• Journal of the Korean Society of Radiology
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• v.7 no.2
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• pp.137-143
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• 2013

This study presents comparison results between axial and spiral scanning in the head and chest region with 64 MDCT to evaluate organ doses in infants and toddlers, who are more radiosensitive to radiation than adults and rise in the number of CT examinations, during CT scanning. Organ doses were significantly lower in spiral scanning than axial scanning regardless of scanned regions. The average organ dose for the chest scan using pitch of 1.355 was found to be significantly higher(average -12.03%) than for the other two pitch settings(0.525 and 0.988) in the spiral scanning mode compared with the axial one. Organ doses in the spiral scanning mode were lower by average 20.54% than the axial scanning mode. The results of the study that evaluated organ doses with an anthropomorphic phantom will help to demonstrate the result values of Monte Carlo simulations and make a contribution to more accurate evaluations of organ doses in toddlers undergoing a CT examination.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.292-293
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• 2003

최근 생체의 단층영상 촬영기법으로 각광을 받고 있는 OCT (Optical Coherence Tomography)는 백색광 간섭계를 근간으로 하여 생체의 깊이 정보를 얻어낸다. 2-D 또는 3-D의 입체영상을 얻기 위해서는 1축 또는 2축의 횡방향 스캔이 필요하다. 횡방향 스캔 기법은 SEM (Scanning electron microscope)이나 공초점현미경 (Confocal microscope) 등에서 널리 사용되고 있으므로 기술적인 흥미는 적으나 축방향 (깊이 방향)의 정보 취득 방법은 OCT만의 특징으로 아직 기술적으로 해결 되어야될 부분이 많다. (중략)

• Proceedings of the Korea Information Processing Society Conference
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• 2000.10a
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• pp.719-722
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• 2000

단일 카메라로 회전하는 물체의 영상을 획득한 후, 그 영상을 분석하여 3차원으로 복구하는 새로운 알고리즘을 제안한다. 제안하는 알고리즘은 물체의 회전과 단 하나의 카메라를 이용하는 방법이기에 기존의 스테레오 영상을 이용하는 방법에 비해 차이를 둘 수 있다. 회전하는 물체에는 회전축과 동일한 방향의 스캔라인을 형성시키고, 이 스캔라인을 적절한 측면에서 하나의 카메라를 이용해 영상으로 획득하여 스캔라인의 굴곡과 이 스캔라인에 인접한 화소의 컬러 정보를 이용하여 3차원의 물체를 재건한다. 이 방법은 3차원의 정보를 얻음에 있어 물체의 회전에 의존하기에 한 방향에서 얻어진 두 스테레오 영상의 정합과 각 방향에서 얻어진 영상을 정합 시킬 때 발생될 수 있는 스테레오 비전의 오류를 피할 수 있다.

• Electronics and Telecommunications Trends
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• v.12 no.6 s.48
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• pp.50-57
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• 1997

CT스캔(Computed Tomography)은 다양한 분야에서 효과적으로 응용되고 있고, 특히 의학 영상에서 비침범 진단, 수술 계획 등에 커다란 영향을 끼쳤다. 이 글에서는 여러 가지 CT스캔의 종류, 그 수학적인 원리와 기본적인 평행 광선(parallel beam)을 이용한 영상의 재구축 알고리즘, 데이터의 추정과 문제점 그리고 그 개선 방향에 대해 논한다

• Journal of Radiation Protection and Research
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• v.30 no.3
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• pp.113-119
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• 2005

The computed tomogrpahy(CT) provides a high quality in images of human body but contributes to the relatively high patient dose. The frequency of CT examination is increasing and, therefore, the concerns about the patient dose are also increasing. In this study the experimental determination of patient dose was performed by using a physical anthropomorphic phantom and thermoluminescent dosimeter(TLD). The measurements were done for the both axial and spiral scan mode. As a result the effective doses for each scan mode were 17.78mSv and 10.01 mSv respectively and the fact that the degree of the reduction in the patient dose depends on the pitch scan parameter was confirmed. The measurement methods suggested in this study can be applied for the reassessment of the patient dose when the technique in CT equipment is developed or the protocol for CT scanning is changed.

• Journal of the Korean Society of Radiology
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• v.16 no.1
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• pp.67-75
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• 2022

The aim of this study is to establish a new QC method that can simultaneously evaluate the resolution of the x/y plane and the z-axis by producing a phantom that can reflect exposure and reconstruction parameter of MDCT system. It was used with Aquilion ONE(Cannon Medical System, Otawara, Japan), and the examination was scanned using of 120 kV, 260 mA, and the D-FOV of 300 mm². It produced new SSP phantom modules in which two aluminum plates inclined at 45° to a vertical axis and a transverse axis to evaluate high contrast resolution of x/y plane and z axis. And it changed factors such as the algorithm, distance from gantry iso-center. All images were reconstructed in five steps from 0.6 mm to 10.0 mm slice thickness to measure resolution of x/y plane and z-axis. The image data measured FWHM and FWTM using Profile tool of Aquarius iNtusion Edition ver. 4.4.13 P6 software(Terarecon, California, USA), and analysed SPQI and signal intensity by ImageJ program(v1.53n, National Institutes of Health, USA). It decreased by 4.09~11.99%, 4.12~35.52%, and 4.70~37.64% in slice thickness of 2.5 mm, 5.0 mm, and 10.0 mm for evaluating the high contrast resolution of x/y plane according to distance from gantry iso-center. Therefore, the high contrast resolution of the x/y plane decreased when the distance from the iso-center increased or the slice thickness increased. Additionally, the slice thicknesses of 2.5 mm, 5.0 mm, and 10.0 mm with a high algorithm increased 74.83, 15.18 and 81.25%. The FWHM was almost constant on the measured SSP graph for evaluating the accuracy of slice thickness which represents the resolution of x/y plane and z-axis, but it was measured to be higher than the nominal slice thickness set by user. The FWHM and FWTM of z-axis with axial scan mode tended to increase significantly as the distance increased from gantry iso-center than the helical mode. Particularly, the thinner slice thickness that increased error range compare with the nominal slice thickness. The SPQI increased with thick slice thickness, and that was closer to 90% in the helical scan than the axial scan. In conclusion, by producing a phantom suitable for MDCT detectors and capable of quantitative resolution evaluation, it can be used as a specific method in the management of research quality and management of outdated equipment. Thus, it is expected to contribute greatly to the discrimination of lesions in the field of CT imaging.

• The Korean Journal of Nuclear Medicine
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• v.30 no.4
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• pp.548-559
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• 1996

A series of performance measurements of positron emission tomography (PET) were performed following the recommendations of the Computer and Instrumentation Council of the Society of Nuclear Medicine and the National Electrical Manufacturers Association. We investigated the performance of the General Electric $Advance^{TM}$ PET. The measurements include the basic intrinsic tests of spatial resolution, scatter fraction, sensitivity, and count rate losses and randoms. They also include the tests of the accuracy of corrections: count rate linearity correction, uniformity correction, scatter correction and attenuation correction. GE $Advance^{TM}$ PET has bismuth germanate oxide crystals (4.0mm transaxial ${\times}$ 8.1mm axial ${\times}$ 30.0mm radial) in 18 rings, which form 35 imaging planes spaced by 4.25mm. The system has retractable tungsten septa 1mm thick and 12cm long. Transaxial resolution was 4.92mm FWHM in 2D and 5.14mm FWHM in 3D at the center. Average axial resolution in 2D decreased from 3.91mm FWHM at the center to 6.49mm FWHM at R=20cm. Average scatter fraction of direct and cross slices was 9.57%. Dead-time losses of 50% corresponded to a radioactivity concentration of $4.86{\mu}Ci/cc$ and a true count rate of 519 kcps in 2D. The accuracy of count rate linearity correction was 1.84% at the activity of $4.50{\mu}Ci/cc$. Non-uniformity was 2.06% in 2D and 2.93% in 3D. Remnant errors after scatter correction were 0.55% in 2D and 4.12% in 3D. The errors of attenuation correction were 6.21% (air), 0.20% (water), -6.32% (teflon) in 2D and 5.00% (air), 6.94% (water), 3.01% (teflon) in 3D. The results indicate the performance of GE $Advance^{TM}$ PET scanner to be well suited for clinical and research applications.

• Composites Research
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• v.29 no.5
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• pp.288-292
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• 2016

In this paper, a novel ultrasonic propagation imaging system, called a full-field pulse-echo ultrasonic propagation imaging (FF PE UPI) system is introduced. The system nondestructively inspected targets with two-axis translation stage. The coincident laser beams for ultrasonic sensing and generation are scanned and pulse-echo mode laser ultrasounds are captured. This procedure makes it possible to generate full-field ultrasound in through-the-thickness direction as large as the scan area. Structural inspection results in the form of full-field ultrasonic wave propagation videos are introduced, which are painted sandwich control surfaces. In addition, the inspection results of FF PE UPI system are compared with conventional ultrasonic testing methods such as waterjet and portable C-scan.

• Journal of the Korean Society of Radiology
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• v.10 no.1
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• pp.45-51
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• 2016

The purpose of this study was tried to remove the noise and improve the spatial resolution in the computed tomography (CT) by using anisotropic 2-dimensional (2D) diffusion based filter. We used 4-channel multi-detector CT and american association of physicists in medicine (AAPM) phantom was used for CT performance evaluation to evaluate the image quality. X-ray irradiation conditions for image acquisition was fixed at 120 kVp, 100 mAs and scanned 10 mm axis with ultra-high resolution. The improvement of anisotropic 2D diffusion filtering that we suggested firstly, increase the contrast of the image by using histogram stretching to the original image for 0.4%, and multiplying the individual pixels by 1.2 weight value, and applying the anisotropic diffusion filtering. As a result, we could distinguished five holes until 0.75 mm in the original image but, five holes until 0.40 mm in the image with improved anisotropic diffusion filter. The noise of the original image was 46.0, the noise of the image with improved anisotropic 2D diffusion filter was decreased to 33.5(27.2%). In conclusion improved anisotropic 2D diffusion filter that we proposed could remove the noise of the CT image and improve the spatial resolution.

• Progress in Medical Physics
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• v.25 no.4
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• pp.233-241
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• 2014

The aim of this study is to develop a new software tool for 3D dose verification using $PRESAGE^{REU}$ Gel dosimeter. The tool included following functions: importing 3D doses from treatment planning systems (TPS), importing 3D optical density (OD), converting ODs to doses, 3D registration between two volumetric data by translational and rotational transformations, and evaluation with 3D gamma index. To acquire correlation between ODs and doses, CT images of a $PRESAGE^{REU}$ Gel with cylindrical shape was acquired, and a volumetric modulated arc therapy (VMAT) plan was designed to give radiation doses from 1 Gy to 6 Gy to six disk-shaped virtual targets along z-axis. After the VMAT plan was delivered to the targets, 3D OD data were reconstructed from 512 projection data from $Vista^{TM}$ optical CT scanner (Modus Medical Devices Inc, Canada) per every 2 hours after irradiation. A curve for converting ODs to doses was derived by comparing TPS dose profile to OD profile along z-axis, and the 3D OD data were converted to the absorbed doses using the curve. Supra-linearity was observed between doses and ODs, and the ODs were decayed about 60% per 24 hours depending on their magnitudes. Measured doses from the $PRESAGE^{REU}$ Gel were well agreed with the TPS doses at central region, but large under-doses were observed at peripheral region at the cylindrical geometry. Gamma passing rate for 3D doses was 70.36% under the gamma criteria of 3% of dose difference and 3 mm of distance to agreement. The low passing rate was resulted from the mismatching of the refractive index between the PRESAGE gel and oil bath in the optical CT scanner. In conclusion, the developed software was useful for 3D dose verification from PRESAGE gel dosimetry, but further improvement of the Gel dosimetry system were required.