Method and apparatus for compensating for scattering of emission gamma photons for PET imaging

A method for operating a positron emission tomography (PET) seamier, the method comprising:

• acquiring, at a plurality of detector blocks of the PET scanner, emission data of 511 keV gamma photons originating from annihilation events associated with radioactivity of a phantom in a field of view of the PET scanner;
• based on the emission data, computing a histogram of counts of 511 keV gamma photons detected at respective detector blocks over a range of incident angles;
• computing a probability of scatter for 511 keV gamma photons as a function of scattering angle for each pair of detector blocks of the scanner, to obtain a set of scatter probabilities;
• for each detector block, computing a probability, for a given gamma photon scattering at said detector block, of scattering to each other detector block in a subset of the plurality of detector blocks, to provide detector block impact probabilities;
• and
• scaling the computed histogram of counts by the scatter probabilities and the block impact probabilities, to generate an emission block-pair scattering model.

A non-transitory machine-readable storage medium, tangibly embodying a program of instructions executable by a system controller to cause the system controller to perform operations comprising:

• acquiring, at a plurality of detector blocks of a PET scanner, emission data of gamma photons of a first energy level originating from annihilation events associated with radioactivity of a phantom in a field of view of the PET scanner;
• based on the emission data, generating an emission block-pair scattering model;
• acquiring counts of gamma photons of a second energy level originating from intrinsic background radiation of scintillator crystals of the detector blocks, without any phantom in the field of view, to provide blank scan data for the second energy level;
• generating a sinogram based on the blank scan data for the second energy level;
• and
• adding the emission block-pair scattering model to a scaled version of the sinogram, to yield a composite model.

A non-transitory machine-readable storage medium, tangibly embodying a program of instructions executable by a system controller to cause the system controller to perform operations comprising:

• acquiring, at a plurality of detector blocks of a PET scanner, emission data of 511 keV gamma photons originating from annihilation events associated with radioactivity of a phantom in a field of view of the PET scanner;
• based on the emission data, computing a histogram of counts of 511 keV gamma photons detected at respective detector blocks over a range of incident angles;
• computing a probability of scatter for 511 keV gamma photons as a function of scattering angle for each pair of detector blocks of the scanner, to obtain a set of scatter probabilities;
• for each detector block, computing a probability, for a given gamma photon scattering at said detector block, of scattering to each other detector block in a subset of the plurality of detector blocks, to provide detector block impact probabilities;
• and
• scaling the computed histogram of counts by the scatter probabilities and the block impact probabilities, to generate an emission block-pair scattering model.