Reconstructing PET image

Patent metadata

Field	Value
Publication number	US-10460480-B2
Application number	US-201715819334-A
Country	US
Kind code	B2
Filing date	Nov 21, 2017
Priority date	Nov 24, 2016
Publication date	Oct 29, 2019
Grant date	Oct 29, 2019

Abstract

Methods, devices, and systems for reconstructing Positron Emission Computed Tomography (PET) images are provided. In one aspect, a method includes: for each of coincidence events including at least one true coincidence event and at least one scattering coincidence event, determining an emission path of the coincidence event according to photon information of the coincidence event, the photon information of the coincidence event including time data, position data, and angle data of each of two photons involved in the coincidence event, determining an annihilation position of the coincidence event according to the emission path of the coincidence event and the time data of each of the two photons involved in the coincidence event, and reconstructing a PET image according to the annihilation position, the emission path and the photon information of each of the coincidence events.

First claim

The invention claimed is:

1. A method of reconstructing a Positron Emission Computed Tomography (PET) image, the method comprising:
for each of coincidence events comprising at least one true coincidence event and at least one scattering coincidence event,
determining an emission path of the coincidence event according to photon information of the coincidence event, wherein the photon information of the coincidence event comprises time data, position data, and angle data of each of two photons involved in the coincidence event;
determining an annihilation position of the coincidence event according to the emission path of the coincidence event and the time data of each of the two photons involved in the coincidence event; and

reconstructing the PET image according to the annihilation position, the emission path and the photon information of each of the coincidence events.

2. The method of claim 1 , wherein determining the emission path of the coincidence event comprises:
for each of the two photons involved in the coincidence event, obtaining a respective emission path according to the position data and the angle data of the photon; and
determining an intersecting point of the respective emission paths of the two photons to obtain the emission path of the coincidence event.

3. The method of claim 2 , further comprising:
for each of the photons involved in the coincidence event, obtaining respective incidence intersecting positions on at least two crystal layers of a crystal array, the incidence intersecting positions indicating a travelling trace of the photon incident into the crystal array; and
obtaining the angle data of the photon incident into the crystal array according to the respective incidence intersecting positions.

4. The method of claim 3 , wherein the position data of the photon includes an incidence intersecting position of the photon on a crystal layer at which the photon arrives finally in the crystal array.

5. The method of claim 1 , wherein determining the annihilation position of the coincidence event comprises:
obtaining a difference of traveling time of the two photons before detected according to the time data of each of the two photons involved in the coincidence event;
determining a difference of traveling distance of the two photons along the emission path according to a velocity of light and the traveling time difference; and
determining the annihilation position in the emission path according to the traveling distance difference and the emission path.

6. The method of claim 1 , further comprising:
performing a random correction to remove a random coincidence event from the coincidence events before determining the respective emission paths of the coincidence events.

7. The method of claim 6 , wherein performing the random correction comprises:
delaying a respective single event in each of the coincidence events by a period of time to obtain delayed coincidence data, a length of the period of time being larger than a coincidence time window; and
removing the delayed coincidence data from coincidence data of the coincidence events.

8. The method of claim 6 , wherein performing the random correction comprises:
for each of the coincidence events, obtaining a Line of Response associated with the determined emission path;
obtaining respective single photon counting rates of two crystals associated with the Line of Response;
determining random coincidence data for the Line of Response according to the single photon counting rates of the two crystals and a coincidence time window; and
removing the random coincidence data for the Line of Response from coincidence data of the coincidence events.

9. The method of claim 1 , wherein reconstructing the PET image according to the annihilation position, the emission path and the photon information of each of the coincidence events comprises:
determining one or more model parameters of an image reconstruction model according to the annihilation position, the emission path and the photon information of each of the coincidence events;
constructing the image reconstruction model according to the model parameters;
deriving an iterative reconstruction formula from the image reconstruction model; and
reconstructing the PET image with the iterative reconstruction formula.

10. The method of claim 9 , wherein the image reconstruction model is expressed as:
Y j =P ij X i A j N j +R j ,
wherein j represents an emission path of the coincidence event,
Y j represents coincidence data of the coincidence event on the emission path j,
X i represents an i-th voxel in the PET image,
P ij represents a probability that the i-th voxel is received by the emission path j,
A j represents an attenuation probability on the emission path j,
N j represents a normalization factor on the emission path j, and
R j represents random coincidence data on the emission path j, and

wherein determining the one or more model parameters of the image reconstruction model comprises:
obtaining j from the determined emission paths of the coincident events,
determining A j and N j based on the emission path j,
determining X i based on the annihilation position, and
determining P ij based on the angle data and the time data of two crystals involved in the i-th voxel and the emission path j.

11. A device for reconstructing a PET image, the device comprising:
a processor; and
a machine-readable storage medium to store machine-executable instructions corresponding to logic for reconstructing a PET image,
by reading and executing the machine-executable instructions, the processor is caused to:
for each of coincidence events comprising at least one true coincidence event and at least one scattering coincidence event,
determine an emission path of the coincidence event according to photon information of the coincidence event, wherein the photon information of the coincidence event comprises time data, position data, and angle data of each of two photons involved in the coincidence event;
determine an annihilation position of the coincidence event according to the emission path of the coincidence event and the time data of each of the two photons involved in the coincidence event; and

reconstruct the PET image according to the annihilation position, the emission path and the photon information of each of the coincidence events.

12. The device of claim 11 , wherein, for determining the emission path of the coincidence event, the machine-executable instructions cause the processor to:
for each of the two photons involved in the coincidence event, obtain a respective emission path according to the position data and the angle data of the photon; and
determine an intersecting point of the respective emission paths of the two photons to obtain the emission path of the coincidence event.

13. The device of claim 12 , wherein the machine-executable instructions further cause the processor to:
for each of the photons involved in the coincidence event, obtain respective incidence intersecting positions on at least two crystal layers of a crystal array, the incidence intersecting positions indicating a travelling trace of the photon incident into the crystal array; and
obtain the angle data of the photon incident into the crystal array according to the respective incidence intersecting positions.

14. The device of claim 13 , wherein the position data of the photon includes an incidence intersecting position of the photon on a crystal layer at which the photon arrives finally in the crystal array.

15. The device

Assignees

• Shenyang Neusoft Medical Sys

Inventors

• Liu Yue
• Sun Zhipeng
• Li Ming

Classifications

• G06T12/20

  Inverse problem, i.e. transformations from projection space into object space · CPC title

• G06T12/10 Primary

  Image preprocessing, e.g. calibration, positioning of sources or scatter correction · CPC title

• G06T12/00 Primary

  Tomographic reconstruction from projections · CPC title

• A61B6/5282

  due to scatter · CPC title

• G06T7/0012

  Biomedical image inspection · CPC title