NECR ANALYSIS OF 3D BRAIN PET SCANNER DESIGNS

A dedicated 3D brain PET scanner has several advantages, most notably increased sensitivity, over a whole body scanner for neurological stud ies. However brain scanners have higher scatter fractions, random coun t-rates and deadtime for the same activity concentration. We have used noise effective count-rate (NECR) analysis to compare brain scanners of 53, 60, and 66 cm diameter with the GE ADVANCE whole body scanner ( 93 cm diameter). Monte Carlo simulations of a brain-sized phantom (16 cm diameter, 13 cm length) in the ADVANCE geometry were used to develo p a model for NECR performance, which was reconciled to results from a decay series measurement. The model was then used to predict the perf ormance of the brain scanner designs. The brain scanners have noise ef fective sensitivities (the slope of the NECR curve at zero activity) a s much as 40% higher than the body scanner. However, their NECR advant age diminishes quickly as the activity concentration increases. The br ain scanners' NECR equals the body scanner with about 0.7-0.8 mCi in t he phantom; the body scanner has superior NECR performance at higher a ctivity levels. hn imaging center concentrating on only very low activ ity imaging tasks would find the efficiency advantage of a smaller det ector diameter valuable, while a center performing higher activity stu dies such as bolus water injections or 5mCi FDG injections might prefe r the count rate performance of a whole body scanner.