Image correction method for an X-ray detector
First Claim
1. An image correction method for a flat dynamic X-ray detector which includes a sensor matrix whose photodiodes are preceded by a scintillator for converting the X-rays into light and succeeded by a light source for uniform illumination of all photodiodes, characterized in that the gain effect is individually determined for each matrix cell of the sensor matrix in thatthe sensor matrix is illuminated at least once, after the decaying of any gain effects due to X-ray exposure (2), by means of the light source (5) instead of the X-ray source (1), the light source reference image thus acquired being stored, at a later instant, before the decaying of the gain effects due to X-ray exposure, the sensor matrix is illuminated again by means of the light source (5) instead of the X-ray source (2), the light source image thus acquired being stored, a correction value (K) is calculated pixel by pixel as the quotient of the pixel values (C) of the light source image and the pixel values (A) of the light source reference image, and subsequently a corrected pixel value (E) is determined, while taking into account the correction value (K), from every pixel value (D) measured pixel by pixel under the influence of X-rays.
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Abstract
The invention relates to an image correction method for an X-ray detector which includes a rear-mounted light source with improved correction of the after-image effects.
The invention is based on the recognition of the fact that the so-called gain effects cannot be eliminated by means of known methods. The gain effects, however, give rise to an increase of the amplification by a few percents, and hence to a bright image with artefacts, already in the case of customary diagnostic X-ray doses.
In accordance with the invention the gain effects are measured by acquisition of light source images by means of the build-in light source; the strength of the gain effect as well as a correction factor are determined pixel by pixel on the basis thereof. The pixel values of the bright image are corrected by means of the correction factor.
11 Citations
5 Claims
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1. An image correction method for a flat dynamic X-ray detector which includes a sensor matrix whose photodiodes are preceded by a scintillator for converting the X-rays into light and succeeded by a light source for uniform illumination of all photodiodes, characterized in that the gain effect is individually determined for each matrix cell of the sensor matrix in that
the sensor matrix is illuminated at least once, after the decaying of any gain effects due to X-ray exposure (2), by means of the light source (5) instead of the X-ray source (1), the light source reference image thus acquired being stored, at a later instant, before the decaying of the gain effects due to X-ray exposure, the sensor matrix is illuminated again by means of the light source (5) instead of the X-ray source (2), the light source image thus acquired being stored, a correction value (K) is calculated pixel by pixel as the quotient of the pixel values (C) of the light source image and the pixel values (A) of the light source reference image, and subsequently a corrected pixel value (E) is determined, while taking into account the correction value (K), from every pixel value (D) measured pixel by pixel under the influence of X-rays.
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5. An X-ray device which includes a flat dynamic X-ray detector (4) with a sensor matrix whose photodiodes are preceded by a scintillator for converting the X-rays (2) into light and succeeded by a light source (5) for uniform illumination of all photodiodes, and also includes at least one correction unit (6) which acquires the image signals from the light source, produced by the sensor matrix, before and after the decaying of any gain effects due to X-rays (2), the correction unit (6) correcting the image signals of the instantaneous bright images in dependence on the presence of gain effects as well as on their intensity.
Specification