Model-based scatter correction for computed tomography

An apparatus, comprising:

• a memory storing pre-calculated scatter values representing angle-dependent scatter for X-ray radiation from a first part of a computed tomography (CT) scanner, the first part being arranged to have a position and orientation that is constant relative to an X-ray source of the CT scanner, when the CT scanner is rotated according to a plurality of views;
• and
• circuitry configured to
• obtain projection data representing an intensity of X-ray radiation transmitted from the X-ray source, through an object, and detected at a plurality of detector elements of the CT scanner, the projection data being obtained for the plurality of views, which correspond to respective projection angles of the X-ray source relative to the object,
• reconstruct, using the projection data, an image of the object to generate a spatial model of scatter of X-ray radiation from the object,
• simulate, for one or more views of the plurality of views, a scatter flux of the one or more views representing an intensity of scattered X-ray radiation detected at the plurality of detector elements, the scatter flux of the one or more views being simulated using a scatter simulation method that uses the pre-calculated scatter values to simulate a scatter flux from the first part, and
• determine, using the simulated scatter flux of the one or more views and a scatter simulation method, primary flux of the plurality of views, the primary flux representing an intensity of X-rays that have not been scattered, which are incident on the plurality of detector elements, wherein
• the circuitry is further configured to simulate the scatter flux of the one or more views using the pre-calculated scatter values to simulate the scattering by the first part, wherein the first part is one of a filter and an anti-scatter grid.

A method, comprising:

• obtaining projection data representing an intensity of X-ray radiation transmitted through an object and detected at a plurality of detector elements, the projection data being obtained for a plurality of views corresponding to respective projection angles relative to the object,
• reconstructing, using the projection data, an image of the object to generate a spatial model of scatter of the X-ray radiation from the object,
• simulating, for one or more views of the plurality of views, a scatter flux of the one or more views representing an intensity of scattered X-ray radiation detected at the plurality of detector elements, the intensity of scattered X-ray radiation being determined using a radiative transfer equation (RTE) method based on integrating a radiative transfer equation, and
• determining, using the simulated scatter flux of the one or more views and an accelerated method, which is accelerated relative to the RTE method, primary flux of the plurality of views, the primary flux representing an intensity of X-rays that are incident on the plurality of detector elements without being scattered, wherein
• a combination of simulating the scatter flux of the one or more views using the RTE method together with determining of the primary flux using the accelerated method is quicker than a method determining the primary flux using the RTE method to simulate scatter flux for all views of the plurality of views.