EPGsim_GREsimple_ng.m

function [om_store,echoes,seq] = EPGsim_GREsimple_ng(alpha,N,TR,rlx)
% [om_store,echoes,seq] = EPGsim_GREsimple_ng(alpha,N,TR,rlx)
% INPUTS (RF phase is always 0)
%       alpha - flip angle
%       N - number of RF pulses
%       TR - interval between RF pulses
%       rlx - relaxation mode ([T1,T2])
% Simulates repeated excitation (same phase and flip angle at same interval)
% without gradients. The result cannot be visualized as an EPG, but echoes
% can be plotted.
%
% Gehua Tong, Nov 19 2018



seq.T1 = rlx(1);
seq.T2 = rlx(2);
seq.name = 'No gradient SSFP-GR';
seq.rf = repmat([0,alpha]',1,N);
seq.events = {};
seq.time = [0,TR/2,TR];
seq.grad = 0;
for u = 1:N-1
    seq.time = [seq.time seq.time(end) seq.time(end)+TR/2 seq.time(end)+TR];
end
for k = 1:N
    seq.events{end+1} = 'rf';
    seq.events{end+1} = 'relax';
    seq.events{end+1} = 'relax';
    
end

[om_store,echoes] = EPG_custom(seq);
echoes = findAllEchoes(seq,om_store);
% %figure(1);display_epg(om_store,seq,1,gca);
% figure(2);stem(echos(:,1),echos(:,2),'.')
% hold on;
% E1 = exp(-0.5*TR/seq.T1); E2 = exp(-0.5*TR/seq.T2);
% level = sind(alpha)*(1-E1)/(1-(E1-E2)*cosd(alpha)-E1*E2);
% plot([seq.time(1),seq.time(end)],[level,level],'-k')
end