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Abstract #2817

The Underlying Cause of the Increasing Performance Gap Between Loop Arrays and the Ultimate SNR with Increasing Field Strength

Riccardo Lattanzi1, 2, Manushka Vaidya1, 2, Graham C. Wiggins1, Daniel K. Sodickson1, 2

1The Bernard and Irene Schwartz Center for Biomedical Imaging, Radiology, New York University Langone Medical Center, New York, NY, United States; 2The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, United States

Using an electrodynamic formulation based on a current mode expansion and dyadic Greens functions, we showed that only 2 divergence-free (i.e. magnetic-type) modes contribute to the ultimate intrinsic SNR (UISNR) in the center of a homogeneous sphere. However, discrete loop coils carry larger noise contributions than the ideal current modes in question, and UISNR cannot therefore be completely achieved with a modest number of loops. At higher field strengths, loops become less and less efficient because noise scales up by a larger factor than the signal. Away from the center, electric-dipole contributions are more significant and loops are increasingly inefficient.