Objectives: The development of specific radiotracers for the detection of vulnerable coronary plaque by means of PET requires precise information about the contrast that can be obtained by a given plaque-to-myocardium uptake ratio. This information is strictly related to the cardiac and respiratory gating settings of the acquisition. The goal of this study is to determine the gating configuration that maximizes plaque contrast in the reconstructed PET image. Methods: Both simulation and in-vivo studies have been performed to determine the impact of cardiorespiratory motion on the plaque. The 4D NCAT phantom has been used to generate images of the moving plaque uptake to be simulated with GATE in an ECAT 962 system. The in-vivo study consisted of a dual-gated PET scan (Siemens Biograph 16 PET/CT) of a live pig who had undergone surgical insertion on the epicardium of four 1.2 mm spherical markers containing different FDG concentrations. Results: In the simulated data the respiratory motion reaches 24 mm, three times larger than the cardiac motion. Furthermore, the respiratory pattern in the NCAT phantom does not contain sufficiently static phases to add cardiac gating without increasing the total scan time beyond the clinically acceptable. In the in-vivo study, however, the observed motion of the markers was 7 mm for respiration and 6.8 mm for cardiac beating. Conclusions: The plaque trajectory observed in simulations suggests the use of respiratory gating only. However, pig in-vivo measurements show that cardiac and respiratory motions have equivalent magnitudes so that dual gating should be preferred. Further patient studies will be performed to assess the clinical variability of the involved cardiorespiratory parameters and determine which model better fits to clinically observed motion.     «

Objectives: The development of specific radiotracers for the detection of vulnerable coronary plaque by means of PET requires precise information about the contrast that can be obtained by a given plaque-to-myocardium uptake ratio. This information is strictly related to the cardiac and respiratory gating settings of the acquisition. The goal of this study is to determine the gating configuration that maximizes plaque contrast in the reconstructed PET image. Methods: Both simulation and in-vi...     »