• Investigative Magnetic Resonance Imaging
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• v.10 no.2
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• pp.63-69
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• 2006

Purpose : Marrow edema and fatty degeneration of the hip joint bones could be initial and late signs in hip joint and its bone diseases respectively, which might be differentiated from age-related marrow conversion pattern. So authors have investigated normal marrow conversion pattern of the femur and acetabulum around the hip joints. Materials and methods : Three coronal MR images of 288 hip joint bones in 144 subjects, aged 2 days to 76 years divided to 8 groups every 10 years, were retrospectively analysed for the location and appearance of the converted yellow marrow. The converted yellow marrow were divided to head, neck, and trochanter in the proximal femur and below and above 50% in acetabulum of the hip. Results : The most common type of marrow conversion is the converted yellow marrow in the entire proximal femur and below 50% of acetabulum of the hip. We observed the start of marrow conversion in just before and after 2 years old and stopped at just before and after 20 years old. Conclusion : The understanding of age-related marrow conversion pattern of the hip joint bones would provide some information for differentiation from pathologic condition of them such as edema, fatty degeneration, metastasis, or leukemia.

• Investigative Magnetic Resonance Imaging
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• v.10 no.2
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• pp.89-97
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• 2006

Purpose : To evaluate MR image qualities we developed a new MRI phantom with the fixation structures necessary to position it into coil firmly. Materials and methods : We designed MRI phantom for eight evaluation items such as slice thickness accuracy, high contrast spatial resolution, low contrast object detectability, geometry accuracy, slice position accuracy, image intensity uniformity, percent signal ghosting and signal to noise ratio. For the positioning of phantom at coils, the fixation structures were set up on the surface of phantom. Six different MRI units were used for test the possibility for the clinical application and their image qualities were evaluated. Results : We acquired appropriate MR image qualities enough for the evaluation on all used MR units and confirmed that their evaluations were within reliable values compared to real ones for some items. The positioning of our phantom into head coils with fixation structures worked well for proper imaging. Conclusion : We found that our prototype of MRI phantom had the possibility of clinical application for MR image quality assessment.

• Investigative Magnetic Resonance Imaging
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• v.18 no.2
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• pp.87-106
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• 2014

Purpose : To describe how a robust implementation of a radial 3D gradient-echo sequence with stack-of-stars sampling can be achieved, to review the imaging properties of radial acquisitions, and to share the experience from more than 5000 clinical patient scans. Materials and Methods: A radial stack-of-stars sequence was implemented and installed on 9 clinical MR systems operating at 1.5 and 3 Tesla. Protocols were designed for various applications in which motion artifacts frequently pose a problem with conventional Cartesian techniques. Radial scans were added to routine examinations without selection of specific patient cohorts. Results: Radial acquisitions show significantly lower sensitivity to motion and allow examinations during free breathing. Elimination of breath-holding reduces failure rates for non-compliant patients and enables imaging at higher resolution. Residual artifacts appear as streaks, which are easy to identify and rarely obscure diagnostic information. The improved robustness comes at the expense of longer scan durations, the requirement for fat suppression, and the nonexistence of a time-to-center value. Care needs to be taken during the configuration of receive coils. Conclusion: Routine clinical use of radial stack-of-stars sequences is feasible with current MR systems and may serve as substitute for conventional fat-suppressed T1-weighted protocols in applications where motion is likely to degrade the image quality.

• Investigative Magnetic Resonance Imaging
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• v.7 no.2
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• pp.108-115
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• 2003

Purpose : To evaluate the effect of the gradient switching noise on the ECD source localization with the EEG data recorded during the MRI scan. Materials and Methods : We have fabricated a spherical EEG phantom that emulates a human head on which multiple electrodes are attached. Inside the phantom, electric current dipole(ECD) sources are located to evaluate the source localization error. The EEG phantom was placed in the center of the whole-body 3.0 Tesla MRI magnet, and a sinusoidal current was fed to the ECD sources. With an MRI-compatible EEG measurement system, we recorded the multi channel electric potential signals during gradient echo single-shot EPI scans. To evaluate the effect of the gradient switching noise on the ECD source localization, we controlled the gradient noise level by changing the FOV of the EPI scan. With the measured potential signals, we have performed the ECD source localization. Results : The source localization error depends on the gradient switching noise level and the ECD source position. The gradient switching noise has much bigger negative effects on the source localization than the Gaussian noise. We have found that the ECD source localization works reasonably when the gradient switching noise power is smaller than $10\%$ of the EEG signal power. Conclusion : We think that the results of the present study can be used as a guideline to determine the degree of gradient switching noise suppression in EEG when the EEG data are to be used to enhance the performance of fMRI.

• Journal of the Korean Society for Railway
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• v.18 no.5
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• pp.401-409
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• 2015

Defects generated in a railroad track that guides the railroad vehicle have the characteristic of growing fast; as such, the detection technology for railroad track defects is very important because defects can eventually cause mass disasters like derailments. In this study, a speed-up test facility was fabricated to investigate the feasibility of using magnetic flux leakage (MFL) technology for defect detection in a railroad track under speed-up condition; a test was conducted using a railroad track specimen with defects. For this purpose, an MFL sensor head dedicated to the configuration of the railroad was designed and test specimens with artificial defects on their surfaces were manufactured. Using the test facility, a speed-up test ranging from 4km/h to 12km/h was performed and defects including locations were successfully detected from MFL signals induced by defects with enhanced visibility by differentiating raw MFL signals. In the future, it should be possible to apply this system to a high-speed railroad inspection car by improving the lift-off stability that is necessary for speed-up of the developed MFL sensor system.

• Journal of The Korean Ophthalmological Society
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• v.59 no.11
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• pp.1087-1090
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• 2018

Purpose: To report a case of trochlear nerve palsy caused by quadrigeminal cistern lipoma located in the dorsal midbrain. Case summary: A 65-year-old male visited our clinic for intermittent vertical diplopia over 2-year period. Symptoms of diplopia had worsened over the past two weeks. He had no previous medical history except having had diabetes for 1 month. The best-corrected visual acuity was 20/25 in the right eye and 20/20 in the left eye. Pupillary examination was not remarkable. Extraocular examination showed 4 prism diopters (PD) left hypertropia at distant gaze and 4 PD exotropia at near gaze, with adduction elevation of the left eye. The Bielschowsky head tilt test revealed 6 PD left hypertropia on the left gaze and orthotropia on the right tilt. Fundus examination showed excyclotorsion of the right eye and incyclotorsion of the left eye. Brain magnetic resonance imaging revealed quadrigeminal cistern lipoma. Prism glasses were prescribed to alleviate diplopia, and we followed up the lesions without further treatment. Conclusions: Trochlear nerve palsy can be caused by quadrigeminal cistern lipoma; however, it is uncommon for this condition to be caused by a compressive lesion. Prompt neuroimaging can be helpful to rule out the causes of this condition in patients with atypical symptoms.

• Pediatric Infection and Vaccine
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• v.26 no.2
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• pp.112-117
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• 2019

Eikenella corrodens rarely causes invasive head and neck infections in immunocompetent children. We report a case of epidural abscess caused by E. corrodens in a previously healthy 13-year-old boy who presented with fever, headache, and vomiting. On physical examination upon admission, there was no neck stiffness, but discharge from the right ear was observed. Brain magnetic resonance imaging (MRI) revealed approximately 4.5-cm-sized epidural empyema on the right temporal lobe as well as bilateral ethmoid and sphenoid sinusitis, right mastoiditis, and right otitis media. During treatment with vancomycin and cefotaxime, purulent ear discharge aggravated, and on follow-up brain MRI, the empyema size increased to $5.6{\times}3.4cm$ with interval development of an abscess at the right sphenoid sinus. Burr hole trephination was performed, and foul-smelling pus was aspirated from the epidural abscess near the right temporal lobe. Pus culture yielded E. corrodens. Endoscopic sphenoidotomy was also performed with massive pus drainage, and the same organism was grown. The patient was treated with intravenous cefotaxime for 3 weeks and recovered well with no other complications. Therefore, E. corrodens can cause serious complications in children with untreated sinusitis.

• Korean Journal of Radiology
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• v.22 no.11
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• pp.1886-1893
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• 2021

Objective: To assess the feasibility of quantitatively assessing pancreatic steatosis using magnetic resonance imaging (MRI) and its correlation with obesity and metabolic risk factors in pediatric patients. Materials and Methods: Pediatric patients (≤ 18 years) who underwent liver fat quantification MRI between January 2016 and June 2019 were retrospectively included and divided into the obesity and control groups. Pancreatic proton density fat fraction (P-PDFF) was measured as the average value for three circular regions of interest (ROIs) drawn in the pancreatic head, body, and tail. Age, weight, laboratory results, and mean liver MRI values including liver PDFF (L-PDFF), stiffness on MR elastography, and T2^* values were assessed for their correlation with P-PDFF using linear regression analysis. The associations between P-PDFF and metabolic risk factors, including obesity, hypertension, diabetes mellitus (DM), and dyslipidemia, were assessed using logistic regression analysis. Results: A total of 172 patients (male:female = 125:47; mean ± standard deviation [SD], 13.2 ± 3.1 years) were included. The mean P-PDFF was significantly higher in the obesity group than in the control group (mean ± SD, 4.2 ± 2.5% vs. 3.4 ± 2.4%; p = 0.037). L-PDFF and liver stiffness values showed no significant correlation with P-PDFF (p = 0.235 and p = 0.567, respectively). P-PDFF was significantly associated with obesity (odds ratio 1.146, 95% confidence interval 1.006-1.307, p = 0.041), but there was no significant association with hypertension, DM, and dyslipidemia. Conclusion: MRI can be used to quantitatively measure pancreatic steatosis in children. P-PDFF is significantly associated with obesity in pediatric patients.

• Korean Journal of Radiology
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• v.22 no.5
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• pp.751-758
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• 2021

Objective: Preoperative differentiation between inverted papilloma (IP) and its malignant transformation to squamous cell carcinoma (IP-SCC) is critical for patient management. We aimed to determine the diagnostic accuracy of conventional imaging features and histogram parameters obtained from whole tumor apparent diffusion coefficient (ADC) values to predict IP-SCC in patients with IP, using decision tree analysis. Materials and Methods: In this retrospective study, we analyzed data generated from the records of 180 consecutive patients with histopathologically diagnosed IP or IP-SCC who underwent head and neck magnetic resonance imaging, including diffusion-weighted imaging and 62 patients were included in the study. To obtain whole tumor ADC values, the region of interest was placed to cover the entire volume of the tumor. Classification and regression tree analyses were performed to determine the most significant predictors of IP-SCC among multiple covariates. The final tree was selected by cross-validation pruning based on minimal error. Results: Of 62 patients with IP, 21 (34%) had IP-SCC. The decision tree analysis revealed that the loss of convoluted cerebriform pattern and the 20th percentile cutoff of ADC were the most significant predictors of IP-SCC. With these decision trees, the sensitivity, specificity, accuracy, and C-statistics were 86% (18 out of 21; 95% confidence interval [CI], 65-95%), 100% (41 out of 41; 95% CI, 91-100%), 95% (59 out of 61; 95% CI, 87-98%), and 0.966 (95% CI, 0.912-1.000), respectively. Conclusion: Decision tree analysis using conventional imaging features and histogram analysis of whole volume ADC could predict IP-SCC in patients with IP with high diagnostic accuracy.

• Journal of Radiation Industry
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• v.17 no.4
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• pp.397-403
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• 2023

The purpose of this study is to obtain brain MRI images through Heavenly T₂ FLAIR and DWI techniques to find out strengths and weaknesses of each image. Data were analyzed on 13 normal people and 17 brain tumor patients. Philips Ingenia 3.0TCX was used as the equipment used for the inspection, and 32 Channel Head Coil was used to acquire data. Using Image J and Infinity PACS Data, 3mm² of gray matter, white matter, cerebellum, basal ganglia, and tumor areas were set and measured. Quantitative analysis measured SNR and CNR as an analysis method, and qualitative analysis evaluated overall image quality, lesion conspicuity, image distortion, susceptibility artifact and ghost artifact on a 5-point scale. The statistical significance of data analysis was that Wilcox-on Signed Rank Test and Paired t-test were executed, and the statistical program used was SPSS ver.22.0 and the p value was less than 0.05. In quantitative analysis, the SNR of gray matter, white matter, cerebellum, basal ganglia, and tumor of Heavily T₂ FLAIR is 41.45±0.13, 40.52±0.45, 41.44±0.51, 40.96±0.09, 35.28±0.46 and the CNR is 15.24±0.13, 16.75±0.23, 16.28±0.41, 15.83±0.17, 16.63±0.51. In DWI, SNR is 32.58±0.22, 36.75±0.17, 30.21±0.19, 35.83±0.11, 43.29±0.08, and CNR is 13.14±0.63, 14.21±0.31, 12.95±0.32, 11.73±0.09, 17.56±0.52. In normal tissues, Heavenly T₂ FLAIR obtained high results, but in disease evaluation, high results were obtained at DWI, b=1000 (p<0.05). In addition, in the qualitative analysis, overall image quality, lesion conspicuity, image distortion, susceptibility artifact and ghost artifact aspects of the Heavily T₂ FLAIR were evaluated, and 3.75±0.28, 2.29±0.24, 3.86±0.23, 4.08±0.21, 3.79±0.22 values were found, respectively, and 2.53±0.39, 4.13±0.29, 1.90±0.20, 1.81±0.21, 1.52±0.45 in DWI. As a result of qualitative analysis, overall image quality, image distortion, susceptibility artifact and ghost artifact were rated higher than DWI. However, DWI was evaluated higher in lesion conspicuity (p<0.05). In normal tissues, the level of Heavenly T₂ FLAIR was higher, but the DWI technique was higher in the evaluation of the disease (tumor). The two results were necessary techniques depending on the normal site and the location of the disease. In conclusion, statistically significant results were obtained from the two techniques. In quantitative and qualitative analysis, the two techniques had advantages and disadvantages, and in normal and disease evaluation, the two techniques produced useful results. These results are believed to be educational data for clinical basic evaluation and MRI in the future.