This is a GPU implementation of the Simultaneous Iterative Reconstruction Technique (SIRT) for 2D data sets. It takes projection data and an initial reconstruction as input, and returns the reconstruction after a specified number of SIRT iterations.

Supported geometries: parallel, fanflat, fanflat_vec.

Configuration options

name type description
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 SIRT 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.GPUindex optional Specifies which GPU to use. Default = 0.
cfg.option.DetectorSuperSampling optional Specifies the amount of detector supersampling, i.e. how many rays are cast per detector.
cfg.option.PixelSuperSampling optional Specifiec the amount of pixel supersampling, i.e. how many (one dimension) subpixels are generated from a single parent pixel.


%% create phantom
V_exact = phantom(256);

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

%% create forward projection
[sinogram_id, sinogram] = astra_create_sino_cuda(V_exact, proj_geom, vol_geom);

%% reconstruct
recon_id = astra_mex_data2d('create', '-vol', vol_geom, 0);
cfg = astra_struct('SIRT_CUDA');
cfg.ProjectionDataId = sinogram_id;
cfg.ReconstructionDataId = recon_id;
cfg.option.MinConstraint = 0;
cfg.option.MaxConstraint = 255;
sirt_id = astra_mex_algorithm('create', cfg);
astra_mex_algorithm('iterate', sirt_id, 100);
V = astra_mex_data2d('get', recon_id);
imshow(V, []);

%% garbage disposal
astra_mex_data2d('delete', sinogram_id, recon_id);
astra_mex_algorithm('delete', sirt_id);

Extra features

SIRT_CUDA supports astra_mex_algorithm(‘get_res_norm’) to get the 2-norm of the difference between the projection data and the projection of the reconstruction. (The square root of the sum of squares of differences.)