Scattered radiation correction method of computerized tomography system and computerized tomography system

Abstract

The present invention relates to a method for scattered radiation correction of a CT system, including at least two focus / detector systems operated angularly offset from one another, is disclosed. In the method, at at least one phantom, similar to the examined object at least in a subregion, for at least one of the focus / detector systems, the scattered radiation intensity occurring is determined in the detector of a focus / detector system during the operation of the at least one focus of at least one other focus / detector system. Further, the spatial distribution thereof is stored for a number of angles of rotation of the focus / detector systems. During scanning of the object, the scattered radiation intensities, determined with the aid of a similar phantom that originate from the at least one other focus / detector system, are subtracted from the measured intensities of the first focus / detector system while taking account of the spatial orientation of the focus / detector systems and the beam respectively considered. Finally, absorption values are calculated with the aid of the intensity values thus corrected, and CT pictures or CT volume data are thereby reconstructed.

Description

technical field [0001] The invention relates to a method for scatter correction of a computed tomography system having at least two focal point / detector systems mounted on a rotatable support angularly offset from one another and operating simultaneously, wherein in order to detect objects Scanning is carried out, the focus / detector system arranged at an angular offset scans the object, wherein they rotate around the system axis of the CT system, and for a plurality of individual rays S according to the measured radiation intensity I and the measured radiation intensity I Attenuated ray intensity I 0 The relationship to determine the absorption value a = -ln (I / I 0 ), and reconstruct the CT image or CT volume data of the object with the aid of the determined absorption data. Background technique [0002] It is known in principle that in CT methods scattering effects occur which lead to inaccurate measurements of the absorption of x-rays. This effect was first observed her...

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Problems solved by technology

However, such a scatter etalon cannot minimize the scattering of rays of the same spatial direction produced by other focal points arranged with an angular offset, which have actually straight rays originating from the focal point arranged relative to the detector, while these rays The strength of the should be measured

In principle, therefore, there is the problem of determining this scatter component at the overall measured radiation intensity and correcting this component for the measured radiation intensity, whereby for the reconstruction practically only the attenuation directly incident on the detector element is used

In order to implement the method, the X-ray sources are at least partially alternated, so that at least the non-operating X-ray tubes in the detector are missing image information from the CT scan at this time, so that gaps appear in the data acquisition

Especially in CT cardiac recordings which require a high temporal resolution, this is unsuitable and the method leads in practice to defective recording results

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