Gain calibration and correction in radiation system

A method of calibrating a computed tomography (CT) system when a field of view is partially obstructed by an object, comprising:

• acquiring a projection, corresponding to a first view angle of a CT scan, from a calibration procedure performed while the field of view was partially obstructed by the object, the projection comprising object projection data indicative of radiation that traversed the object and calibration projection data indicative of radiation that did not traverse the object;
• separating the calibration projection data from the object projection data, the separating comprising:
• averaging measurements of the projection acquired from a plurality of detector cells to determine an average measurement for the projection;
• and
• comparing the average measurement for the projection to a measurement acquired from each detector cell of the plurality of detector cells to identify the calibration projection data;
• and
• computing one or more gain corrections as a function of the calibration projection data, the one or more gain corrections utilized during an examination procedure to correct measurements yielded from a detector array of the CT system.