Systems and methods for determining true coincidence events

A method for determining true coincidence events, implemented on a computing device including at least one processor, at least one storage device, and a communication platform connected to a network, comprising:

• determining original coincidence events based on time of occurrence of a plurality of single events;
• determining random coincidence events by processing the plurality of single events based on cycle offsets of detector units that detect the plurality of single events, wherein a difference of any two cycle offsets is greater than a predetermined coincidence window width;
• and
• determining the true coincidence events based on the original coincidence events and the random coincidence events, wherein the determining original coincidence events comprises:
• obtaining a cycle difference between a first clock cycle at which a first single event occurs and a second clock cycle at which a second single event occurs;
• obtaining a first time-to-digital converter (TDC) value of the first single event and a second TDC value of the second single event;
• determining a time difference between a time of occurrence of the first single event and a time of occurrence of the second single event based on the cycle difference, the first TDC value, and the second TDC value;
• and
• in response to a determination that the time difference is less than the predetermined coincidence window width, determining the first single event and the second single event as an original coincidence event.

A system for determining true coincidence events, comprising:

• at least one storage device including a set of instructions;
• at least one processor in communication with the at least one storage device, wherein when executing the set of instructions, the at least one processor is configured to cause the system to:
• determine original coincidence events based on time of occurrence of a plurality of single events;
• determine random coincidence events by processing the plurality of single events based on cycle offsets of detector units that detect the plurality of single events, wherein a difference of any two cycle offsets is greater than a predetermined coincidence window width;
• and
• determine the true coincidence events based on the original coincidence events and the random coincidence events, wherein to determine original coincidence events, the at least one processor is further configured to cause the system to:
• obtain a cycle difference between a first clock cycle at which a first single event occurs and a second clock cycle at which a second single event occurs;
• obtain a first time-to-digital converter (TDC) value of the first single event and a second TDC value of the second single event;
• determine a time difference between a time of occurrence of the first single event and a time of occurrence of the second single event based on the cycle difference, the first TDC value, and the second TDC value;
• and
• in response to a determination that the time difference is less than the predetermined coincidence window width, determine the first single event and the second single event as an original coincidence event.