• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6A
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• pp.592-601
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• 2002

A postprocessing method for blocking artifact reduction in block coded images is presented. The proposed method consists of classification, adaptive inter-block filtering, and intra-block filtering. First, each block is classified as one of seven classes according to the characteristics of 8x8 DCT coefficients. Then each block boundary is faltered by adaptive inter-block filters, which use the block classes. Finally to the blocks which are classified as edge block classes, intra-block filtering is performed. Experimental tests produced that the proposed method gives better results than the convectional methods from both a subjective and an objective viewpoint.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.18 no.2
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• pp.157-166
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• 2014

If there are metals located in the X-ray scanned object, a point outside the metals has its range of projection angle at which projections passing through the point are disturbed by the metals. Roughly speaking, this implies that attenuation information at the point is missing in the blocked projection range. So conventional projection completion MAR algorithms to use the undisturbed projection data on the boundary of the metaltrace is less efficient in reconstructing the attenuation coefficient in detailed parts, in particular, near the metal region. In order to overcome this problem, we propose the algebraic correction technique (ACT) to utilize a pre-reconstructed interim image of the attenuation coefficient outside the metal region which is obtained by solving a linear system designed to reduce computational costs. The reconstructed interim image of the attenuation coefficient is used as prior information for MAR. Numerical simulations support that the proposed correction technique shows better performance than conventional inpainting techniques such as the total variation and the harmonic inpainting.

• Journal of the Korea Society of Computer and Information
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• v.17 no.4
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• pp.75-82
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• 2012

The Photoplethysmogram is a similar periodic signal that synchronized to a heartbeat. In this paper, we propose a periodic moving average filter that use similarity of Photoplethysmogram. This filtering method has the average value of each samples through separating the cycle of PPG signal. If there are some motion artifacts in continuous PPG signal, disjoin the signal based on cycle. And then, we made these signals to have same cycle by coordinating the number of sample. After arrange these cycles in 2 dimension, we put the average value of each samples from starting till now. So, we can eliminate the motion artifacts without damaged PPG signal.

• ETRI Journal
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• v.32 no.3
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• pp.380-389
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• 2010

This paper presents a new edge-protection algorithm and its very large scale integration (VLSI) architecture for block artifact reduction. Unlike previous approaches using block classification, our algorithm utilizes pixel classification to categorize each pixel into one of two classes, namely smooth region and edge region, which are described by the edge-protection maps. Based on these maps, a two-step adaptive filter which includes offset filtering and edge-preserving filtering is used to remove block artifacts. A pipelined VLSI architecture of the proposed deblocking algorithm for HD video processing is also presented in this paper. A memory-reduced architecture for a block buffer is used to optimize memory usage. The architecture of the proposed deblocking filter is verified on FPGA Cyclone II and implemented using the ANAM 0.25 ${\mu}m$ CMOS cell library. Our experimental results show that our proposed algorithm effectively reduces block artifacts while preserving the details. The PSNR performance of our algorithm using pixel classification is better than that of previous algorithms using block classification.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12B
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• pp.2369-2381
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• 1999

In this paper, we propose an iterative algorithm for reducing the blocking artifact in block transform-coded images by using a wavelet transform. In the proposed method, an image is considered as a set of one-dimensional horizontal and vertical signals and one-dimensional wavelet transform is utilized in which the mother wavelet is the first order derivative of a Gaussian like function. The blocking artifact is reduced by removing the blocking component, that causes the variance at the block boundary position in the first scale wavelet domain to be abnormally higher than those at the other positions, using a minimum mean square error (MMSE) filter in the wavelet domain. This filter minimizes the MSE between the ideal blocking component-free signal and the restored signal in the neighborhood of block boundaries in the wavelet domain. It also uses local variance in the wavelet domain for pixel adaptive processing. The filtering and the projection onto a convex set of quantization constraint are iteratively performed in alternating fashion. Experimental results show that the proposed method yields not only a PSNR improvement of about 0.56-1.07 dB, but also subjective quality nearly free of the blocking artifact and edge blur.

• Journal of Magnetics
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• v.21 no.3
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• pp.421-424
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• 2016

The purpose of this study is to evaluate an effectiveness of switching turbo direction to improve motion artifacts of small bowels and aorta. From June to October 2015, 60 patients suspected of having Crohn's disease were enrolled. The MR Enterography scans were performed using same protocol other than the turbo direction: with the Z phase encoding (group A) and with Y phase encoding (group B). Qualitative analysis of each group was performed to evaluate the effectiveness of switching turbo direction from Z to Y. As a result, the 5-point Likert scale for paired observers were $2.33{\pm}0.88$ for group A and $3.80{\pm}0.85$ for group B on dynamic contrast enhanced coronal images. In conclusion, group B is proved to be superior to group A and can lessen the motion artifacts derived from phase shifts.

• Proceedings of the KOSOMBE Conference
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• v.1990 no.11
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• pp.19-23
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• 1990

A new technique for reducing the susceptibility artifact in gradient echo imaging which uses a tailored RF pulse is proposed. It is applied to the case of imaging where artifacts and distortions arise due to the high local magnetic field inhomogeneity i. e., the susceptibility. The signal loss and void phenomena due to susceptibility in a voxel are studied and a correction method using a tailored RF pulse is proposed. Applications of this method in imaging are given and experimental results obtained using an human volunteer with a 2.0 T KAIS NMR system are presented.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.437-440
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• 2000

This paper proposes a method to improve video quality on images that have blocking artifacts at block boundary. Block image transform coding suffers from blocking artifact that is a main cause of degrading video quality because of the quantization error of transform coefficients in quantization process. filtering and DPCM for DC components have been widely used to reduce blocking artifact. Recently, lots of works focus on the technique that minimizes block effects using discontinuity of block boundaries. In this paper, image blurring in decoding stage is improved by adding compensation factor to each transformed blocks so that discontinuity of block boundaries can be decreased. The compensation factor is applied on each block without much loss of edge components.

• The Korean Journal of Nuclear Medicine Technology
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• v.17 no.1
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• pp.71-75
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• 2013

Purpose: Currently, decrement revision using LDCT is used in PET/CT. But cold artifacts are often found in decrement revision image by mismatch between LDCT image and Emission image near diaphragm due to patient's respiration. This research studied reduction of cold artifact by patient's respiration using CTAC Shift among revision methods. Materials and Methods: From March to September in 2012, 30 patients who had cold artifacts by respiration were targeted using PET/CT Discovery 600 (GE Healthcare, MI, USA) equipment. Patients with cold artifacts were additionally scan in diaphragm area, and the image shown cold artifacts at whole body test were revised using CTAC Shift. Cold artifacts including image, additional scan image and CTAC Shift revision image were evaluated as 1~5 points with naked eye by one nuclear medicine expert, 4 radiotechnologists with over 5 year experience. Also, standard uptake value of 3 images was compared using paired t-test. Results: Additional scan image and CTAC Shift revision image received relatively higher score in naked eye evaluation than cold artifacts including image. The additional scan image and CTAC Shift revision image had high correlation as the results of ANOVA test of standard uptake value and did not show significant difference. Conclusion: When cold artifacts are appeared by patient's respiration at PET/CT, it causes not only patient inconvenience but troubles in test schedule due to extra radiation exposure and time consumption by additional scan. But if CTAC Shift revision image can be acquired with out additional scan, it is considered to be helped in exact diagnosis without unnecessary extra radiation exposure and additional scan.

• Journal of the Korean Society of Radiology
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• v.15 no.3
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• pp.273-279
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• 2021

Metal material inserted into the body have a large difference in density from human tissues or bones around the Metal during CT scans.. Therefore, the Metal material inserted into the body produces Artifact. Metal Artifact, which occurs around Metals, can degrade the quality of CT images, causing confusion when medical team diagnose lesions. Through this experiment, we confirm that the occurrence of Artifacts decrease by using Dual energy CT and MAR algorithm in Single source Dual energy CT. We also want to present basic data on clinical application methods by comparing and analyzing the characteristics of images obtained by each method. Using GE 750HD CT, artificial implants were scanned using general method and Dual energy. Then we apply the MAR algorithm to each image obtained. And all previously acquired images were compared and analyzed the characteristics of the examination, such as image quality evaluation and dose evaluation. Images with MAR algorithm and Dual Energy confirmed a decrease in Metal Artifact. Images with MAR algorithm have reduced Metal Artifact, but have the disadvantage of distorting the details of artificial joint implants. On the other hand images teseted with Dual Energy have the advantage of being able to implement details than those applied with MAR algorithms, it takes longer to reconstruct the image and the exposure dose was about four times higher than those applied with MAR algorithm. In order to locate Metals, such as the post-operative follow-up period, it is useful to apply MAR algorithm to obtain images. And it is more useful to examine with Dual Energy when micro lesion identification, such as cardiac examination, and surgical planning or when tests are performed in diagnostic way.