A computationally e cient postprocessing technique to reduce compression artifacts in low-bit-rate video coding is proposed in this paper. Blocking and ringing e ects are two majors artifacts observed in block DCT-based codec, such as H.263, when coding at very low bit rates. Reduction of these artifacts can signi cantly improve the overall visual quality of decoded video. In this work, a new t...

Although shimming can improve static field inhomogeneity, local field imperfections induced by tissue susceptibility differences cannot be completely corrected and can cause substantial signal loss in gradient echo images through intravoxel dephasing. Dephasing increases with voxel size so that one simple method of reducing the effect is to use thin slices. Signal-to-noise ratio (SNR) can then ...

Figure 1. Typical out-of-plane artifacts from high-attenuation objects at consecutive heights in the reconstructed volume. Top: needle insertion position is parallel to the X-ray emitter motion lane. Bottom: Needle insertion direction is perpendicular to the X-ray emitter motion lane. Pictures courtesy of Siemens Healthcare Sector. Metal Artifact Reduction of Biopsy Needles in Digital Breast To...

This study proposes a new method for removal of metal artifacts from megavoltage cone beam computed tomography (MVCBCT) and kilovoltage CT (kVCT) images. Both images were combined to obtain prior image, which was forward projected to obtain surrogate data and replace metal trace in the uncorrected kVCT image. The corrected image was then reconstructed through filtered back projection. A similar...

OBJECTIVE Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) combines advantages of both methods, namely high temporal resolution of EEG and high spatial resolution of fMRI. However, EEG quality is limited due to severe artifacts caused by fMRI scanners. APPROACH To improve EEG data quality substantially, we introduce methods that use a reusable referen...

PURPOSE Metal artifact reduction (MAR) produces images with improved quality potentially leading to confident and reliable clinical diagnosis and therapy planning. In this work, the authors evaluate the performance of five MAR techniques for the assessment of computed tomography images of patients with hip prostheses. METHODS Five MAR algorithms were evaluated using simulation and clinical st...

Introduction With specific combinations of B0-field, B1-field, and gradient field, peripheral signals outside the prescribed field of view (FOV) can fold back onto the image, resulting in a bright spot, a series of spots, a band, or a “feather-like” artifact along the phase encoding direction. In a fast spin echo (FSE) image, this type of artifact has been termed as cusp artifact [1,2], annefac...

Block-based coding is used extensively both in image and video coding systems. Image coding systems that divide an image into sub-images have problems in very low bit rate applications. In low bit rate applications, this scheme gives rise to “blocking artifacts” that arise due to image segmentation which severely reduce the visual quality of an image or video. Reducing blocking artifacts is ess...

In radial MR imaging, streaking artifacts contaminating the entire field of view can arise from regions at the outer edges of the prescribed field of view. This can occur even when the Nyquist criterion is satisfied within the desired field of view. These artifacts become exacerbated when parts of the object lie in the superior/inferior regions of the scanner where the gradient strengths become...

PURPOSE The problem of metal artifact reduction (MAR) is almost as old as the clinical use of computed tomography itself. When metal implants are present in the field of measurement, severe artifacts degrade the image quality and the diagnostic value of CT images. Up to now, no generally accepted solution to this issue has been found. In this work, a method based on a new MAR concept is present...