Abstract
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Objectives The 18F-labeled fatty acid, trans-9(RS)-18F-fluoro-3,4(RS,RS) methyleneheptadecanoic acid (18F-FCPHA / CardioPET) is undergoing Phase II evaluation as an imaging agent for myocardial perfusion and fatty acid uptake in patients with known or suspected coronary artery disease (CAD). We assessed the feasibility and kinetic modeling of 18F-FCPHA as a perfusion radiotracer.
Methods Five male patients (64 ± 11yrs) with known or suspected CAD, 2 at rest and 3 during dipyridamole stress, underwent dynamic imaging for 60 min after IV administration of 273 ± 4 MBq of 18F-FCPHA. Conventional rest/stress 99mTc/99mTc SPECT MPI was performed on separate days. The 18F-FCPHA images from 2-8 min were compared with the corresponding SPECT images. Myocardial time activity curves were generated for each of 17-segments and the left ventricular cavity. Using this data, 1-compartment 2-parameter (1C2P) and 2-compartment 3-parameter models were evaluated. The data were fitted to 10, 15, and 20 min of image data. Standard measures of goodness-of-fit were used to assess the quality of the fits. Kinetic parameters for each model and fitting time were compared for global and regional stress and rest data.
Results All stress 18F-FCPHA images exhibited perfusion defects in the same areas as the SPECT images (Fig). The rest images for both radiotracers exhibited homogenous uptake. A 1C2P compartment model using 15 min of data achieved the best fit. Global K1 values during stress (0.22 ± 0.11) were higher than rest values (0.12 ± 0.0006). On the stress images, K1 values in defect zones were significantly lower (0.11 ± 0.05) compared with zones with preserved radiotracer uptake (0.28 ± 0.08, P < 0.01). The coefficient of variation for K1 values was 20% on the rest images.
Conclusions This preliminary evaluation suggests that relative and quantitative perfusion measurements may be possible with PET and 18F-FCPHA.