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Abstract #0195

Optimal Diffusion-Gradient Waveforms for Measuring Axon Diameter

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.