Background 18F-Fluoride positron emission tomography (PET) and computed tomography (CT) can measure disease activity and progression in aortic stenosis. We aimed to optimise imaging methodology, analysis and scan-rescan reproducibility.

Methods Fifteen patients with aortic stenosis underwent 18F-fluoride PET-CT twice within 1 month. We compared non-gated PET and non-contrast CT, with a modified approach that incorporated contrast CT and ECG-gated PET. We explored a range of image analysis techniques including estimation of blood pool activity at differing vascular sites and a most-diseased segment (MDS) approach.

Results Contrast-enhanced ECG-gated PET-CT provided superior spatial localisation of 18F-fluoride uptake that permitted localisation to individual valve leaflets (Figure). Scan-rescan reproducibility was markedly improved using enhanced analysis techniques leading to a reduction in variability from 25% to <10% (tissue-to-background MDS: mean value 1.55, difference 0.05, limits of agreement -0·10 to 0·20).

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Abstract 117 Figure 1

Blood pool correction was performed by sampling from the right atrium instedad of the brachio-cephalic vein. 2. The most diseased segment method was used to quantify the PET signal within 2 hottest slices rather than the whole valve/ 3. Contrase CT fused with ECG-gated PET gacilitated better localization to leaflets compared to the original approach 4. Bland-Altmanplots emonstrated superior sacn-rescan reproducibility for the modified technique (2b) compared to the previous approach (2a)

Conclusion Optimised 18F-fluoride PET-CT provides excellent spatial resolution and scan-rescan reproducibility. It holds major promise as a marker of disease activity in aortic stenosis and has major potential as a biomarker end-point of trials of novel therapies in aortic stenosis.