System and method for image reconstruction in positron emission tomography

1 . A positron emission tomography (PET) system, comprising:

a plurality of detector units arranged along an axial direction, each detector unit of the plurality of detector units being configured to generate a plurality of single event counts;

a plurality of distributed coincidence logic circuits, each distributed coincidence logic circuit of the plurality of distributed coincidence logic circuits being operably connected to at least one of the plurality of detector units, wherein the plurality of single event counts generated by the each detector unit is transmitted, through a data bus, to all of the distributed coincidence logic circuits of the plurality of distributed coincidence logic circuits that are connected to the each detector unit, the each distributed coincidence logic circuit being configured to:

obtain the single event counts generated by the at least one of the plurality of detector units that is connected to the each distributed coincidence logic circuit; and

generate one or more coincidence counts relating to the at least one of the plurality of detector units synchronically with the rest of the plurality of distributed coincidence logic circuits; and

a computing system configured to reconstruct an image by performing, based on a plurality of coincidence counts generated by the plurality of distributed coincidence logic circuits, forward projection calculation and backward projection calculation.

2 . The system of claim 1 , wherein the computing system includes a plurality of computing nodes, and each of the plurality of computing nodes connects to one or more of the plurality of distributed coincidence logic circuits, and the plurality of computing nodes synchronically determine directions of forward projection and backward projection according to a coincidence pairing relation of the plurality of detector units.

3 . The system of claim 1 , wherein

the plurality of detector units include a first detector unit and a second detector unit;

the first detector unit is spaced apart from the second detector by at least another detector unit of the plurality of detector units; and

at least a portion of coincidence events corresponding to the plurality of coincidence counts include intra-unit coincidence events acquired by the first detector unit, and cross-unit coincidence events acquired by the first detector unit and the second detector unit.

4 . The system of claim 1 , wherein single event data generated by the plurality of detector units is unevenly distributed to the plurality of distributed coincidence logic circuits for coincidence counting.

5 . The system of claim 1 , wherein at least part of the plurality of distributed coincidence logic circuits perform coincidence counting for single event data from a unit single detector unit.

6 . The system of claim 1 , wherein a count of the plurality of distributed coincidence logic circuits is equal to a count of the plurality of detector units in the PET system.

7 . The system of claim 6 , wherein each of the plurality of distributed coincidence logic circuits is provided on a corresponding detector unit.

8 . The system of claim 1 , wherein a count of the plurality of distributed coincidence logic circuits is smaller than a count of the plurality of detector units in the PET system.

9 . The system of claim 1 , wherein

the computing system includes a first processor connected to the plurality of distributed coincidence logic circuits;

the one or more coincidence counts generated by the each distributed coincidence logic circuit are transmitted to the first processor;

the first processor performs backward projection of the one or more coincidence counts; and

the computing system performs forward projection based on the backward projection.

10 . The system of claim 1 , wherein:

the computing system includes a plurality of first processors;

each of the first processors is connected to one or more of the plurality of distributed coincidence logic circuits;

the one or more coincidence counts generated by the each distributed coincidence logic circuit are transmitted to each of the plurality of first processors; and

the plurality of first processors synchronically perform backward projection of the plurality of coincidence counts.

11 . The system of claim 10 , wherein the one or more coincidence counts generated by the each distributed coincidence logic circuit is transmitted to the each of the plurality of first processors randomly.

12 . The system of claim 10 , wherein:

the computing system further includes a second processor;

the second processor is connected to the plurality of first processors;

a result of backward projection generated by each of the plurality of first processors is transmitted to the second processor;

the second processor superimposes the results of backward projection; and

the computing system performs forward projection based on the superimposed result of backward projection.

13 . The system of claim 3 , wherein the first detector unit matches with the second detector unit according with a pairing rule, the pairing rule comprising:

numbering the plurality of detector units in a sequential order, wherein the Nth detector unit only matches a detector unit associated with a number that is subsequent to N, wherein N is less than K, wherein Kis the total number of the detector units, and wherein N and K are natural numbers.

14 . The system of claim 1 , wherein the computing system includes a plurality of computing nodes, and each of the plurality of computing nodes connects to a portion of the plurality of coincidence logic circuits.

15 . The system of claim 1 , wherein

the plurality of detector units are numbered in a sequential order;

one of the plurality of coincidence logic circuits is configured to only perform a coincidence count for two single events from an Nth detector unit of the plurality of detector units and a coincidence count for two single events that are from the Nth detector unit and one of the plurality of detector units that is with a number subsequent to N;

N is less than a total number of the plurality of detector units.

16 . The system of claim 2 , wherein the computing system includes an image accumulation node connected with the plurality of computing nodes, the plurality of computing nodes synchronically generate a plurality of backward projection images by using an Ordered Subsets Expectation Maximization (OSEM) technique, the plurality of backward projection images are transmitted to the image accumulation node to be accumulated, and the backward projection images which are accumulated undergo a next forward projection.

17 . The system of claim 1 , wherein each of at least one of the plurality of distributed coincidence logic circuits is connected to at least three detector units of the plurality of detector units.

18 . A method for image reconstruction in a PET system, comprising:

generating, by each detector unit of a plurality of detector units arranged along an axial direction, a plurality of single event counts;

transmitting single event data generated by the each detector unit to one or more of a plurality of coincidence logic circuits, wherein each of the plurality of coincidence logic circuits is operably connected to one or more of the plurality of detector units;

generating coincidence counts relating to the plurality of detector units synchronically with the rest of the plurality of coincidence logic circuits, wherein a single coincidence logic circuit of the plurality of coincidence logic circuits is configured to perform a coincidence count for two single events from the same detector unit, and perform a coincidence count for two single events that are from two different detector units respectively; and

reconstructing an image by performing, based on the coincidence counts, forward projection calculation and backward projection calculation.

19 . The method of claim 18 , wherein the reconstructing an image comprising:

determining a direction of backward projection according to a coincidence pairing relation of one or more detector units relating to each of the coincidence counts; and

performing the forward projection calculation and the backward projection calculation based on the direction.

20 . A non-transitory computer readable medium storing instructions, the instructions, when executed by at least one processor, causing the at least one processor to implement a method for image reconstruction in a positron emission tomography (PET) system comprising:

generating, by each detector unit of a plurality of detector units arranged along an axial direction, a plurality of single event counts;

transmitting single event data generated by the each detector unit to one or more of a plurality of coincidence logic circuits, wherein each of the plurality of coincidence logic circuits is operably connected to one or more of the plurality of detector units;

for each of the plurality of coincidence logic circuits, generating, by the coincidence logic circuit, one or more coincidence counts relating to the one or more of the plurality of detector units synchronically with the rest of the plurality of coincidence logic circuits, wherein a single coincidence logic circuit of the plurality of coincidence logic circuits is configured to perform a coincidence count for two single events from the same detector unit and perform a coincidence count for two single events that are from two non-adjacent detector units respectively, and the two non-adjacent detector units refer to two of the plurality of detector units that are separated, along the axial direction, by at least one other detector unit of the plurality of detector units; and

reconstructing an image by performing, based on the coincidence counts, forward projection calculation and backward projection calculation.