Improvements in scan speed and signal-to-noise ratio are essential for enhancing disease detection sensitivities of MRI, especially in cardiac, vascular and neurofunctional applications. Improving speed and SNR with strong gradients and high magnetic field strength however faces looming constraints due to human physiological limits. We propose new technique, called parallel excitation, is based on a parallel transmit system that is composed of multiple transmit coils with corresponding RF pulse synthesizers and amplifiers, as well as pulse design methods that embody the novel concept of orchestrating RF field spatiotemporal variations for a substantial boost in excitation and imaging performance. The specific program aims include 1) design and build prototype MRI systems and coil arrays, 2) develop pulse design methods that use parallel excitation to achieve multi-fold excitation acceleration and flip-angle uniformity improvement, and 3) develop parallel excitation-based methods for reducing RF power absorption. We will further develop high-speed imaging applications based on the novel use of 2D or 3D flip-angle profiles, with and without parallel-receive MRI. Upon successful completion, two fully functioning systems (1.5T and 3T) will have been established that can be readily disseminated for further application development, or used, with slight modification, to enable body and head imaging at still higher field strengths with SAR and flip-angle issues effectively managed. Meanwhile, a body of knowledge on parallel excitation will have been generated and disseminated that changes the way RF excitation is performed in MRI, yielding new directions in MRI system instrumentation, RF pulse design, pulse sequence optimization, and diagnostic imaging opportunities. ? ? ?
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