Background : Arterial sampling in PET studies for the purposes of kinetic modeling remains an invasive, time intensive and expensive procedure. Alternatives to derive the blood time-activity curve (BTAC) non-invasively are either reliant on large vessels in the field of view or are laborious to implement and analyse as well as being prone to many processing errors. An alternative method is proposed in this work by the simulation of a non-invasive coincidence detection unit.
Results: We utilized GATE simulations of a human forearm phantom with a blood flow model, as well as a model for dynamic radioactive bolus activity concentration based on clinical measurements. A fixed configuration of 14, and also separately, 8 detectors were employed around the phantom, and simulations performed to investigate signal detection parameters. BGO crystals proved to show the highest detection efficiency and sensitivity to a simulated BTAC with a maximum coincidence rate of 575 cps. Repeatable location of the blood vessels in the forearm allowed a half-ring design with only 8 detectors. Using this configuration, maximum coincident rates of 250 cps and 42 cps were achieved with simulation of activity concentration determined from 15 O and 18 F arterial blood sampling. NECR simulated in a water phantom at 3 different vertical positions inside the 8-detector system (Y=-1 cm, Y=-2 cm and Y=-3 cm) was 8360 cps, 13041 cps and 20476 cps at an activity of 3.5 MBq. Addition of extra axial detection planes to the half-ring configuration provided increases in system sensitivity by a factor of approximately 10.
Conclusions: Initial simulations demonstrated that the configuration of a single half-ring 8 detector of monolithic BGO crystals could describe the a simulated BTAC in a clinically relevant forearm phantom with good signal properties, and an increased number of axial detection planes can provide increased sensitivity of the system. The system would find use in the derivation of the BTAC for use in the application of kinetic models without physical arterial sampling or reliance on image-based techniques.