Summary of changes in STIR release 5.1

This version is 100% backwards compatible with STIR 5.0.

Overall summary

This release includes the first open-source code available for reconstructing pinhole-SPECT datasets (see PR #1100). It contains code by Carlés Falcón (Neuroimaging Group, Barcelonaβeta Brain Research Center) to create the pinhole-SPECT system matrix. Integration into STIR was completed by Matthew Strugari (Dalhousie University) and Kris Thielemans (UCL). This work is reported in
- Matthew Strugari, Carles Falcon, Kjell Erlandsson, Brian Hutton, G. Andrew Reid, Ian Pottie, Sultan Darvesh, Steven Beyea, Kimberly Brewer, Kris Thielemans,
  Integration of advanced 3D SPECT modelling for pinhole collimators into the open-source STIR framework,
  Proc. IEEE MIC 2022, Milan, Italy
Improvements to listmode reconstruction by Nikos Efthimiou, see PR #1030.
Support for PENNPET Explorer listmode data (if proprietary libraries are found) by Nikos Efthimiou, see PR #1028.
Scatter simulation, estimation and down/up-sampling, randoms handling and ML normalisation estimation adapted for scanner with Block geometry by Daniel Deidda (NPL) and Kris Thielemans (UCL).
Various small changes to add functionality to Python interface, mainly by Markus Jehl (Positrigo).
Python projection data visualiser (in examples/python) by Robert Twyman (UCL).

Of course, there is also the usual code-cleanup and improvements to the documentation. See also the 5.1 milestone on GitHub and the full release notes

Overall code management and assistance by Kris Thielemans (UCL and ASC).