# Known problems in the current release of the STIR software

See also the release notes for the current version and the issue tracker on GitHub.

- Currently the implementation if the incremental interpolating backprojector can have problems on certain processors due to floating point rounding errors. You would notice problems in the central voxel, which will influence neighboring voxels in the iterative algorithms. Running the recon_test_pack will tell you if you have the problem (but there might still be a problem for your particular scanner/pixel size). Update Thanks to an update by Bing Bai, this seems less of an issue now, but it does still occur. Please notify the mailing list if this problem still occurs on your system (give details of OS, processor, compiler and compiler switches). See the User's Guide for details on how to choose another backprojector.
- Currently the implementation if the incremental interpolating backprojector fails when the number of views is not even. Images are wrong, even though the programs might run till the end.
- Images have to have the default number of planes. Trying to forward project images with smaller or larger number of planes will show up some problems, which we thought to have removed already :-/ .
- Dead-time code for ECAT7 files might currently give wrong results due to uncertainty in units for singles rates
- CPU times reported are invalid on Windows 9?, maybe ME as well. They are fine on NT and later.There doesn't seem to be a way to get CPU times in the older Windows versions.
- In STIR 2.x, the default settings for the forward projector/back projector pair result in unmatched projectors. This can give problems in certain situations. It is strongly recommended to change this to use the ray tracing matrix projectors (use some extra rays to approximate strip-integrals).

Last modified: Mon Jan 13 20:03:14 GMT 2014