Comparing Semiquantitative and Qualitative Methods of Vascular ¹⁸F-FDG PET Activity Measurement in Large-Vessel Vasculitis

Abstract

The study rationale was to assess the performance of qualitative and semi-quantitative scoring methods for 18 F-fluorodeoxyglucose positron emission tomography (FDG-PET) assessment in large-vessel vasculitis (LVV). MethodsPatients with giant cell arteritis (GCA) or Takayasu's arteritis (TAK) underwent clinical and imaging assessment, blinded to each other, within a prospective observational cohort. FDG-PET-CT scans were interpreted for active vasculitis by central reader assessment. Arterial FDG uptake was scored by qualitative visual assessment using the PET vascular activity score (PETVAS) and by semi-quantitative assessment using standardized uptake values (SUV) and target-to-background ratios (TBR) relative to liver/blood activity. Performance of each scoring method was assessed by intra-rater reliability using the intra-class coefficient (ICC) and area under receiver-operator characteristic curves (AUC), using physician assessment of clinical disease activity and reader interpretation of vascular PET activity as independent reference standards. Wilcoxon signed-rank test was used to analyze change in arterial FDG uptake over time. ResultsNinety-five patients (GCA=52; TAK=43) contributed 212 FDG-PET studies. The ICC for semiquantitative evaluation [0.99 (range 0.98-1.00)] was greater than the ICC for qualitative evaluation [0.82 (range 0.56-0.93)]. PETVAS and TBR metrics were more strongly associated with reader interpretation of PET activity than SUV metrics. All assessment methods were

Clinical Utility of C-Reactive Protein and White Blood Cell Count for Scheduling an [18F]FDG PET/CT in Patients with Giant Cell Arteritis

“…For instance, in a recent study with 95 LVV patients who underwent [ 18 F]FDG PET/CT, the performance of qualitative and semi-quantitative methods (SUV, TBR using liver and blood pool uptake as reference) were tested. Relative to SUV, semi-quantification had superior reliability, with TBR derived from liver having a slightly better performance than that of blood pool [14]. This is in line with an observation by Lensen and coworkers who reported a Fleiss' kappa of up to 0.96 when uptake in vessels was compared to liver [13].…”

Whole-Body [18F]FDG PET/CT Can Alter Diagnosis in Patients with Suspected Rheumatic Disease

“…As a possible explanation, (supra)aortic vessels have a relatively small diameter, so that partial volume effects may have a significant impact on the derived values, while for the joints, a larger VOI was placed [33]. However, a recent study in LVV also reported on high reliability and improved response monitoring in cases of severe inflammation when the liver was used as a reference [34]. Therefore, one may speculate whether significance for the semi-quantitative assessment for GCA may have also been reached if a larger number of subjects or different background tissue, such as the blood pool, were utilized [29].…”

Outcome Measures and Biomarkers for Disease Assessment in Takayasu Arteritis

“…The authors calculated TBR compared to the liver (TBR Liver ) or to the blood flow (TBR Blood ), SUV Artery (by averaging SUV max across nine arterial territories), and the PETVAS at each of these visits. Each of these parameters had moderate performance, comparable with each other, to distinguish active TAK (AUC for TBR Liver 0.66 (95% CI 0.58–0.73) at a cut-off of 1.46, TBR Blood 0.65 (95% CI 0.57–0.73) at a cut-off of 2.39, SUV Artery 0.59 (95% CI 0.51–0.68) at a cut-off of 3.58, and PETVAS 0.65 (95% CI 0.57–0.73) at a cut-off of 22.5) [ 69 ]. Another study assessed 100 patients with LVV (49 TAK, 51 GCA) who had experienced 476 PET-CTs over more than 8 years of follow-up.…”