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PET sinogram symmetries ``parallelproj.sinogram_symmetries``
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Utilities for exploiting the geometric symmetries of regular-polygon sinograms to
save memory and computation (for example when precomputing sensitivity images).
The typical workflow is to compute the sinogram-plane symmetry classes, build the
per-axis class indices, reduce a sinogram to its unique classes, operate on the
reduced data, and finally expand back to the full sinogram.  These are advanced
helpers; most users do not need them directly.

.. automodule:: parallelproj.sinogram_symmetries