Abstract #0007

Overestimation of CSF fraction in NODDI: possible correction techniques and the effect on neurite density and orientation dispersion measures

Samira Bouyagoub¹, Nicholas G. Dowell¹, Samuel A. Hurley², Tobias C. Wood³, and Mara Cercignani¹

¹Clinical Imaging Sciences Centre, Brighton and Sussex Medical School, Brighton, United Kingdom, ²FMRIB Centre, University of Oxford, Oxford, United Kingdom, ³Neuroimaging, IoPPN, King’s College London, London, United Kingdom

NODDI is a diffusion MRI technique based on combining a 3 compartment tissue model with a (HARDI) protocol. NODDI overestimates CSF volume fractions (fiso), particularly in white matter regions. This is possibly due to the single T2 assumption for all compartments. High fiso could lead to inaccurate measure of neurite density (ficvf) and orientation dispersion (odi). We propose a method to correct these errors by scaling fiso with voxel-based T2 maps from DESPOT. We acquired NODDI data for 5 healthy subjects, and we run original NODDI analysis and another NODDI analysis using rescaled fiso. Results showed rescaling fiso generated low fiso measures consistent with those reported in literature. It also generated more physiologically acceptable measures of ficvf, whereas odi was not sensitive to the change.

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