Small flip-angle spokes with SAR constraints
Guérin B, Gebhardt M, Cauley S, Adalsteinsson E, Wald LL (2014). "Local specific absorption rate (SAR), global SAR, transmitter power, and excitation accuracy trade‐offs in low flip‐angle parallel transmit pulse design." Magnetic Resonance in Medicine 71(4): 1446-1457.
What this code does
This Matlab code (no MEX, no GPU code) computes least-squares and magnitude least-squares pTx spoke pulses. The MLS problem can be solved using the phase adoption approach of Setsompop et al. or a full optimization strategy (see the file spokes_3/run_spokes.m and options therein). Spokes can be optimized for several frequencies (spatio-spectral design) in order to build in robustness to off-resonance effects.
Pre-scan data format
The format of the pre-scan data (e.g., B0 map, B1+ maps, slice information in the SODA file) matches the Siemens data format (pTx "Step 2" system).
Unzip the code folder and add it to your path. Unzip the data folder and run the script run_spokes.m. There are several options in it that are straightforward to understand (e.g., LS/MLS, spatio-spectral design). Most of the spoke options (such as slice-thickness, slice-selection gradient, time-bandwidth product etc...) are specified in the text file spokes_def.txt and can be changed there.