Illustrations on MRI Techniques Using Matlab - Digital Signal Processing for Medical Imaging Using Matlab - page 60

3.2.2.1 Spinechodemonstration.m
siz=11;
K=0.2; %Initial phase
Mxyit=[];
gamma=2*pi*42.58*(10ˆ6);
d1=((10ˆ3)/(11*42.58*10ˆ6*0.1));
d2=((10ˆ3)/(11*42.58*10ˆ6*0.1));
B0=1;
n=round(rand(siz,siz)*9+1);
for x=1:1:siz
for y=1:1:siz
for i=1:1:n(x,y)
k(x,y,i)=rand*2-1;
end
end
end
KSPACE=zeros(11,11);
for i=1:1:3
KKSPACE{i}=zeros(11,11);
end
for Gx=-5:1:5;
for Gy=-5:1:5;
Gx1=Gx/(10ˆ3);
Gy1=Gy/(10ˆ3);
for x=0:1:siz-1
for y=0:1:siz-1
for i=1:1:n(x+1,y+1)
phi1=k(x+1,y+1,i)*0.1*2*pi;
%The magnetic moments after applying positive y-gradient for the duration of
%0.1
temp1(x+1,y+1,i)=exp(-j*((B0*gamma+gamma*y*d2*Gy1)*0.1-phi1+K));
%Case 1:
%At time instant=0.2 (refer section 3.2.2)
phi2=k(x+1,y+1,i)*0.1*2*pi;
temp2(x+1,y+1,i)=exp(-j*((B0*gamma+d2*gamma*y*Gy1)*0.1-phi1+K))...
*exp(-j*((B0*gamma+gamma*d1*x*Gx1)*0.1-phi2));
%Case 2:
%At time instant=0.4 (refer section 3.2.2)
phi3=k(x+1,y+1,i)*0.2*2*pi;
temp3(x+1,y+1,i)=exp(j*((B0*gamma+gamma*d2*y*Gy1)*0.1-phi1+K))...
*exp(j*((B0*gamma+gamma*d1*x*Gx1)*0.1-phi2))*...
exp(-j*((B0*gamma+gamma*d1*x*Gx1)*0.2-phi3));
%Case 3:
%At time instant=0.8 (refer section 3.2.2)
phi4=k(x+1,y+1,i)*0.1*2*pi;
phi5=k(x+1,y+1,i)*0.2*2*pi;
temp4(x+1,y+1,i)=exp(j*((B0*gamma+gamma*d2*y*Gy1)*0.1-phi1+K))...
*exp(j*((B0*gamma+gamma*d1*x*Gx1)*0.1-phi2))*...
exp(-j*((B0*gamma)*0.1-phi4))*exp(-j*((B0*gamma+gamma*d1*x*Gx1)*0.2-phi5));
end
end
end
for x=0:1:siz-1
for y=0:1:siz-1