TECHNICAL FIELD

This disclosure generally relates to systems and methods for image reconstruction, and more particularly, relates to systems and methods for reconstructing a positron emission tomography (PET) image.

BACKGROUND

Motions (e.g., a respiratory motion, a cardiac motion) during PET scans can cause resolution degradation and introduce artifacts in a PET image that affect diagnoses performed on the basis of the PET image. For example, the respiratory motion of a subject leads to motion artifacts and blurring in the PET image, which hinders an accurate detection, localization and quantification of possible lesions and tumors. Respiratory gating techniques have been developed to reduce motion blurring effects by dividing PET data into a plurality of bins or sections based on a motion signal. Each section corresponds to a certain respiratory phase with reduced motion blurring. Since each section only contains a fraction of the total count of detected coincidence events, the gain in resolving involuntary motion through gating is compromised by the increase of noise when the PET data is divided into too many bins. Thus, it is desirable to develop methods and systems for reconstructing data acquired by a scanner with reduced motion blur without over-gating of a region of the subject that is not significantly affected by a motion of the subject during the scanning.

SUMMARY

According to an aspect of the present disclosure, a method for reconstructing a positron emission tomography (PET) image may be implemented on a computing device having one or more processors and one or more storage devices. The method may include obtaining PET data of a subject. The PET data may correspond to a plurality of voxels in a reconstructed image domain. The method may include obtaining a motion signal of the subject. The method may include obtaining motion amplitude data. The motion amplitude data may indicate a motion range for each voxel of the plurality of voxels. The method may include determining gating data based at least in part on the motion amplitude data. The gating data may include useful percentage counts each of which corresponds to at least one voxel of the plurality of voxels. The method may include gating the PET data based on the gating data and the motion signal. The method may include reconstructing a PET image of the subject based on the gated PET data.

In some embodiments, the method may include obtaining an attenuation map of the subject. The method may include determining the motion amplitude data based on the attenuation map.

In some embodiments, the method may include determining a plurality of intermediate images based on the PET data. The method may include determining a vector field for the plurality of voxels based on the plurality of intermediate images. The method may include determining the motion amplitude data based on the vector field.

In some embodiments, the plurality of intermediate images may be determined by performing a back-projection operation on the PET data.

In some embodiments, the plurality of intermediate images may be reconstructed by gating the PET data.

In some embodiments, the method may include obtaining a motion amplitude threshold. The method may include determining the gating data based on the motion amplitude data and the motion amplitude threshold.

In some embodiments, the motion amplitude threshold may relate to a desired spatial resolution of the reconstructed PET image.

In some embodiments, the method may include determining first processed motion amplitude data by performing a maximum intensity projection operation on the motion amplitude data. The method may include determining the gating data based on the first processed motion amplitude data and the motion amplitude threshold.

In some embodiments, the method may include determining second processed motion amplitude data by performing a projection operation on the motion amplitude data. The method may include determining the gating data based on the second processed motion amplitude data and the motion amplitude threshold.

In some embodiments, the method may include, for each voxel of the plurality of voxels, determining a useful percentage count for the voxel based on a motion range for the voxel and the motion amplitude threshold.

In some embodiments, the PET data may include TOF information. The PET data may correspond to a plurality of lines of response (LORs). Each LOR of the plurality of LORs may include a plurality of bins. Each bin of the plurality of bins may correspond to at least one voxel of the plurality of voxels in the reconstructed image domain. A length of each bin may relate to the TOF information. The method may include, for each LOR of the plurality of LORs, determining a useful percentage count for the each bin of the plurality of bins based on the motion amplitude data, the motion amplitude threshold, and the TOF information.

In some embodiments, a first motion range for a first voxel may correspond to a first useful percentage count. A second motion range for a second voxel may correspond to a second useful percentage count. The first useful percentage count may be different from the second useful percentage count.

In some embodiments, the first motion range may be greater than the second motion range. The first useful percentage count may be lower than the second useful percentage count.

According to an aspect of the present disclosure, a system for reconstructing a positron emission tomography (PET) image may include at least one storage device storing a set of instructions, and at least one processor in communication with the at least one storage device. When executing the stored set of instructions, the at least one processor may cause the system to perform a method. The method may include obtaining PET data of a subject. The PET data may correspond to a plurality of voxels in a reconstructed image domain. The method may include obtaining a motion signal of the subject. The method may include obtaining motion amplitude data. The motion amplitude data may indicate a motion range for each voxel of the plurality of voxels. The method may include determining gating data based at least in part on the motion amplitude data. The gating data may include useful percentage counts each of which corresponds to at least one voxel of the plurality of voxels. The method may include gating the PET data based on the gating data and the motion signal. The method may include reconstructing a PET image of the subject based on the gated PET data.

In some embodiments, the method may include obtaining an attenuation map of the subject. The method may include determining the motion amplitude data based on the attenuation map.

In some embodiments, the method may include determining a plurality of intermediate images based on the PET data. The method may include determining a vector field for the plurality of voxels based on the plurality of intermediate images. The method may include determining the motion amplitude data based on the vector field.

In some embodiments, the plurality of intermediate images may be determined by performing a back-projection operation on the PET data.

In some embodiments, the plurality of intermediate images may be reconstructed by gating the PET data.

In some embodiments, the method may include obtaining a motion amplitude threshold. The method may include determining the gating data based on the motion amplitude data and the motion amplitude threshold.

According to still another aspect of the present disclosure, a non-transitory computer readable medium may include at least one set of instructions. When executed by at least one processor of a computing device, the at least one set of instructions may cause the at least one processor to effectuate a method. The method may include obtaining PET data of a subject. The PET data may correspond to a plurality of voxels in a reconstructed image domain. The method may include obtaining a motion signal of the subject. The method may include obtaining motion amplitude data. The motion amplitude data may indicate a motion range for each voxel of the plurality of voxels. The method may include determining gating data based at least in part on the motion amplitude data. The gating data may include useful percentage counts each of which corresponds to at least one voxel of the plurality of voxels. The method may include gating the PET data based on the gating data and the motion signal. The method may include reconstructing a PET image of the subject based on the gated PET data.

Additional features will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or may be learned by production or operation of the examples. The features of the present disclosure may be realized and attained by practice or use of various aspects of the methodologies, instrumentalities and combinations set forth in the detailed examples discussed below.

