A method includes accumulating counts for each pixel in a set of pixels of one or more gamma cameras of a SPECT imaging system from a plurality of imaging examinations and each energy peak of each isotope used in the plurality of imaging examinations to produce an energy spectrum for each of the pixels at each of the energy peaks of each of the isotopes, determining, for the pixels and for the energy peaks, an energy calibration factor that converts an energy detected by each of the pixels to an energy of a corresponding energy peak and populating an energy map with the factors, and determining, for the pixels and for the energy peaks, a uniformity calibration factor that converts a number of counts detected by each of the pixels to a predetermined number of counts for a corresponding energy peak and populating a uniformity map with the factors.

A method of processing radiation from a source is described comprising: positioning a detector to receive radiation from the source; positioning a collimator between the source and the detector, wherein the collimator has a plurality of apertures; allowing radiation from the source to pass through the collimator and be incident upon the detector; receiving a plurality of responses each being a response to an interaction with incident radiation occurring within the detector; determining, for each of the plurality of responses, a characteristic of the interaction, wherein the characteristic comprises at least a position and depth of the interaction within the detector; processing the said plurality of responses by simultaneously processing position and depth of interaction data in such manner as to accommodate the effect of multiplexing due to overlap of the projected radiation pathways from multiple apertures in the collimator at the detector on the detected position on the detector. A radiation detection system for the detection of radiation from a source, in particular to perform the method, is also described.

A sensitivity calibration method includes: obtaining a mapping relationship between a plurality of groups of calibration parameters and a plurality of state variations of a target system; obtaining a first energy response during a first time period and a second energy response during a second time period; wherein the target system is in a first state during the first time period, and the target system is in a second state during the second time period; determining a state variation of the target system in the second state relative to the first state based on a comparison result of the first energy response and the second energy response; calibrating a sensitivity of the target system based on the mapping relationship between the plurality of groups of calibration parameters of the target system and the plurality of state variations of the target system and the current state variation of the target system.