A projector using the ASTRA toolbox: the ASTRAProjector module

class nnfbp.ASTRAProjector.ASTRAProjector2D(proj_geom, vol_geom, offsets=None)

Bases: object

Implementation of the projector interface using the ASTRA toolbox with CUDA.

A projector needs to implement:

• Forward projecting
• Back projecting
• Creating a FBP reconstruction with a custom filter

You can use this class as an abstracted weight matrix \(W\): multiplying an instance proj of this class by an image results in a forward projection of the image, and multiplying proj.T by a sinogram results in a backprojection of the sinogram:

proj = ASTRAProjector2D(...)
fp = proj*image
bp = proj.T*sinogram

Parameters:

• proj_geom (dict) – The projection geometry.
• vol_geom (dict) – The volume geometry.
• offsets (numpy.ndarray) – Optional offsets for the detectors

backProject(sinogram)

Backproject a sinogram.

Parameters:sinogram (numpy.ndarray) – The sinogram data Returns:numpy.ndarray – The backprojection.

forwProject(image)

Forward project an image.

Parameters:image (numpy.ndarray) – The image data. Returns:numpy.ndarray – The forward projection.

reconstruct(method, sinogram, nIters=1, fbpfilter=None)

Helper function to reconstruct a sinogram using the ASTRA toolbox.

This function does not have to be implemented by other projectors, as it is not used by PyNN-FBP.

Parameters:

• method (string) – Name of the reconstruction algorithm.
• sinogram (numpy.ndarray) – The sinogram data
• nIters (int) – Number of iterations to run.
• fbpfilter (string) – Optional string to specify FBP filter (hamming, hann, etc)

Returns:

numpy.ndarray – The reconstruction.

reconstructWithFilter(sinogram, filt)

Create a FBP reconstruction of the sinogram with a custom filter

Parameters:

• sinogram (numpy.ndarray) – The sinogram data
• filt (numpy.ndarray) – 1D custom filter

Returns:

numpy.ndarray – The reconstruction.

class nnfbp.ASTRAProjector.ASTRAProjector2DTranspose(parentProj)

Implements the proj.T functionality.

Do not use directly, since it can be accessed as member .T of an ASTRAProjector2D object.