Physical characteristics of TTV03, a new high spatial resolution time-of-flight positron tomograph

TTV03, a novel high-spatial-resolution TOF-PET (time-of-flight positron emission tomography) system, is presented. The machine consists of four 89-cm-diameter rings made of 7-mm-wide, 18-mm-high, 45-mm-deep BaF₂ crystals (324 per ring) individually coupled to 11-mm-diameter phototubes. The transaxial resolution (full width at half maximum or FWHM) in the reconstructed image is 5.7 mm at center, 5.7 mm (tangential), and 6.5 mm (radial) at 10 cm. The axial resolution is 8.8 mm (direct plane) and 6.7 mm (crossplane) at center, and 10.3 mm (direct) and 11.2 mm (cross) at 10 cm from center. With a 150-keV threshold, the TOF resolution is 750 ps (FWHM), and, with a 4.18-ns coincidence window, the sensitivity (true evts/s per μCi/cm³ ) is 9800 (direct plane) and 14300 (crossplane). At 1 μCi/cm ³, the ratio of random events to true events is .20 for the total and .03 per image element, and the scatter fraction is 22%. Dead time losses are 8.3% at 2.5 μCi/cm³ (four rings), but the tomograph can handle activities over 50 μCi/cm³ in small regions with negligible losses. These characteristics make TTV03 particularly suitable for dynamic brain and heart H₂¹⁵ bolus studies