• Progress in Medical Physics
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• v.32 no.4
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• pp.92-98
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• 2021

Purpose: This study automatically discriminates homogeneous and structure edge regions on computed tomography (CT) images, and it evaluates the noise level and edge preservation ratio (EPR) according to the different types of iterative reconstruction (IR). Methods: The dataset consisted of CT scans of 10 patients reconstructed with filtered back projection (FBP), statistical IR (iDose⁴), and iterative model-based reconstruction (IMR). Using the 10th and 85th percentiles of the structure coherence feature, homogeneous and structure edge regions were localized. The noise level was estimated using the averages of the standard deviations for five regions of interests (ROIs), and the EPR was calculated as the ratio of standard deviations between homogeneous and structural edge regions on subtraction CT between the FBP and IR. Results: The noise levels were 20.86±1.77 Hounsfield unit (HU), 13.50±1.14 HU, and 7.70±0.46 HU for FBP, iDose⁴, and IMR, respectively, which indicates that iDose⁴ and IMR could achieve noise reductions of approximately 35.17% and 62.97%, respectively. The EPR had values of 1.14±0.48 and 1.22±0.51 for iDose⁴ and IMR, respectively. Conclusions: The iDose⁴ and IMR algorithms can effectively reduce noise levels while maintaining the anatomical structure. This study suggested automated evaluation measurements of noise levels and EPRs, which are important aspects in CT image quality with patients' cases of FBP, iDose⁴, and IMR. We expect that the inclusion of other important image quality indices with a greater number of patients' cases will enable the establishment of integrated platforms for monitoring both CT image quality and radiation dose.

• 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 Medicine and Life Science
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• v.20 no.2
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• pp.83-88
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• 2023

Metal artifacts cause inaccuracies in target delineation, radiation treatment planning, and delivery when computed tomography images of a radiotherapy patient implanted with a high-density material in the body are acquired. In this study, we investigated the possibility of obtaining improved images in clinical trials through metal artifact reduction using silicon impression materials without the need for a specific metal artifact reduction algorithm. A silicon impression material exhibiting a constant Hounsfield unit (HU) value according to the mixing ratio of the catalysts and bases was selected. The material did not exhibit any change in weight or shape over time. For both the instances of inserting the metal material and applying the silicon impression material, the HU value and dose were compared with homogeneous cases filled with water-equivalent materials. When the silicon impression material was applied to the region where the high-density material was located, the HU value was within 5% and the dose was within 3% compared with those of the homogeneous cases. In this study, the silicon impression materials reduced metal artifacts. However, because the composition, shape, size, and location of high-density materials differ, further studies are required to consider these factors in clinical applications.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.199-206
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• 2014

Purpose : According to the rapid increase recently in image-guided radiation therapy, It is necessary to control of the image guidance system completely. In particular for the main subject to the accuracy of image guided radiation therapy device to be done essentially the quality assurance. We made efficient phantom in AMC for the management of the accurate and efficient. Materials and Methods : By setting up of five very important as a quality assurance inventory of the Image guidance system, we made (AMC G-Box) phantom for quality assurance efficient and accurate. Quality assurance list were the Iso-center align, the real measurement, the center align of four direction, the accuracy of table movement and the reproducibility of Hounsfield Unit. The rectangular phantom; acrylic with a thickness of 1 cm to $10cm{\time}10cm{\time}10cm$ was inserted the three materials with different densities respectively for measure the CBCT HU. The phantom was to perform a check of consistency centered by creating a marker that indicates the position of the center fixed. By performing the quality assurance using the phantom of existing, comparing the resulting value to the different resulting value using the AMC G-Box, experiment was analyzed time and problems. Therapy equipment was used Varian device. It was measured twice at 1-week intervals. Results : When implemented quality assurance of an image guidance system using AMC G-Box and a phantom existing has been completed, the quality assurance result is similar in $0.2mm{\pm}0.1$. In the case of the conventional method, it was 45 minutes at 30 minutes. When using AMC G-Box, it takes 20 minutes 15 minutes, and declined to 50% of the time. Conclusion : The consistency and accurate of image guidance system tend to decline using device. Therefore, We need to perform thoroughly on the quality assurance related. It needs to be checked daily to consistency check especially. When using the AMC G-Box, It is possible to enhance the accuracy of the patient care and equipment efficiently performing accurate quality assurance.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.36 no.5
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• pp.417-422
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• 2010

Introduction: Bone density is one of the important factors for the long term success of endosseous implants. The bone density varies from site to site and from patient to patient. A preoperative evaluation of the bone density is quite useful to oral surgeons for planning dental implantation. More accurate information on the bone density will help surgeons identify suitable implant sites, thereby increase the success rate of dental implantation. This study examined the correlation between the bone density measured preoperatively by computed tomography (CT) and the implant primary stability measured by resonance frequency analysis. Furthermore, the effects of the implant sites, gender, age and generalized systemic disorder patients on the bone density and primary implant stability were examined. Materials and Methods: One hundred and fourteen patients were selected. None of the patients had undergone a tooth extraction or bone graft history in the previous year. Preoperatively, the patients underwent CT scanning to evaluate the Hounsfield unit (HU), and resonance frequency analysis (RFA) was used to evaluate the implant primary stability at the time of implant installation. All implants were 4.0 mm diameter and 11.5 mm length US II. All patients were recorded and the HU and implant stability quotient (ISQ) value were evaluated according to the sites, gender and age. Results: The highest HU values were found in the mandibular anterior site ($827.6{\pm}151.4$), followed by the mandibular molar site ($797{\pm}135.1$), mandibular premolar site ($753.8{\pm}171.2$), maxillary anterior site ($726.3{\pm}154.4$), maxillary premolar site ($656.7{\pm}173.8$) and maxillary molar site ($621.5{\pm}164.9$). The ISQ value was the highest in the mandibular premolar site ($81.5{\pm}2.4$) followed by the mandibular molar site ($80.0{\pm}5.7$), maxillary anterior site ($77.4{\pm}4.1$), mandibular anterior site ($76.4{\pm}11.9$), maxillary premolar site ($74.2{\pm}14.3$) and maxillary molar site ($73.7{\pm}7.4$). The mean HU and ISQ value were similar in females and males. (HU: P=0.331, ISQ: P=0.595) No significant difference was also found in the age group respectively. However, the correlation coefficients between the variables showed a closed correlation between the HU and ISQ value. Conclusion: These results showed close correlation between the bone density (HU) and primary stability value (ISQ) at the time of implant installation (Correlation coefficients=0.497, P<0.01). These results strengthen the hypothesis that it might be possible to predict and quantify the initial implant stability and bone density from a presurgical CT diagnosis.

• Tuberculosis and Respiratory Diseases
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• v.43 no.4
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• pp.519-526
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• 1996

Background : Clinical and Radiographic studies to differentiate benign from malignant pulmonary nodules have previously focused on clinical status and the morphologic and the computed tomographic attenuation characteristics of the lung nodules. Distinctive differences in the vascularity and pathophysiology of malignant versus benign pulmonary nodules were identified. We evaluated the diagnostic method for differentiating malignant from benign solitary pulmonary nodule by contrast enhancement on the spiral CT. Method : Sixteen patients with solitary pulmonary nodule were examined(Tuberculoma 8, primary lung cancer 8). Serial thin section on the spiral CT was performed before and after(45second, 2min, 5min) the onset of the injection of 100mL of nonionic contrast material(2mL/sec). Results : There was no difference in size of nodule and pre-contrast CT number (Hounsfield unit) between benign and malignant nodules. At forty-five second after the onset of the injection, malignant neoplasms($19.6{\pm}7.9$ HU) enhanced significantly more than tuberculomas($4.9{\pm}9.4$ HU, p=0.008). At 2minute and 5 minute after, malignant neoplasms($34.0{\pm}19.2$HU, $34.0{\pm}15.4$HU) enhanced significantly more than tuberculomas ($6.7{\pm}9.7$HU, p=0.007 and $7.7{\pm}11.5$HU, p=0.011). On cut-off value 20HU(contrast enhancement) 2minute after the injection of contrast media, sensitivity was 87% and specificity was 87%. No correlation between the contrast enhancement and size of the nodules was observed. Conclusion : Studies with the use of an intravenously administered noniodinated contrast medium in examining the enhancement properties of lung nodules was performed. The contrast enhancement was useful in differential diagnosis of solitary pulmonary nodules.

• 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.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.1
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• pp.19-25
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• 2009

Purpose: The aims of this study were to analyze correlation between the maximum standardized uptake value (SUVmax) of 2-[F-18]-fluoro-2-deoxy-d-glucose (FDG) on positron emission computed tomography (PET-CT) scan and the degree of contrast enhancement on computed tomography (CT) scan in lung cancers, and to recognize the difference in SUVmax and CT enhancement between groups of different histopathologic subtypes. Materials and Methods: Our study included 53 patients of pathologically confirmed primary lung cancer, who were performed PET-CT and post-contrast chest CT. We calculated initial and delayed SUVmax (SUV1, SUV2), difference between SUV1 and SUV2 (SUVd), retention index (RI), and the degrees of CT contrast enhancement of lung cancers. We analyzed these variables for subtypes of lung cancers. Results: The values (mean$\pm$ standard deviation) were $8.3{\pm}4.4$ for SUV1, $10.7{\pm}5.7$ for SUV2, $2.4{\pm}1.6$ for SUVd, $30{\pm}14$ for RI and $47.1{\pm}14.8$ HU (Hounsfield Unit) for degree of CT contrast enhancement. The difference of SUV1 and degree of CT enhancement between subtypes was not meaningful. SUV1 showed positive correlations with SUVd (r=0.74, p<0,01) and tumor size (r=0.58, p<0.01), but no significant correlation with degree of CT enhancement (r=0.06, p=0.69). In 10 cases, there was discrepancy in the same mass between the area of highest FDG-uptake and the area of highest contrast enhancement. Conclusion: We suggest that FDG uptake in lung cancer does not have a positive linear correlation with degree of CT enhancement. And there is no significant difference in FDG uptake and degree of CT enhancement between different subtypes of lung cancers.

• Journal of radiological science and technology
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• v.39 no.4
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• pp.517-526
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• 2016

This study analyzed the correlation between BMD (bone mineral density) value calculated in the MDCT (multidetector computed tomography) and lifestyle, physical features and social characteristics. From July 15 2015 to June 6 2016, we converted from HU (hounsfield unit) value measured by using MDCT to T-score for BMD of 141 patients (male: 63, female: 78) in W medical center. We measured the 2nd, 3rd and 4th lumbar spine and analyzed the correlation between gender differences in BMD and lifestyle, physical features and social characteristics. Statistical significance was validated using independent sample T test with one way Anova. Gender BMD was confirmed that a statistically significant difference (p<0.05). BMD values decreased with increasing age but for the statistically men, there was no significant difference from 20s to 50s, it only showed a significant difference in 20s and 60s (p<0.001). For the statistically women, there was no significant difference from 20s to 40s. but since 50s BMD was decreased rapidly, which showed a significant difference (p<0.001). women showed significant differences for the menstruation and menopause, childbirth, alcohol, cereals and greasy food in bone mineral density (p<0.05) but there were no significant differences in men. The bone mineral density values calculated by the MDCT and lifestyle, physical features and social characteristics correlation analysis method is considered to be used as a basis for estimating the state in BMD and osteoporosis management.

• Journal of the Korean Society of Radiology
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• v.16 no.6
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• pp.673-680
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• 2022

In this study, based on PLA, we analyzed the Hounsfield Unit (HU) of materials containing 20% each of aluminum, wood, copper, carbon, and marble, and tried to analyze how they affect the image. A cylindrical phantom of 5×30×30 ㎣ (thickness×diameter×height) was fabricated using a entry-level 3D printer. The kV was changed to 80, 100 and 120, and the mAs was changed to 100 and 200 mAs, and the phantom in the center of the table was cross-scanned under a total of six conditions. A circular ROI was set using image J program and the quantification value of the material part HU and the quantification value of the peripheral part CNR were obtained. The HU average of the material part increased in the order of [PLA - wood 20%], [PLA - marble 20%], [PLA - carbon 20%], [PLA 100%], [PLA - aluminum 20%], [PLA - copper 20%] (p<0.05) a negative correlation was confirmed with the HU by increasing kV. It was confirmed that the CNR value in the peripheral area increased in the order of [PLA - marble 20%], [PLA - copper 20%], [PLA - carbon 20%], [PLA - wood 20%], [PLA - aluminum 20%], and [PLA - 100%] (p<0.05). Human organs with similar HU values for each material are [PLA - copper 20%] compact bone, [PLA - aluminum 20%] cancellous bone, [PLA 100%] coagulated blood, [PLA - carbon 20%] and [PLA - marble 20%] liver, muscle, spleen and [PLA - wood 20%] had similar values to fat. In addition, we confirmed the blur phenomenon that blurs the image around the filament with all materials, and confirmed that [PLA 100%] especially has the most blur around the filament. Therefore, it is considered desirable to reflect the HU value of the target organ and consider cloudiness around the phantom when selecting materials for medical phantom fabrication, and this research can provide basic data.