• The Korean Journal of Applied Statistics
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• v.16 no.2
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• pp.305-319
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• 2003

This paper provides a non-Bayesian method based on the expanded EM algorithm for segmenting the magnetic resonance images degraded by bias field. For the images with the intensity as a pixel value, many segmentation methods often fail to segment it because of the bias field(with low frequency) as well as noise(with high frequency). Our contextual approach is appropriately designed by using normal mixture model incorporated with Markov random field for noise-corrective segmentation and by using the penalized likelihood to estimate bias field for efficient bias filed-correction.

• Journal of Trauma and Injury
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• v.26 no.3
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• pp.229-232
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• 2013

Traumatic fracture-dislocations of the hip frequently result from high-energy injury, and hip dislocations are commonly associated with severe concomitant injuries. Sciatic nerve injury often accompanies traumatic fracture-dislocation of the hip, but neurologic examination at the time of injury is difficult in severely traumatized patients with decreased consciousness. We present such a case of multiple traumas with traumatic hip dislocation and sciatic nerve injury after reduction, and we found that magnetic resonance image (MRI) played an important role in developing a management plan.

• Journal of Biomedical Engineering Research
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• v.17 no.3
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• pp.305-312
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• 1996

A new three dimensional fractal coding is proposed with a perceptually enhanced matching. Since most of medical images (e.g. computed tomoyaphy or magnetic resonance images) have three dimensional characters, searching regions are extended to adjacent slices. For a perceptually enhanced matching, a high frequency boost filter is used for pre-filtering images to be encoded, and a least mean square error matching is applied to the edge enhanced Images rather than the original images. From simulation with magnetic resonance images($255\times255$, 8bits/pixel), reconstructed images by the proposed compression algorithm show much improved subjective image quality with higher peak signnal-to-noise ratio compared to those by existing fractal coding algorithms at compression ratios of about 10.

• ETRI Journal
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• v.31 no.2
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• pp.237-239
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• 2009

A whole-body voxel model of a 7-year-old male volunteer was developed from 384 axial magnetic resonance images (MRIs). The MRIs were acquired with intervals of 3 mm for the entire body in a body coil. In order to reduce the MRI acquisition time for the child, the repetition and echo times under T1 weighted image were chosen to be 566 ms and 8 ms, respectively. The MRIs were classified according to 30 types of tissues with known electrical parameters. The developed voxel model was adjusted to the physical average of 7-year-old Korean boys. The body weight of the adjusted model, calculated with the mass tissue densities, is within a 6% difference from the 50th percentile weight.

• Journal of Magnetics
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• v.21 no.2
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• pp.281-285
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• 2016

The purpose of study was to evaluate SNR and CNR with different contrast agent contents (1.0 mmol/mL gadobutrol and 0.5 mmol/mL gadoterate meglumine) for spin echo (SE) and 3-dimension contrast-enhanced fast field echo (3D CE-FFE) pulse sequences. In this study, we compared the SNR and the CNR between 0.5 mmol/mL gadoterate meglumine and 1.0 mmol/mL gadobutrol according to the concentration of contrast agent in brain MRI. When we compared between SE and 3D CE-FFE pulse sequences, the higher SNR and CNR using 3D CE-FFE pulse sequence can be acquire regardless of contrast agent contents. Also, a statistically significant difference was found for SNR and CNR between all protocols. In conclusion, our results demonstrated that the SNR and CNR have not risen proportionately with contrast agent contents. We hope that these results presented in this paper will contribute to decide contrast agent contents for brain MRI.

• Journal of Pharmacopuncture
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• v.14 no.3
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• pp.99-107
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• 2011

Objectives : The purpose of this study is to report the image changes of two cases of Lumbar intervertebral Disc Sequestration after oriental medical treatment. Methods : We examined 2 patients with Lumbar intervertebral Disc Sequestration who showed changes on MRI images before/after the treatment. And we assessed clinical symptoms by using numeric rating scale(NRS) and straight leg raising test(SLRT). Results & Conclusions : In this study, the first MRI examination of Lumbar intervertebral Disc Sequestration patients was performed at the first visit and re-examination of MRI was done after treatment. In each case, the size of the disc sequestration was considerably reduced in MRI image. And both patients represented effective improvment in NRS score and SLRT test angle.

• The Korean Journal of Nuclear Medicine
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• v.37 no.1
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• pp.63-72
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• 2003

Functional MRI (fMRI) provides an indirect mapping of cerebral activity, based on the detection of the local blood flow and oxygenation changes following neuronal activity (Blood Oxygenation Level Dependent). fMRI allows us to study noninvasively the normal and pathological aspects of functional cortical organization. Each fMRI study compares two different states of activity. Echo-Planar Imaging is the technique that makes it possible to study the whole brain at a rapid pace. Activation maps are calculated from a statistical analysis of the local signal changes. fMRI is now becoming an essential tool in the neurofunctional evaluation of normal volunteers and many neurological patients as well as the reference method to image normal or pathologic functional brain organization.

• Progress in Medical Physics
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• v.30 no.4
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• pp.89-93
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• 2019

Purpose: This study aims to develop new markers based on silicone rubber and urethane rubber to enhance visibility in low magnetic field magnetic resonance (MR) imaging. Methods: Four types of markers were fabricated using two different base materials. Two of the markers were composed of two different types of silicone rubber: DragonSkin™ 10 MEDIUM and BodyDouble™ SILK. The other two markers were composed of types of urethane rubber: PMC™ 780 DRY and VytaFlex™ 20. Silicone oil (KF-96 1000cs) was added to the fabricated markers. The allocated amount of oil was 20% of the weight (wt%) of each respective marker. The MR images of the markers, with and without the silicone oil, were acquired using MRIdian with a low magnetic field of 0.35 T. The signal intensities of each MR image for the markers were analyzed using ImageJ software and the visibility for each was compared. Results: The highest signal intensity was observed in VytaFlex™ 20 (279.67±3.57). Large differences in the signal intensities (e.g., 627% in relative difference between BodyDouble™ SILK and VytaFlex™ 20) among the markers were observed. However, the maximum difference between the signal intensities of the markers with the silicone oil showed only a 62% relative difference between PMC™ 780 DRY and DragonSkin™ 10 MEDIUM. An increase in the signal intensity of the markers with the silicone oil was observed in all markers. Conclusions: New markers were successfully fabricated. Among the markers, DragonSkin™ 10 MEDIUM with silicone oil showed the highest MR signal intensity.

• Journal of Korean Neurosurgical Society
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• v.63 no.3
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• pp.386-396
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• 2020

Objective : To generate synthetic spine magnetic resonance (MR) images from spine computed tomography (CT) using generative adversarial networks (GANs), as well as to determine the similarities between synthesized and real MR images. Methods : GANs were trained to transform spine CT image slices into spine magnetic resonance T2 weighted (MRT2) axial image slices by combining adversarial loss and voxel-wise loss. Experiments were performed using 280 pairs of lumbar spine CT scans and MRT2 images. The MRT2 images were then synthesized from 15 other spine CT scans. To evaluate whether the synthetic MR images were realistic, two radiologists, two spine surgeons, and two residents blindly classified the real and synthetic MRT2 images. Two experienced radiologists then evaluated the similarities between subdivisions of the real and synthetic MRT2 images. Quantitative analysis of the synthetic MRT2 images was performed using the mean absolute error (MAE) and peak signal-to-noise ratio (PSNR). Results : The mean overall similarity of the synthetic MRT2 images evaluated by radiologists was 80.2%. In the blind classification of the real MRT2 images, the failure rate ranged from 0% to 40%. The MAE value of each image ranged from 13.75 to 34.24 pixels (mean, 21.19 pixels), and the PSNR of each image ranged from 61.96 to 68.16 dB (mean, 64.92 dB). Conclusion : This was the first study to apply GANs to synthesize spine MR images from CT images. Despite the small dataset of 280 pairs, the synthetic MR images were relatively well implemented. Synthesis of medical images using GANs is a new paradigm of artificial intelligence application in medical imaging. We expect that synthesis of MR images from spine CT images using GANs will improve the diagnostic usefulness of CT. To better inform the clinical applications of this technique, further studies are needed involving a large dataset, a variety of pathologies, and other MR sequence of the lumbar spine.

• Journal of radiological science and technology
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• v.6 no.1
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• pp.3-19
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• 1983