• Investigative Magnetic Resonance Imaging
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• v.26 no.1
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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.

• Journal of the Korean Magnetics Society
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• v.14 no.2
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• pp.65-70
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• 2004

Read out signal and temperature distribution of magnetic amplifying magnetooptical disk were studied. Temperature distribution of recording layer and adjacent layers were calculated when the disk was at rest. Mark size, length and location were simulated from a chain of recording beam pulses. In addition, signal amplitude depending on the shape of the marks, readout signals from the recording layer and amplified marks of the readout layer, were simulated. Simplified thermal conduction model was used to calculate the temperature distribution of recording and adjacent layers as a function of time as well as to calculate the mark size, length and location. Readout signal was calculated by the convolution of the disk reflectivity and the Gaussian beam intensity. Readout signal from the mark in the readout layer amplified to the size of the laser beam fumed out to be twice as large as the signal from the crescent shaped mark in the recording layer.

• Journal of Biomedical Engineering Research
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• v.27 no.4
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• pp.154-163
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• 2006

A 64-channel magnetocardiogram (MCG) system using low-noise superconducting quantum interference device (SQUID) planar gradiometers was developed for the measurements of cardiac magnetic fields generated by the heart electric activity. Owing to high flux-to-voltage transfers of double relaxation oscillation SQUID (DROS) sensors, the flux-locked loop electronics for SQUID operation could be made simpler than that of conventional DC SQUIDs, and the SQUID control was done automatically through a fiber-optic cable. The pickup coils are first-order planar gradiometers with a baseline of 4 em. The insert has 64 planar gradiometers as the sensing channels and were arranged to measure MCG field components tangential to the chest surface. When the 64-channel insert was in operation everyday, the average boil-off rate of the dewar was 3.6 Lid. The noise spectrum of the SQUID planar gradiometer system was about 5 fT$_{rms}$/$\checkmark$Hz at 100 Hz, operated inside a moderately shielded room. The MCG measurements were done at a sampling rate of 500 Hz or 1 kHz, and realtime display of MCG traces and heart rate were displayed. After the acquisition, magnetic field mapping and current mapping could be done. From the magnetic and current information, parameters for the diagnosis of myocardial ischemia were evaluated to be compared with other diagnostic methods.

• Journal of Yeungnam Medical Science
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• v.37 no.2
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• pp.90-97
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• 2020

Background: To minimize damage to the ovarian reserve, it is necessary to evaluate the follicular density in the ovarian tissue surrounding endometriosis on preoperative imaging. The purpose of the present study was to evaluate the usefulness of subtraction pelvic magnetic resonance imaging (MRI) to detect ovarian reserve. Methods: A subtracted T1-weighted image (^subT1WI) was obtained by subtracting unenhanced T1WI from contrast-enhanced T1WI (^ceT1WI) with similar parameters in 22 patients with ovarian endometriosis. The signal-to-noise ratio (SNR) in ovarian endometriosis, which was classified into the high signal intensity and iso-to-low signal intensity groups on the T2-weighted image, was compared to that in normal ovarian tissue. To evaluate the effect of contrast enhancement, a standardization map was obtained by dividing ^subT1WI by ^ceT1WI. Results: On visual assessment of 22 patients with ovarian endometriosis, 16 patients showed a high signal intensity, and 6 patients showed an iso-to-low signal intensity on T1WI. Although SNR in endometriosis with a high signal intensity was higher than that with an iso-to-low signal intensity, there was no difference in SNR after the subtraction (13.72±77.55 vs. 63.03±43.90, p=0.126). The area of the affected ovary was smaller than that of the normal ovary (121.10±22.48 vs. 380.51±75.87 ㎟, p=0.002), but the mean number of pixels in the viable remaining tissue of the affected ovary was similar to that of the normal ovary (0.53±0.09 vs. 0.47±0.09, p=0.682). Conclusion: The subtraction technique used with pelvic MRI could reveal the extent of endometrial invasion of the normal ovarian tissue and viable remnant ovarian tissue.

• Journal of radiological science and technology
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• v.46 no.2
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• pp.115-122
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• 2023

The purpose of this study was to examine the association between the shapes and colors of emergency exit symbols, magnetic field warning symbols, and radiation zone symbols used in hospitals for staff and patient safety and their effects on cognitive memory. The hippocampal region's signal intensity(SI) was analyzed using fMRI. The Symbol 2 (1.75±0.54) with a green background had the highest signal intensity (SI) for emergency exits, according to the findings. The black symbol 2 (1.60±0.51) with a yellow background had the highest signal intensity (SI) for the magnetic field warning symbol, followed by the black symbol 1 (1.59±0.65) with an orange background. The black symbol 2 (1.59±0.59) with a yellow background and the black symbol 3 (1.58±0.52) with an orange background had the low signal intensity with slight differences as for the radiation zone symbols. In conclusion, it was determined that the signal intensity of the black symbol with a yellow background was the highest in the magnetic field area and radiation area. This implies that symbols with a high signal intensity (SI) must be utilized intensively. To ensure that the correct meaning of the symbols is communicated in the future, they must also be utilized regularly and continually in disaster safety education.

• Clinics in Shoulder and Elbow
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• v.26 no.3
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• pp.260-266
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• 2023

Background: Knowledge of the base rate of signal changes consistent with distal biceps tendinopathy on magnetic resonance imaging (MRI) has the potential to influence strategies for diagnosis and treatment of people that present with elbow pain. The aim of this study is to measure the prevalence of distal biceps tendon signal changes on MRIs of the elbow by indication for imaging. Methods: MRI data for 1,306 elbows were retrospectively reviewed for mention of signal change in distal biceps tendon. The reports were sorted by indication. Results: Signal changes consistent with distal biceps tendinopathy were noted in 197 of 1,306 (15%) patients, including 34% of patients with biceps pain, 14% of patients with unspecified pain, and 8% of patients with a specific non-biceps indication. Distal biceps tendon changes noted on radiology reports were associated with older age, male sex, and radiologists with musculoskeletal fellowship training. Conclusions: The finding that distal biceps MRI signal changes consistent with tendinopathy are common even in asymptomatic elbows reduces the probability that symptoms correlate with pathology on imaging. The accumulation of signal changes with age, also independent of symptoms, suggests that tendon pathology persists after symptoms resolve, that some degree of distal biceps tendinopathy is common in a human lifetime, and that tendinopathy may often be accommodated without seeking care. Level of evidence: IV.

• Proceedings of the Korean Magnetic Resonance Society Conference
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• 2001.02a
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• pp.15-15
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• 2001

• Steel and Composite Structures
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• v.19 no.3
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• pp.601-614
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• 2015

The Metal Magnetic Memory (MMM) method is a non-destructive testing method based on an analysis of the self-magnetic leakage field distribution on the surface of a component. It is used for determining the stress concentration zones or any irregularities on the surface or inside the components fabricated from ferrous-based materials. Thus, this paper presents the MMM signal behaviour due to the application of fatigue loading. A series of MMM data measurements were performed to obtain the magnetic leakage signal characteristics at the elastic, pre-crack and crack propagation regions that might be caused by residual stresses when cyclic loadings were applied onto the A283 Grade C steel specimens. It was found that the MMM method was able to detect the defects that occurred in the specimens. In addition, a justification of the Self Magnetic Flux Leakage patterns is discussed for demonstrating the effectiveness of this method in assessing the A283 Grade C steel under cyclic loadings.

• Journal of Magnetics
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• v.5 no.1
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• pp.19-22
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• 2000

The effects of a hard-biased Held on the magnetic and magnetoresistive properties of a crossed spin-valve head are investigated by computer simulation with particular emphasis on the asymmetry of the output signal. The spin-valve considered in this work is NiMn (25 nm)/NiFe (2.5 m)/Cu (3 nm)/NiFe (5.5 m), with a length of 1500 m and a width of 600 nm. A simple model is used where each magnetic layer consists of a single domain, and the magnetoresistance is a function of the angle between the magnetization directions of the two magnetic layers. The ideal crossed spin-valve structure is not realized with the present model and magnetic parameters, but the deviation from ideality is decreased by the hard-biased field. This results in the improvement of the linearity of the output signal with the use of the bias field. The magnetoresistance ratio and magnetoresistive sensitivity, however are reduced. The magnetic properties including the magnetoresistance are found to be strongly affected by magnetostatic interactions, particularly the inter-layer magnetostatic field.

• Imaging Science in Dentistry
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• v.35 no.4
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• pp.207-213
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• 2005

Purpose: To classify and describe the characteristic features of MRI of some ameloblastoma variants. Materials and Methods: The MR images, CT images, and panoramic radiographs in 5 cases were retrospectively examined as follows. First, the contents of ameloblastomas were devided into two portions of either solid or cystic components on the basis of MR signal intensities. The signal intensity within the solid or cystic portions was classified as homogeneous or heterogeneous. Next, the characteristic internal feature of the lesion on T1W1 or T2WI was described. The signal intensities were classified into low, intermediate, slightly high, high, and strong high signal intensity. Results: Unicystic lesion showed homogeneous high signal intensity (SI) on T2W2 and the rim enhancement of the surrounding area including the mural nodule and the thick wall except the central portion on Gd- T1W1. Solid type revealed heterogeneous and high SI area with strong high SI area on T2W2. On Gd- T1W1, the area corresponding to the low signal spot on T1W1 and the strong high signal spot on T2W1 showed low SI. Hybrid type showed slightly enhanced capsular structures and low SI for the round bony septa and the areas connecting the mixed and cystic lesions on T2Wl and Gd-T1W1. Conclusion: MRI could easily assess the relationship between the mixed and cystic findings in ameloblastoma.