Abstract:
Invasive fungal disease (IFD) leads to increased mortality, morbidity, and costs of treatment
in patients with immunosuppressive conditions. The definitive diagnosis of IFD relies on the isolation
of the causative fungal agents through microscopy, culture, or nucleic acid testing in tissue samples
obtained from the sites of the disease. Biopsy is not always feasible or safe to be undertaken in
immunocompromised hosts at risk of IFD. Noninvasive diagnostic techniques are, therefore, needed
for the diagnosis and treatment response assessment of IFD. The available techniques that identify
fungal-specific antigens in biological samples for diagnosing IFD have variable sensitivity and
specificity. They also have limited utility in response assessment. Imaging has, therefore, been
applied for the noninvasive detection of IFD. Morphologic imaging with computed tomography (CT)
and magnetic resonance imaging (MRI) is the most applied technique. These techniques are neither
sufficiently sensitive nor specific for the early diagnosis of IFD. Morphologic changes evaluated
by CT and MRI occur later in the disease course and during recovery after successful treatment.
These modalities may, therefore, not be ideal for early diagnosis and early response to therapy
determination. Radionuclide imaging allows for targeting the host response to pathogenic fungi or
specific structures of the pathogen itself. This makes radionuclide imaging techniques suitable for
the early diagnosis and treatment response assessment of IFD. In this review, we aimed to discuss
the interplay of host immunity, immunosuppression, and the occurrence of IFD. We also discuss the
currently available radionuclide probes that have been evaluated in preclinical and clinical studies
for their ability to detect IFD.
