Abstract: The present application relates to a gain compensation method and module and a target voltage determination method. The gain compensation method includes: acquiring angle data of the photomultiplier tube of the detector; the angle data being used for representing a relative angle between the photomultiplier tube and an environmental magnetic field; and outputting a voltage compensation signal to an adjustable power supply circuit according to the angle data; the voltage compensation signal is used for instructing the adjustable power supply circuit to adjust a supply voltage output to each photomultiplier tube, so as to cause an output amplitude of the photomultiplier tube to reach an expected output amplitude.

Abstract: The embodiments of the present disclosure provide a state detection method and system for an imaging device. The method includes: obtaining a first background event of a crystal of a detector of the imaging device, the first background event being related to an inherent radiating particle of the crystal; correcting a crystal position look-up table based on the first background event; correcting an energy state of the imaging device; obtaining the second background event of the crystal, the second background event being related to the inherent radiating particle of the crystal; and correcting a state of time of flight of the detector based on the first background event and the second background event.