Abstract #2009

Axon diameter distribution influences diffusion-derived axonal density estimation in the human spinal cord: in silico and in vivo evidence

Francesco Grussu¹, Torben Schneider^1,2, Ferran Prados^1,3, Carmen Tur¹, Sébastien Ourselin³, Hui Zhang⁴, Daniel C. Alexander⁴, and Claudia Angela Michela Gandini Wheeler-Kingshott^1,5

¹NMR Research Unit, Queen Square MS Centre, Department of Neuroinflammation, UCL Institute of Neurology, University College London, London, United Kingdom, ²Philips Healthcare, Guildford, Surrey, England, United Kingdom, ³Translational Imaging Group, Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom, ⁴Department of Computer Science and Centre for Medical Image Computing, University College London, London, United Kingdom, ⁵Brain Connectivity Center, C. Mondino National Neurological Institute, Pavia, Italy

Diffusion MRI-derived neurite density is a potential biomarker in neurological conditions. In the brain, neurites are commonly modelled as sticks for sufficiently long diffusion times and gradient durations. However, in the spinal cord, large axons are present and typical diffusion times (20-30 ms) may not be sufficiently long to support this model. We investigate via simulations and in vivo whether neurite density estimation is affected by the diffusion time in the spinal cord. Short diffusion times lead to bias, while long diffusion times improve accuracy but reduce precision. Therefore, a trade-off accuracy-precision needs to be evaluated depending on the application.

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