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.