  Lutetium (Lu) based scintillators such as LSO and LYSO, are widely used in
modern PET detectors due to their high stopping power for 511 keV gamma rays,
high light yield and short decay time. However, 2.6% of naturally occurring Lu
is 176Lu, a long-lived radioactive element including a beta decay and three
major simultaneous gamma decays. This phenomenon introduces random events to
PET systems that affects the system performance. On the other hand, the
advantages of intrinsic radiation of 176Lu (IRL) continues to be exploited. In
this paper, research literatures about IRL in PET detectors are reviewed.
Details about the adverse effects of IRL to PET and their solutions, as well as
the useful applications are presented and discussed.
