Jørgen Frøkiær

Background: Dynamic PET can be used to extract forward stroke volume (FSV) by the indicator dilution principle. The technique employed can be automated and is in theory independent on the tracer used and may therefore be added to any dynamic cardiac PET protocol. The aim of this study was to validate automated methods for extracting FSV directly from dynamic PET studies for two different tracers and to examine potential scanner hardware bias. Methods: 21 subjects underwent a dynamic 27 min 11C-acetate PET scan on a Siemens Biograph TruePoint 64 PET/CT scanner (scanner I). In addition, 8 subjects underwent a dynamic 6 min 15O-water PET scan followed by a 27 min 11C-acetate PET scan on a GE Discovery ST PET/CT scanner (scanner II). The LV-aortic time-activity curve (TAC) was extracted automatically from dynamic PET data using cluster analysis. The first-pass peak was isolated by automatic extrapolation of the down-slope of the TAC. FSV was then calculated as the injected dose divided by the product of heart rate and the area under the curve of the first-pass peak. Gold standard FSV was measured using cardiovascular magnetic resonance (CMR) and Phase Velocity Mapping within two weeks of PET imaging. Results: Cluster analysis could be performed successfully for all scans. FSV-PET was highly correlated with FSV-CMR (r=0.88, slope=0.86, offset=19.6 mL for scanner I, r=0.88, slope=1.44, offset=9.2 mL and r=0.91, slope=1.56, offset=-5.6 mL for scanner II for 15O-water and 11C-acetate, respectively) although a systematic bias was observed for both scanners (p=0.02 for scanner I, p<0.001 for scanner II for both 11C-acetate and 15O-water). FSV based on 11C-acetate and 15O-water correlated highly (r=0.99, slope=1.05) with no significant difference between FSV estimates for each tracer (p=0.17). Conclusion: FSV can be obtained automatically and reliably using dynamic PET/CT and cluster analysis. Results are similar for 11C-acetate and 15O-water although a scanner-dependent bias was observed and a scanner calibration factor might be required. This method could potentially be generalized to other tracers and more scanners, although this requires further validation.