Error-Tolerant RF Litz Coils for Double-Resonance MRI

Introduction: A new class of NMR/MRI rf volume coils is being developed that permits improved tuning range, tuning stability, B1 homogeneity, sensitivity, and ease of use compared to birdcages over a wide range of practical conditions, esp ecially for double-resonance microscopy and wraparound flexible applications. They are denoted litz coils (after the German word for "braided'), as the desired flux transparency is achieved using woven foil with insulated crossovers. While it has been shown that the low-order quadrature and homog eneity errors in the birdcage can be corrected with just two trimmer capacitors [1], the remaining rungcurrent errors may exceed 30% and can only be addressed by a complex tuning procedure [2]. Moreover, the magnetic filling factor ηF of bir dcages with closely spaced external shields is us ually b elow 5%.