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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