makeSLRpulse

Generates a selective excitation RF pulse using the Shinnar-Le Roux (SLR) algorithm. This function acts as a wrapper for a Python function that utilizes the sigpy library. It designs RF pulses for various applications, including excitation, refocusing, and inversion.

Syntax

function [rf, gz, gzr, delay] = makeSLRpulse(flip,varargin)

Calling Pattern

mr.makeSLRpulse(...)
mr.makeSLRpulse('ParameterName', value, ...)

Parameters

This function accepts both positional parameters and name-value pairs.

Required Parameters

Parameter Name	Value Type	Description	Example	Units
flip	double	The desired flip angle of the RF pulse.	pi/2	radians

Name-Value Pair Arguments

Parameter Name (string)	Value Type	Default	Description	Example
system	struct	[]	A structure containing system parameters (e.g., from mr.opts()). If empty, default parameters will be used.	mr.opts()
duration	double	1e-3	The duration of the RF pulse. (Units: seconds)	0.004
freqOffset	double	0	Frequency offset of the RF pulse. (Units: Hz)	100
phaseOffset	double	0	Phase offset of the RF pulse. (Units: radians)	pi/4
freqPPM	double	0	Frequency offset in parts per million (ppm). (Units: ppm)	10
phasePPM	double	0	Phase offset in parts per million (ppm). (Units: ppm)	5
timeBwProduct	double	4	Time-bandwidth product of the pulse.	6
passbandRipple	double	0.01	Passband ripple of the filter.	0.005
stopbandRipple	double	0.01	Stopband ripple of the filter.	0.005
filterType	char	'mt'	Type of filter used for pulse design ('mt', 'ms', 'pm', 'min', 'max', 'ls').	'ls'
apodization	double	0	Apodization parameter (currently not used).	0.1
centerpos	double	0.5	Center position (currently not used).	0.6
maxGrad	double	0	Maximum gradient amplitude. (Units: Hz/m)	2000
maxSlew	double	0	Maximum gradient slew rate. (Units: Hz/m/s)	100000
sliceThickness	double	0	Slice thickness. (Units: meters)	0.005
delay	double	0	Additional delay before the pulse. (Units: seconds)	0.001
dwell	double	0	Dwell time (currently not used). (Units: seconds)	0.000001
use	char	'excitation'	Pulse type ('excitation', 'refocusing', etc.).	'refocusing'
pythonCmd	char	''	Python command (currently not used).	''

Returns

Output	Value Type	Description
rf	struct	The designed RF pulse (Pulseq sequence).
gz	struct	The slice-selective gradient (Pulseq sequence).
gzr	struct	The refocusing gradient (Pulseq sequence, might be empty).
delay	double	The total delay associated with the pulse

Examples

% 90-degree excitation pulse with detailed control
[rf_ex, gz, gzr] = mr.makeSLRpulse(pi/2, 'duration', rfDur1, 'SliceThickness', sliceThickness*sth_ex, ...
    'timeBwProduct', 5, 'dwell', rfDur1/500, 'passbandRipple', 1, 'stopbandRipple', 1e-2, ...
    'filterType', 'ms', 'system', system, 'use', 'excitation', 'PhaseOffset', pi/2);

% 180-degree refocusing pulse
[rf_ref, g_ref] = mr.makeSLRpulse(pi, 'duration', rfDurRef, 'PhaseOffset', pi/2, ...
    'SliceThickness', voxel(2), 'timeBwProduct', 6, 'passbandRipple', 1, 'stopbandRipple', 1e-2, ...
    'filterType', 'ms', 'system', system, 'use', 'refocusing');

% Multi-slice excitation
[rf_ex, g_ex, g_exReph] = mr.makeSLRpulse(pi/2, 'Duration', rfDurEx, ...
    'SliceThickness', voxel(1), 'timeBwProduct', 6, 'passbandRipple', 1, 'stopbandRipple', 1e-2, ...
    'filterType', 'ms', 'system', system, 'use', 'excitation');

See Also

mr.opts