Apparatus, method and computer program for producing a corrected image of a region of interest from acquired projection data

A method for producing a corrected image of a region of interest from acquired projection data, wherein the method comprises following steps:

• reconstructing an uncorrected intermediate image of the region of interest from the acquired projection data by a reconstructing unit,
• correcting artifacts within the uncorrected intermediate image to generate a corrected intermediate image by a correction unit,
• classifying image elements of the corrected intermediate image at least into high density, medium density and low density classes,
• replacing image element values of image elements of the corrected intermediate image that are of the high density and low density classes by image element values which depend on the image element values of the low density class to generate a synthetic image by an image element replacement unit,
• forward projecting the synthetic image to generate synthetic projection data by a forward projecting unit,
• replacing acquired projection data contributing to the image elements of the high density class with corresponding synthetic projection data to generate corrected projection data by a projection replacement unit, and
• reconstructing a corrected image of the region of interest from the corrected projection data by a reconstructing unit;
• wherein the correcting further comprises identifying high density image elements within the uncorrected intermediate image for correcting artifacts generated by the high density image elements and wherein the classifying the image elements of the corrected intermediate image into the high density class by using the identified high density image elements of the uncorrected intermediate image such that the image elements of the high density class of the corrected intermediate image correspond to the identified high density image elements of the uncorrected intermediate image.

An apparatus for producing a corrected image of a region of interest from acquired projection data, the apparatus comprising:

• means for reconstructing an uncorrected intermediate image of the region of interest from the acquired projection data,
• means for correcting artifacts within the uncorrected intermediate image to generate a corrected intermediate image,
• means for classifying image elements of the corrected intermediate image at least into high density, medium density and low density classes,
• means for replacing image element values of image elements of the corrected intermediate image that are of the high density and low density classes by image element values which depend on the image element values of the low density class to generate a synthetic image,
• means for forward projecting the synthetic image to generate synthetic projection data, and
• means for replacing acquired projection data contributing to the image elements of the high density class with corresponding synthetic projection data to generate corrected projection data, wherein the means for reconstructing reconstructs a corrected image of the region of interest from the corrected projection data;
• wherein the means for correcting comprises means for identifying high density image elements within the uncorrected intermediate image for correcting artifacts generated by the high density image elements and wherein the classifying unit is adapted for classifying the image elements of the corrected intermediate image into the high density class by using the identified high density image elements of the uncorrected intermediate image such that the image elements of the high density class of the corrected intermediate image correspond to the identified high density image elements of the uncorrected intermediate image.