The NEXT collaboration aims to observe the neutrinoless double beta decay (β β 0ν) of $^{136}Xe$.
If exisiting, the rareness of this decay demands an exceptional background rejection. This can
be obtained with an excellent energy resolution, which has been already demonstrated in NEXT
prototypes. In addition to this, any additional tool that can improve background rejection is of
extreme utility. Neutrinoless double beta decay in xenon gas produces a characteristic topological
signal that can be used as an extremely useful extra handle to veto background events. There-
fore, for NEXT, the capability of having track reconstruction is of great value. This need for a
satisfactory topology reconstruction has led the NEXT Collaboration to implement the Maximum
Likelihood Expectation Maximization algorithm (ML-EM) in the data processing scheme. ML-
EM is a generic iterative algorithm for solving many kinds of inverse problems which has never
been applied before to a time projection chamber. Early results and performance of the method
in the collaboration current running detector, NEW, shows promising track reconstruction while
offering a resolution better than 0.5% for energy depostions of energy equal to the Q β β value for
$^{136}Xe$.