.. _ParallelBeamModelDocs:

===================
Parallel Beam Model
===================

The ``ParallelBeamModel`` class implements a geometry and reconstruction model for parallel-beam computed tomography.
This class inherits all behaviors and attributes of the :ref:`TomographyModelDocs`.
It also implements some parallel-beam specific functions such as FBP (Filtered Back Projection) reconstruction.

Note that for parallel-beam geometry the default value of ``delta_voxel`` = ``delta_det_channel`` = 1 ALU,
which results in pixel spacing that is the same as detector channel spacing.
However, these parameters can be changed by the user with the ``TomographyModel.set_params()`` method.
The spacing between slices of the reconstruction are fixed to be the same as the spacing between detector rows.

See the API docs for the :class:`~mbirjax.TomographyModel` class for details on a wide range
of functions that can be implemented using the ``ParallelBeamModel``.

Constructor
-----------

.. autoclass:: mbirjax.ParallelBeamModel
   :show-inheritance:

Alternative Reconstruction
--------------------------

.. automethod:: mbirjax.ParallelBeamModel.fbp_recon