The PET SOURCE NA22/0.37 IM NU4 D0.25 phantom, referred from now simply as point source, is used both in the Acceptance Procedure and in the maintenance tasks that are carried out during the life of the instrument.

The point source complies with the NEMA NU4 2008 specifications and therefore can also be used when performing a NEMA performance characterization and in particular when measuring the spatial resolution and the sensitivity.