Asymmetric Tapered Solenoid Designs for Halbach based Portable Magnetic
Resonance Imaging
Abstract
Halbach array is a popular permanent magnet array used in head dedicated
portable MRI. It supplies transversal main magnetic field (B0), and it
works well with solenoid RF coils when B0 inhomogeniety is small. The B0
a Halbach array supplies is low. To compensate this, it is desired to
have a high coil sensitivity of the solenoid coil that works in such a
system. Hence in this paper, an asymmetrical tapered solenoid was
proposed and an optimization was carried out for both the coil profile
and pitches between turns for high coil sensitivity and homogeneity.
Multi-objective genetic algorithm was used. The optimized solenoid coils
are constructed and compared with a reference coil of comparable
dimension. The optimal design shows B1 field increase of ∼33% and
minimal tradeoff in homogeneity of ∼10 %. The measured results are in
good agreement with simulated and calculated results.