Radionuclide Imaging of Invasive Fungal Disease in Immunocompromised Hosts

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.

The F 1 F o -ATP synthase α subunit of Candida albicans induces inflammatory responses by controlling amino acid catabolism

“…To further reveal the important impact of the F 1 F o -ATP synthase α subunit on host inflammatory responses, according to the fact that the uptake and accumulation of [ 18 F]FDG in active inflammatory cells was obviously higher than that in normal cells [ 47 ], microPET/CT combined with radioactivity measurement by γ-counting [ 48 ] was used to monitor the inflammatory response in tissues and organs – especially the kidney, the target organ of IC [ 17 ]—in infected mice. The microPET/CT imaging displayed that the uptake of [ 18 F]FDG in the systemic organs of atp1 Δ/Δ-infected mice had no difference from that in NS-control mice, while was obviously decreased compared with that in WT-infected mice ( Figure 2a ).…”

Imaging of Invasive Fungal Infections- The Role of PET/CT

“…Some comprehensive reviews have discussed the role of FDG PET/CT in IFD in the immunocompromised host, in children and monitoring therapy. 18,29,30 This review discusses the added value of FDG PET/CT to other imaging modalities used in evaluating FDG PET/CT.…”

“…FDG PET/CT is a non-invasive marker of disease and standard uptake value, and other metabolic indices provide a semi-quantitative measure of the disease activity within lesions. This allows longitudinal followup of IFD lesions over time, 19,29,30,72 Again, the earlier physiological FDG PET data changes may detect response to antifungal therapy earlier than other morphological images in response to antifungal treatment. In a study from a single Medical Centre in the Netherlands, FDG PET/CT was found to have altered the treatment of IFD in 50% of patients leading to the cessation, switch in antifungal therapy or increase in the dose of antifungal therapy.…”

Molecular Imaging of Tuberculosis

“…This dynamism afforded by molecular imaging techniques makes the characterization of the biological behavior and metabolic pathways that drive diseases, including TB, possible. 29,30 Radionuclide Imaging of Tuberculosis: The Possibilities Radionuclide imaging techniques have been applied in interrogating the various aspects of Tb, including disease diagnosis, lesion characterization, disease evolution, treatment response assessment, prognostication, relapse prediction, and pharmacokinetic study of current and novel anti-TB drugs. 20,21,31,32 This array of applications of radionuclide imaging techniques explored in studying TB infection and disease in humans and laboratory animals has advanced the knowledge regarding the disease.…”