Comparison of magnetic resonance angiography and 18F-fluorodeoxyglucose positron emission tomography in large-vessel vasculitis

Abstract

Objectives: To assess agreement between interpretation of magnetic resonance angiography (MRA) and 18F-fluorodeoxyglucose positron emission tomography (PET) for disease extent and disease activity in large-vessel vasculitis (LVV) and determine associations between imaging and clinical assessments.

Methods: Patients with giant cell arteritis (GCA), Takayasu's arteritis (TAK) and comparators were recruited into a prospective, observational cohort. Imaging and clinical assessments were performed concurrently, blinded to each other. Agreement was assessed by per cent agreement, Cohen's kappa and McNemar's test. Multivariable logistic regression identified MRA features associated with PET scan activity.

Results: Eighty-four patients (GCA=35; TAK=30; comparator=19) contributed 133 paired studies. Agreement for disease extent between MRA and PET was 580 out of 966 (60%) arterial territories with Cohen's kappa=0.22. Of 386 territories with disagreement, MRA demonstrated disease in more territories than PET (304vs82, p<0.01). Agreement for disease activity between MRA and PET was 90 studies (68%) with Cohen's kappa=0.30. In studies with disagreement, MRA demonstrated activity in 23 studies and PET in 20 studies (p=0.76). Oedema and wall thickness on MRA were independently associated with PET scan activity. Clinical status was associated with disease activity by PET (p<0.01) but not MRA (p=0.70), yet 35/69 (51%) patients with LVV in clinical remission had active disease by both MRA and PET.

Conclusions: In assessment of LVV, MRA and PET contribute unique and complementary information. MRA better captures disease extent, and PET scan is better suited to assess vascular activity. Clinical and imaging-based assessments often do not correlate over the disease course in LVV.

Trial registration number: NCT02257866.

Keywords: Takayasu’s arteritis; giant cell arteritis; magnetic resonance angiography; positron emission tomography; vasculitis.

Conflict of interest statement

Competing interests: None declared.

© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Figures

Figure 1. Associations between Features of MRA and Imaging Activity Assessed by MRA and PET

Patients were divided based on imaging assessment of disease activity (active versus inactive) by MRA and PET into 4 subgroups (MRA+/PET+, MRA+/PET−, MRA−/PET+, MRA−/PET). Associations of the 4 subgroups with the MRA features of edema, wall thickness, and stenosis are displayed. Patients with active disease on both MRA and PET (MRA+/PET+) had the greatest median number of territories with edema (A) and wall thickness (B), while there were fewer significant associations between number of territories with stenosis and imaging activity (C).

Figure 2. Association of Imaging-Based Interpretation of Vasculitis Disease Activity and Clinical Features of Disease in Large-Vessel Vasculitis

There were few significant clinical differences between patients whose imaging studies [magnetic resonance angiography (MRA) or positron emission tomography (PET)] were interpreted as active vasculitis versus normal. Clinically active disease compared to clinical remission was associated with increased PET interpretation of active vasculitis (A), and older age was significantly associated with increased MRA interpretation of active vasculitis (B). Type of vasculitis (giant cell arteritis (GCA) vs Takayasu’s arteritis (TAK)), daily prednisone dose, and acute phase reactant levels were not significantly associated with image interpretation by MRA or PET (C–F).

Figure 3. Representative Abnormal FDG-PET and MRA Studies in a Patient with Giant Cell Arteritis in Clinical Remission

A 72 year-old woman with giant cell arteritis underwent imaging studies 5 years after diagnosis. At the time of imaging, the patient was in clinical remission and had been tapered off all vasculitis-related medications. Erythrocyte sedimentation rate was within normal limits at 25mm/hr and c-reactive protein was 4.6 mg/L (normal