Multi-coil B0 shimming
This page contains resources related to multi-coil B0 shimming research being conducted in the Wald lab. The page is currently under construction...
Matlab tools available for download include:
(1.) Simulations of the static magnetic field (B0) generated by wire loops arrayed in various geometries on helmets and other structures. These fields are useful for simulated multi-coil B0 shim performance.
(2.) Calculation of optimal shim currents for a given shim coil geometry and one or more brain B0 field maps. The optimization uses Matlab function "fmincon" to incorporate constraints on the loop shim currents.
(3.) Method for choosing the optimal subarray of M coils in a multi-coil shim array with N elements, M < N. The method uses a genetic algorithm to try to find the subarray that minimizes the standard deviation of the shimmed B0 field maps across all slices and subjects.
All of this functionality is included in the following download:
---> Click here to download the Matlab scripts. <---
After unzipping the downloaded file, please see the README text file for details on running the scripts.
NOTE: The shimming optimization requires "fmincon" from the Optimization Toolbox and "ga" from the Global Optimization Toolbox. In order to use the script for brain masking and phase unwrapping, FSL must be installed on the system. To the best of our knowledge, FSL only runs on Max and LINUX.
Related work
Jason P. Stockmann, Thomas Witzel, Boris Keil, Jonathan R Polimeni, Azma Mareyam, Cristen LaPierre, Kawin Setsompop, Lawrence L Wald. A 32-channel combined RF and B0 shim array for 3T brain imaging. Magn. Reson. Med. 77(1);2016:441-451. Journal link. Open PMC version
Jason P. Stockmann, Bastien Guerin, Lawrence Wald (2016). Improving the efficiency of integrated RF-shim arrays using hybrid coil designs and channel placement and compression via a genetic algorithm. Proc. Int. Soc. Magn. Reson. Med. (2016), p. 1153. HTML version of abstract
