• Journal of the Korean Arthroscopy Society
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• v.12 no.1
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• pp.40-44
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• 2008

Purpose: The purpose of this study was to report the real geometry of Resident's ridge doing in anterior cruciate ligament reconstruction Materials and Methods: From Jan 2007 to Aug 2007, 48 cases which had normal distal femoral condyle analyzed with Multidetector-Row Computed Tomography. Resident's ridge was defined as change of height above 1 mm in lateral wall of intercondylar notch. Anterior-posterior length of intercondylar notch, length and height of Resident's ridge, distance of Resident's ridge from posterior cortex were estimated with 3-D reconstruction using $Lucion^{(R)}$ program. Results: Cases were $59{\pm}16$ years olds and male was 16 cases, female was 32 cases. 9 cases had no Resident's ridge, anterior-posterior length of intercondylar notch was $25.4{\pm}3.5$ mm, average of length and height of the Resident's ridge was $8.2{\pm}2.6,\;3.5{\pm}1.5$ mm. Distance of the Resident's ridge from posterior cortex was $7.6{\pm}2.6$ mm. Conclusion: Resident's ridge was used as landmark in anterior cruciate ligament reconstruction, which presented in many cases and which had distinct length and height.

• Imaging Science in Dentistry
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• v.32 no.1
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• pp.27-33
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• 2002

Purpose: To evaluate the influence of threshold value of computed tomography on the accuracy of rapid prototyping (RP) medical model Material and Methods : CT datas of a human dry skull were transferred from CT scanner via compact disk to a personal computer (PC). 3-dimensional image reconstruction on PC by V-works/sup TM/ 3.0 (CyberMed. Inc.) software and RP models fabrication were followed. 2-RP models were produced by threshold value of 500 and 800 selected in surface rendering process. Linear measurements between arbitrary 12 anatomical landmarks on dry skull, 3-D image model, and 2-RP models were done and compared. Thus, the accuracy of 500 RP and 800RP models was respectively evaluated. Results: There was mean difference (% difference) in absolute value of 2.27 mm (2.73%) between linear measurements of dry skull and 500 RP model. There was mean difference (% difference) in absolute value of 1.94 mm (2.52%) between linear measurements of dry skull and 800 RP model. Conclusion: Slight difference of threshold value in rendering process of 3-D modelling made a influence on the accuracy of RP medical model.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.149-153
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• 2003

AC 부하를 갖는 동기전동기에 있어서, 동기전동기의 속도리플을 저감시키기 위한 문제를 풀기위해 3가지 제어기법에 대해 비교를 한 후 가장 강인한 제어기법에 대해 분석하였다. AC 부하를 갖는 특별한 제어 대상으로 엑스선 전산화 단층촬영 장치(CT)용 겐트리를 선정하였으며 시스템이 갖는 특별한 구조에 의해 이러한 시스템 특성을 갖는다. 동기전동기의 출력 축에 링(Fing) 모양의 원판 프레임을 갖으며, 이 원판 표면에 무게가 서로 다른 여러 장치(X_선 튜브, X-선 검출기, 고압발생장치, DAS 장치, 온도조절장치 등)를 부착하여 영상 획득 시스템의 회전부를 구축하기 때문이다. 이러한 시스템에서는 무게 평형을 갖지 못하는 편심 무게가 존재하게 되며 이로써 전동기 관점에서는 AC 부하처럼 인식되는 제어 조건으로 인식 될 수 있다. AC 부하를 갖는 동기전동기에 대해 일반적인 벡터제어 알고리즘으로 제어를 수행하면 정상상태에서도 속도 오차가 "0" 으로 줄어들지 않고 AC 형태의 오차 성분이 존재하며 편심 무게의 크기에 비례하여 진폭이 커지는 특성을 갖는다. 이러한 문제점을 해결하기 위하여 Sine파 보상전류를 갖는 속도제어기법, 펀심부하토크 관측기를 이용한 속도제어기법, 그리고 기준모델제어기법을 소개하였다. 각 방법에 대한 실험 결과로부터 편심무게의 변동과 편심 위치의 변동 조건에서 기준모델제어기법이 강인한 제어 특성과 리플저감 측면에서 가장 우수함을 검증하였다. 이로써 AC 부하 조건에서 고정도 속도 제어기가 요구되는 경우 좋은 선택의 지침이 될 수 있다고 본다.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.18 no.1
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• pp.67-73
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• 1988

This study was performed to clarify the mechanism of clicking sound and locking on temporomandibular joint and to determine the radiographic findings of them by using computed tomogram. Through the preliminary study with cadavers, the proper scanning condition and the correlatonship between the anatomy of cadaver and computed tomogram had been determined. The subjects were consisted of 10 controls and 16 patients having clicking sound or locking on temporomandibular joint. By using Hitachi-W500 as computed tomographic device, direct axial views and sagittal views reformed according to the changes in window setting and using the non-linear fraction were taken and analyzed by visual method and measuring the attenuation numbers. The obtained results were as follows: 1. The density of the anterior band of meniscus showed isodense to the surrounding muscles in normal. 2. In patient group, affected side showed increased radiopaque area anterior to condyle and underneath articular eminence as the feature of anteriorly displaced meniscus on axial and sagittal views. 3. In patient group, the condyle was rotated postero-laterally in affected side. 4. Non-linear fraction highlightened the feature of anteriorly displaced meniscus.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.19 no.1
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• pp.137-147
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• 1989

CT findings of proven 25 malignant tumors of the maxillary sinus were retrospectively analyzed to be of help in the diagnosis and treatment. The results were follows: 1. Average age was 54 years old, and eighteen were males and seven were females with a ratio of 2.6:1 2. The most common histopathologic feature was squamous cell carcinoma (19 cases) and others were two cases of adenoid cystic carcinoma, one case of malignant fibrous histiocytoma, mucoepidermoid tumor, histiocytic lymphoma, unidentified malignant tumor. 3. CT findings were sinus opacificaqtion (4%), soft tissue mass (92%), low densities within soft tissue mass (44.%), air densities within soft tissue mass (24%), osteosclerosis (4%), bone destruction (92%), bone displacement (32%), fat plane obliteration (76%). 4. CT in the malignant maxillary sinus tumors approved the value in evaluation of tumor extension to nasal cavity, ethmoid sinus, orbit, infratemporal fossa, pterygopalatine fossa, pterygoid fossa, pterygoid muscle, cheek skin and intracranial cavity. 5. Twenty four cases (96%) were stage Ⅲ, stage Ⅳ according to AJCC TNM classification. 6. Bone findings were destruction, displacement, sclerosis and most frequent site of bone destruction was the medial wall of the antrum(92%). 7. Tumor growth pattern showed destructive pattern in 18 cases(72%), and squamous cell carcinoma showed destructive pattern. (P<0.05)

• Investigative Magnetic Resonance Imaging
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• v.17 no.4
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• pp.321-325
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• 2013

Metastases from hepatocellular carcinoma (HCC) can be found in the multiple organs including adrenal gland. But adrenal metastasis of HCC without obvious hepatic lesion is very rare. We report CT and MR findings of a patient who presented with adrenal metastasis as the first clinical manifestation of HCC. Signal intensity and enhancement pattern of adrenal metastastic mass of HCC were similar to those of HCC on MRI.

• Journal of Yeungnam Medical Science
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• v.16 no.2
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• pp.237-243
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• 1999

We conducted this study to find the optimal correction factor(${\alpha}$) of Lassen's linearization algorithm which has been applied for correction of flow-limited uptake at a high flow range in $^{99m}Tc$ d,l-hexamethylpropy leneamine oxime(HMPAO) and $^{99m}Tc$ ethyl cysteinate dimer(ECD). Ten patients with chronic cerebral infarction were involved in this study. We obtained the corrected $^{99m}Tc$ HMPAO and $^{99m}Tc$-ECD brain SPECT(single photon emission computed tomography) using the algorithm with ${\alpha}$ values that varied from 0.1 to 10 and compared the results with regional cerebral blood flow determined by positron emission tomography (PET-rCBF). The multi-modal volume registration by maximization of mutual information was used for matching between PET-rCBF and SPECT images. The highest correlation coefficient between $^{99m}Tc$-HMPAO and $^{99m}Tc$-ECD brain uptake and PET-rCBF was revealed at ${\alpha}$ 1.4 and 2.1, respectively. We concluded that the ${\alpha}$ values of Lassen's linearization algorithm for $^{99m}Tc$-HMPAO and $^{99m}Tc$-ECD brain SPECT images were 1.4 and 2.1, respectively to indicate cerebral blood flow with comparison of PET-rCBF.

• Journal of the Korean Society of Radiology
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• v.17 no.4
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• pp.541-549
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• 2023

The aim of this study wasto conduct a quantitative analysis of CT image quality according to an algorithm designed to reduce metal artifacts induced by metal components. Ten baseline images were obtained with the standard filtered back-projection algorithm using spectral detector-based CT and CT ACR 464 phantom, and ten images were also obtained on the identical phantom with the standard filtered back-projection algorithm after inducing metal artifacts. After applying the to raw data from images with metal artifacts, ten additional images for each were obtained by applying the virtual monoenergetic algorithm. Regions of interest were set for polyethylene, bone, acrylic, air, and water located in the CT ACR 464 phantom module 1 to conduct compare the Hounsfield units for each algorithm. The algorithms were individually analyzed using root mean square error, mean absolute error, signal-to-noise ratio, peak signal-to-noise ratio, and structural similarity index to assess the overall image quality. When the Hounsfield units of each algorithm were compared, a significant difference was found between the images with different algorithms (p < .05), and large changes were observed in images using the virtual monoenergetic algorithm in all regions of interest except acrylic. Image quality analysis indices revealed that images with the metal artifact reduction algorithm had the highest resolution, but the structural similarity index was highest for images with the metal artifact reduction algorithm followed by an additional virtual monoenergetic algorithm. In terms of CT images, the metal artifact reduction algorithm was shown to be more effective than the monoenergetic algorithm at reducing metal artifacts, but to obtain quality CT images, it will be important to ascertain the advantages and differences in image qualities of the algorithms, and to apply them effectively.

• Journal of the Korean Society of Radiology
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• v.15 no.3
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• pp.273-279
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• 2021

Metal material inserted into the body have a large difference in density from human tissues or bones around the Metal during CT scans.. Therefore, the Metal material inserted into the body produces Artifact. Metal Artifact, which occurs around Metals, can degrade the quality of CT images, causing confusion when medical team diagnose lesions. Through this experiment, we confirm that the occurrence of Artifacts decrease by using Dual energy CT and MAR algorithm in Single source Dual energy CT. We also want to present basic data on clinical application methods by comparing and analyzing the characteristics of images obtained by each method. Using GE 750HD CT, artificial implants were scanned using general method and Dual energy. Then we apply the MAR algorithm to each image obtained. And all previously acquired images were compared and analyzed the characteristics of the examination, such as image quality evaluation and dose evaluation. Images with MAR algorithm and Dual Energy confirmed a decrease in Metal Artifact. Images with MAR algorithm have reduced Metal Artifact, but have the disadvantage of distorting the details of artificial joint implants. On the other hand images teseted with Dual Energy have the advantage of being able to implement details than those applied with MAR algorithms, it takes longer to reconstruct the image and the exposure dose was about four times higher than those applied with MAR algorithm. In order to locate Metals, such as the post-operative follow-up period, it is useful to apply MAR algorithm to obtain images. And it is more useful to examine with Dual Energy when micro lesion identification, such as cardiac examination, and surgical planning or when tests are performed in diagnostic way.

• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.2
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• pp.106-117
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• 2013

Normal eruption of the canine is important for the transition to the permanent dentition. Etiologies, including premature loss or delayed retention of deciduous teeth, neoplasm and abnormality of lateral incisor can cause impaction of the maxillary canine. Untreated canine impaction can result in malocclusion, cyst formation and obstacles in orthodontic treatment. The aim of this study is to evaluate location of the impacted maxillary canine and to identify correlation between location and management of the impaction including complications. Using panoramic radiographs and CBCT scan, images of 89 children diagnosed with impaction of the maxillary canine, location of impacted canines was evaluated. The choice of treatment and complications were investigated to identify correlation. Results show that the most commonly impacted location of the maxillary canine was in the mid-alveolar area, followed by buccal side and palatal side. Orthodontic traction was selected more frequently than the other treatments. As complications, displacement of adjacent tooth was occurred most frequently. Buccally impacted canines showed increased tendency towards displacement. The more buccally the canine was impacted, the less orthodontic traction was chosen as the treatment. The canine impacted mesially to the central incisor showed increased tendency to occur root resorption. Therefore, early diagnosis by periodic examination, appropriate treatment and intervention is required.