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Abstract #0587

The muscle twitch profile assessed with Motor Unit Magnetic Resonance Imaging (MUMRI)

Linda Heskamp1, Matthew Birkbeck1,2,3, Roger Whittaker1, Ian Schofield1, and Andrew Blamire1
1Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University, Newcastle upon Tyne, United Kingdom, 2Newcastle Biomedical Research Centre, Newcastle University, Newcastle upon Tyne, United Kingdom, 3Northern Medical Physics and Clinical Engineering, Freeman Hospital, Newcastle upon Tyne NHS Foundation Trust, Newcastle upon Tyne, United Kingdom

Motor units (MUs) play a fundamental role in muscle physiology and disease. Contraction of muscle fibres belonging to a MU induces signal voids on diffusion weighted (DW) images enabling us to image these MUs (MUMRI). We demonstrated that MUMRI can also extract the twitch profile of single MUs. Computational modelling showed that the attenuation of net magnetisation and the cumulative phase changes increase with twitch magnitude. Therefore, we can measure the MU time profile by altering the timing of electrical nerve stimulation relative to the diffusion-encoding gradients. We applied this experimentally and measured in-vivo contraction times of human MUs.

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