pytomography.transforms.PET#

Submodules#

Package Contents#

Classes#

PETAttenuationTransform

proj2proj mapping used to model the effects of attenuation in PET.

PETPSFTransform

proj2proj transform used to model the effects of PSF blurring in PET. The smoothing kernel is assumed to be independent of \(\theta\) and \(z\), but is dependent on \(r\).

class pytomography.transforms.PET.PETAttenuationTransform(CT)[source]#

Bases: pytomography.transforms.Transform

proj2proj mapping used to model the effects of attenuation in PET.

Parameters:
  • CT (torch.tensor) – Tensor of size [batch_size, Lx, Ly, Lz] corresponding to the attenuation coefficient in \({\text{cm}^{-1}}\) at a photon energy of 511keV.

  • device (str, optional) – Pytorch device used for computation. If None, uses the default device pytomography.device Defaults to None.

configure(object_meta, proj_meta)[source]#

Function used to initalize the transform using corresponding object and projection metadata

Parameters:
  • object_meta (ObjectMeta) – Object metadata.

  • proj_meta (ProjMeta) – Projection metadata.

Return type:

None

forward(proj)[source]#

Applies forward projection of attenuation modeling \(B:\mathbb{V} \to \mathbb{V}\) to 2D PET projections.

Parameters:

proj (torch.Tensor) – Tensor of size [batch_size, Ltheta, Lr, Lz] which transform is appplied to

Returns:

Tensor of size [batch_size, Ltheta, Lr, Lz] corresponding to attenuation-corrected projections.

Return type:

torch.Tensor

backward(proj, norm_constant=None)[source]#

Applies back projection of attenuation modeling \(B^T:\mathbb{V} \to \mathbb{V}\) to 2D PET projections. Since the matrix is diagonal, its the backward implementation is identical to the forward implementation; the only difference is the optional norm_constant which is needed if one wants to normalize the back projection.

Parameters:
  • proj (torch.Tensor) – Tensor of size [batch_size, Ltheta, Lr, Lz] which transform is appplied to

  • norm_constant (torch.Tensor | None, optional) – A tensor used to normalize the output during back projection. Defaults to None.

Returns:

Tensor of size [batch_size, Ltheta, Lr, Lz] corresponding to attenuation-corrected projections.

Return type:

torch.tensor

class pytomography.transforms.PET.PETPSFTransform(kerns)[source]#

Bases: pytomography.transforms.Transform

proj2proj transform used to model the effects of PSF blurring in PET. The smoothing kernel is assumed to be independent of \(\theta\) and \(z\), but is dependent on \(r\).

Parameters:

kerns (Sequence[callable]) – A sequence of PSF kernels applied to the Lr dimension of the projections with shape [batch_size, Lr, Ltheta, Lz]

configure(object_meta, proj_meta)[source]#

Function used to initalize the transform using corresponding object and proj metadata

Parameters:
  • object_meta (ObjectMeta) – Object metadata.

  • proj_meta (ProjMeta) – Projection metadata.

Return type:

None

construct_matrix()[source]#

Constructs the matrix used to apply PSF blurring.

forward(proj)[source]#

Applies the forward projection of PSF modeling \(B:\mathbb{V} \to \mathbb{V}\) to a PET proj.

Parameters:

proj (torch.tensor]) – Tensor of size [batch_size, Ltheta, Lr, Lz] corresponding to the projections

Returns:

Tensor of size [batch_size, Ltheta, Lr, Lz] corresponding to the PSF corrected projections.

Return type:

torch.tensor

backward(proj, norm_constant=None)[source]#

Applies the back projection of PSF modeling \(B^T:\mathbb{V} \to \mathbb{V}\) to PET projections .

Parameters:
  • proj (torch.tensor]) – Tensor of size [batch_size, Ltheta, Lr, Lz] corresponding to the projections norm_constant (torch.tensor, optional): A tensor used to normalize the output during back projection. Defaults to None.

  • norm_constant (torch.Tensor | None) –

Returns:

Tensor of size [batch_size, Ltheta, Lr, Lz] corresponding to the PSF corrected projections.

Return type:

torch.tensor