Unipolar design of head gradients for eliminating the encoding ambiguity

Gradients with a conventional, bipolar design generally face a trade-off between performance, encoding ambiguity, and circumventing the latter by means of RF selectivity. This problem is particularly limiting in cutting-edge brain imaging performed at field strengths ≥ 7T and using high-performance head gradients. To address this issue, the present work proposes to fundamentally eliminate the encoding ambiguity in head gradients by using a unipolar z-gradient design that takes advantage of the signal-free range on one side of the imaging volume. This concept is demonstrated by design of a unipolar high-performance head gradient and simulated 7T imaging with such a system.