feComputeVoxelSignal

 Predict the signal in a single voxel given the fiber going through the
 voxel.

   voxDSig = feComputeVoxelSignal(fe,voxelIndex)

 Copyright (2013-2014), Franco Pestilli, Stanford University, pestillifranco@gmail.com.

0001 function voxDSig = feComputeVoxelSignal(fe,voxIndex)
0002 % Predict the signal in a single voxel given the fiber going through the
0003 % voxel.
0004 %
0005 %   voxDSig = feComputeVoxelSignal(fe,voxelIndex)
0006 %
0007 % Copyright (2013-2014), Franco Pestilli, Stanford University, pestillifranco@gmail.com.
0008 
0009 % Extract information regarding, voxels, signal and fibers.
0010 S0                = feGet(fe,'b0signalimage',   voxIndex);  % non diffusion-weighted signal
0011 bvecs             = feGet(fe,'bvecs');                      % bvecs
0012 bvals             = feGet(fe,'bvals');                      % bvals
0013 tot_fibers_num    = feGet(fe,'tot f num',       voxIndex);  % number of total fibers in the voxel
0014 unique_fibers_num = feGet(fe,'unique f num',    voxIndex);  % number of unique fibers in the voxel
0015 tot_fiber_index   = cell2mat(feGet(fe,'totf',   voxIndex)); % indexes to the total fibers in the voxels
0016 unique_fiber_index= cell2mat(feGet(fe,'uniquef',voxIndex)); % indexes to the unique fibers in the voxels
0017 voxTensors        = feGet(fe,'voxeltensors',    voxIndex);  % Get the tensors for each node in each fiber
0018                                                             % going through this voxel
0019 
0020 % Compute the predicted signal by each tensors of each node in this voxel.
0021 voxDSig = feComputeSignal(S0, bvecs, bvals, voxTensors);
0022 
0023 % Combine the diffusion predictions across nodes of a single fiber.
0024 % Use only the prediction from the unique fibers, not from all the fibers.
0025 if tot_fibers_num ~= unique_fibers_num
0026   combineM = zeros(tot_fibers_num, unique_fibers_num);
0027   
0028   % The matrix combineM is a set of 0s and 1s that will sum together the
0029   % nodes from a single fiber.
0030   for ii=1:unique_fibers_num
0031     combineM(:,ii) = ( tot_fiber_index == unique_fiber_index(ii) );
0032   end
0033   
0034   % The matrix for this voxel starts with each node, and when we multiply
0035   % by combineM. The resulting matrix represents each fiber
0036   % (not each node) as a column
0037   voxDSig = voxDSig*combineM;
0038 end
0039 
0040 return