Abstract:
With Tuberculosis (TB) affecting millions of people worldwide, novel imaging modalities
and tools, particularly nuclear medicine and molecular imaging, have grown with greater
interest to assess the biology of the tuberculous granuloma and evolution thereof. Much
early work has been performed at the pre-clinical level using gamma single photon
emission computed tomography (SPECT) agents exploiting certain characteristics of
Mycobacterium tuberculosis (MTb). Both antituberculous SPECT and positron emission
tomography (PET) agents have been utilised to characteriseMTb. Other PET tracers have
been utilised to help to characterise the biology of MTb (including Gallium-68-labelled
radiopharmaceuticals). Of all the tracers, 2-[18F]FDG has been studied extensively over
the last two decades in many aspects of the treatment paradigm of TB: at diagnosis,
staging, response assessment, restaging, and in potentially predicting the outcome of
patients with latent TB infection. Its lower specificity in being able to distinguish different
inflammatory cell types in the granuloma has garnered interest in reviewing more specific
agents that can portend prognostic implications in the management of MTb. With the
neutrophil being a cell type that portends this poorer prognosis, imaging this cell type
may be able to answer more accurately questions relating to the tuberculous granuloma
transmissivity and may help in characterising patients who may be at risk of developing
active TB. The formyl peptide receptor 1(FPR1) expressed by neutrophils is a key marker
in this process and is a potential target to characterise these areas. The pre-clinical work
regarding the role of radiolabelled N-cinnamoyl –F-(D) L – F – (D) –L F (cFLFLF) (which
is an antagonist for FPR1) using Technetium 99m-labelled conjugates and more recently
radiolabelled with Gallium-68 and Copper 64 is discussed. It is the hope that further work with this tracer may accelerate its potential to be utilised in responding to many of
the current diagnostic dilemmas and challenges in TB management, thereby making the
tracer a translatable option in routine clinical care.
