD measurement function for surgeon-specific shape volumes will be added to clinical imaging systems.

• Korean Journal of Radiology
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• v.24 no.4
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• pp.294-304
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• 2023

Objective: We aimed to investigate whether image standardization using deep learning-based computed tomography (CT) image conversion would improve the performance of deep learning-based automated hepatic segmentation across various reconstruction methods. Materials and Methods: We collected contrast-enhanced dual-energy CT of the abdomen that was obtained using various reconstruction methods, including filtered back projection, iterative reconstruction, optimum contrast, and monoenergetic images with 40, 60, and 80 keV. A deep learning based image conversion algorithm was developed to standardize the CT images using 142 CT examinations (128 for training and 14 for tuning). A separate set of 43 CT examinations from 42 patients (mean age, 10.1 years) was used as the test data. A commercial software program (MEDIP PRO v2.0.0.0, MEDICALIP Co. Ltd.) based on 2D U-NET was used to create liver segmentation masks with liver volume. The original 80 keV images were used as the ground truth. We used the paired t-test to compare the segmentation performance in the Dice similarity coefficient (DSC) and difference ratio of the liver volume relative to the ground truth volume before and after image standardization. The concordance correlation coefficient (CCC) was used to assess the agreement between the segmented liver volume and ground-truth volume. Results: The original CT images showed variable and poor segmentation performances. The standardized images achieved significantly higher DSCs for liver segmentation than the original images (DSC [original, 5.40%-91.27%] vs. [standardized, 93.16%-96.74%], all P < 0.001). The difference ratio of liver volume also decreased significantly after image conversion (original, 9.84%-91.37% vs. standardized, 1.99%-4.41%). In all protocols, CCCs improved after image conversion (original, -0.006-0.964 vs. standardized, 0.990-0.998). Conclusion: Deep learning-based CT image standardization can improve the performance of automated hepatic segmentation using CT images reconstructed using various methods. Deep learning-based CT image conversion may have the potential to improve the generalizability of the segmentation network.

• 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.