Derivation of the input function from dynamic PET images with the HRRT

The High Resolution Research Tomograph (HRRT) with its improved spatial resolution (<2.5 mm), extended axial FOV (25 cm) and high sensitivity offers the possibility to obtain an image derived input function for quantitative PET studies. From the carotid artery in the region of the neck and the petrous bone, the time course of the blood activity can be derived with sufficient counting statistics in human studies. However an online motion correction system is a must. With medium sized animals like cats, the FOV of the HRRT covers both, the brain and the heart, which allows to determine the input function from the blood pool in the heart In cat studies with ¹⁵O-tracers the time course of the tracer activity in arterial blood has been measured with an arteriovenous shunt connected to a blood sampling system. The direct comparison to the input function derived from the blood pool in the left heart chamber in kinetic PET images reconstructed with OSEM3D in short time frames demonstrates the high accuracy and precision of the image derived input function.