METHODS AND SYSTEMS FOR IMAGE PROCESSING

1 . A method for image processing, implemented on a computing device having at least one processor and at least one storage device, comprising:

obtaining first positron emission tomography (PET) data and second PET data of a subject;

determining, based on the first PET data, first reference data relating to first target events occurred in the first PET scan, the first target events at least including first backscatter events;

determining, based on the second PET data, second reference data relating to second target events occurred in the second PET scan, the second target events at least including second backscatter events; and

determining a motion vector field based on the first reference data and the second reference data.

2 . The method of claim 1 , wherein the first target events further include first background events, the second target events further include second background events, the first background events and the second background events are caused by radioactive decay of a crystal material.

3 . The method of claim 1 , wherein the first reference data and the second reference data are determined by:

determining coincident windows, the coincident windows including a first energy window, a second energy window, and a time window;

determining, based on the first PET data and the coincident windows, the first reference data relating to the first target events occurred in the first PET scan; and

determining, based on the second PET data and the coincident windows, the second reference data relating to the second target events occurred in the second PET scan.

4 . The method of claim 1 , wherein the determining a motion vector field based on the first reference data and the second reference data includes:

generating a first attenuation image of the subject based on the first reference data;

generating a second attenuation image of the subject based on the second reference data; and

determining the motion vector field based on the first attenuation image and the second attenuation image of the subject.

5 . The method of claim 4 , wherein the generating a first attenuation image of the subject based on the first reference data includes one or more iterations, each of the iterations comprises:

determining an initial attenuation image and an initial PET image of the iteration;

determining third reference data relating to third target events occurred in a blank scan without the subject based on the initial attenuation image and the initial PET image;

generating an updated attenuation image by updating the initial attenuation image based on the third reference data and the first reference data;

generating an updated PET image by updating the initial PET image based on the updated attenuation image and the first PET data; and

determining the first attenuation image of the subject based on the updated PET image.

6 . The method of claim 5 , wherein the third target events include third backscatter events and third background events, and the determining third reference data includes:

determining the third reference data relating to the third backscatter events based on the initial attenuation image and the initial PET image;

obtaining blank scan data collected by performing the blank scan; and

determining the third reference data relating to the third background events based on the blank scan data.

7 . The method of claim 5 , wherein each iteration further comprising:

determining fourth reference data relating to scatter events in the first target events and fifth reference data relating to random events in the first target events, wherein the updated attenuation image is determined further based on the fourth reference data and the fifth reference data.

8 . The method of claim 1 , further comprising:

obtaining an anatomical image;

generating a corrected anatomical image matching a PET image corresponding to the second PET data by processing the anatomical image based on the motion vector field; and

generating an attenuation corrected PET image based on the PET image and the corrected anatomical image.

9 . The method of claim 8 , wherein the anatomical image includes a computed tomography (CT) image or a magnetic resonance (MR) image.

10 . The method of claim 8 , wherein the first PET data is collected by a first PET scan performed on the subject at a first time, and the second PET data is collected by a second PET scan performed on the subject at a second time.

11 . The method of claim 10 , wherein the anatomical image is collected by an anatomical scan performed on the subject at the first time.

12 . The method of claim 10 , wherein the anatomical image is collected by an anatomical scan performed on the subject at any time other than the first time and the second time.

13 . The method of claim 10 , wherein the second time is before or after the first time, and the second PET scan is performed before or after the first PET scan.

14 . The method of claim 1 , further comprising:

obtaining an anatomical image;

generating a corrected anatomical image matching a PET image corresponding to the second PET data by processing the anatomical image based on the motion vector field; and

performing at least one of image segmentation or treatment plan planning based on at least the corrected anatomical image.

15 . A system, comprising:

at least one storage device including a set of instructions; and

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 causes the system to perform operations including:

obtaining first positron emission tomography (PET) data and second PET data of a subject;

determining, based on the first PET data, first reference data relating to first target events occurred in the first PET scan, the first target events at least including first backscatter events;

determining, based on the second PET data, second reference data relating to second target events occurred in the second PET scan, the second target events at least including second backscatter events; and

determining a motion vector field based on the first reference data and the second reference data.

16 . The system of claim 15 , wherein the first target events further include first background events, the second target events further include second background events, the first background events and the second background events are caused by radioactive decay of a crystal material.

17 . The system of claim 15 , wherein the first reference data and the second reference data are determined by:

determining coincident windows, the coincident windows including a first energy window, a second energy window, and a time window;

determining, based on the first PET data and the coincident windows, the first reference data relating to the first target events occurred in the first PET scan; and

determining, based on the second PET data and the coincident windows, the second reference data relating to the second target events occurred in the second PET scan.

18 . The system of claim 15 , wherein the determining a motion vector field based on the first reference data and the second reference data includes:

generating a first attenuation image of the subject based on the first reference data;

generating a second attenuation image of the subject based on the second reference data; and

determining the motion vector field based on the first attenuation image and the second attenuation image of the subject.

19 . The system of claim 15 , wherein the operations further comprise:

obtaining an anatomical image;

generating a corrected anatomical image matching a PET image corresponding to the second PET data by processing the anatomical image based on the motion vector field; and

generating an attenuation corrected PET image based on the PET image and the corrected anatomical image.

20 . A non-transitory computer readable medium, comprising executable instructions that, when executed by at least one processor, direct the at least one processor to perform a method, the method comprising:

obtaining first positron emission tomography (PET) data and second PET data of a subject;

determining, based on the first PET data, first reference data relating to first target events occurred in the first PET scan, the first target events at least including first backscatter events;

determining, based on the second PET data, second reference data relating to second target events occurred in the second PET scan, the second target events at least including second backscatter events; and

determining a motion vector field based on the first reference data and the second reference data.