SART

This is a CPU implementation of the Simultaneous Algebraic Reconstruction Technique (SART) for 2D data sets. It takes projection data and an initial reconstruction as input, and returns the reconstruction after a specified number of SART iterations. Each iteration of SART consists of an FP and BP of one single projection direction. The order of the projections can be specified.

Supported geometries: parallel, fanflat, fanflat_vec, matrix.

Configuration options

name

type

description

cfg.ProjectorId

required

The astra_mex_projector ID of the projector.

cfg.ProjectionDataId

required

The astra_mex_data2d ID of the projection data

cfg.ReconstructionDataId

required

The astra_mex_data2d ID of the reconstruction data. The content of this when starting SART is used as the initial reconstruction.

cfg.option.SinogramMaskId

optional

If specified, the astra_mex_data2d ID of a projection-data-sized volume to be used as a mask.

cfg.option.ReconstructionMaskId

optional

If specified, the astra_mex_data2d ID of a volume-data-sized volume to be used as a mask.

cfg.option.MinConstraint

optional

If specified, all values below MinConstraint will be set to MinConstraint. This can, for example, be used to enforce non-negative reconstructions.

cfg.option.MaxConstraint

optional

If specified, all values above MaxConstraint will be set to MaxConstraint.

cfg.option.ProjectionOrder

optional

This specifies the order in which the projections are used. Possible values are: ‘random’ (default), ‘sequential’, and ‘custom’. If ‘custom’ is specified, the option.ProjectionOrderList is required.

cfg.option.ProjectionOrderList

optional

Required if option.ProjectionOrder = ‘custom’, ignored otherwise. A matlab vector containing the custom order in which the projections are used.

Example

%% create phantom
V_exact = phantom(256);

%% create geometries and projector
proj_geom = astra_create_proj_geom('parallel', 1.0, 256, linspace2(0,pi,180));
vol_geom = astra_create_vol_geom(256,256);
proj_id = astra_create_projector('linear', proj_geom, vol_geom);

%% create forward projection
[sinogram_id, sinogram] = astra_create_sino(V_exact, proj_id);

%% reconstruct
recon_id = astra_mex_data2d('create', '-vol', vol_geom, 0);
cfg = astra_struct('SART');
cfg.ProjectorId = proj_id;
cfg.ProjectionDataId = sinogram_id;
cfg.ReconstructionDataId = recon_id;
cfg.option.ProjectionOrder = 'custom';
cfg.option.ProjectionOrderList = [0:5:175 1:5:176 2:5:177 3:5:178 4:5:179];
sart_id = astra_mex_algorithm('create', cfg);
astra_mex_algorithm('iterate', sart_id, 10*180);
V = astra_mex_data2d('get', recon_id);
imshow(V, []);

%% garbage disposal
astra_mex_data2d('delete', sinogram_id, recon_id);
astra_mex_projector('delete', proj_id);
astra_mex_algorithm('delete', sart_id);

Further examples regarding the different projection orders can be found in example_sart_order.m .