U.S. Philips Corporation

Robert Boschgmbh

Olympus Winter Ibe Gmbh

Til Aach

Dietmar W Kunz

Miha Fuderer

Thorsten Manuel Buzug

Thomas Pralow

Martin Stahl

Dietmar U Koch

Rudolf Mester

Stefan H Ludeke

Ansgar Springub

Ingo Maack

Thomas Stehle

An x-ray examination apparatus comprises an x-ray source for generating an x-ray image and an image analysis system derives brightness variations from the x-ray image and derives a dose control signal dependent on said brightness variations in order to control the x-ray source. The image analysis system derives a distribution of said brightness variations and derives the dose control signal from the distribution of brightness variations. Preferably, the image analysis system is arranged to derive the brightness variations from the processed image and a histogram analysis is employed to derive the dose control signal.

X-Ray examination apparatus with dose control

The invention relates to an image processing method in which an original image is first decomposed into a series of detail images, with each of which there is associated a respective spatial frequency range, low contrasts being enhanced before assembly of a final image from the images which are produced by the decomposition and are subsequently modified. The modification of the detail images is performed in dependence on the relevant image value as well as in dependence on the mean image value and/or the variation of the image values in a window around the relevant pixel.

Processing method for an original image

The invention discloses a method of processing an image including the steps of decomposing the image into detail images at successive resolution levels. The detail images at successive resolution levels contain image information at respective spatial scales. Filtering of detail images is carried-out in dependence on at least one subsequent detail image having a lower resolution level than the current detail image. A processed image is reconstructed from the filtered detail images.

Noise reduction in an image

An image is processed taking into account the direction of a predominant structure of the image. Said predominant direction is derived from image information in the image. In particular, the covariance matrix having matrix elements depending on products of differences between pixel-values in separate directions is calculated. The eigenvectors of the covariance matrix correspond with the predominant direction of the image structure and the eigenvalues of the covariance matrix represent the strength of the structure in the image. The covariance matrix is computed locally, i.e. for separate regions in the images so as to take variations of the direction of predominant structures into account.

Directional adaptive noise reduction

In a method of processing an image the image is divided in one or more blocks. Separate blocks are spatially frequency transformed in that pixel-values of the blocks are transformed into spectral coefficients. A noise level of the image is estimated and reduced spectral coefficients are derived from spectral coefficients and the estimated noise level. Pixel-values for a processed block are synthesized from the reduced spectral coefficients and the processed blocks are assembled into a processed image. The noise level is estimated from the image information within the image. Preferably, a few parameters relating to the circumstances under which the image was acquired are also taken into account for estimating the noise level.

An image processing method includes multi-resolution decomposition to decompose an input image into frequency-band images, which are subsequently filtered according to an order statistics filtering. Preferably, a finite impulse response median hybrid is employed. The filtered frequency-band images are synthesized to form the filtered output image.

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Aachen, Germany

Til Aach