
This directory has various system models for tomographic image reconstruction
and related problems.

@Fatrix
This object provides a general "container" for linear operations A*x and A'*y.

@Gblock
block system models (based on one of Gtomo2_dsc, Gtomo2_sparse, Gtomo2_wtfmex)
for ordered-subsets (aka block iterative) algorithms.  this is largely obsolete;
the newer @Fatrix object includes this functionality

@Gtomo2_dsc
on-the-fly forward or backprojection using a .dsc file (see ASPIRE user manual)

@Gtomo2_wtfmex
uses .wtf created by ASPIRE - loaded in mex memory space rather than matlab
to save memory (singles instead of floats)


Gblur
linear shift invariant blur (image restoration)

Gdsft
discrete-space Fourier transform (nonuniform k-space samples).
a slow but exact version of Gnufft.

Glinear
tomographic system matrix based on pixel-driven linear interpolation.
not recommended.

Gmri
For MRI image reconstruction, possibly including nonuniform k-space samples,
off-resonance effects, and relaxation effects.

Gnearest
tomographic system matrix based on pixel-driven nearest-neighbor interpolation.
not recommended.

Gnufft
Nonuniform FFT (NUFFT) for applications like MRI that record Fourier samples.

Gsparse
an object made from matlab sparse matrix, essentially for testing.
also useful as a base for Gblock objects

Gtomo2_strip
strip integral tomographic system model.  useful but uses lots of memory.

Gtomo2_table
table-based tomographic system model.  fast yet small memory.  recommended.

Gtomo3
3D system models, some precomputed, some on-the-fly, based on f3d_mex.

Gtomo_blob
work in progress

Gtomo_nufft
NUFFT-based forward/backprojection for 2D tomography

Final option:
	!wt gen tomo.dsc
	(creates tomo.wtf using ASPIRE)
	A = wtfmex('load', 'file.wtf');
