Functional MRI at 1.5 T

Human studies were conducted to determine the feasibility of functional MRI during auditory stimulation using conventional hardware (i.e., without echo-planar imaging) in a Philips 1.5 T Gyroscan system. A gradient-echo pulse sequence was optimized to minimize the effect of gradient sound. Simple tonal stimulation and linguistic stimuli designed to activate regions responsible for comprehension were investigated. Also, functional images in response to visual and somatosensory stimulation were generated, albeit with a different gradient-echo sequence to optimize contrast and temporal resolution. A registration technique was developed to reduce head motion artifacts. Cerebrospinal fluid pulsation artifacts however, were not removable even with flow compensating gradient pulses. A phase-shift imaging technique was investigated which has the potential to separate the relatively large blood vessels from the microvasculature. Results of functional imaging indicate a 2-9% increase in signal intensity localized to the corresponding auditory, visual or somatosensory brain regions during stimulation