Computerized roentgenographing apparatus

Abstract

In an X-ray computed tomography apparatus with retrospective beam hardening correction, an overall image of a body slice under examination is determined from overall attenuation values that are obtained from the body slice. At least one partial image that shows essentially only one body substance, such as bone substance, is extracted from this overall image. Attenuation partial values are employed for determining a correction value. The attenuation values are determined for each overall attenuation value from the at least one partial image by re-projection. A correction value is derived from the beam hardening error that is determined for a material combination of two different reference materials.

Description

technical field

[0001] The invention relates to a radiation hardening correction in a computed tomography apparatus. Background technique

[0002] In computed tomography, a shift of the mean energy of the x-rays to greater values ​​occurs due to the multichromatic nature of the radiation emitted by the x-ray source and to the energy-dependent absorption of the x-rays in the body of the patient under examination. This effect is called ray hardening (Strahlaufhaertung). This effect is stronger the longer the path of transmission in the body. This radiation hardening effect leads to undesired image distortions in the reconstructed image of the transmitted tomography, which distortions impede a medically accurate interpretation of this image.

[0003] To correct such image distortions due to radiation hardening, standard algorithms are known (e.g. so-called polynomial corrections) which lead to satisfactory results, e.g. as long as the spectral absorption...

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