• Proceedings of the KSME Conference
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• 2002.08a
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• pp.295-298
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• 2002

In the analysis of the mass distribution and SMD (Sauter Mean Diameter), planar laser imaging technique Is a convenient and useful one when compared to the mechanical patternator or PDPA (Phase Doppler Particle Analyzer). But for the accurate usage of this laser technique, it is required to compensate the signal attenuation and to find the attenuation coefficients. In the present research, we considered effects of the spray distributions on the attenuation coefficient and improved the accuracy of planar laser imaging technique by the reduction of errors issuing from the signal attenuation.

• Journal of ILASS-Korea
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• v.7 no.3
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• pp.24-30
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• 2002

In the analysis of the mass distribution and SMD(Sauter Mean Diameter), planar laser imaging technique is a convenient and useful one when compared to the mechanical pattemator or PDPA (Phase Doppler Particle Analyzer). But recorded signals at cameras and intensity of laser are distorted by attenuation. Using experimental datum and assumptions, we study measurement errors due to attenuation in plannar image technique.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.1
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• pp.72-79
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• 1997

Most open magnetic resonance imaging systems have used the planar gradient coils whose inductances were minimized through the magnetic energy minimization procedure in the spatial frequency domain. Though the planar gradient coils have smaller inductance than conventional gradient coils, the planar gradient coils often suffer from their poor magnetic field linearity. Scaling the spatial frequencies of the current density function designed by the magnetic energy minimization, magnetic field linearity of the planar gradient coils can be greatly improved with small sacrifice of gradient coil inductance. We have found that the figure of merit of the planar gradient coils, defined by the gradient strength divided by the linearity error and the inductance, can be improved by proposed technique.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.1
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• pp.93-101
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• 2000

The characteristics of spray nozzle have been quantified with the measurement of fluorescence and Mie scattering images. To correct the attenuation of the incident light sheet, a sequential double-pass light sheet system and the geometrical averaging of two images was implemented. Quantitative mass flux distribution of spray was obtained from fluorescence image. 3-D image is reconstructed using 2-D radial images. Sauter mean diameter (SMD) distribution was determined using the ratio of fluorescence signal intensity and Mie scattering signal intensity and the values were quantified with PDP A data. The measurement of mass flux and SMD using planar imaging technique agee with PDP A data fairly well in the low density region. However, in dense region， there are significant errors caused by secondary scattering. It was found that the planar imaging technique provides many advantages over the point measurement technique, such as PDP A, and can be implemented for quantitative measurement, especially in low density region.

• Journal of ILASS-Korea
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• v.5 no.2
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• pp.12-21
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• 2000

• Journal of radiological science and technology
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• v.44 no.1
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• pp.25-30
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• 2021

The purpose was to reduce the distortion of the image that occurs in the temporal bone area due to the very strong differences in susceptibility. A new SS-TSE technique was applied when examining the diffusion-weighted image of the temporal bone, where the auditory and facial nerves to be imaged were very thin and were adjacent to the cranial base including bone and air. This study was conducted from March 2020 to August of the same year, targeting 32 subjects who underwent the diffusion-weighted imaging of the temporal bone. To compare the distortion, existing SS-EPI technique and the new SS-TSE technique were both applied on the temporal bone area. As a result of the study, applying the new SS-TSE technique appeared to lower the distortion of images by 87.44, 46.13 and 42.35 % on the b-value 0, 800 and the ADC images, respectively. In conclusion, when using the new SS-TSE technique on the temporal bone DWI, distortion can be reduced, and thus images with high diagnostic value can be obtained.

• Journal of electromagnetic engineering and science
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• v.11 no.4
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• pp.290-297
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• 2011

Recent progresses in the live electrooptic imaging (LEI) technique are reviewed with emphasis on its functionality of real-time visual accesses to traveling electric waves in the GHz range. Together with the principles, configurations, and procedures for the visual observation experiments by an LEI camera system, the following results are described as examples indicating the wide application ranges of the technique; Ku-band waves on arrayed planar antennas, waves on a Gb/s-class digital circuit, W-band waves traveling both in slab-waveguide modes and aerially, backward-traveling wave along composite right/left-handed transmission line, and, waves in monolithic microwave integrated circuit module case.

• Investigative Magnetic Resonance Imaging
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• v.25 no.1
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• pp.1-9
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• 2021

The aim of this study was to provide a new assessment of rotator cuff muscle activity. Eight male subjects (24.7 ± 3.2 years old,171.2 ± 9.8 cm tall, and weighing 63.8 ± 11.9 kg) performed the study exercises. The subjects performed 10 sets of the exercise while fixing the elbow at 90 degrees flexure and lying supine on a bed. One exercise set consisted of the subject performing external shoulder rotation 50 times using training equipment. Two imaging protocols were employed: (a) true fast imaging with steady precession (TrueFISP) at an acquisition time of 12 seconds and (b) multi-shot spin-echo echo-planar imaging (MSSE-EPI) at an acquisition time of 30 seconds for one echo. The main method of assessing rotator cuff muscle activity was functional T2 mapping using ultrafast imaging (fast-acquired muscle functional MRI [fast-mfMRI]). Fast-mfMRI enabled real-time imaging for the identification and evaluation of the degree of muscle activity induced by the exercise. Regions of interest were set at several places in the musculus subscapularis (sub), musculus supraspinatus (sup), musculus teres minor (ter), and deltoid muscle (del). We used the MR signal of the images and transverse relaxation time (T2) for comparison. Most of the TrueFISP signal was not changed by exercise and there was no significant difference from the resting values. Only the T2 in the musculus teres minor was increased after one set and the change were seen on the T2 images. Additionally, except for those after one and two sets, the changes in T2 were significant compared to those at rest (P < 0.01). We also demonstrated identify and visualize the extent to which muscles involved in muscle activity by exercise. In addition, we showed that muscle activity in a region such as a shoulder, which is susceptible to B0 inhomogeneity, could be easily detected using this technique.

• Journal of Biomedical Engineering Research
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• v.20 no.1
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• pp.53-58
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• 1999

Eddy current in MRI systems degrades gradient field linearity and distorts gradient waveform. When the waveform distortion is spatially variant, it is very difficult to perform special imaging techniques such as the echo planar imaging technique or the fast spin echo imaging technique. In this study, we have developed a new technique to estimate the distorted gradient waveforms at any points inside the imaging region using the finite element method. After obtaining the eddy-current-effect transfer function, which represents magnitude and phase characteristics of the gradient field at a particular point, we have used the transfer function to estimate the actual gradient waveforms at the point. To verify the proposed technique, we have compared the estimated gradient waveforms with the measured ones.

• Investigative Magnetic Resonance Imaging
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• v.21 no.4
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• pp.223-232
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• 2017

Purpose: To report the use of multiband accelerated echo-planar imaging (EPI) for resting-state functional MRI (rs-fMRI) to achieve rapid high temporal resolution at 3T compared to conventional EPI. Materials and Methods: rs-fMRI data were acquired from 20 healthy right-handed volunteers by using three methods: conventional single-band gradient-echo EPI acquisition (Data 1), multiband gradient-echo EPI acquisition with 240 volumes (Data 2) and 480 volumes (Data 3). Temporal signal-to-noise ratio (tSNR) maps were obtained by dividing the mean of the time course of each voxel by its temporal standard deviation. The resting-state sensorimotor network (SMN) and default mode network (DMN) were estimated using independent component analysis (ICA) and a seed-based method. One-way analysis of variance (ANOVA) was performed between the tSNR map, SMN, and DMN from the three data sets for between-group analysis. P < 0.05 with a family-wise error (FWE) correction for multiple comparisons was considered statistically significant. Results: One-way ANOVA and post-hoc two-sample t-tests showed that the tSNR was higher in Data 1 than Data 2 and 3 in white matter structures such as the striatum and medial and superior longitudinal fasciculus. One-way ANOVA revealed no differences in SMN or DMN across the three data sets. Conclusion: Within the adapted metrics estimated under specific imaging conditions employed in this study, multiband accelerated EPI, which substantially reduced scan times, provides the same quality image of functional connectivity as rs-fMRI by using conventional EPI at 3T. Under employed imaging conditions, this technique shows strong potential for clinical acceptance and translation of rs-fMRI protocols with potential advantages in spatial and/or temporal resolution. However, further study is warranted to evaluate whether the current findings can be generalized in diverse settings.