Ivana
Drobnjak1, Bernard Siow2, Daniel C. Alexander1
1Center for Medical Image Computing,
Department of Computer Science, University College London, London, United
Kingdom; 2Center for Advanced Biomedical Imaging, University
College London, London, United Kingdom
Measuring
microstructure parameters of brain tissue in vivo is a challenge in diffusion
MRI. Non-standard diffusion-gradient pulses may provide more sensitivity to
microstructure features. Here, we optimize the shape of the
diffusion-gradient waveform, constrained only by hardware limits and fixed
orientation, to give the best estimate of axon radius based on a simple model
of the diffusion within white matter. Our results suggest that square-wave
oscillating gradients maximize sensitivity to pore size over the set of PGSE
sequences. They also show that the frequency of the waves increases as the
radius size decreases.