Method and apparatus for computed tomography using asymetric filter for volume half reconstruction

A computed-tomography (CT) apparatus, comprising:

• a radiation source radiating radiation into an object space;
• a plurality of detector elements configured to detect the radiation transmitted from the radiation source and through the object space, the plurality of detector elements configured to generate projection data;
• a rotation mount configured to rotate the radiation source around the object space, wherein the radiation source is fixedly connected to the rotation mount;
• and
• processing circuitry configured to
• obtain the projection data representing an irradiance of the radiation detected at the plurality of detectors, the radiation having been transmitted through the object space,
• calculate first weighted data by weighting the projection data using short-scan weights,
• calculate second weighted data by weighting the projection data using difference weights representing a difference between full-scan weights and the short-scan weights,
• filter the second weighted data using a view-dependent filter, which is defined by a function having at least one variable of a projection angle corresponding to a center view of a short-scan subset of the projection data,
• combine the first weighted data with the filtered second weighted data to obtain combined weighted data, and
• reconstruct an image from the combined weighted data using a computed-tomography image reconstruction method.

An image-processing apparatus, comprising:

• an interface configured to receive projection data representing an irradiance of radiation detected at a plurality of detectors;
• and
• processing circuitry configured to
• reconstruct a full-scan image using the projection data,
• reconstruct a short-scan image using the projection data,
• generate a difference image by obtaining a difference between the full-scan image and the short-scan image,
• filter the difference image using an asymmetric filter, which is defined by a function having at least one variable of a projection angle corresponding to a center view of a short-scan subset of the projection data, and
• combine the filtered difference image with the short-scan image to obtain a corrected short-scan image.