• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.74-74
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• 2003

Purpose: To investigate whether there are significant changes in regional brain metabolism in patients with Parkinson's disease after thalamotomy using proton magnetic resonance spectroscopy (lH MRS). Methods: Fifteen patients with Parkinson's disease of mean age 56.5 years (7 males and 8 females; mean age, 56.5 years) that have treated with levodopa were included. All patients with tremor experienced amelioration of their symptoms on the side contralateral to the thalamotomy. As a single-voxel technique, 1H MR spectra were obtained from the volume of interested regions in thalamus and primary motor cortex. Spectral parameters were: 20 ms TE, 2000 ms TR, 128 averages, 2500 Hz spectral width, and 2048 data points. Results: We found that NAA/Cho ratios showed generally low levels in thalamus in Parkinson's disease patients with clinical improvement following thalamotomy. Conclusions: 1H MRS may be a useful utility for the aid in better understanding the pathophy-siologic process in Parkinson's disease patients on the basis of the variation of NAA/Cho ratio. Acknowledgement: This study was supported by a grant of the Center for Functional and Metabolic Imaging Technology, Ministry of Health & Welfare, Republic of Korea (02-PJ3-PG6-EV07-0002).

• Macromolecular Research
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• v.14 no.5
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• pp.559-564
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• 2006

The improvement of spatial resolution is a fundamental issue in the two-photon, polymerization-based, laser writing. In this study, a voxel tuning method using a radical quencher was proposed to increase the resolution, and the quenching effect according to the amount of radical quencher was experimentally investigated. Employing the proposed method, the lateral resolution of the line patterns was improved almost to 100 nm. However, a shortcoming of the quenching effect was the low mechanical strength of polymerized structures due to their short chain lengths. Nano-indentation tests were conducted to evaluate quantitatively the relationship between mechanical strength and the mixture ratio of the radical quencher into the resins. The elastic modulus was dramatically reduced from an average value of 3.015 to 2.078 GPa when 5 wt% of radical quencher was mixed into the resin. Three-dimensional woodpile structures were fabricated to compare the strength between the resin containing radical quencher and the original resin.

• Proceedings of the KSMRM Conference
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• 2002.11a
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• pp.80-80
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• 2002

Purpose： Three tesla high field MR has been important to those disciplines that are SNR limited, such as MR spectroscopy. Additionally, increased spectral dispersion is critical for minimizing spectral overlap and simplifying resonance structures. The purpose of this study was to assess clinical proton MR spectroscopy (MRS) as a noninvasive method for evaluating brain tumor malignancy at 3T high field system Materials and Methods： Using 3T MRI/MRS system, localized water-suppressed single-voxel technique in patients with brain tumors was employed to evaluate spectra with peaks of N-acetyl aspartate (NAA), choline-containing compounds (Cho), creatine/phosphocreatine (Cr) and lactate. On the basis of Cr, these peak areas were quantificated as a relative ratio.

• Journal of Ocean Engineering and Technology
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• v.35 no.3
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• pp.183-190
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• 2021

Tomographic particle image velocimetry (PIV) is a widely used method that measures a three-dimensional (3D) flow field by reconstructing camera images into voxel images. In 3D measurements, the setting and calibration of the camera's mapping function significantly impact the obtained results. In this study, a camera self-calibration technique is applied to tomographic PIV to reduce the occurrence of errors arising from such functions. The measured 3D particles are superimposed on the image to create a disparity map. Camera self-calibration is performed by reflecting the error of the disparity map to the center value of the particles. Vortex ring synthetic images are generated and the developed algorithm is applied. The optimal result is obtained by applying self-calibration once when the center error is less than 1 pixel and by applying self-calibration 2-3 times when it was more than 1 pixel; the maximum recovery ratio is 96%. Further self-correlation did not improve the results. The algorithm is evaluated by performing an actual rotational flow experiment, and the optimal result was obtained when self-calibration was applied once, as shown in the virtual image result. Therefore, the developed algorithm is expected to be utilized for the performance improvement of 3D flow measurements.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2004.11a
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• pp.75-77
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• 2004

Stereotactic radiosurgery(SRS) is a technique to deliver a high dose to a particular target region and a low dose to the critical organ using only one or a few irradiations while the patient is fixed with a stereotactic frame. The optimized plan is decided by repetitive work to combine the beam parameters and identify prescribed doses level in a tumor, which is usually called a trial and error method. This requires a great deal of time, effort, and experience. Therefore, we developed the automatic arrangement of multi-isocenter within irregularly shaped tumor. At the arbitrary targets, which is this method based on the voxel unit of the space, well satisfies the dose conformity and dose homogeneity to the targets relative to the RTOG radiosurgery plan guidelines

• Journal of Korean Neurosurgical Society
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• v.29 no.12
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• pp.1606-1611
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• 2000

Objective : To obtain more reliable sample in stereotactic biopsy, authors adopted proton chemical shift imaging ($^1H$-CSI)-directed biopsy. Until now, proton single voxel spectroscopy($^1H$-SVS) technique has been reported as a technique using metabolic information in stereotactic biopsy. The authors performed $^1H$-CSI with a stereotactic headframe in place and evaluated the pathologic results obtained from local metabolic information through $^1H$-CSI. Methods : $^1H$ CSI-directed stereotactic biopsy was performed in four patients. $^1H$-CSI and conventional Gd-enhancement stereotactic MRI was done simultaneously after application of the stereotatic frame. After reconstruction of metabolic maps of NAA/Cr, Cho/Cr, and Lactate/Cr ratios, the focal areas of increased Cho/Cr ratios and decreased NAA/Cr ratios were selected for target sites in the MR images Results : There was no difficulty in performing $^1H$-CSI with the stereotactic headframe in place. In pathologic examinations, the samples taken in area of increased Cho/Cr ratios and decreased NAA/Cr ratios showed the features of increased cellularity, mitoses and cellular atypism, thus facilitated the diagnosis. The pathologic samples taken from the area of increased Lactate/Cr ratios showed prominent feature of necrosis. Conclusion : $^1H$-CSI was feasible with stereotactic head frame in place. The final pathologic results obtained in our samples were concordant with the local metabolic informations from $^1H$-CSI. Authors believe that $^1H$ CSI-directed stereotactic biopsy may provide us advantages in obtaining more reliable tissue specimen in stereotactic biopsy.

• Imaging Science in Dentistry
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• v.47 no.2
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• pp.75-86
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• 2017

Purpose: The purpose of this study was to apply a newly developed free software program, at low cost and with minimal time, to evaluate the quality of dental and maxillofacial cone-beam computed tomography (CBCT) images. Materials and Methods: A polymethyl methacrylate (PMMA) phantom, CQP-IFBA, was scanned in 3 CBCT units with 7 protocols. A macro program was developed, using the free software ImageJ, to automatically evaluate the image quality parameters. The image quality evaluation was based on 8 parameters: uniformity, the signal-to-noise ratio (SNR), noise, the contrast-to-noise ratio (CNR), spatial resolution, the artifact index, geometric accuracy, and low-contrast resolution. Results: The image uniformity and noise depended on the protocol that was applied. Regarding the CNR, high-density structures were more sensitive to the effect of scanning parameters. There were no significant differences between SNR and CNR in centered and peripheral objects. The geometric accuracy assessment showed that all the distance measurements were lower than the real values. Low-contrast resolution was influenced by the scanning parameters, and the 1-mm rod present in the phantom was not depicted in any of the 3 CBCT units. Smaller voxel sizes presented higher spatial resolution. There were no significant differences among the protocols regarding artifact presence. Conclusion: This software package provided a fast, low-cost, and feasible method for the evaluation of image quality parameters in CBCT.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.5
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• pp.447-455
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• 2014

In this paper, we consider a representative integral imaging method in glasses-free 3D image processing and propose a prioritized transmission scheme for guaranteeing a received video quality in error-prone environments. According to the correlation of pixels consisting of each voxel of integral image, we set the priority differently and apply the modulation level according to this priority value. That is to say, the corresponding pixels with small variance are set to a high priority and transmitted by using a low level modulation that is robust under transmission errors, but the corresponding pixels with greater variance are set to a lower priority and transmitted by using a high level modulation that has a high bit error rate but fast transmission rate. Result shows that the proposed scheme that applies the error-robust modulation level to the important image bit stream with the high priority improves the peak to sidelobe ratio (PSR) of the received 3D image, compared with a typical method that use the same modulation level without distinction of priorities.

• Progress in Medical Physics
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• v.14 no.3
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• pp.203-210
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• 2003

PET (positron emission tomography) permits the investigation of physiological and biochemical processes in vivo. The accuracy of quantifying PET data is affected by its finite spatial resolution, which causes partial volume effects. In this study, we developed a method for partial volume correction using Hoffman phantom PET and MR data, and applied various FWHM (full width at half maximum) levels. We also applied this method to PET images of normal controls and tested for the possibility of clinical application. $^{18}$ F-PET Hoffman phantom images were co-registered to MR slices. The gray matter and white matter regions were then segmented into binary images. Each binary image was convolved by 4, 8, 12, 16 mm FWHM levels. These convolved images of gray and white matter were merged corresponding to the same level of FWHM. The original PET images were then divided by the convolved binary images voxel-by-voxel. These corrected PET images were multiplied by binary images. The corrected PET images were evaluated by analyzing regions of interests, which were drawn on the gray and white matter regions of the original MR image slices. We calculated the ratio of white to gray matter. We also applied this method to the PET images of normal controls. On analyzing the corrected PET images of Hoffman phantom, the ratios of the corrected images increased more than that of the uncorrected images. With the normal controls, the ratio of the corrected images increased more than that of the uncorrected images. The ratio increase of the corrected PET images was lower than that of the corrected phantom PET images. In conclusion, the method developed for partial volume correction in PET data may be clinically applied, although further study may be required for optimal correction.

• Journal of the Korean Society of Radiology
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• v.18 no.1
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• pp.1-9
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• 2024

Proton therapy is known for its superior treatment method due to Bragg peak. To enhance the therapeutic effects of protons, research has been conducted on distributing gold nanoparticles within tumors to increase the absorbed dose. While previous studies focused on handling gold nanoparticles at micrometer and nonometer scale, this study proposes a method to computationally estimate the effect of gold nanoparticles at the millimeter scale. The Geant4 toolkit was applied to computational modeling. Assuming a uniform distribution of water, similar to the human body, and gold nanoparticles, the concentration of gold nanoparticles was adjusted using density ratios. When the density ratio was 5%, the gain in absorbed energy due to gold nanoparticles was nearly twice that of the pure water phantom at the Bragg peak. As the density ratio increased, the gain in absorbed energy linearly increased. When gold nanoparticles were distributed in only one voxel at the Bragg peak, the energy of the protons affected only the neighboring voxels. However, in cases where gold nanoparticles were distributed over a wide area, the volume showing 95% of the maximum absorbed energy (9.46 keV) for the pure water phantom (9.95 keV) exhibited an improvement in absorbed energy over a region 16 times larger, and this region increased as the density ratio increased. Further research is needed to quantify the relationship between the density ratio of gold nanoparticles and the relative biological effect (RBE) in the millimeter scale.