Maintaining a given focal spot size during a kVp switched spectral (multi-energy) imaging scan

An image processing method, comprising:

• controlling an X-ray tube peak voltage of an X-ray radiation source to switch between at least two different X-ray tube peak voltages during a kVp switched spectral scan;
• and
• controlling a grid voltage of the X-ray radiation source to follow the X-ray tube voltage peak during the spectral scan based on a predetermined mapping between X-ray tube peak voltages and grid voltages for a particular focal spot size in order to maintain the particular focal spot size throughout the spectral scan, wherein the mapping is between X-ray tube peak voltages and grid voltages for each respective focal spot size of a plurality of focal spot sizes.

A non-transitory computer-readable storage medium storing computer executable instructions, which when executed by a processor, cause the processor to:

• control an X-ray tube peak voltage of an X-ray radiation source to switch between at least two different X-ray tube peak voltages during a kVp switched spectral scan;
• and
• control a grid voltage of the X-ray radiation source to follow the X-ray tube peak voltage during the spectral scan based on a predetermined mapping between X-ray tube peak voltages and grid voltages for a particular focal spot size to maintain the particular focal spot size throughout the spectral scan, wherein the mapping is between X-ray tube peak voltages and grid voltages for each respective focal spot size of a plurality of focal spot sizes.