• The Bulletin of The Korean Astronomical Society
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• 제46권2호
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• pp.40.3-41
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• 2021

Minor mergers leave behind long lived, but extremely faint and extended tidal features including tails, streams, loops and plumes. These act as a fossil record for the host galaxy's past interactions, allowing us to infer recent accretion histories and place constraints on the properties and nature of a galaxy's dark matter halo. However, shallow imaging or small homogeneous samples of past surveys have resulted in weak observational constraints on the role of galaxy mergers and interactions in galaxy assembly. The Rubin Observatory, which is optimised to deliver fast, wide field-of-view imaging, will enable deep and unbiased observations over the 18,000 square degrees of the Legacy Survey of Space and Time (LSST), resulting in samples of potentially of millions of objects undergoing tidal interactions. Using realistic mock images produced with state-of-the-art cosmological simulations we perform a comprehensive theoretical investigation of the extended diffuse light around galaxies and galaxy groups down to low stellar mass densities. We consider the nature, frequency and visibility of tidal features and debris across a range of environments and stellar masses as well as their reliability as an indicator of galaxy accretion histories. We consider how observational biases such as projection effects, the point-spread-function and survey depth may effect the proper characterisation and measurement of tidal features, finding that LSST will be capable of recovering much of the flux found in the outskirts of L* galaxies at redshifts beyond local volume. In our simulated sample, tidal features are ubiquitous In L* galaxies and remain common even at significantly lower masses (M*>10^10 Msun). The fraction of stellar mass found in tidal features increases towards higher masses, rising to 5-10% for the most massive objects in our sample (M*~10^11.5 Msun). Such objects frequently exhibit many distinct tidal features often with complex morphologies, becoming increasingly numerous with increased depth. The interpretation and characterisation of such features can vary significantly with orientation and imaging depth. Our findings demonstrate the importance of accounting for the biases that arise from projection effects and surface-brightness limits and suggest that, even after the LSST is complete, much of the discovery space in low surface-brightness Universe will remain to be explored.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제18권2호
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• pp.144-148
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• 2015

Hepatocellular adenomas are a benign, focal, hepatic neoplasm that have been divided into four subtypes according to the genetic and pathological features. The ${\beta}$-catenin activated subtype accounts for 10-15% of all hepatocellular adenomas and specific magnetic resonance imaging features have been defined for different hepatocellular adenomas subtypes. The current study aimed to report the magnetic resonance imaging features of a well differentiated hepatocellular carcinoma that developed on the basis of ${\beta}$-catenin activated hepatocellular adenomas in a child. In this case, atypical diffuse steatosis was determined in the lesion. In the literature, diffuse steatosis, which is defined as a feature of the hepatocyte nuclear factor-$1{\alpha}$-inactivated hepatocellular adenomas subtype, has not been previously reported in any ${\beta}$-catenin activated hepatocellular adenomas case. Interlacing magnetic resonance imaging findings between subtypes show that there are still many mysteries about this topic and larger studies are warranted.

• Imaging Science in Dentistry
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• 제52권2호
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• pp.123-131
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• 2022

Purpose: The aim of this study was to characterize the cone-beam computed tomographic (CBCT) imaging features of central giant cell granuloma (CGCG) of the jawbone. Materials and Methods: This study retrospectively reviewed 26 CBCT studies of histologically proven cases of CGCG during a period of 20 years, from 1999 to 2019. Patients' demographic data were recorded, and radiographic features were assessed (location, border, cortication, appearance of the internal structure, locularity, septation, expansion, cortical perforation, effects on surrounding tissue, whether the lesion crossed the midline, and lesion volume). Results: In this study, CGCGs were seen almost twice as often in the mandible than in the maxilla, and 64.7% of mandibular lesions involved the anterior region. Only 26.9% of lesions crossed the midline, a feature that was considered characteristic of CGCG. Furthermore, 65.4% of lesions were unilocular and 34.6% were multilocular. The correlation between a lesion's size and its locularity was statistically significant, and larger lesions showed a multilocular appearance. The mean volume of multilocular lesions was greater than that of unilocular lesions. Conclusion: CGCGs showed variable radiographic features on CBCT, and this imaging modality is highly effective at demonstrating the radiographic spectrum and lesional extent of CGCGs in the jawbone.

• Imaging Science in Dentistry
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• 제54권2호
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• pp.207-210
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• 2024

Ameloblastic fibrodentinoma (AFD) is a rare benign odontogenic tumor that resembles an ameloblastic fibroma with dysplastic dentin. This report presents a rare case of mandibular AFD with imaging features in a young patient. Panoramic radiography and computed tomography revealed a well-defined lesion with internal septa and calcified foci, causing inferior displacement of the adjacent molars as well as buccolingual cortical thinning and expansion of the posterior mandible. The lesion was surgically removed via mass excision, and the involved tooth was extracted under general anesthesia. During the 5-year follow-up period, no evidence of recurrence was observed. Radiologic features of AFD typically reveal a moderately to well-defined mixed lesion with varying degrees of radiopacity, reflecting the extent of dentin formation. Radiologists should consider AFD in the differential diagnosis when encountering a multilocular lesion with little dense radiopacity, particularly if it is associated with delayed eruption, impaction, or absence of involved teeth, on radiographic images of young patients.

• Journal of Korean Neurosurgical Society
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• 제65권3호
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• pp.397-407
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• 2022

Abusive head trauma (AHT) is the most common and serious form of child abuse and a leading cause of traumatic death in infants and young children. The biomechanics of head injuries include violent shaking, blunt impact, or a combination of both. Neuroimaging plays an important role in recognizing and distinguishing abusive injuries from lesions from accidental trauma or other causes, because clinical presentation and medical history are often nonspecific and ambiguous in this age group. Understanding common imaging features of AHT can increase recognition with high specificity for AHT. In this review, we discuss the biomechanics of AHT, imaging features of AHT, and other conditions that mimic AHT.

• Investigative Magnetic Resonance Imaging
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• 제26권1호
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• pp.76-81
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• 2022

The number of women undergoing breast augmentation surgery with a prosthesis for cosmetic purposes or reconstruction after a mastectomy is steadily increasing. Hematoma is one of complications associated with breast augmentation surgery. It usually occurs early in the postoperative period. It rarely occurs late (after six months). However, chronic hematomas after prosthesis removal have not yet been reported in the radiological literature. We present a case of unilateral chronic organizing hematoma that developed late and grew persistently over long period after breast explantation, mimicking a soft tissue tumor of the chest wall clinically. Meanwhile, characteristic magnetic resonance imaging features of heterogeneous signal intensities on T1-weighted and T2-weighted images and dark signal intensity with a persistent enhancement of the peripheral wall of the lesion were found. These can be used for a differential diagnosis.

• Korean Journal of Radiology
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• 제25권1호
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• pp.43-54
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• 2024

Objective: To evaluate the added value of diffusion-weighted imaging (DWI)-based quantitative parameters to distinguish uterine sarcomas from atypical leiomyomas on preoperative magnetic resonance imaging (MRI). Materials and Methods: A total of 138 patients (age, 43.7 ± 10.3 years) with uterine sarcoma (n = 44) and atypical leiomyoma (n = 94) were retrospectively collected from four institutions. The cohort was randomly divided into training (84/138, 60.0%) and validation (54/138, 40.0%) sets. Two independent readers evaluated six qualitative MRI features and two DWI-based quantitative parameters for each index tumor. Multivariable logistic regression was used to identify the relevant qualitative MRI features. Diagnostic classifiers based on qualitative MRI features alone and in combination with DWI-based quantitative parameters were developed using a logistic regression algorithm. The diagnostic performance of the classifiers was evaluated using a cross-table analysis and calculation of the area under the receiver operating characteristic curve (AUC). Results: Mean apparent diffusion coefficient value of uterine sarcoma was lower than that of atypical leiomyoma (mean ± standard deviation, 0.94 ± 0.30 10^-3 mm²/s vs. 1.23 ± 0.25 10^-3 mm²/s; P < 0.001), and the relative contrast ratio was higher in the uterine sarcoma (8.16 ± 2.94 vs. 4.19 ± 2.66; P < 0.001). Selected qualitative MRI features included ill-defined margin (adjusted odds ratio [aOR], 17.9; 95% confidence interval [CI], 1.41-503, P = 0.040), intratumoral hemorrhage (aOR, 27.3; 95% CI, 3.74-596, P = 0.006), and absence of T2 dark area (aOR, 83.5; 95% CI, 12.4-1916, P < 0.001). The classifier that combined qualitative MRI features and DWI-based quantitative parameters showed significantly better performance than without DWI-based parameters in the validation set (AUC, 0.92 vs. 0.78; P < 0.001). Conclusion: The addition of DWI-based quantitative parameters to qualitative MRI features improved the diagnostic performance of the logistic regression classifier in differentiating uterine sarcomas from atypical leiomyomas on preoperative MRI.

• Investigative Magnetic Resonance Imaging
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• 제20권1호
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• pp.75-79
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• 2016

We report a case of perivalvular abscess in a 66-year-old man with infective endocarditis, diagnosed by late gadolinium-enhanced (LGE) cardiovascular magnetic resonance (CMR) imaging. No clinical features suspicious of infective endocarditis were noted, however, transthoracic echocardiography revealed non-specific echogenic focal wall thickening at mitral-aortic intervalvular fibrosa. Perivalvular abscess in the aortic valve was demonstrated as focal wall thickening between the anterior mitral leaflet and the non-coronary cusp of the aortic valve with peripheral enhancement and central low signal intensity on LGE CMR imaging. Other features suggestive of infective endocarditis, such as neither vegetation nor valvular perforation were present. The perivalvular abscess did not grow after intensive intravenous antibiotics therapy, and the patient was discharged without surgical treatment. CMR with LGE provided an early accurate diagnosis of perivalvular abscess. The diagnosis of perivalvular abscess using LGE CMR imaging was not previously reported in Korea.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 한국방송공학회 1999년도 KOBA 방송기술 워크샵 KOBA Broadcasting Technology Workshop
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• pp.213.1-218
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• 1999

A virtual studio is a new video production environment using interactive computer graphics and imaging media technology. The traditional chroma-keying with two-dimensional background is replaced by an advanced keying method with a dynamic computer-generated, three-dimensional background. We have developed a virtual studio system that is practical to use in the real production environment. It has not only essential features that are common among various commercial virtual studio systems, but also unique feature that help the producer to construct virtual studio sets and scenarios efficiently such as span graph, robust backup controller, and 3 dimensional character generator supporting all languages. Our virtual studio system was used in live broadcasting and proved that the system was practical enough. In this paper, we will introduce the structure and the major features of our system, called VdreamSet, and application examples to broadcasting.

• Journal of the Korean Arthroscopy Society
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• 제1권1호
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• pp.31-35
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• 1997

MRI(magnetic resonance imaging) is very useful to visualize the anterior cruciate ligament (ACL) injury of the knee. Differential features of ACL injury at MRI according to acute and chronic stage should be evaluated to enable accurate assessment of the integrity or ACL. Distinguishing features of normal anatomy. acute and chronic injuries or ACL at MRI will be reviewed.