• Journal of Biomedical Engineering Research
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• v.43 no.4
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• pp.193-198
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• 2022

Contrast enhanced magnetic resonance imaging using gadolinium-based contrast agent (GBCA) is a very useful in vivo technique to visualize the inner ear pathology including endolymphatic hydrops. Although systemic intravenous (IV) administration can visualize the perilymph space, the visualization was possible by indirect passage of contrast agent through blood-perilymph barrier. All animal experimental procedures were performed under anesthesia with 5% isoflurane. Lipopolysaccharide (LPS) was instilled into the left tympanic cavity through the tympanic membrane using a sterile 27gauge needle to induce hydrops model. Tucker-Davis Technologies system was used to measure Auditory Brainstem Responses (ABRs). For intracerebroven-tricular (ICV) administration, 25 µmol of GADOVIST (Bayer, Berlin, Germany) was used and diluted GADOVIST injection was 10 µl. MR imaging was acquired with a 9.4 Tesla MRI scanner. Transmit-receive volume coil with 40 mm inner diameter and 75 mm out diameter was used. ICV administration well demonstrated the strong enhancement along the cerebrospinal fluid (CSF) microcirculation pathway including CSF fluid in the subarachnoid space and CSF space of the inner ear structures. On the other hand, IV administration showed no contrast enhancement along the CSF microcirculation pathway and showed weak enhancement in the inner ear structures. In case of rat hydrops model, ICV administration showed that the reduced contrast enhancement in the perilymph space of the hydrops induced inner ear compared to the contrast enhancement in the perilymph space of the normal inner ear. New systemic ICV administration method provide contrast enhancement of GBCA in the inner ear through CSF microcirculation pathway.

• Investigative Magnetic Resonance Imaging
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• v.10 no.1
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• pp.1-7
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• 2006

Purpose : Recent development of diffusion tensor imaging enables the evaluation of the microstructural characteristics of the brain white matter. However, optimal imaging parameters for diffusion tensor imaging, particularly concerning the number of diffusion gradient direction, have not been studied thoroughly yet. The purpose of this study was to evaluate the influence of the number of diffusion gradient direction on the fiber tracking of the white matter. Materials and methods : 13 healthy volunteers (ten men and three women, mean age 30 years, age range 23-37 years) were included in this study. Diffusion tensor imaging was performed with different numbers of diffusion gradient direction as 6, 15, and 32, keeping the other imaging parameters constant. The imaging field ranged from 1 cm below the pons to 2-3 cm above the lateral ventricle, parallel to the anterior commissure-posterior commissure line. FA (fractional anisotropy) maps were created via image postprocessing, and then FA and its standard deviation were calculated in the genu and the splenium of the corpus callosum on each of FA maps. Fiber tracking of the corticospinal tract in the brain was performed and the number of the reconstructed fibers of the tract was measured. FA, standard deviation of FA and the number of the reconstructed fibers were compared statistically between the different diffusion gradient directions. Results : FA is not statistically significantly different between the different diffusion gradient directions. By increasing the number of diffusion gradient direction, standard deviation of FA decreased significantly, and the number of the reconstructed fibers increased significantly. Conclusion : The higher number of diffusion gradient direction provided better quality of fiber tracking.

• Investigative Magnetic Resonance Imaging
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• v.6 no.1
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• pp.64-72
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• 2002

Purpose : To introduce and demonstrate the advantages of the new hybrid two-dimensional (2D) proton spectroscopic imaging (SI) over the single voxel spectroscopy (SVS) and conventional 2D SI in the clinical application of spectroscopy for pediatric cerebral disease. Materials and Methods : Eighty-one hybrid 2D proton spectroscopic imaging was performed in 79 children (36 normal infants and children, 10 with hypoxic-ischemic injury, 20 with toxic-metabolic encephalopathy, seven with brain tumor, three with meningoencephalitis, one with neurofibromatosis, one with Sturge-Weber syndrome and one with lissencephaly) ranging in age from the third day of life to 15 years. In adult volunteers (n=5), all three techniques including hybrid 2D proton SI, SVS using PRESS sequence, and conventional 2D proton SI were performed. Both hybrid 2D proton SI and SVS using PRESS sequence were performed in clinical cases (n=). All measurements were performed with a 1.5-T scanner using standard head quadrature coil. The 16$\times$16 phase encoding steps were set on variable field of view (FOV) depending on the size of the brain. The hybrid volume of interest inside FOV was set as $75{\times}75{\times}15{\;}\textrm{mm}^3$ or smaller to get rid of unwanted fat signal. Point-resolved spectroscopy (TR/TE=1,500 msec/135 or 270msec) was employed with standard chemical shift selective saturation (CHESSI pulses for water suppression. The acquisition time and spectral quality of hybrid 2D proton SI were compared with those of SVS and conventional 2D proton SI. Results : The hybrid 2D proton SI was successfully conducted upon all patients.

• Investigative Magnetic Resonance Imaging
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• v.3 no.2
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• pp.173-178
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• 1999

Purpose : To evaluate the usefulness of functional MRI (fMRI) of visual cortex in patients with ischemic infarction in the occipital lobe. Materials and Methods : Four patients with the symptoms and signs of visual cortical ischemia were included. Functional MRI was performed by 2D-FLASH technique with the parameter of 90/56msec TR/TE, $40^{\circ}$ flip angle, $240{\times}240{\;}FOV,{\;}64{\times}128$ matrix number, 8.32 seconds acquisition time, 8mm slice thickness. An axial slice including both visual cortices was selected and alternative activation and resting of the visual cortex was performed using red color photostimulator. all patients undertook visual field test, and vascular abnormality was examined by MRA (n=4) and DSA (n=2). fMRI results were compared with the results of a visual field test, conventional MRI and cerebral angiography. Results : On fMRI, decreased activity of the visual cortex was found in the occipital lobe corresponding to stenosis of the posterior cerebral artery or its branch noted on angiogram. However, 2 of 4 patients showed no abnormal findings on conventional MRI. Visual field defect was noted in 3 patients, one and of whom showed no abnormality on conventional MRI and diffusion-weighted image, but revealed decreased activity in the corresponding visual cortex on fMRI. Conclusion : fMRI may be a sensitive method for detection of the status of decreased blood flow or vascular reserve which other methods can not.

• Journal of Korean Neurosurgical Society
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• v.29 no.11
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• pp.1421-1428
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• 2000

Objectives : The aim of this study is to evaluate the sequential metabolic changes in experimental hydrocephalus and the clinical applicability to the diagnosis and prognosis of hydrocephalus using proton MR spectroscopy. Methods : Hydrocephalus was experimentally induced in 30 cats(2-3kg body weight) by injecting 1ml of sterile kaolin suspension(250mg/ml) into the cisterna magna. Proton MRS was performed with a 1.5 T MRI/MRS unit (Vision Plus, Siemens) at pre-treatment and at 1, 3, 7, 14, 21, and 28 days after the kaolin injection. PRESS(TR/TE＝1500/270msec) technique was employed. The major metabolites which include N-acetyl aspartate (NAA), creatine(Cr), choline(Cho), and lactate(Lac) were quantitatively analyzed and the relative concentrations ratios were evaluated. Multislice $T_2$-weighted images were also obtained using fast spin echo sequence(TR/TE＝ 2500/96msec) to monitor the morphologic changes along with progression of hydrocephalus. Results : Hydrocephalus was successfully induced in all 30 cats. Twenty five cats died within 3 days and one at the end of the second week. In all animals, the NAA/Cr ratios initially decreased during the acute stage. In 4 surviving cats, the NAA/Cr ratios initially decreased during the acute stage(<14 days) and then gradually increased to the prekaolin level as follows : pre-kaolin($1.49{\pm}0.04$), day 1($1.11{\pm}0.07$), day 7($1.17{\pm}0.04$), day 14($1.40{\pm}0.03$), day 21 ($1.46{\pm}0.06$), day 28($1.43{\pm}0.03$). These levels were relatively well correlated with the symptomatologic improvement. Lactate peak, which reflects the evidence of ischemia, did not appear throughout the entire period except in one case which expired at the end of the second week. Conclusions : The NAA/Cr ratio of the sequential proton MRS in kaolin-induced hydrocephalic cats reflects a metabolic aspect of the hydrocephalus at each stage. A decreased NAA level at the early stage is from both neuronal and axonal damage which may provide diagnostic information in the acute stage of hydrocephalus. In addition, the initial fall of NAA/Cr ratio and recovery in the late stage, when no lactate peak emerges, may suggest that the main insult of the parenchyma is not to the neuron itself but to the axon, which may be related to a good prognosis. However, emergence of the lactate peak and unrecoverable NAA/Cr at the end of the acute phase may be a poor prognostic factor. In the chronic stage, recovery of NAA/Cr ratio may provide a diagnostic clue for the differentiation between hydrocephalus and cortical atrophy.

• Progress in Medical Physics
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• v.10 no.1
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• pp.33-40
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• 1999

Purpose: To simulate and measure the signal intensity of various tissues near bone interface in 2D and 3D neurological MR images. Materials and Methods: In neurological proton density (PD) weighted images, every component in the head including cerebrospinal fluid (CSF), muscle and scalp, with the exception of bone, are visualised. It is possible to acquire images in 2D or 3D. A 2D fast spin-echo (FSE) sequence is chosen for the 2D acquisition and a 3D gradient-echo (GE) sequence is chosen for the 3D acquisition. To find out the signal intensities of CSF, muscle and fat (or scalp) for the 2D spin-echo(SE) and 3D gradient-echo (GE) imaging sequences, the theoretical signal intensities for 2D SE and 3D GE were calculated. For the 2D fast spin-echo (FSE) sequence, to produce the PD weighted image, long TR (4000 ms) and short TE$_{eff}$ (22 ms) were employed. For the 3D GE sequence, low flip angle (8$^{\circ}$) with short TR (35 ms) and short TE (3 ms) was used to produce the PD weighted contrast. Results: The 2D FSE sequence has CSF, muscle and scalp with superior image contrast and SNR of 39 - 57 while the 3D GE sequence has CSF, muscle and scalp with broadly similar image contrast and SNR of 26 - 33. SNR in the FSE image were better than those in the GE image and the skull edges appeared very clearly in the FSE image due to the edge enhancement effect in the FSE sequence. Furthermore, the contrast between CSF, muscle and scalp in the 2D FSE image was significantly better than in the 3D GE image, due to the strong signal intensities (or SNR) from CSF, muscle and scalp and enhanced edges of CSF. Conclusion: The signal intensity of various tissues near bone interface in neurological MR images has been simulated and measured. Both the simulation and imaging of the 2D SE and 3D GE sequences have CSF, fat and muscle with broadly similar image intensity and SNR's and have succeeded in getting all tissues about the same signal. However, in the 2D FSE sequence, image contrast between CSF, muscle and scalp was good and SNR was relatively high, imaging time was relatively short.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.12 no.1
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• pp.14-22
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• 2012

Objectives: This study was performed to review clinical manifestations of hyperphenylalaninemia patients in Korean. Methods: 178 cases of hyperphenyalaninemia were diagnosed at department of pediatrics, Soonchunhyang University Hospital from January, 1983 to August. We reviewed DNA analysis, MR imaging, EEG, radiography of the left hand and wrist, bone densitometry (BMD), IQ test of hyperphenyalaninemia patients. Results: Out of 178 cases, 161 cases were diagnosed classic phenylketonuria and 17 cases were diagnosed BH4 deficiency. 122 cases performed DNA analysis. R243Q (10.3%), Y204C (9.9%), and IVS4-1G>A (8.1%) mutations were predominant. 22 cases underwent MR imaging. Varying degrees of symmetrical high signal intensity were noted on T2-weighted sequences in the periventricular deep white matter of 15 cases. 23 cases were performed EEG. 12 cases (52.3%) showed abnormal pattern. EEG abnormalities showed in 11 cases. On lumbar BMD four of 11 cases (36%) showed reduced bone density of more than 1 S.D. in four of 11 cases, bone age was less than chronological age by at least one year. 18 cases were performed IQ test. Mean IQ scores was $84{\pm}21.6$. Among older than 15 years (9 cases), Mean IQ scores was $72{\pm}21.2$. PTPS deficiency was 14 cases, DHPR deficiency was 2 cases, and GTPCH deficiency was 1 case. Conclusion: We confirmed there were varieties of DNA mutations. And MR imaging and EEG were nonspecific in PKU patients. Older children showed lower IQ score. Low phenylalanine diet prevents brain damage in PKU patient. Not only first few years of life but also lifetime, Keeping low phenylalanine diet is important.

• Investigative Magnetic Resonance Imaging
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• v.13 no.2
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• pp.161-170
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• 2009

Purpose : A parallel imaging method provides us to improve temporal resolution to obtain three-dimensional (3D) MR images. The objective of this study was to optimize three 3D MRI techniques by adjusting 2D SESNE factors of the parallel imaging method in phantom and human brain. Materials and Methods : With a 3 Tesla MRI system and an 8-channel phase-array sensitivity-encoding (SENSE) coil, three 3D MRI techniques of 3D T1-weighted imaging (3D T1WI), 3D T2-weighted imaging (3D T2WI) and 3D fluid attenuated inversion recovery (3D FLAIR) imaging were optimized with adjusting SESNE factors in a water phantom and three human brains. The 2D SENSE factor was applied on the phase-encoding and the slice-encoding directions. Signal-to-noise ratio(SNR), percent signal reduction rate(%R), and contrast-to-noise ratio(CNR) were calculated by using signal intensities obtained in specific regions-of-interest (ROI). Results : In the phantom study, SENSE factor = 3 was provided in 0.2% reduction of signals against without using SENSE with imaging within 5 minutes for 3D T1WI. SENSE factor = 2 was provided in 0.98% signal reduction against without using SENSE with imaging within 5 minutes for 3D T2WI. SENSE factor = 4 was provided in 0.2% signal reduction against without using SENSE with imaging around 6 minutes for 3D FLAIR. In the human brain study, SNR and CNR were higher with SENSE factors = 3 than 4 for all three imaging techniques. Conclusion : This study was performed to optimize 2D SENSE factors in the three 3D MRI techniques that can be scanned in clinical time limitations with minimizing SNR reductions. Without compromising SNR and CNR, the optimum 2D SENSE factors were 3 and 4, yielding the scan time of about 5 to 6 minutes. Further studies are necessary to optimize 3D MRI techniques in other areas in human body.

• Investigative Magnetic Resonance Imaging
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• v.18 no.4
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• pp.332-340
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• 2014

Purpose : A relative increase in deoxyhemoglobin levels in hypoperfused tissue can cause prominent hypointense signals in the draining veins (PHSV) within areas of impaired perfusion in susceptibility-weighted imaging (SWI). The purpose of this study is to evaluate the usefulness of SWI in patients with acute cerebral infarction by evaluating PHSV within areas of impaired perfusion and to investigate the usefulness of PHSV in predicting prognosis of cerebral infarction. Materials and Methods: In 18 patients with acute cerebral infarction who underwent brain MRI with diffusion-weighted imaging and SWI and follow-up brain MRI or CT, we reviewed the presence and location of the PHSV within and adjacent to areas of cerebral infarction qualitatively and measured the signal intensity difference ratio of PHSVs to contralateral normal appearing cortical veins quantitatively on SWI. The relationship between the presence of the PHSV and the change in the extent of infarction in follow-up images was analyzed. Results: Of the 18 patients, 10 patients showed progression of the infarction, and 8 patients showed little change on follow- up imaging. On SWI, of the 10 patients with progression 9 patients showed peripheral PHSV and the newly developed infarctions corresponded well to area with peripheral PHSV on initial SWI. Only one patient without peripheral PHSV showed progression of the infarct. The patients with infarction progression revealed significantly higher presence of peripheral PHSV (p=0.0001) and higher mean signal intensity difference ratio (p=0.006) comparing to the patients with little change. Conclusion: SWI can demonstrate a peripheral PHSV as a marker of penumbra and with this finding we can predict the prognosis of acute infarction. The signal intensity difference of PHSV to brain tissue on SWI can be used in predicting prognosis of acute cerebral infarction.

• Investigative Magnetic Resonance Imaging
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• v.13 no.1
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• pp.47-53
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• 2009

Purpose : Although it's been known for half a century that unique structures have evolved in the cerebellum and they then became greatly enlarged in the human brain, the function of these structures still remains unknown. The purpose of this study was to assess cerebellar activation during motor, sensory, word generation, listening comprehension, and working memory tasks with using functional magnetic resonance imaging (fMRI). Materials and Methods : Eleven healthy right-handed subjects (Male: female, 6:5, mean age: 27.4years) were imaged on a Siemens 1.5T scanner. Whole brain functional maps were acquired using BOLD EPI sequences in the axial plane. Each paradigm consisted of five epochs of activation vs. the control condition. The activation tasks consisted of left finger complex movement, sensory stimulation of the left hand, word generation, listening comprehension, and working memory tasks. The reference function was a boxcar waveform. The activation maps were thresholded at p = 0.001. SPM 5 evaluated the activated areas and responses within the cerebellum. Results : Cerebellar activation was observed on motor task, word generation task, and working memory task. There were 949 activated areas and the mean fitted and adjusted response was 0.68 during the motor task. There were 319 activated areas and the mean fitted and adjusted response was 0.15 during the word generation task. There were 330 activated areas and the mean fitted and adjusted response was 0.26 during the working memory task. Conclusion : Our results suggest that the cerebellum is involved in a variety of functional tasks, including motor, word generation, and working memory tasks. However, during the motor task, the cerebellum showed a large activated area and a high response. Cerebellar function can be evaluated by fMRI.