Ross Callaghan1, Daniel C Alexander1, Marco Palombo1, and Hui Zhang1
1Department of Computer Science and Centre for Medical Image Computing, University College London, London, United Kingdom
1Department of Computer Science and Centre for Medical Image Computing, University College London, London, United Kingdom
The fibre response function (FRF) may not be constant, even across fibres within a single bundle. This means that assuming any single FRF for all fibres in a voxel can cause misestimation of the fibre orientation distribution function which will affect subsequent techniques like tractography.
Figure 2. Variability in fibre responses within a voxel at b=2000 s/mm2 along with geometrical variation in fibres responsible for median, 10th and 90th percentile response. Notably, the 10th percentile fibres tend to be more stick-like while 90th percentile have more beading. Solid green line in FRF figures represents median response, shaded green area represents 10th and 90th percentile response. Same values for representative cylinders are in blue to demonstrate the variability due to noise.
Figure 3. fODFs estimated using different FRFs showing how assuming a different FRF can result in vastly different fODFs. Green outline in rightmost plots shows gold standard fODF for comparison. All fODFs are normalised to integrate to 1 for comparison.