Method and apparatus for performing single gating in positron emission tomograpy sytems
A method for performing single gating in a positron emission tomography (PET) system includes: receiving list-mode data acquired by scanning an imaging object using the PET system, the list-mode data being affected by quasi-periodic motion of the imaging object; producing a plurality of vectors based on the received list-mode data; generating a reference vector based on the produced plurality of vectors; selecting, from the produced plurality of vectors, a set of vectors corresponding to a single gate, based on respective differences compared with the generated reference vector; and generating an image of the imaging object based on the selected set of vectors.
1 . A method for processing list-mode data obtained by a positron emission tomography (PET) system scanning an imaging object, the method comprising:
dividing the list-mode data into a plurality of sets of data;
generating a first plurality of vectors corresponding to a different one of the plurality of sets of data;
generating a reference vector corresponding to a target respiration phase included in a cycle of a respiration of the imaging object based on a second plurality of vectors included in the first plurality of vectors, each of the second plurality of vectors corresponding to the target respiration phase;
selecting, from the plurality of sets of data, a set of data to be used to reconstruct an image, based on respective differences between the generated reference vector and the first plurality of vectors; and
generating the image based on the selected set of data.
2 . The method of claim 1 , further comprising:
obtaining information indicating a waveform of respiration of the imaging object, the waveform having a plurality of cycles,
wherein each of the second plurality of vectors corresponding to a different one of the target respiration phase in the plurality of cycles of the waveform, and
wherein the reference vector is generated by calculating an average of the second plurality of vectors.
3 . The method of claim 2 , wherein the target respiration phase includes:
a smallest amplitude point in a cycle of the waveform.
4 . The method of claim 2 , wherein the target respiration phase includes:
a point having a smallest derivative term in a cycle of the waveform, the derivative term being a first-order derivative of the waveform, a second-order derivative of the waveform, or a combination thereof.
5 . The method of claim 2 , wherein the information is acquired by a sensor detecting the respiration.
6 . The method of claim 1 , further comprising:
obtaining a count percentage (P %) indicating a ratio of a number of the selected set of data to a number of the plurality of sets of data each corresponding to a different one of the first plurality of vectors, and
determining, as the selected set of data, a first P % of the plurality of sets of data when ranked from smallest difference to largest difference, compared with the reference vector.
7 . The method of claim 6 , further comprising:
sorting, based on the respective differences, the first plurality of vectors to create a curve, the created curve representing a relationship between a count percentage of the first plurality of vectors and a corresponding variation of the respective differences,
identifying a turning point on the created curve, and
deriving, as the obtained count percentage, a count percentage corresponding to the identified turning point on the created curve.
8 . The method of claim 1 , wherein the target respiration phase is designated by a user of the PET system.
9 . The method of claim 1 , wherein the respective differences are calculated as one of:
a Euclidian distance between the generated reference vector and the first plurality of vector,
a covariance between the generated reference vector and the first plurality of vector,
a mean squared error (MSE) between the generated reference vector and the first plurality of vector, and
an L1 norm distance between the generated reference vector and the first plurality of vector.
10 . The method of claim 1 , further comprising generating a plurality of sinograms, each corresponding to a different one of the plurality of sets of data,
wherein each of the first plurality of vectors indicates a different one of the plurality of sinograms.
11 . The method of claim 1 , wherein each of the plurality of vectors is a different one of a plurality of images reconstructed based on the plurality of sets of data.
12 . The method of claim 1 , wherein the information is acquired by analyzing the first plurality of vectors.
13 . The method of claim 1 , further comprising generating a plurality of sinograms, each corresponding to a different one of the plurality of sets of data,
wherein each of the first plurality of vectors indicates a different one of downsampled plurality of sinograms obtained by performing downsampling on the generated plurality of sinograms.
14 . The method of claim 1 , further comprising generating a plurality of sinograms, each corresponding to a different one of the plurality of sets of data,
wherein each of the first plurality of vectors indicates a different one of a plurality of latent vectors extracted from the generated plurality of sinograms.
15 . The method of claim 1 , further comprising generating a plurality of images, each corresponding to a different one of the plurality of sets of data,
wherein each of the plurality of vectors indicates a different one of downsampled plurality of images obtained by performing downsampling on the generated plurality of images.
16 . The method of claim 1 , further comprising generating a plurality of images, each corresponding to a different one of the plurality of sets of data,
wherein each of the plurality of vectors indicates a different one of a plurality of latent vectors extracted from the generated plurality of images.
17 . The method of claim 1 , wherein the target respiration phase is a period included in the cycle of the respiration and a length of the period is shorter than a length of the cycle of the respiration.
18 . An apparatus for processing list-mode data obtained by a positron emission tomography (PET) system scanning an imaging object, the apparatus comprising:
processing circuitry configured to
divide the list-mode data into a plurality of sets of data;
generate a first plurality of vectors corresponding to a different one of the plurality of sets of data;
generate a reference vector corresponding to a target respiration phase included in a cycle of a respiration of the imaging object based on a second plurality of vectors included in the first plurality of vectors, each of the second plurality of vectors corresponding to the target respiration phase;
select, from the plurality of sets of data, a set of data to be used to reconstruct an image, based on respective differences between the generated reference vector and the first plurality of vectors; and
generate the image based on the selected set of data.