[Contribution of time of flight and point spread function modeling to the performance characteristics of the PET/CT Biograph mCT scanner]

Objective: To characterize the performance of the Biograph mCT PET/CT TrueV scanner with time of flight (TOF) and point spread function (PSF) modeling.

Material and methods: The PET/CT scanner combines a 64-slice CT and PET scanner that incorporates in the reconstruction the TOF and PSF information. PET operating characteristics were evaluated according to the standard NEMA NU 2-2007, expanding some tests. In addition, different reconstruction algorithms were included, and the intrinsic radiation and tomographic uniformity were also evaluated.

Results: The spatial resolution (FWHM) at 1 and 10cm was 4.4 and 5.3mm, improving to 2.6 and 2.5mm when PSF is introduced. Sensitivity was 10.9 and 10.2 Kcps/MBq at 0 and 10cm from the axis. Scatter fraction was less than 34% at low concentrations and the noise equivalent count rate (NECR) was maximal at 27.8 kBq/mL with 182 Kcps, the intrinsic radiation produced a rate of 4.42 true coincidences per second. Coefficient of variation of the volume and system uniformity were 4.7 and 0.8% respectively. The image quality test showed better results when PSF and TOF were included together. PSF improved the hot spheres contrast and background variability, while TOF improved the cold spheres contrast.

Conclusions: The Biograph mCT TrueV scanner has good performance characteristics. The image quality improves when the information from the PSF and the TOF is incorporated in the reconstruction.