Enhancing fMRI contrast in awake-behaving primates using intravascular magnetite dextran nanopartieles

Functional MRI in awake-behaving primates is an emerging tool for bridging the gap between human fMRI and neurophysiology information from nonhuman pr imates. We report the use of magnetite dextran nanoparticles (Feridex) as a blood-pool agent to enhance fMRI contrast-to-noise (CNR) in primate FMRI T he intravascular half-life of the magnetite dextran was long compared to la nthanide chelates (T-1/2 = 198 min) with shortened T-2 relaxation observed in blood and cerebral cortex. Greater than 3-fold enhancement in the percen tage MR signal change was observed using nanoparticles (13%) compared with conventional BOLD fMRI (4%). The calculated regional cerebral blood volume in macaque primary visual cortex increased 32% with photic stimulation. The increased CNR allows greater flexibility in the design of awake-behaving p rimate fMRI studies with the potential for improvements in resolution and s ignificantly shortened imaging times. NeuroReport 12:2335-2340 (C) 2001 Lip pincott Williams & Wilkins.