NOVEL ENCODING TECHNOLOGY FOR MRI

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This proposal's goal is to explore a radically new spatial encoding field for MRI. The field, called PERL, is PERiodic in the x-dimension and Linear in the y-dimension. It is unique because it is a function of two orthogonal spatial variables and is spatially periodic. The reconstruction is also unique, involving a Fourier transform in one dimension and the solution of a Bessel function integral transform in the other. Theoretical analysis shows that PERL offers several exciting possibilities for MRI. For example, the spatial resolution for PERL MRI can be increased with no cost in either imaging time or SNR and thus may be well suited for high-resolution tumor imaging. Further, the basis functions for the PERL reconstruction are spatially localized and thus PERL may be an ideal candidate for surgical guidance where only a portion of the field of view is changing. In addition, the periodic nature of the field enables an elegant flow measurement technique, i.e. a moving phase front, allowing velocity dependent measurements relative to a moving reference frame. Theory also shows that successive PERL spin echoes are 90 out of phase with each other, implying that data acquisition may be increased by a factor of two over traditional methods. Furthermore, the PERL analysis provides a way to enhance the FOV in traditional MRI that uses standard "linear" gradient coils by providing a mechanism to include nonlinear regions of these traditional coils. A PERL coil is naturally implemented on a flat coil form and can thus be positioned immediately adjacent to the body, thereby operating as a high efficiency surface "gradient" coil. The PERL coil is also desirable in that it has zero Lorentz force, minimal eddy currents and very low inductance. In the research proposed, we will design and build PERL coils, including an integrated RF coil, and experimentally implement PERL MRI. Basic experiments and numerical simulations will be performed to test the above-mentioned unique features of PERL to obtain an understanding of where its real strengths and weaknesses lie relative to potential clinical applications.