Some physical characteristics of a time-of-flight positron tomography (CEA-LETI-TTV03) obtained with the EEC emission phantom

We present measurements performed on the time-of-flight positron emission tomograph CEA-LETI-TTV03 with the EEC Emission Phantom. The transaxial resolution for a direct plane in the reconstructed image (Ramp filter, fc = 0.25 mm-1) was found to be 6.2 mm (radial and tangential) at center, 6.8 mm (radial) and 6.1 mm (tangential) at 45 mm from the center and 8.6 (radial) and 5.3 (tangential) mm at 90 mm from the center; in an image reconstructed with a Hanning filter at the same frequency cut-off and with a scatter correction, these values are degraded to 7.1 mm (tangential) and 7.2 mm (radial) at center, 7.6 mm (radial) and 6.9 mm (radial) at 45 mm from the center and 9.5 mm (radial) and 6.1 mm (tangential) at 90 mm from the center. Values were identical for direct and cross planes and correcting from the scatter radiation did not modify the resolution. Recovery coefficients for a 17 cm diameter sphere were equal to 0.85 in a direct plane and 1. for a cross plane, this being due to the axial resolution which is 9.1 mm and 7.1 mm at 5.5 cm from the center for direct and cross planes respectively. With 10 mCi in the phantom simulating abdominal imaging the maximum recorded coincidences on a cross plane was 84.4 kevents/sec, 50.2 kevents/sec on a direct plane and 343.4 kevents/sec for the entire machine. The dead time losses in terms of trues were equal to 24% and 17% for direct and cross planes respectively while the single rate was 19900/sec/detector. Scatter fraction, evaluated using a uniform cylinder, was found to be 15% for a cross plane.