La tomographie d'émission de positons en médecine interne : applications actuelles et perspectives d'avenir

[Vasculitis assessment with [18F]FDG positron emission tomography]

[18F]fluorodeoxyglucose positron emission tomography (PET) is a noninvasive metabolic imaging modality that is well-suited to the assessment of activity and extent of large vessel vasculitis. PET imaging has demonstrated its usefulness in diagnosing giant cell arteritis (notably in its silent form), Takayasu's arteritis, and unclassified aortitis. PET imaging could be more effective than magnetic resonance imaging in detecting the earliest stages of vascular wall inflammation. The visual grading of vascular [18F]FDG uptake makes it possible to discriminate arteritis from active atherosclerosis, providing therefore high specificity. High sensitivity can also be achieved provided scanning is performed during active inflammatory phase, preferably before starting corticosteroid treatment. Prospective studies are needed to determine the exact value of PET imaging in assessing other vasculitis subsets, infectious aortitis, and large vessel vasculitis outcome and response to immunosuppressive treatment.

Value of (18)F-FDG-PET/CT in patients with fever of unknown origin and unexplained prolonged inflammatory syndrome: a single centre analysis experience

OBJECTIVE

The aim of our study was to evaluate the diagnostic contribution of (18)F-fluoro-deoxyglucose ((18)F-FDG)-positron emission tomography (PET)/computed tomography (CT) in patients with fever of unknown origin (FUO) or unexplained prolonged inflammatory syndrome (UPIS) in real life.

PATIENTS AND METHODS

We performed a retrospective study including 14 patients with FUO or UPIS hospitalised in our institution (Strasbourg University Hospital, France) between January 2005 and July 2006. (18)F-FDG-PET/CT was considered helpful when abnormal results allowed an accurate diagnosis.

RESULTS

(18)F-FDG-PET/CT was helpful in half the patients (7/14) for final diagnosis. A diagnosis was reached in 87.5% of the patients (7/8) with an abnormal (18)F-FDG-PET/CT but only in 50% of the patients (3/6) with a normal (18)F-FDG-PET/CT. Conventional chest and abdominal CT was performed in 13 patients before ordering (18)F-FDG-PET/CT. We considered that (18)F-FDG-PET/CT was essential to establish the final diagnosis in only 23% of the patients (3/13) since neither chest nor abdominal CT identified abnormalities consistent with the final diagnosis. However, among the three patients, two were diagnosed with large vessel vasculitis and one patient with local prosthetic infection.

CONCLUSIONS

Our study supports the potential interest of (18)F-FDG-PET/CT in the diagnostic workup of FUO and UPIS as it helped establish a fine diagnosis in half of the cases. However, (18)F-FDG-PET/CT appeared to be essential to the final diagnosis in only 23% of the cases. In our opinion, this protocol should be performed as a second level test, especially when conventional CT is normal or is unable to discriminate between active and silent lesions.

[Central nervous system involvement in Wegener's granulomatosis]

INTRODUCTION

Wegener's granulomatosis (WG) is a systemic necrotizing vasculitis associated with c-ANCA antibodies. The involvement of the central nervous system in WG is uncommon and usually caused by in situ vasculitis, intracranial granuloma formation or contiguous invasion from extracranial sites.

CASE REPORT

Here, we report on a tumour-like expansion of a severe nasosinusal WG into the brain, which was confirmed by brain biopsy examination.

CONCLUSION

The positivity of positron emission tomography in our observation supports the potential role of such functional imaging in the staging, as well as in the follow-up of WG.

Intérêt de la tomographie par émission de positons couplée au scanner dans la maladie d'Erdheim-Chester

INTRODUCTION

Erdheim-Chester disease is a rare non-Langerhans form of histiocytosis. We report the use of combined fluorodeoxyglucose positron emission tomography and computed tomography (18F-FDG PET-CT) in this disease.

EXEGESIS

Three men, aged from 55 to 74 years with confirmed Erdheim-Chester disease were included. 18F-FDG PET-CT allowed to detect visceral and vascular involvement of the disease which were overlooked with CT-scan or magnetic resonance imaging: left common carotid and ilio-femoral artery in one patient, coronary, femoral and tibia in the second, aortic, common carotid, femoral and mandibula in the remaining patient. Also, sequential 18F-FDG PET-CT was useful to appreciate treatment efficiency (decrease hyperfixation) and decide treatment modification (interferon alpha).

CONCLUSION

18F-FDG PET-CT combined imaging allows to assess the extent of involvement in Erdheim-Chester disease. 18F-FDG PET-CT may be also a useful tool in the management of Erdheim-Chester disease.