splitGradientAt¶

Splits a trapezoidal or arbitrary gradient into two parts at a specified time point. The function divides a gradient waveform, either a trapezoid or an arbitrary shaped gradient, into two separate gradients at a given time. It adjusts the delays to ensure that combining the resulting gradients using addGradients recreates the original gradient. For trapezoidal gradients, it returns extended trapezoids; for arbitrary gradients, it returns arbitrary gradient objects.

Syntax¶

function [varargout] = splitGradientAt(grad, timepoint, varargin)

Calling Pattern¶

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

Parameters¶

Required Parameters¶

Parameter Name	Value Type	Description	Example	Units
`grad`	struct	Structure representing the gradient waveform to be split. This structure contains fields like 'type' ('grad' or 'trap'), 'tt' (time points), 'waveform' (amplitude values), 'channel', and 'delay'.	`{type:'trap', tt:[0 1 2 3], waveform:[0 100 100 0], channel:'x', delay:0}`
`timepoint`	double	Time point (in seconds) at which to split the gradient waveform.	`0.002`	seconds

Name-Value Pair Arguments¶

Parameter Name (string)	Value Type	Default	Description	Example
`system`	struct	`[]`	Structure containing system parameters, such as `gradRasterTime`. If not provided, default system parameters are used (via `mr.opts()`). Valid values: A structure with fields such as `gradRasterTime`.	`mr.opts()`

Returns¶

Output	Value Type	Description
`grads`	cell	Cell array containing the two resulting gradient structures. If nargout == 1, it returns a single cell array with both gradients. If nargout > 1, it returns each gradient separately.

Examples¶

% Example 1: Split gradient for slice selection timing
gz_parts = mr.splitGradientAt(gz, rf.delay + rf.t(end));
gz_parts(1).delay = mr.calcDuration(gzReph);
gz_1 = mr.addGradients({gzReph, gz_parts(1)}, 'system', sys);

% Example 2: Split readout gradient at ADC end for optimal timing
gx_parts = mr.splitGradientAt(gx, ceil((adc.dwell*adc.numSamples+adc.delay+adc.deadTime)/sys.gradRasterTime)*sys.gradRasterTime);
gx_parts(1).delay = mr.calcDuration(gxPre);
gx_1 = mr.addGradients({gxPre, gx_parts(1)}, 'system', sys);

% Example 3: Split blip gradient for EPI sequence
gyBlip_parts = mr.splitGradientAt(gyBlip, blip_dur/2, sys);
[gyBlip_up, gyBlip_down, ~] = mr.align('right', gyBlip_parts(1), 'left', gyBlip_parts(2), gx);