Parallel MRI for High Field Neuroimaging

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DESCRIPTION (provided by applicant): This is a renewal of a Research Project Grant R01DA019912 "Parallel MRI for High Field Neuroimaging" for the development of techniques for rapid, artifact free functional MRI (fMRI). During the previous funding period numerous methods were developed for correcting image artifacts using "parallel transmission" (PTX) and "tailored RF" (TRF) pulses. These artifacts include RF field (B1+) inhomogeneity and susceptibility artifacts (B0 inhomogeneity). B1+ inhomogeneity produces large intensity variations in images and B0 inhomogeneity creates large signal voids that obscure many brain regions crucial to understanding disease in the brain including addictive disorders. Recently Simultaneous Multi-Slice (SMS) imaging has been shown to be a promising technique for ultra-fast fMRI. SMS imaging excites multiple overlapping slices that are unfolded during reconstruction using multiple receiver coils. SMS imaging is significant for numerous applications including fMRI because it allows for increased acquisition speed on the order of four to eight. Although SMS imaging is gaining popularity, there has been little work done on improving SMS RF pulse excitations, extending it to PTX, and to non-Cartesian spiral data acquisitions. Improved pulse designs and PTX will allow for SMS excitations with reduced B1+ and B0 inhomogeneity. Spiral imaging has a highly efficient gradient usage allowing for shorter acquisition times and further increases in acquisition speed. This renewal will focus on these innovations to SMS imaging at 3T. The PI has assembled a team of internationally recognized scientists including Dr. Lawrence Wald at Massachusetts General Hospital, who is a world expert in PTX coil design and SMS imaging, and Dr. William Grissom at Vanderbilt University, who is a top researcher in PTX and RF pulse design. We will pursue the following Specific Aims: (1) Develop SMS excitations for PTX; (2) develop SMS TRF pulses that compensate for B1+ and B0 inhomogeneity; (3) develop non-Cartesian spiral acquisitions and reconstructions for ultra-fast SMS imaging; and (4) validate the methods with fMRI in control subjects.