Novel RF-pulses and parallel-transmit methods for compensation of signal loss in functional MRI at 3 and 7 Tesla

• Applicant: Professor Dr. Benedikt Andreas Poser
• Subject Area: Human Cognitive and Systems Neuroscience
• Term: from 2011 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 194410021

Functional magnetic resonance imaging (fMRI) allows unprecedented insights into the functioning of our brain. Activated regions are identified non-invasively by detecting local blood oxygenation-level dependent (BOLD) signal changes that accompany neuronal activity. The widely used method for BOLD fMRI is echo-planar imaging (EPI) which offers favorable sensitivity at good spatio-temporal resolution. The serious drawback is that EPI is not only sensitive to the desired microscopic magnetic changes during neuronal activation, but also undesired macroscopic magnetic field variations near regions of differing magnetic susceptibility, especially the air cavities. These susceptibility artifacts result in signal loss that effectively prohibits activation detection in many brain areas that are highly relevant in modern neuroscience. Development of artifact free techniques therefore remains a crucial requirement for many neuroscientific and clinical applications of fMRI. It would for instance facilitate studies of the still poorly understood memory network, and help understand ailments like Alzheimer disease or mood and stress disorders.I propose a set of highly innovative developments to compensate the EPI signal loss artifact by means of tailored RF pulses and parallel transmit (pTX) techniques.Specifically, the aim is to develop a simultaneous 3D shim for use at 3 and 7 Tesla that has the potential of generating virtually artifact free images. This incorporates the design of 1D and 2D spectral-spatial pulses on an eight-channel pTX system, combined with the recently developed simultaneous z-shim technique.The endeavor will be assessed by simulations, phantom experiments and application to clinical fMRI studies on volunteers. If successful the methods will have considerable impact on the abilities of fMRI in its neuroscientific and clinical applications, and will constitute a significant and innovative contribution to field of tailored RF pulse design.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor V Andrew Stenger, Ph.D.