IMTtugraz/mr.control

mr.control

Magnetic resonance RF pulse design by time optimal control

This software solves the time-optimal control problem introduced in the paper "Simultaneous Multislice Refocusing via Time Optimal Control" [submitted, TBA] by Armin Rund, Christoph Aigner, Karl Kunisch, and Rudolf Stollberger. The code implements the diffusion examples.

Introduction

The lower-level solver tr_semism_quasiNewton() and objfun() are based on the paper "Magnetic Resonance RF pulse design by optimal control with physical constraints" [https://doi.org/10.1109/TMI.2017.2758391] by the same authors.

The examples are taken from the ISMRM Challenge 2015/2016, see http://challenge.ismrm.org/node/71. Some initial guesses (RF and Gs) were created by using the PINS principle with a SLR subpulse, others by a superposition of the phase shifted SLR subpulses (RF) with a matched const Gs shape, similar to the code supplied by the ISMRM challenge organizers.

Test script (run this):

    main.m                              test script to start the optimization

Routines called by the test script:

    time_optimal_control.m              implements the time optimal control method
    prep_init.m:                        problem definition
    optimization_parameters.m:          parameters of the time-optimal control method
    check_and_transform_input.m         basic input parameter check
    reduce_PINS_duration.m              shortens PINS pulses instantaneously by deleting most of the parts with Gs=0 
    reduce_duration_and_warmstart.m     cut points out of the time grid
    tr_semism_quasiNewton.p             implements trust region semismooth quasi Newtion
    objfun.p                            computes the objective function
    prepare_globalization.p             find good candidate time points for cut/reduction        
    globalization.p                     upper level method with globalization (further description in time_optimal_control.m)
    globalization_fast.p                fast variant of the globalization (further description in time_optimal_control.m)
    blochsd.m                           spin domain bloch simulation
    store_solution.m                    saves the optimized RF and Gs shape
    plot_results.m                      plots optimized RF, Gs, slew-rate of Gs and the refocusing profile

Data files used by the test scripts:

    inits/CDIFF%_%.mat                  binary file containing a DIFF PINS init (challenge constraints)
    inits/CDIFF%_%_SUP.mat              binary file containing a DIFF superposition init (challenge constraints)
    inits/PDIFF1_4.mat                  binary file containing a DIFF PINS init (scanner 1 constraints)
    inits/SDIFF1_4.mat                  binary file containing a DIFF PINS init (scanner 2 constraints)

Usage

The code is started with the MATLAB script main.m and was tested with MATLAB version R2016a (9.0.0.341360) 64-bit (glnxa64). Parameters can be changed in 'prep_init.m' (problem definition) and 'optimization_parameters.m' (parameters of the time-optimal control method).

License

This work is licensed under the Creative Commons Attribution-NonCommercial 4.0 International License. To view a copy of this license, see license_CC_BY-NC.txt, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

mr.control is distributed WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

IMTtugraz / mr.control