• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.14 no.1
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• pp.35-42
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• 2010

A goal of Magnetic Resonance Imaging is reproducing a spatial map of the effective spin density from the measured Fourier coefficients of a specimen. The imaging procedure can be done by inverse Fourier transformation or backward fast Fourier transformation if the data are sampled on a regular grid in frequency space; however, it is still a challenging question how to reconstruct an image from a finite set of Fourier data on irregular points in k-space. In this paper, we describe some mathematical and numerical properties of imaging techniques from non-uniform MR data using the pseudo-inverse or the diagonal-inverse weight matrix. This note is written as an easy guide to readers interested in the non-uniform MRI techniques and it basically follows the ideas given in the paper by Greengard-Lee-Inati [10, 11].

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.4
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• pp.639-642
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• 2012

Optical coherence tomography(OCT) can provide real-time and non-invasive subsurface imaging with ultra-high resolution of micrometer scale. However, conventional OCT systems generally have a limited imaging depth range within a depth of only 1-2 mm. To overcome the limitation, we have proposed an active surface tracking algorithm used in common-path Fourier-domain OCT system in order to extend the imaging depth range. The surface tracking algorithm based on the threshold and Savitzky-Golay filter of A-scan data was applied to real-time tracking. The algorithm has controlled a moving stage according to the sample's surface variance in real time. An OCT image obtained by the algorithm clearly show an extended imaging depth range. Consequently, the proposed algorithm demonstrated the potential for improving the conventional OCT systems with limitary depth range.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.230-234
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• 1997

The matching pursuit (MP) algorithm developed by S. Mallat and Z. Zhang is applied to magnetic resonance (MR) imaging. Since matching pursuit is a greedy algorithm to find waveforms which are the best match for an object-signal, the signal can be decomposed with a few iterations. In this paper, we propose an application of the MP algorithm to the MR imaging to reduce imaging time. Inner products of residual signals and selected waveforms in the MP algorithm are derived from the MR signals by excitation of RF pulses which are fourier transforms of selected waveforms. Results from computer simulations demonstrate that the imaging time is reduced by using the MP algorithm and further a progressive reconstruction can be achieved.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.18-18
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• 2003

목적： MRI 시스템에서 얻어지는 Data는 TR(Repetition Time)과 TE(Echo Time)에 따라서 신호 대잡음비(SNR), 조직들간의 대조도(Contrast), Artifact 및 촬영시간이 결정된다. 이 연구에서는 TR/TE를 줄이는 기법을 이용한 Radial Imaging 영상기법을 제시하고자 한다. 대상 및 방법： 일반적인 Radial Imaging 기법에 HASTE 기법과 Non-uniform sampling 기법의 특징을 이용하여 구현하였으며, TR/TE를 줄일 수 있었으며 얻어진 K-space Data는 가변주파수 역 Fourier Transform을 이용하여 Projection Data를 재구성한 후 Back Projection 기법을 이용하여 최종 영상을 재구성한다.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.19-19
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• 2003

목적： MRI 시스템에서 얻어지는 기초 Data는 K-space 즉 촬영대상의 Fourier Transform 된 Data 이다. 이 K-space Data는 영상 촬영 기법에 따라 다른 형식으로 얻어지게 되는데, 이 연구에서는 Radial Imaging에서 Repetition Time 과 Echo Time을 줄이기 위해 구현된 영상기법을 이용하여 얻어진 Data를 이용하여 영상을 재구성하는 방법을 제시하고자 한다.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.3
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• pp.257-260
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• 2010

Advancements in the imaging and computing technology have opened the path to digital holography for non-destructive investigations of technical samples, material property measurement, vibration analysis, flow visualization and stress analysis in aerospace industry which has widened the application of digital holography in the above fields. In this paper, we demonstrate the non-destructive investigation and micro-structure measurement application of digital holography to the small particles and a biological sample. This paper gives a brief description of the digital holograms recorded with this system and illustratively demonstrated.

• Journal of radiological science and technology
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• v.35 no.4
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• pp.309-314
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• 2012

Nowadays, digital Radiography (DR) systems are widely used in clinical sites and substitute the analog-film x-ray imaging systems. The resolution of DR images depends on several factors such as characteristic contrast and motion of the object, the focal spot size and the quality of x-ray beam, x-ray scattering, the performance of the DR detector (x-ray conversion efficiency, the intrinsic resolution). The DR detector is composed of an x-ray capturing element, a coupling element and a collecting element, which systematically affect the system resolution. Generally speaking, the resolution of a medical imaging system is the discrimination ability of anatomical structures. Modulation transfer function (MTF) is widely used for the quantification of the resolution performance for an imaging system. MTF is defined as the frequency response of the imaging system to the input of a point spread function and can be obtained by doing Fourier transform of a line spread function, which is extracted from a test image. In clinic, radiologic technologists, who are in charge of system maintenance and quality control, have to evaluate or make routine check on their imaging system. However, it is not an easy task for the radiologic technologists to measure MTF accurately due to lack of their engineering and mathematical backgrounds. The objective of this study is to develop and provide for radiologic technologists a medical system imaging evaluation tool, so that they can measure and quantify system performance easily.

• Journal of Biosystems Engineering
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• v.39 no.3
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• pp.215-226
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• 2014

Recently, spectroscopy has emerged as a potential tool for quality evaluation of numerous food and agricultural products because it provides information regarding both spectral distribution and image features of the sample (i.e., hyperspectral imaging). Spectroscopic techniques reveal hidden information regarding the sample and do so in a non-destructive manner. This review describes the various approaches of spectroscopic modalities, especially hyperspectroscopy and vibrational spectroscopies (i.e., Raman spectroscopy and Fourier transform near infrared spectroscopy) combined with chemometrics for the non-destructive assessment of contaminations and defects in agro-food products.

• Information Display
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• v.15 no.5
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• pp.22-32
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• 2014

The current research intends to quantify the surround luminance effects on the shape of spatial luminance CSF and to propose an image quality evaluation method that is adaptive to both surround luminance and spatial frequency of a given stimulus. The proposed image quality method extends to a model called SQRI[8]. The non-linear behaviour of the HVS was taken into account by using CSF. This model can be defined as the square root integration of multiplication between display MTF and CSF. It is assumed that image quality can be determined by considering the MTF of the imaging system and the CSF of human observers. The CSF term in the original SQRI model was replaced by the surround adaptive CSF quantified in this study and it is divided by the Fourier transform of a given stimulus. A few limitations of the current work should be addressed and revised in the future study. First, more accurate model predictions can be achievable when the actual display MTF is measured and used instead of the approximation. Then, a further improvement to the model prediction accuracy can be made when chromatic adaptation of the HVS is taken into account[45-46].

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3153-3155
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• 1999

최근 수년간 의료영상분야는 국내외적으로 급격한 발전을 거듭하고 있다. 특히 자기공명영상장치 (Magnetic Resonance Imaging), X-ray CT(Computed Tomography)와 단층촬영장치는 인체내부를 비침습적(non-invasive)으로 영상화함으로써 해부학적인 질병진단에 많은 장점을 가지고 있다. 이와같은 단층영상 재구성에는 역매트릭스법(matrix inversion). 반복재구성법(interative method), 역투영 법(back-projection), 2차원 Fourier 변환법(2D FFT), 중첩재구성법(Filtered back-projection) 등의 다양한 알고리즘을 사용하고 있다. 본 연구에서는 X-ray CT에서의 단층영상재구성 기법 중 널리 사용되고 있는 Filtered Back Projection 기법의 연산순서도와 연산량을 분석하고 이를 시뮬레이션을 통하여 확인하고 실시간 영상재구성을 위하여 범용 Digital Signal Processor의 병렬처리시스템 구성에 기반된 최적 Architecture를 선정하고자 한다.