SIRT_CUDA¶
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. |
Example¶
%% 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.)