• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1584-1589
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• 2014

This study analyzed CT values of radiolucent and radiopaque materials by energy region after selecting radiolucent and radiopaque materials at random using GE's DECT((Dual Energy Com-puted Tomography) at S University Hospital located in Gyeonggi-province from July through August in 2013. Besides, it drew out the most analogous energy region to the value of 120kVp CT, which is applied to existing SECT(Single Energy Computed Tomography), by utilizing the analysis method of CT values and tried to find out the most useful and appropriate materials when contrast was applied within visible area in clinical application. As a result, there was little decrease of CT value after 90KeV in the case of materials with low density and high moisture content such as normal saline, methyl-cellulose and gels used in ultra-sonic waves test; energy does not influence much on materials with extremely low or high density such as air and contrast medium; methyl-cellulose and gels used in ultra-sonic waves test are considered to be the most useful materials for clinical applications.

• Progress in Medical Physics
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• v.32 no.4
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• pp.165-171
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• 2021

Purpose: This study aimed to evaluate the effect of collimator width on effective atomic number (EAN), relative electron density (RED), and stopping power ratio (SPR) measured by dual-layer dual-energy computed tomography (DL-DECT). Methods: CIRS electron density calibration phantoms with two different arrangements of material plugs were scanned by DL-DECT with two different collimator widths. The first phantom included two dense bone plugs, while the second excluded dense bone plugs. The collimator widths selected were 64 mm×0.625 mm for wider collimators and 16 mm×0.625 mm for narrow collimators. The scanning parameters were 120 kVp, 0.33 second gantry rotation, 3 mm slice thickness, B reconstruction filter, and spectral level 4. An image analysis portal system provided by a computed tomography (CT) manufacturer was used to derive the EAN and RED of the phantoms from the combination of low energy and high energy CT images. The EAN and RED were compared between the images scanned using the two different collimation widths. Results: The CT images with the wider collimation width generated more severe artifacts, particularly with high-density material (i.e., dense bone). RED and EAN for tissues (excluding lung and bones) with the wider collimation width showed significant relative differences compared to the theoretical value (4.5% for RED and 20.6% for EAN), while those with the narrow collimation width were closer to the theoretical value of each material (2.2% for EAN and 2.3% for RED). Scanning with narrow collimation width increased the accuracy of SPR estimation even with high-density bone plugs in the phantom. Conclusions: The effect of CT collimation width on EAN, RED, and SPR measured by DL-DECT was evaluated. In order to improve the accuracy of the measured EAN, RED, and SPR by DL-DECT, CT scanning should be performed using narrow collimation widths.

• Journal of Radiation Protection and Research
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• v.36 no.2
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• pp.79-85
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• 2011

OThe purpose of this article was to measure and compare the value of the metal artifact reduction (MAR) algorithm by Dual energy(kVp switching) CT (Computed Tomography) for non using MAR and we introduced new variable Dual energy CT applications through a clinical scan. The used equipment was GE Discovery 750HD with Dual-Energy system(kVp switching). CT scan was performed on the neck and abdomen area subject for patients. Studies were from Dec 20 2010 to Feb 10 2011 and included 25 subject patients with prosthesis. We were measured the HU (Hounsfield Unit) and noise value at metal artifact appear(focal loss of signal and white streak artifact area) according to the using MAR algorithm. Statistical analyses were performed using the paired sample t-test. In patient subject case, the statistical difference of showing HU was p=0.01 and p=0.04 respectively. At maximum black hole artifact area and white streak artifact area according to the using MAR algorithm. However noise was p=0.05 and p=0.04 respectively; and not the affected black hole and white streak artifact area. Dual Energy CT with the MAR algorithm technique is useful reduce metal artifacts and could improve the diagnostic value in the diagnostic image evaluation of metallic implants area.

• Journal of Radiation Protection and Research
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• v.45 no.4
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• pp.171-177
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• 2020

Background: This study aims to determine the effective atomic number (Zeff) from dual-energy image sets obtained using a conventional computed tomography (CT) simulator. The estimated Zeff can be used for deriving the stopping power and material decomposition of CT images, thereby improving dose calculations in radiation therapy. Materials and Methods: An electron-density phantom was scanned using Philips Brilliance CT Big Bore at 80 and 140 kVp. The estimated Zeff values were compared with those obtained using the calibration phantom by applying the Rutherford, Schneider, and Joshi methods. The fitting parameters were optimized using the nonlinear least squares regression algorithm. The fitting curve and mass attenuation data were obtained from the National Institute of Standards and Technology. The fitting parameters obtained from stopping power and material decomposition of CT images, were validated by estimating the residual errors between the reference and calculated Zeff values. Next, the calculation accuracy of Zeff was evaluated by comparing the calculated values with the reference Zeff values of insert plugs. The exposure levels of patients under additional CT scanning at 80, 120, and 140 kVp were evaluated by measuring the weighted CT dose index (CTDIw). Results and Discussion: The residual errors of the fitting parameters were lower than 2%. The best and worst Zeff values were obtained using the Schneider and Joshi methods, respectively. The maximum differences between the reference and calculated values were 11.3% (for lung during inhalation), 4.7% (for adipose tissue), and 9.8% (for lung during inhalation) when applying the Rutherford, Schneider, and Joshi methods, respectively. Under dual-energy scanning (80 and 140 kVp), the patient exposure level was approximately twice that in general single-energy scanning (120 kVp). Conclusion: Zeff was calculated from two image sets scanned by conventional single-energy CT simulator. The results obtained using three different methods were compared. The Zeff calculation based on single-energy exhibited appropriate feasibility.

• Progress in Medical Physics
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• v.19 no.4
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• pp.276-284
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• 2008

A computed tomography (CT) is a powerful system for the effectively fast and accurate diagnosis. The CT system, therefore, has used substantially and developed for improving the performance over the past decade, resulting in growing concerns over the radiation dose from the CT. Advanced CT techniques, such as a multidetector row CT scanner and dual energy or dual source CT, have led to new clinical applications that could result in further increases of radiation does for both patients and workers. The objective of this study was to review the international guidelines of the shielding requirements for a CT facility required for a new installation or when modifying an existing one. We used Google Search Engine to search the following keywords: computed tomography, CT regulation or shield or protection, dual energy or dual source CT, multidetector CT, CT radiation protection, and regulatory or legislation or regulation CT. In addition, we searched some special websites, that were provided for sources of radiation protection, shielding, and regulation, RSNA, AAPM, FDA, NIH, RCR, ICRP, IRPA, ICRP, IAEA, WHO (See in Table 1 for full explanations of the abbreviations). We finally summarized results of the investigated materials for each country. The shielding requirement of the CT room design was very well documented in the countries of Canada, United States of America, and United Kingdom. The wall thickness of the CT room could be obtained by the iso-exposure contour or the point source method. Most of documents provided by international organizations were explained in importance of radiation reduction in patients and workers. However, there were no directly-related documents of shielding and patient exposure dose for the dual energy CT system. Based international guidelines, the guideline of the CT room shielding and radiation reduction in patients and workers should be specified for all kinds of CT systems, included in the dual energy CT. We proposed some possible strategies in this paper.

• Journal of the Korean Society of Radiology
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• v.83 no.6
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• pp.1342-1353
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• 2022

Purpose We compared the radiation dose and image quality between the 2nd generation and the 3rd generation dual-source single-energy (DSSE) and dual-source dual-energy (DSDE) CT of the abdomen. Materials and Methods We included patients undergoing follow-up abdominal CT after partial or radical nephrectomy in the first 10 months of 2019 (2nd generation DS CT) and the first 10 months of 2020 (3rd generation DS CT). We divided the 320 patients into 4 groups (A, 2nd generation DSSE CT; B, 2nd generation DSDE CT; C, 3rd generation DSSE CT; and D, 3rd generation DSDE CT) (n = 80 each) matched by sex and body mass index. Radiation dose and image quality (objective and subjective qualities) were compared between the groups. Results The mean size-specific dose estimation of 3rd generation DSDE CT group was significantly lower than that of the 2nd generation DSSE CT (42.5%, p = 0.013) and 2nd generation DSDE CT (46.9%, p = 0.015) groups. Interobserver agreement was excellent for the overall image quality (intraclass correlation coefficient [ICC]: 0.8867) and image artifacts (ICC: 0.9423). Conclusion Our results showed a considerable reduction in the radiation dose while maintaining high image quality with 3rd generation DSDE CT as compared to the 2nd generation DSDE CT and 2nd generation DSSE CT.

• Journal of the Korean Society of Radiology
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• v.14 no.7
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• pp.1003-1011
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• 2020

This study aims to compare and evaluate the image differences between single and dual sources in applying a technique to reduce metal artifacts using dual energy CT. Discovery CT 256 (GE, USA) as a single source device and Somatom Definition Flash (Siemens Health Care, Forchheim, Germany) as a dual source device. The self-made phantom (pigs with medical titanium screws inserted) was quantitative and qualitatively evaluated under the same conditions by varying the dose under the same conditions using a dual energy CT. The evaluation method was compared by measuring SNR for metal artifacts (scattering, stripe) generated by metal inserts, divided around bones and around tissues. There was a difference in images in the method of reducing metal artifacts between single-source and dual-source devices. In a single source device, the linearized prosthesis by metal implantation showed a greater decrease than the image obtained from a double source device, and the surrounding tissue was well observed without interference from the artifact. In dual-source devices, scattering and stripe artifacts caused by metal inserts decreased more than on a single source device, and signals from adjacent tissues surrounding the metal implant were well observed without diminishing. If the examination is conducted separately between single source and dual source devices depending on whether the area to which the patient is intended to be viewed during the examination is adjacent to the metal insert or the total tissue surrounding the metal insert, it is believed that diagnostic helpful images can be obtained.

• Journal of the Korean Society of Radiology
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• v.9 no.1
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• pp.9-16
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• 2015

The purpose of this study is finding optimum contrast medium quantity during abdominal CT using dual energy technique. The study subjects are 30 patients who had received general single energy abdominal CT and received double energy technique follow-up abdominal CT. dual energy technique abdominal CT images were obtained after setting contrast medium quantities at 30%, 40%, 50%, 60% and 70% of contrast medium quantity at the time of single energy technique. Then the contrast enhancement (Hounsfield Unit; HU) was estimated by setting-up the regions of interest at aorta, inferior vena cava, hepatic portal vein and hepatic parenchymal. The obtained values were compared to the values of the same parts measured during single energy technique abdominal CT. The results of the study were as following. The 60% set up group had HU in aorta : $210.80{\pm}13.609$, IVC : $190.40{\pm}25.215$, hepatic portal vein : $198.40{\pm}21.232$ and hepatic parenchymal : $119.20{\pm}7.98$, The single energy abdomianl CT images had HU in aorta : $205.40{\pm}16.426$, IVC : $188.20{\pm}21.476$, hepatic portal vein : $195.40{\pm}22.744$ and hepatic parenchymal : $121.00{\pm}6.595$. Therefore, it is possible to obtain contrast enhancement by dual energy technique abdominal CT similar to the same by single energy technique abdominal CT by setting-up the quantity of contrast medium at 60% of contrast medium at the time of single energy technique abdominal CT. Based on the result of this study, it is possible to decrease existing quantity of contrast medium by _% and the injection velocity can be also decreased. Accordingly, it is believed that the result of study would be quite useful for patients who have renal function disorder, weak vein or side effect of contrast medium in the past.

• Korean Journal of Radiology
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• v.22 no.6
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• pp.970-982
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• 2021

Dual-energy CT (DECT) provides insights into the material properties of tissues and can differentiate between tissues with similar attenuation on conventional single-energy imaging. In the conventional CT scanner, differences in the X-ray attenuation between adjacent structures are dependent on the atomic number of the materials involved, whereas in DECT, the difference in the attenuation is dependent on both the atomic number and electron density. The basic principle of DECT is to obtain two datasets with different X-ray energy levels from the same anatomic region and material decomposition based on attenuation differences at different energy levels. In this article, we discuss the clinical applications of DECT and its potential robust improvements in performance and postprocessing capabilities.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.1
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• pp.35-42
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• 2008