The Impact of FDG-PET/CT on Management of Takayasu Arteritis

Introduction: Large vessel vasculitis includes Takayasu Arteritis (TA) and Giant Cell Arteritis (GCA). TA can result in general constitutional symptoms, claudication, weak pulses of mainly upper extremities, difference in blood pressure between two upper limbs and may lead to more serious complications if remains untreated. Controversies in both clinical and para-clinical evaluation of these entities, especially in TA in which tissue sampling is impossible, highlights the need for other diagnostic modalities in order to prevent or decrease complications of delayed management (CVA, aortic valve insufficiency, abortion, etc). Due to frequent discordance between clinical findings and CTA/MRA results as well as laboratory data (mainly ESR and CRP levels), the need for a procedure with more diagnostic accuracy is highlighted. Because of Involvement of intracranial vessels in GCA, (with high normal brain FDG uptake and hence low contrast resolution) and more frequency of atherosclerosis (which can be a confounding factor) in elder patients with GCA, we focus on evaluating only TA patients. The aim of this study was to assess the concordance of FDG-PET/CT results, both qualitatively and semi-quantitatively (number, location, intensity, SUVs of vascular inflammatory lesions) with clinical criteria and other imaging and laboratory findings to help rheumatologists for better management of these patients and to decrease complications of over or under treatments.Patients and Method: This case series is a preliminary data of our study. According to low incidence of TA and undefined role of FDG-PET/CT scan in this disease, number of patients are limited. These patients with clinical diagnosis of TA underwent FDG-PET/CT scan for assessment of disease activity. The same protocol used for oncologic evaluation of patients, with PET-CT Siemens Biograph T6 Series scanner, was used. The images were reconstructed via OSEM method and after insertion of Regions of Interest (ROIs) on suspicious lesions, maximum standardized uptake value (SUVmax), location and number of the lesions as well as accumulated SUV for all lesions were calculated. After interpretation, two nuclear physicians, already blind from other results, compared PET/CT findings with each patient’s history, physical examination, results of CTA and /or MRA and laboratory data.Results: Up to now, six patients (four women and two men with the mean age at the onset of disease= 30.0 ± 5.2 years) have been studied. In these cases, there was a good agreement between clinical findings and PET/CT results especially in the cases with normal CTA or MRA results, avoiding underestimation of disease activity. FDG-PET/CT results also lead to detection of more metabolically active vascular lesions than CTA/MRA and better depicted extent and burden of the disease. In patients with clinical criteria in favor of inactive vasculitis, PET/CT scan did not show any metabolically active lesions.Conclusion: Preliminary data in a small population show usefulness of FDG-PET/CT scan in evaluation of disease activity in TA patients. More detailed studies as well as follow up of patients are needed for better determining the role of FDG-PET/CT scan in TA management.

Keywords:

Large vessel vasculitis , Takayasu Arteritis , FDG-PET/CT