## New features
- User-customizable fields in Datafile
- New tools for normalization correction factors estimation
- Event by event TOF resolution kernel for list-mode PET
- Add proximity factors in Markov Random Field penalties that can be described following a Gaussian distribution
- Add a quadratic penalty in order to penalize the quadratic difference between the reconstructed image and a provided target image.
- Updated GATE to CASToR conversion tools 
  -- Option to incorporate normalization from additional simulated data
  -- Improve multi-layers geometry management
- Implementation of different features concerning optimization algorithms:
  -- a mechanism for optimization algorithms making use of sub iterations (such as ADMM)
  -- implementation of ADMM from Lim et al (maximum likelihood with positivity constraint in the projection space),
  -- a mechanism for processing of data before and after optimization for any pre or post processing step necessitating a loop over data elements,
  -- the APPGML algorithm from Millardet et al (shifted version of the PPGML algorithm from Nuyts et al),
  -- the possibility to provide additional input in the data space.
- Add the MLMUMAP optimizer that allows to reconstruct an attenuation image (mumap in units of 1/mm) from the attenuation correction factors
  included in a PET histogram datafile.

## Bug corrections, code changes, that can affect the results in some way
- Hotfix: The generation of the detector principal axes was incorrect when its orientation had a non-null Z components.

## Small bug fixes
- SPECT: Bug fix related to the computation of non-constant camera surface to COR distance 

## Note
- Special thanks to Aurelien Coussat, Damian Trybek, Maxime Toussaint, and others developers for their kind contributions in this release!