The block discrete cosine transform (BDCT) is extensively used for compression of image and videos. One of its disadvantages, however, is the blocking artifacts at the block boundaries at low bit-rates. Most previous techniques for removing block artifacts utilize low-pass ltering or projection-on-convex-set (POCS) concept that gives an iterative restoration. These techniques produce unnecessar...

A new method for reducing metal artifacts in X-ray computed tomography (CT) images is presented. It bases on the solution of a convex optimization problem with inequality constraints on the sinogram, and total variation regularization for the reconstructed image. The Chambolle-Pock algorithm is used to numerically solve the discretized version of the optimization problem. As proof of concept we...

Electrocardiogram (ECG) is required during Magnetic Resonance Imaging (MRI) for two reasons, patient monitoring and MRI sequence synchronization for cardiovascular imaging. The MRI environment severely distorts ECG signals. The Magnetic Field Gradients (MFG) especially induce artifacts, which make ECG analysis during MRI acquisition challenging. Specific signal processing is thus required. An M...

Block transform coding is widely used in image and video compression methods. Due to quantization error, there are blocking artifacts in the decoded image. This paper presents a pre-processing method, called pre-distortion, to reduce both the bitrate and blocking artifacts. The proposed algorithm is an iterative algorithm which reduces the blocking artifacts of the decoded image by introducing ...

■ Through-plane distortion: The local field offset leads to curved and frayed slices instead of the expected flat image plane (Fig. 1). Since both in-plane and through-plane distortions shift image pixels away from their real positions, image geometry appears to be distorted. In both cases, regions with severe field changes will lead to signal voids visible as black spots and signal pileups vis...

Tamás Szirányi Hungarian Academy of Sciences Analogical and Neural Computing Laboratory Computer and Automation Instrumentation H-1111 Budapest Kende u. 13-17 Hungary and University of Veszprém Department of Image Processing and Neurocomputing H-8200 Veszprém Egyetem u. 10, Hungary E-mail: [email protected] Abstract. We evaluate a preprocessing method for image compression artifact reduction b...

A major drawback of block-based still-image or video-compression methods at low rates is the visible block boundaries that are also known as blocking artifacts. Several methods have been proposed in the literature to reduce these artifacts. Most are single image methods, which do not distinguish between video and still images. However, video has a temporal dimension that can lead to better reco...

All algorithms were capable of isolating the heart beat and most algorithms succeeded for the eye movements. Reduction of eye movement artifact is important in clinical applications as patients often cannot control their eye movements. The suggested comparative framework is of high practical value as demonstrated on a limited data set. Future work will assess the separability between cortical a...

This correspondence presents a scheme for artifact reduction of low bit rate discrete-cosine-transform-compressed (DCT-compressed) images. First, the DC coefficients are calibrated using gradient continuity constraints. Then, an improved Huber-Markov-random-field-based (HMRF-based) smoothing is applied. The constrained optimization is implemented by the iterative conditional mode (ICM). Final r...

Eddy current effects can severely degrade image quality when using balanced steady-state free precession imaging with rapidly varying phase encode ordering schemes, which have common use in cardiac cine MRI. In this work, we explore and characterize a previouslyproposed technique, through-slice dephasing, as the sole technique for eddy current artifact removal. We demonstrate that artifacts var...