Added new function for aligining the edit-on/off subspectra of mega-p…

…ress data prior to subtraction. This function is similar to op_alignMPSubspecs.m, except that it uses only a limited frequency range to perform the alignment.

processingTools/op_alignMPSubspecs_fd.m

@@ -0,0 +1,136 @@
+% op_alignMPSubspecs_fd.m
+% Jamie Near, McGill University 2014.
+% 
+% USAGE:
+% [out,fs,phs]=op_alignMPSubspecs_fd(in,initPars);
+% 
+% DESCRIPTION:
+% Apply spectral registration to align MEGA-PRESS subspectra prior to 
+% subtraction.  This function is designed to minimize subtraction artefacts 
+% from choline, and residual water.  This is intended to be used after averaging.
+% 
+% INPUTS:
+% in        = Input data structure.
+% initPars	= (Optional) Initial fit parameters [freq(Hz), phase(degrees)]. Default=[0,0];
+
+function [out,fs,phs]=op_alignMPSubspecs_fd(in,initPars)
+
+if ~in.flags.addedrcvrs
+    error('ERROR:  I think it only makes sense to do this after you have combined the channels using op_addrcvrs.  ABORTING!!');
+end
+
+if in.dims.subSpecs==0
+    error('ERROR:  Must have multiple subspectra.  ABORTING!!');
+end
+
+if in.dims.averages
+   error('ERROR:  Signal averaging must be performed before this step.  ABORTING!!');
+end
+
+if nargin<3
+    parsGuess=[0,0];
+else
+    parsGuess=initPars;
+end
+
+fs=0;
+phs=0;
+fids=zeros(in.sz(in.dims.t),1);
+
+
+disp('aligning the MEGA-PRESS edit-ON sub-spectrum to the edit-OFF sub-spectrum');
+
+%NOTE:  Alignment is not performed in the regions of the spectrum where
+%the difference spectrum is large (ie.  near NAA, 3ppm GABA, or 3.7ppm
+%Glx).
+minfrq1=2.46;
+maxfrq1=2.9;
+minfrq2=3.1;
+maxfrq2=3.6;
+minfrq3=3.85;
+maxfrq3=4.1;
+minfrq4=4.6;
+maxfrq4=5.2;
+
+%freqWindow1=in.ppm>minfrq1 & in.ppm<maxfrq1; 
+%freqWindow2=in.ppm>minfrq2 & in.ppm<maxfrq2; 
+%freqWindow3=in.ppm>minfrq3 & in.ppm<maxfrq3; 
+%freqWindow4=in.ppm>minfrq4 & in.ppm<maxfrq4;
+
+%freqWindows=freqWindow1+freqWindow2+freqWindow3+freqWindow4;
+%freqWindows=logical(freqWindows);
+
+base0=op_freqrange(op_takesubspec(in,1),minfrq3,maxfrq4);
+start=op_freqrange(op_takesubspec(in,2),minfrq3,maxfrq4);
+
+%base=[real(base0.specs( freqWindows ));imag(base0.specs( freqWindows ))];
+base=[real(base0.fids);imag(base0.fids)];
+begin=1;
+
+%size(in.ppm(freqWindows))
+%size(base)
+%plot([in.ppm(freqWindows) in.ppm(freqWindows)],base,'.');
+
+%DO FITTING
+n=1;
+%disp(['fitting subspec number ' num2str(m) ' and average number ' num2str(n)]);
+parsFit=nlinfit(start.fids,base,@op_freqPhaseShiftComplexNest,parsGuess);
+A=op_freqPhaseShiftNest(parsFit,in.fids(:,2));
+size(A);
+size(fids);
+fids(:,1)=in.fids(:,1);
+fids(:,2)=A;
+fs=parsFit(1);
+phs=parsFit(2)+180;
+%plot(in.ppm,fftshift(ifft(fids(:,1,m))),in.ppm,fftshift(ifft(fids(:,n,m))));
+
+%re-calculate Specs using fft
+specs=fftshift(ifft(fids,[],in.dims.t),in.dims.t);
+
+
+%FILLING IN DATA STRUCTURE
+out=in;
+out.fids=fids;
+out.specs=specs;
+
+%FILLING IN THE FLAGS
+out.flags=in.flags;
+out.flags.writtentostruct=1;
+out.flags.freqcorrected=1;
+
+
+    function y=op_freqPhaseShiftComplexNest(pars,input)
+        f=pars(1);     %Frequency Shift [Hz]
+        p=pars(2);     %Phase Shift [deg]
+
+
+        dwelltime=start.dwelltime;
+        t=0:dwelltime:(length(input)-1)*dwelltime;
+        fid=input;
+
+        shiftedFids=addphase(fid.*exp(-1i*t'*f*2*pi),p);
+%         shiftedSpecs=fftshift(ifft(shiftedFids,[],1),1);
+%         shiftedSpecsWindow=shiftedSpecs(ppm>minfrq3 & ppm<maxfrq4);
+        %y=real(shiftedSpecs);
+        y=[real(shiftedFids);imag(shiftedFids)];
+        %y=real(fid.*exp(-1i*t'*f*2*pi));
+
+    end
+
+    function y=op_freqPhaseShiftNest(pars,input)
+        f=pars(1);     %Frequency Shift [Hz]
+        p=pars(2);     %Phase Shift [deg]
+
+
+        dwelltime=start.dwelltime;
+        t=0:dwelltime:(length(input)-1)*dwelltime;
+        fid=input;
+        p=p+180;
+
+        shiftedFids=addphase(fid.*exp(-1i*t'*f*2*pi),p);
+        y=shiftedFids;
+        %y=real(fid.*exp(-1i*t'*f*2*pi));
+
+    end
+
+end