• Physical Therapy Korea
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• v.10 no.3
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• pp.17-27
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• 2003

Repetitive transcranial magnetic stimulation (rTMS) modulates cortical excitability beyond the duration of the rTMS trains themselves. Depending on rTMS parameters, a lasting inhibition or facilitation of cortical excitability can be induced. Therefore, rTMS of high or low frequency over motor cortex may change certain aspects of motor learning performance and cortical activation. This study investigated the effect of high and low frequency subthreshold rTMS applied to the motor cortex on motor learning of sequential finger movements and brain activation using functional MRI (fMRI). Three healthy right-handed subjects (mean age 23.3) were enrolled. All subjects were trained with sequences of seven-digit rapid sequential finger movements, 30 minutes per day for 5 consecutive days using their left hand. 10 Hz (high frequency) and 1 Hz (low frequency) trains of rTMS with 80% of resting motor threshold and sham stimulation were applied for each subject during the period of motor learning. rTMS was delivered on the scalp over the right primary motor cortex using a figure-eight shaped coil and a Rapid(R) stimulator with two Booster Modules (Magstim Co. Ltd, UK). Functional MRI (fMRI) was performed on a 3T ISOL Forte scanner before and after training in all subjects (35 slices per one brain volume TR/TE = 3000/30 ms, Flip angle $60^{\circ}$, FOV 220 mm, $64{\times}64$ matrix, slice thickness 4 mm). Response time (RT) and target scores (TS) of sequential finger movements were monitored during the training period and fMRl scanning. All subjects showed decreased RT and increased TS which reflecting learning effects over the training session. The subject who received high frequency rTMS showed better performance in TS and RT than those of the subjects with low frequency or sham stimulation of rTMS. In fMRI, the subject who received high frequency rTMS showed increased activation of primary motor cortex, premotor, and medial cerebellar areas after the motor sequence learning after the training, but the subject with low frequency rTMS showed decreased activation in above areas. High frequency subthreshold rTMS on the motor cortex may facilitate the excitability of motor cortex and improve the performance of motor sequence learning in normal subject.

• The Journal of the Korea Contents Association
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• v.10 no.2
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• pp.286-294
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• 2010

This study was performed to identify the cerebral network associated with sensation through the tickling stimulation, which is distinctive from the rest of other networks processing normal stimulation and to investigate the difference of laughing mechanism which is closely related to tickling using functional MRI(fMRI). A 16 healthy volunteers (mean age: 28.9) on a 3.0T MR scanner during two sensation conditions. Counterbalanced stimulus were presented across the participants, and the stimulation was used block design. Acquired data was analyzed by the statistical parametric mapping (SPM 99). Subject and group analysis was performed. Individual analysis showed the activation of somatic sensation area in both tasks and the tickling sensation test showed more activated area in the Wernicke's area(BA40) compared to the normal sensation. The group analysis result shows that under normal stimulations, both sides of somatosensory cortices(BA 1,2 and 3) were activated and under tickling stimulation, not only the cortices but also those huge activation on thalamus, cingulate gyrus and insular lobe were detected. When the tickling was stopped, significant activations were shown in right cingulate gyrus, left MFG area and left insular lobe. A cerebral area responsible for recognizing tickling sensation was examined and the primitive stimulation such as tickling is much closely related to laugh, which is an important factor for various social activities.

• Investigative Magnetic Resonance Imaging
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• v.16 no.2
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• pp.136-141
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• 2012

Purpose : To investigate the pharmacologic modulation of motor task-dependent physiologic responses by antiplatelet agent, clopidogrel, during hand motor tasks in healthy subjects. Materials and Methods: Ten healthy, right-handed subjects underwent three functional magnetic resonance (fMRI) sessions: one before drug administration, one after high dose drug administration and one after reaching drug steady state. For the motor task fMRI, finger flexion-extension movements were performed. Blood oxygenation level dependent (BOLD) contrast was collected for each subject using a 3.0 T VHi (GE Healthcare, Milwaukee, USA) scanner. $T2^*$-weighted echo planar imaging was used for fMRI acquisition. The fMRI data processing and statistical analyses were carried out using SPM2. Results: Second-level analysis revealed significant increases in the extent of activation in the contralateral motor cortex including primary motor area (M1) after drug administration. The number of activated voxels in motor cortex was 173 without drug administration and the number increased to 1049 for high dose condition and 673 for steady-state condition respectively. However, there was no significant difference in the magnitude of BOLD signal change in terms of peak T value. Conclusion: The current results suggest that cerebral motor activity can be modulated by clopidogrel in healthy subjects and that fMRI is highly senstive to evidence such changes.

• Journal of Acupuncture Research
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• v.21 no.6
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• pp.177-186
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• 2004

Introduction : Recent studies Suggested that there is a strong correlation between acupuncture stimulation and its related cortical activation. Anther study showed that either positive or negative BOLD effects could be observed depending on anatomical structure in acupuncture stimulation. In ttis study, we investigated a new acupoint $KI_6$ (照海), which was known as motor-related acupoint and obtained an evidence that the stimulation of $KI_6$ resulted in either negative or positive BOLD response to stimulation. Methods & Results : 1. Subjects and paradigms : Two separate stimulation paradigms were performed on five healthy (aged 22-23 yrs) in this study. First, the paradigm of acupuncture stimulation was that the acupuncture needle was inserted in acupoints $KI_6$, which is located in lateral side of the foot and then continuously twisted(補瀉를 除外한 捻轉法) for 70 seconds for 10 cycles of activation. During rest period (70 seconds), the needle was completed removed from acupoint. Total 60 cycles were performed and 10 images were obtained per cycle. Second, nonacupoint was randomly selected and the same paradigm was performed as acupoint stimulation. The stimulation protocol comprised 10 cycles of alternating. activation and rest (10 images per cycle). Total 60 cycles were performed and each cycle take about 1.5 sec for motor task. Subjects take an at least 15 minutes break before starting anther paradigm. 2. fMRI mapping : Multi-slice functional images were obtained on a 1.5T Magnetom Vision MRI scanner (Simens Medical, Erlangen, Germany) equipped with high performance whole-body gradients. The BOLD T2 * - weighted images were acquired with acho planar imaging sequence (TR = 1.2 sec, TE = 60 msec, and flip angle = $90_{\circ}$). The other sequence parameter are : FOV = 210 mm, matrix=$64{\times}128$ or $64{\times}64$, slice number=10 and slice thickness = 5 or 8 mm. the anatomic images were obtained with Spin-echo T1-weighted images. The resulting images were then anaiyzed with STIMULATE (CMRR, U. of Minnesota) to generate functional maps using a student T-test (p < 0.005) and cluster analysis. Both positive and negative response were evaluated. Conclusions : We have observed the activation of the motor cortex by stimulating motor-related acupoint ($KI_6$). Among five subjects, negative BOLD response was shown in four and positive response in one. All subjects showed positive response to conventional finger flexion-extension task. To understand the detailed mechanisms of correlation between acupuncture stimulation and BOLD fMRI changes and two typs of response, further study strongly required.

• Investigative Magnetic Resonance Imaging
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• v.14 no.2
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• pp.115-120
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• 2010

Purpose : To separate and evaluate the low frequency spontaneous fluctuation BOLD signals from the functional magnetic resonance imaging data using sensorimotor active task. Materials and Methods : Twenty female archery players and twenty three control subjects were included in this study. Finger-tapping task consisted of three cycles of right finger tapping, with a subsequent 30 second rest. Blood oxygenation level-dependent (BOLD) data were collected using $T2^*$-weighted echo planar imaging at a 3.0 T scanner. A 3-D FSPGR T1-weighted images were used for structural reference. Image processing and statistical analyses were performed using SPM5 for active finger-tapping task and GIFT program was used for statistical analyses of low frequency spontaneous fluctuation BOLD signal. Results : Both groups showed the activation in the left primary motor cortex and supplemental motor area and in the right cerebellum for right finger-tapping task. ICA analysis using GIFT revealed independent components corresponding to contralateral and ipsilateral sensorimotor network and cognitive-related neural network. Conclusion : The current study demonstrated that the low frequency spontaneous fluctuation BOLD signals can be separated from the fMRI data using finger tapping paradigm. Also, it was found that these independent components correspond to spontaneous and coherent neural activity in the primary sensorimotor network and in the motor-cognitive network.

• Investigative Magnetic Resonance Imaging
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• v.18 no.1
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• pp.52-58
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• 2014

Purpose : To establish a pH measurement system for a mouse tumor study using a clinical scanner, to develop the $^1H$ and 31P radio frequency (RF) coil system and to test pH accuracy with phantoms. Materials and Methods: The $^1H$ and the $^{31}P$ surface coils were designed to acquire signals from mouse tumors. Two coils were positioned orthogonally for geometric decoupling. The pH values of various pH phantoms were calculated using the $^1H$ decoupled $^{31}P$ MR spectrum with the Henderson-Hasselbalch equation. The calculated pH value was compared to that of a pH meter. Results: The mutual coil coupling was shown in a standard $S_{12}$. Coil coupling ($S_{12}$) were -73.0 and -62.3 dB respectively. The signal-to-noise ratio (SNR) obtained from the homogeneous phantom $^1H$ image was greater than 300. The high resolution in vivo mice images were acquired using a $^{31}P$-decoupled $^1H$ coil. The pH values calculated from the $^1H$-decoupled $^{31}P$ spectrum correlated well with the values measured by pH meter ($R^2$=0.97). Conclusion: Accurate pH values can be acquired using a $^1H$-decoupled $^{31}P$ RF coil with a clinical scanner. This two-surface coil system could be applied to other nuclear MRS or MRI.

• Journal of radiological science and technology
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• v.41 no.5
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• pp.413-419
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• 2018

Magnetic Resonance Imaging for patients with metallic implant has poor image quality, and signal loss and artifacts including distortion can occur. The purpose of this study is to carry out a comparative evaluation on high receive bandwidth(hiBW), O-MAR, O-MAR XD to reduce artifacts in knee implant. To take MRI, 3.0T scanner and dual-source radiofrequency transmission were used. O-MAR XD technique's strong option showed a significant difference (p<0.001) with O-MAR XD technique's weak option, O-MAR and hiBW excluding the medium option. O-MAR XD's medium option had a significant difference (p<0.01) with O-MAR XD's weak, O-MAR and hiBW. O-MAR XD technique's weak option had a significant difference (p<0.01) with O-MAR XD's strong and medium options, O-MAR and hiBW. O-MAR technique had a significant difference (p<0.001) with strong, medium, weak options of O-MAR XD technique except for hiBW. HiBW had a significant difference (p<0.001) with strong, medium and weak options of O-MAR XD technique except for O-MAR. The results showed that O-MAR XD technique was more useful for MRI scan for patients with knee replacement surgery than traditional techniques such as hiBW or O-MAR, and susceptibility artifacts decreased more when O-MAR XD technique's strong or medium option was applied. Based on the results above, it is considered that it will be possible to acquire images whose susceptibility artifacts were highly decreased by using O-MAR XD technique's strong or medium option when conducting MRI for artificial knee joint and it will be helpful for checking and monitoring patients with knee joint replacement.

• Journal of the Korean Society of Radiology
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• v.8 no.5
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• pp.271-278
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• 2014

The purpose of this study is to know optimized fat suppression techniques for brachial plexus compared with STIR and SPAIR T1, T2 techniques. A total of 30 normal volunteers without brachial plexus disease were studied on a 3.0 T MRI scanner. As an analytical method, SNR, CNR, 4-point grading scale were evaluated by using three pulse sequences. As a quantitative analysis, the SNR, CNR for SPAIR T1 technique provided high value in branchial plexus roots (03.07, -2.25), branchial plexus trunks(06.70, 36.31)(p<0.05). As a qualitative Analysis, The visibility for delineation of brachial plexus, fat suppression, artifact was significantly better on SPAIR T1(3.2, 3.6, 3.4) technique(p<0.05).

• Korean Institute of Interior Design Journal
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• v.15 no.4 s.57
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• pp.89-96
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• 2006

Magnetic Resonance Imaging (MRI) scanner is the device to draw an image of conditions and the spread of various tissue in the body. It is used by making the patient into rounded superconductor and using high frequency which cause resonances. It uses superconduction magnet and high frequency that is non-ionizing radiation so can acquire biochemical, physical, and functional information of tissue. It is also very useful because it can scan tomography from many different angles to diagnose disease of a nervous system, the heart, and a skeletal structure. It also has advantages of that there is no risk of radiation exposure and the ability of observation on organizations such as brains, livers and the spinal cord of people. Since these features, the rate of use has been increased accordingly more considerations of the security are required when it plans. The weight of devices and the cover problem of the strong magnetic field which is occurred by magnetic resonance at the time of diagnosis can cause very important structure problems and architectural condition. That also the recent tendency which needs stronger equipment means that planning of the MRI unit should generally aim at purposing of the proximity for the device maintenance and up-grade and of further expansion. However there are not enough studies and data on the magnet resonance imaging in domestic hospitals. According to these reasons, this study has an object of indicating basic data on MRI unit plan standard and alternative proposals.

• Journal of KIISE:Software and Applications
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• v.27 no.8
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• pp.815-826
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• 2000

This study is for the segmentation and volume calculation of the white matter and gray matter from brain MRI. In general, the volume of white and gray matter is reduced by contraction of each components in the case of mental retardation which are Alzheimer's disease and Down's syndrome. As results, it is useful for diagnostic and early detection for various mental retardation through the tracing of variation for its volume from the brain MRI. But, until now, it was very difficult to calculate the partial volume of each components existing in some thickness, because MR image was represented by single gray value after scanning by MR scanner. Accordingly, new segmentation algorithm proposed in this paper is to calculate the partial volume of the white and gray matter existing in some thickness through the analysis of the blurred gray value, and is to determine the threshold for segmentation of white and gray matter, and is to calculate the volume of each segmented component. And finally, proposed algorithm was applied the models which was created manually, and then acquired results was compared with that of original model.