Jørgen Frøkiær

Dynamic cardiac positron emission tomography (PET) is used to quantify molecular processes in vivo. However, measurements of left-ventricular (LV) mass and volumes require electrocardiogram (ECG)-gated PET data. The aim of this study was to explore the feasibility of measuring LV geometry using non-gated dynamic cardiac PET.

METHODS: Thirty-five patients with aortic-valve stenosis and 10 healthy controls (HC) underwent a 27-min (11)C-acetate PET/CT scan and cardiac magnetic resonance imaging (CMR). HC were scanned twice to assess repeatability. Parametric images of uptake rate K1 and the blood pool were generated from non-gated dynamic data. Using software-based structure recognition the LV wall was automatically segmented from K1 images to derive mLV and wall thickness (WT). End-systolic (ESV) and end-diastolic (EDV) volumes were calculated using blood pool images and used to obtain stroke volume (SV) and LV ejection fraction (LVEF). PET measurements were compared with CMR.

RESULTS: High and linear correlations were found for LV mass (r=0.95), ESV (r=0.93) and EDV (r=0.90), and slightly lower for SV (r=0.74), LVEF (r=0.81) and WT(r=0.78). Bland Altman analyses showed significant differences for mLV and WT only and an overestimation for LVEF at lower values. Intra- and inter-observer correlations were >0.95 for all PET measurements. PET repeatability accuracy in HC was comparable to CMR.

CONCLUSION: LV mass and volumes are accurately and automatically generated from dynamic (11)C-acetate PET without ECG-gating. This method can be incorporated in a standard routine without any additional workload and can, in theory, be extended to other PET tracers.