Multi-Tuned Cable Traps for Multinuclear MRI and MRS.

Abstract

The method of pole-insertion for multi-tuning cable traps was studied for multinuclear MRI and MRS applications. Relative efficiency of the different cable trap modes was studied as component values were varied and at four different magnetic field strengths. In all cases, efficiencies were compared to equivalent single-tuned designs. The multi-tuned traps were able to block shield currents at multiple frequencies with only slightly degraded efficiencies as compared to their single-tuned counterparts. As in double-tuned coil design, the cable trap effectiveness at each frequency was found to be highly dependent on the trap inductor value with larger trap inductances leading to worse efficiency at the lower frequency but better efficiency at the higher frequency. This relationship held at all field strengths examined. This work presents design guidelines for the double-tuning method that are useful when designing RF coils for multinuclear studies. The design takes up less space than using two single-tuned cable traps mounted in series as is commonly done. Triple-tuned and "floating" designs were also demonstrated as proofs-of-concept for a single field strength and showed great promise to prove similarly useful in future studies. For many applications such as when using high-density array coils, finding a space-efficient solution to eliminate common-mode currents could be of significant benefit. This multi-tuned approach provides space efficiency at a small cost in trapping efficiency.