Quantifying cerebral PET with FDG using dynamic internal carotid arteries imaging

The improvement of the PET sensitivity and resolution allows the measurement of the input function using dynamic scanning of the internal carotid arteries. Five subjects were scanned on an ECAT EXACT HR+ with the following sequence (number×length in seconds): 12×10, 2×30, 2× 150, 3×300, 1×600, 1×1200 and 1×150. The scan started with the injection of the 18-FDG (168 MBq in average for the 5 subjects). The latter scan was used to calculate rCMRglc images with the autoradiographic model using the 4 “PHELPS constants”. A plasma input function was measured in a radial artery. Venous samples were also taken 5 minutes after the injection at the same rate as the arterial samples (venous function). The effects of the limited resolution on the carotid measurements were corrected using geometrical factors computed from each MRI registered to the PET images. The carotid input function was then obtained after correction for blood to plasma difference using each venous function. The relative differences between the rCMRglc values calculated with an input function measured in the carotid and the radial arteries were 6%, 2%, 27%, 20%, and 8% respectively for the 5 subjects. In conclusion, for tracer modelling sensitive to the integral of the input function (such as FDG modelling), this method is adequate for quantification