• Korean Journal of Radiology
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• v.22 no.4
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• pp.672-676
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• 2021

• Journal of Trauma and Injury
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• v.20 no.2
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• pp.144-148
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• 2007

Purpose: The management of hemorrhagic shock is critical for trauma patients. To assess hemorrhagic shock, the clinician commonly uses a change in positional blood pressure, the shock index, an estimate of the diameter of inferior vena cava based on sonography, and an evaluation of hypoperfusion complex shown on a CT scan. To add the finding for the hypoperfusion complex, the 'halo sign' was introduced recently. To our knowledge, this 'halo sign' has not been evaluated for its clinical usefulness, so we designed this study to evaluate its usefulness and to find the useful CT signs for hypoperfusion complex. Methods: The study was done from January 2007 to May 2007. All medical records and CT images of 124 patients with trauma were reviewed, of which 103 patients were included. Exclusion criteria was as follows: 1) age < 15 year old and 2) head trauma score of AIS ${\geq}$ 5. Results: The value of kappa, to assess the inter-observer agreement, was 0.51 (p < 0.001). The variables of the halo-sign-positive group were statistically different from those of the halo-sign-negative group. The rate of transfusion for the halo-sign-positive group was about 10 times higher than that of the halo-sign-negative group and the rate of mortality was about 6 times higher. Conclusion: In the setting of trauma, early abdominal CT can show diffuse abnormalities due to hypoperfusion complex. Recognition of these signs is important in order to prevent an unwanted outcome in hemorrhagic shock. We conclude that the halo sign is a useful one for hypoperfusion complex and that it is useful for assessing the degree of hemorrhagic shock.

• Investigative Magnetic Resonance Imaging
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• v.22 no.2
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• pp.94-101
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• 2018

Purpose: To determine the value of the appearance of the high signal intensity halo sign for detecting carotid intraplaque hemorrhage (IPH) on maximum intensity projection (MIP) of time-of-flight (TOF) MR angiography (MRA), based on high signal intensity on magnetization-prepared rapid acquisition with gradient-echo (MPRAGE) sequencing. Materials and Methods: A total of 78 carotid arteries in 65 patients with magnetization-prepared rapid acquisition gradient-echo (MPRAGE) positive on carotid plaque MR imaging were included in this study. High-resolution MR imaging was performed on a 3.0-T scanner prior to carotid endarterectomy or carotid artery stenting. Fast spin-echo T1- and T2-weighted axial imaging, TOF, and MPRAGE sequences were obtained. Carotid plaques with high signal intensity on MPRAGE > 200% that of adjacent muscle on at least two consecutive slices were defined as showing IPH. Halo sign of high signal intensity around the carotid artery was found on MIP from TOF MRA. Continuous and categorical variables were compared among groups using the Mann-Whitney test and Fisher's exact tests. Results: Of these 78 carotid arteries, 53 appeared as a halo sign on the TOF MRA. The total IPH volume of patients with a positive halo sign was significantly higher than that of patients without a halo sign ($75.0{\pm}86.8$ vs. $16.3{\pm}18.2$, P = 0.001). The maximum IPH axial wall area in patients with a positive halo sign was significantly higher than that of patients without a halo sign ($11.3{\pm}9.9$ vs. $3.7{\pm}3.6$, P = 0.000). Conclusion: High signal intensity halo of IPH on MIP of TOF MRA is associated with total volume and maximal axial wall area of IPH.

• Korean Journal of Radiology
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• v.21 no.10
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• pp.1161-1164
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• 2020

The epidemic of 2019 novel coronavirus, later named as coronavirus disease (COVID-19), began in Wuhan, China in December 2019 and has spread rapidly worldwide. Early diagnosis is crucial for the management of the patients with COVID-19, but the gold standard diagnostic test for this infection, the reverse transcriptase polymerase chain reaction, has a low sensitivity and an increased turnaround time. In this scenario, chest computed tomography (CT) could play a key role for an early diagnosis of COVID-19 pneumonia. Here, we have reported a confirmed case of COVID-19 with an atypical CT presentation showing a "double halo sign," which we believe represents the pathological spectrum of this viral pneumonia.

• Investigative Magnetic Resonance Imaging
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• v.19 no.3
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• pp.153-161
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• 2015

Purpose: To identify the differential MRI findings between myxoid tumors and benign peripheral nerve sheath tumors (BPNSTs) in the musculoskeletal system. Materials and Methods: The study participants included a total of 35 consecutive patients who underwent MRI between September 2011 and December 2013. The patients were pathologically diagnosed with myxoid tumors (22 patients) or BPNSTs (13 patients). Evaluation was done by two radiologists, based on the following characteristics: size, margin, degree of signal intensity (SI) on T2-weighted images (T2WI), homogeneity of SI on T2WI, enhancement pattern, enhancement homogeneity, presence of cystic portion, internal fat component, presence of fat split sign, presence of target sign, presence of continuation with adjacent neurovascular bundle, and presence of surrounding halo. Results: Large size, high SI on T2WI, heterogeneous enhancement, and internal fat component were commonly observed in myxoid tumors, while homogenous enhancement, fat split sign, target sign were common in BPNSTs. The differences were statistically significant (P < 0.05). Other findings, such as margin, homogeneity of SI on T2WI, enhancement pattern (peripheral or solid), internal cystic portion, continuation with neurovascular bundle, and surrounding halo, did not show significant difference between myxoid tumors and BPNSTs (P > 0.05). Conclusion: In the differential diagnosis of myxoid tumors and BPNSTs involving the musculoskeletal system, several MRI findings such as degree of SI on T2WI, enhancement homogeneity, internal fat component, fat split sign, and target sign, may be helpful in establishing the diagnosis.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.55.1-55.1
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• 2014

on the observation with the Gemini Multi-Object Spectrograph on the Gemini-South 8.1 m telescope. The radial velocities of four ESCs do not display any sign of systematic motion, unlike the intermediate age carbon stars in NGC 6822. The ages and metallicities derived using the Lick indices show that the ESCs are old (>=8 Gyr) and metal poor ([Fe/H] <= -1.5). NGC 6822 is found to have both metal poor ($[Fe/H]{\approx}-2.0$) and metal rich ($[Fe/H]{\approx}-0.9$) star clusters within 15' (2 kpc) from the center, whereas only metal poor clusters are observed in the outer halo with r >= 20'(2.6 kpc). Based on the kinematics, old ages, and low metallicities of ESCs, we discuss the possible origin of ESCs and the formation of the outer halo of a small dwarf irregular galaxy NGC6822.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.82-82
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• 2010

We measure the topology of the galaxy distribution using the Seventh Data Release of the Sloan Digital Sky Survey (SDSS DR7), examining the dependence of galaxy clustering topology on galaxy properties. The observational results are used to test galaxy formation models. A volume-limited sample defined by Mr<-20.19 enables us to measure the genus curve with amplitude of G=378 at 6h-1Mpc smoothing scale, with 4.8% uncertainty including all systematics and cosmic variance. The clustering topology over the smoothing length interval from 6 to 10h-1Mpc reveals a mild scale-dependence for the shift and void abundance (A_V) parameters of the genus curve. We find strong bias in the topology of galaxy clustering with respect to the predicted topology of the matter distribution, which is also scale-dependent. The luminosity dependence of galaxy clustering topology discovered by Park et al. (2005) is confirmed: the distribution of relatively brighter galaxies shows a greater prevalence of isolated clusters and more percolated voids. We find that galaxy clustering topology depends also on morphology and color. Even though early (late)-type galaxies show topology similar to that of red (blue) galaxies, the morphology dependence of topology is not identical to the color dependence. In particular, the void abundance parameter A_V depends on morphology more strongly than on color. We test five galaxy assignment schemes applied to cosmological N-body simulations to generate mock galaxies: the Halo-Galaxy one-to-one Correspondence (HGC) model, the Halo Occupation Distribution (HOD) model, and three implementations of Semi-Analytic Models (SAMs). None of the models reproduces all aspects of the observed clustering topology; the deviations vary from one model to another but include statistically significant discrepancies in the abundance of isolated voids or isolated clusters and the amplitude and overall shift of the genus curve. SAM predictions of the topology color-dependence are usually correct in sign but incorrect in magnitude.

• Journal of Korean Neurosurgical Society
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• v.58 no.4
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• pp.357-362
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• 2015

Objective : To investigate risk factors for S1 screw loosening after lumbosacral fusion, including spinopelvic parameters and paraspinal muscles. Methods : We studied with 156 patients with degenerative lumbar disease who underwent lumbosacral interbody fusion and pedicle screw fixation including the level of L5-S1 between 2005 and 2012. The patients were divided into loosening and non-loosening groups. Screw loosening was defined as a halo sign larger than 1 mm around a screw. We checked cross sectional area of paraspinal muscles, mean signal intensity of the muscles on T2 weight MRI as a degree of fatty degeneration, spinopelvic parameters, bone mineral density, number of fusion level, and the characteristic of S1 screw. Results : Twenty seven patients showed S1 screw loosening, which is 24.4% of total. The mean duration for S1 screw loosening was $7.3{\pm}4.1$ months after surgery. Statistically significant risk factors were increased age, poor BMD, 3 or more fusion levels (p<0.05). Among spinopelvic parameters, a high pelvic incidence (p<0.01), a greater difference between pelvic incidence and lumbar lordotic angle preoperatively (p<0.01) and postoperatively (p<0.05). Smaller cross-sectional area and high T2 signal intensity in both multifidus and erector spinae muscles were also significant muscular risk factors (p<0.05). Small converging angle (p<0.001) and short intraosseous length (p<0.05) of S1 screw were significant screw related risk factors (p<0.05). Conclusion : In addition to well known risk factors, spinopelvic parameters and the degeneration of paraspinal muscles also showed significant effects on the S1 screw loosening.

• Journal of Trauma and Injury
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• v.20 no.2
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• pp.83-89
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• 2007

Purpose: This research was performed to determine which clinical signs and symptoms of brain injury are sensitive indicators of skull fracture (SF) and intracranial injury (ICI) in head injured children. Methods: We conducted a prospective study of minor head trauma in children younger than 2 years of age for a 1-year period. Skull radiographs, brain computed tomography (CT), and data forms, including mechanism of injury, symptoms, physical findings, and hospital course, were completed for each child. Results: Of 137 study subjects, 17 (12.4%) had SF/ICI. Falls were the most common mechanism of injury, and heights of fall above 1 meter were associated with incidence of SF/ICI (p<0.05). Scalp abnormalities were not associated with incidence of SF/ICI. As for clinical symptoms, lethargy and a grouping of features (irritability & vomiting) were associated with incidence of SF/ICI (p<0.05). The incidence of seizure, loss of consciousness, vomiting, irritability, and scalp abnormality did not differ significantly between those with normal radiologic findings and those with SF/ICI. Among asymptomatic patients, 11 (14.5%) patients had SF/ICI, and among patients with normal scalp findings, 9 (12.7%) patients had SF/ICI. Conclusion: Clinical signs and symptoms, except for lethargy and a grouping of features (irritability & vomiting), were not sensitive predictors of SF/ICI. Nevertheless, SF/ICI occurred among normal children. In such a case, a liberal policy of CT scanning is warranted.

• Korean Journal of Radiology
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• v.21 no.4
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• pp.494-500
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• 2020

Objective: This study presents a preliminary report on the chest radiographic and computed tomography (CT) findings of the 2019 novel coronavirus disease (COVID-19) pneumonia in Korea. Materials and Methods: As part of a multi-institutional collaboration coordinated by the Korean Society of Thoracic Radiology, we collected nine patients with COVID-19 infections who had undergone chest radiography and CT scans. We analyzed the radiographic and CT findings of COVID-19 pneumonia at baseline. Fisher's exact test was used to compare CT findings depending on the shape of pulmonary lesions. Results: Three of the nine patients (33.3%) had parenchymal abnormalities detected by chest radiography, and most of the abnormalities were peripheral consolidations. Chest CT images showed bilateral involvement in eight of the nine patients, and a unilobar reversed halo sign in the other patient. In total, 77 pulmonary lesions were found, including patchy lesions (39%), large confluent lesions (13%), and small nodular lesions (48%). The peripheral and posterior lung fields were involved in 78% and 67% of the lesions, respectively. The lesions were typically ill-defined and were composed of mixed ground-glass opacities and consolidation or pure ground-glass opacities. Patchy to confluent lesions were primarily distributed in the lower lobes (p = 0.040) and along the pleura (p < 0.001), whereas nodular lesions were primarily distributed along the bronchovascular bundles (p = 0.006). Conclusion: COVID-19 pneumonia in Korea primarily manifested as pure to mixed ground-glass opacities with a patchy to confluent or nodular shape in the bilateral peripheral posterior lungs. A considerable proportion of patients with COVID-19 pneumonia had normal chest radiographs.