The use of (18)F-FDG-PET/CT for diagnosis and treatment monitoring of inflammatory and infectious diseases

Abstract

FDG-PET, combined with CT, is nowadays getting more and more relevant for the diagnosis of several infectious and inflammatory diseases and particularly for therapy monitoring. Thus, this paper gives special attention to the role of FDG-PET/CT in the diagnosis and therapy monitoring of infectious and inflammatory diseases. Enough evidence in the literature already exists about the usefulness of FDG-PET/CT in the diagnosis, management, and followup of patients with sarcoidosis, spondylodiscitis, and vasculitis. For other diseases, such as inflammatory bowel diseases, rheumatoid arthritis, autoimmune pancreatitis, and fungal infections, hard evidence is lacking, but studies also point out that FDG-PET/CT could be useful. It is of invaluable importance to have large prospective multicenter studies in this field to provide clear answers, not only for the status of nuclear medicine in general but also to reduce high costs of treatment.

Figure 1

FDG-PET examples of vasculitis: (a) giant cell arteritis and polymyalgia rheumatica: high FDG uptake in the large vessels (aorta, subclavian arteries, carotid arteries, iliac arteries, and femoral arteries) accompanied by high uptake in the large joints (shoulders and hips), (b) Takayasu's arteritis: high FDG uptake located more centrally (aorta and main branches in the thoracic region) and in this case uptake in reactive lymph nodes in mediastinum and hili (confirmed by biopsy), and (c) polyarteritis nodosa and polychondritis: high uptake in the medium- and small-sized arteries (best visible in the legs) accompanied by uptake in the nose, the ears, and the costochondral regions.

Figure 2

FDG-PET classification of sarcoidosis. Type I: thoracic lymph node involvement (in this image: mediastinal and hilar regions), type II: involvement of the lung parenchyma, type III: diffuse lymph node involvement (in this image all lymph node regions of the body are involved), and type IV: organ involvement (in this image involvement of the spleen and bones) (images courtesy by R. Keijsers).

Figure 3

An example of the value of FDG-PET/CT in a patient with sarcoidosis: (a) baseline scan, (b) scan after 3 months of corticosteroid therapy with progression of lung infiltration, and (c) scan after 3 months of treatment with corticosteroids and methotrexate together, resulting in complete remission (the linear uptake is located in a muscle in the back and considered physiological muscle uptake).

Figure 4

A 14-year-old girl known with Crohn's disease. FDG-PET/CT (left: MIP image of the FDG-PET, right: fused FDG-PET/CT transaxial slice) showed inflammation of the caecum.

Figure 5

FDG-PET of a patient with spondylodiscitis and involvement of the psoas muscles. (a) Coronal MIP view, (b) fused PET/CT sagittal view, and (c) fused PET/CT transaxial view.

Figure 6

FDG-PET of a neutropenic patient (due to leukemia) with a fungal infection (aspergillosis) before (left image) and during antifungal therapy (right image) resulting in a decrease in FDG uptake in the lung lesions. Because on the last FDG-PET scan (right image) there is still no complete remission, the patient is still treated with antifungal drugs.