Low power small size magnetic resonance imaging signal acquisition system with optical connections
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In Magnetic Resonance Imaging (MRI) systems echo signals received by a coil are sampled and subjected to digital signal processing. The physical link between the sampling system and the signal processor is coaxial cables in conventional applications. However, coaxial cables possess risks and limitations when placed in gradient and radio frequency fields, both of which are present in an MRI system. The complexity of issues related to coaxial cables increases rapidly as the number of channels scales up in parallel imaging applications. To overcome the drawbacks of coaxial cables, systems that employ fiber optic cables for the transmission of the analog signal have been proposed. In this work, we designed a system which transmits sampled and digitized analog signal through fiber optic cables, while the power required to perform acquisition and conversion operations is also delivered to the module using an optical link. To increase the number of channels that can be placed in a typical birdcage compartment, dimensions of the module are kept as small as possible. The module is designed to be used in a project with a 10.5 Tesla MRI system operating at 447 MHz which is currently available only at the University of Minnesota. The circuit design for one of the proposed approaches is completed at both the schematic and the layout levels to perform feasibility analysis. Theoretical estimations show that the power consumption is 263 mW and occupied cross-sectional area is 900 mm2 per channel while attaining more than 95 dBFS SNR figure using 65 MSPS sampling rate.