Presentation 

Full exploitation of ultra high field magnetic resonance imaging (MRI) requires innovative methods to control the homogeneity and the safety of the high frequency radiofrequency (RF) waves used to acquire images. This can be achieved by using parallel transmission of the RF waves to boost the number of degrees of freedom, but its complexity has thus far deterred its wide use. The aim of EXPAT is to apply sophisticated quantum information processing (QIP) techniques to manipulate the nuclear spins efficiently with parallel transmission at ultra high field MRI on the state-of-the art 7 Tesla and the unique 11.7 Tesla MRI scanner that will be installed at NeuroSpin/CEA. By bringing a practical solution to parallel transmission at such high field strength, EXPAT will be a major breakthrough for MRI of the brain.

Radiofrequency pulse design departing from traditional MRI concepts thus will be a central aspect of this project. Mathematical concepts will be applied to describe efficiently sub-classes of RF waveforms leading to non-trivial and useful dynamics, thereby providing a minimum number of parameters to be used as ingenious "control knobs" to design parallel transmission pulses and explore regimes of spin excitation hardly accessible by current formalisms. Another novel aspect will be to revisit entirely the way RF safety is handled by taking directly into account the temperature in the human head during scanning and at pulse design stage, rather than the indirect specific absorption rate currently used in MRI. Tracking temperature will relax the constraints in RF pulse design as well as in data acquisition strategies by at least a factor of two, while strictly enforcing safety. Subject-based radiofrequency field characterization, model validations, MRI sequence developments, numerical studies and careful monitoring of the experiments will be conducted to optimize the implementation of the new methods.