A refined circuit model of high temperature superconducting spiral coils for MRI

A high temperature superconducting (HTS) spiral coil for magnetic resonance imaging (MRI) usually contains many turns of thin track patterned on an HTS film. The total length of the coil track is long (up to few meters) in order to meet the requirement of fitting the resonance frequency to that of the MRI scanner, in the range from 4 MHz (0.1 T of magnetic field) to about 100 MHz (high field). It takes too long time for commercially available software to simulate such circuits because of the relatively large size and small track width of the coil. A new computational frequency-domain model is developed for design and analysis of HTS spiral surface coils for application to MRI. The model is faster in the simulation of the resonance frequencies and s-parameters of the HTS spiral coils because some approximations are used for the coils with long track and low resonance frequency. The new model is based on the circuit analyses theory. The 2-inch coils were simulated for a field of 0.5 T. Tuning and matching are studied by using this model.