145 results about "Ring Artifact" patented technology

The invention relates to an angiographic x-ray diagnostic device for rotation angiography with an x-ray emitter which can be moved on a circular path about a patient located on a patient support table, with an image detector unit which can moved on the circular path facing the x-ray emitter, with a digital image system for recording a plurality of projection images by means of rotation angiography, with a device for image processing, by means of which the projection images are reconstructed into a 3D volume image, and with a device for correcting physical effects and / or inadequacies in the recording system such as truncation correction, scatter correction, ring artifact correction, correction of the beam hardening and / or of the low frequency drop for the soft tissue display of projection images and the 3D volume images resulting therefrom.

A method for calculating a flip angle schedule for a train of refocusing radio frequency (RF) pulses with reduced flip angles allows control of RF power deposition and use of a longer echo train. A target signal is defined for each echo in the echo train, and flip angles are then calculated from the target signals. The target signal schedule includes two phases. In the first phase, the target signals drop asymptotically to efficiently establish a pseudo-steady state at a pre-defined minimum signal level, Smin. In the second phase, the target signal is increased monotonically for the remainder of the train to a pre-defined maximum signal level, Smax. By increasing the target signal, the effect of relaxation may be reduced, decreasing blurring and ringing artifacts. Flip angles are then calculated from the target signal schedule, using a simplified method that requires no information about the tissues' relaxation properties.

A system and method facilitating progressively transforming and coding digital pictures is provided. The present invention via employment of a multi-resolution lapped transform provides for progressive rendering as well as mitigation of blocking artifacts and ringing artifacts as compared to many conventional compression systems. The invention includes a color space mapper, a multi-resolution lapped transform, a quantizer, a scanner and an entropy encoder. The multi-resolution lapped transform outputs transform coefficients, for example, first transform coefficients and second transform coefficients. A multi-resolution representation can be obtained utilizing second transform coefficients of the multi-resolution lapped transform. The color space mapper maps an input image to a color space representation of the input image. The color space representation of the input image is then provided to the multi-resolution lapped transform. The quantizer receives the first transform coefficients and / or the second transform coefficients and provides an output of quantized coefficients for use by the scanner and / or the entropy encoder. The scanner scans the quantized coefficients in order to produce a one-dimensional vector for use by the entropy encoder. The entropy encoder encodes the quantized coefficients received from the quantizer and / or the scanner resulting in data compression.

Ringing artifacts are removed from a quantized image by an image de-ringing filter that includes a determination unit, an adaptive filter and a nonlinear low-pass filter. The determination unit determines whether each selected pixel of a first set of selected pixels of an image contains a ringing artifact based on, for example, gray-level values of selected pixels within a determination kernel of pixels relating to the selected pixel. The adaptive filter generates a filtered gray-level value for each pixel determined by the determination unit to contain a ringing artifact based on, for example, gray-level values of selected pixels within a filtering kernel of pixels relating to the pixel. The nonlinear low-pass filter generates a low-pass-filtered gray-level value for each selected pixel of a second set of selected pixels of the image.