Abstract
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Objectives A recent bolus/infusion (BI) study of [18F]FPEB using a Kbol of 190 minutes reported good stability of uptake for most regions with higher receptor levels, but marginal stability of uptake and underestimated receptor levels in the hippocampus while overestimating levels in moderate and lower uptake regions (Sullivan, 2013) . The purpose of this study was to examine whether an optimized BI schedule could be defined.
Methods Simulations of BI schedules were performed based on previously published modeling studies following bolus administration of [18F]FPEB (Wong, 2013). Based on these simulations, B/I studies were performed in six healthy subjects (4 M, 2F, mean age of 20.2 years). A mean dose of 4.4 mCi [18F]FPEB was administered using a Kbol of 205 minutes and 180 min infusion time. Data from one subject could not be used due to extreme motion.
Results Simulations showed that Kbol's of 200 to 220 produced good stability of uptake in regions with higher receptor levels including the hippocampus while a Kbol of 190 minutes produced somewhat better stability in regions with lower uptake after 130 minutes. For human BI studies a Kbol of 205 produced good stability of total uptake (1.6-5.1%,mean=2.8%) at 90 to 130 min in higher uptake regions, anterior hippocampus, caudate, putamen, ventral striatum, anterior cingulate, ventromedial prefrontal cortex, insula. Moderate uptake was seen in the thalamus which had marginal stability (10%/hr). Adequate stability of uptake (<10%/hr) was not seen in lower uptake regions. Uptake in potential reference regions showed that cerebellar white matter (WM) had lower uptake than pons while WM in the centrum semiovale had lower uptake than either. The appropriateness of possible reference regions and BI versus bolus studies will be discussed.
Conclusions A Kbol of 205 with an infusion time of 130 min allows attainment of stable uptake in high uptake regions including the hippocampus but only marginal stability of uptake in thalamus.
Research Support This study supported by NIDA grant 1R21DA031441.