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Abstract #1760

Translating AxCaliber on a clinical system : 600mT/m versus optimized 80mT/m protocol

Tanguy Duval1, Tom Mingasson1,2, Eric Klawiter3, Nikola Stikov1,4, and Julien Cohen-Adad1,5

1Polytechnique Montreal, Montreal, QC, Canada, 2Ecole Centrale de Nantes, Nantes, France, 3A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, 4Montreal Heart Institute, Montreal, QC, Canada, 5Functional Neuroimaging Unit, CRIUGM, Universite de Montreal, Montreal, QC, Canada

Most model-based diffusion metrics (AxCaliber metrics) have been shown to be less stable and more biased on clinical systems due to the limited gradient strength (40-80mT/m versus >300mT/m on preclinical scanners). In this work we wanted to (i) find the best AxCaliber protocol at 80mT/m and (ii) quantify the bias in the estimated metrics. For these aims, we first optimized an 80mT/m AxCaliber protocol using simulations, then compared experimentally (on an ex vivo cat spinal cord) a 600mT/m protocol versus the optimized 80mT/m protocol. Using the 600mT/m maps as a ground truth, our results show that even though axon diameter cannot be estimated robustly, the fraction of restricted water can be measured accurately (<3% error) and precisely (r2 >0.76) on clinical systems. The short duration of the optimized protocol opens the way to the use of reliable model-based diffusion MRI metrics on a clinical system, metrics that would be particularly useful to measure the degree of myelination through the fiber g-ratio.

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