Abstract #3480

Multi-echo NODDI with released intrinsic diffusivity: Initial insights for rat brain tissue

Ezequiel Farrher¹, Chia-Wen Chiang², Kuan-Hung Cho², Chang-Hoon Choi¹, Ming-Jye Chen², Sheng-Ming Huang², Li-Wei Kuo^2,3, and N. Jon Shah^1,4,5,6

¹Institute of Neuroscience and Medicine - 4, Medical Imaging Physics, Forschungszentrum Jülich, Juelich, Germany, ²Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, Miaoli, Taiwan, ³Institute of Medical Device and Imaging, National Taiwan University College of Medicine, Taipei, Taiwan, ⁴Department of Neurology, Faculty of Medicine, RWTH Aachen University, Aachen, Germany, ⁵JARA – BRAIN – Translational Medicine, RWTH Aachen University, Aachen, Germany, ⁶Institute of Neuroscience and Medicine - 11, Forschungszentrum Jülich, Juelich, Germany

Synopsis

Keywords: Diffusion Modeling, Microstructure, relaxometry; multi-dimensional; stroke; ischaemia; pre-clinical

Motivation: The applicability of NODDI and its spinoffs, e.g. multi-echo (MTE) NODDI, is limited to those tissue conditions where the intrinsic diffusivity is known a priori.

Goal(s): We propose an estimation approach for MTE-NODDI parameters in which the intrinsic diffusivity is released whilst ensuring fitting stability by adding an l₂-norm regularisation term to the cost function.

Approach: The regularisation parameter was optimised via the generalised cross-validation approach. The MTE-NODDI with released intrinsic diffusivity was tested in a healthy rat at 3 T.

Results: The estimation of MTE-NODDI with released intrinsic diffusivity is well-conditioned if an l₂-norm regularisation term is used.

Impact: The proposed estimation approach for MTE-NODDI parameters with released intrinsic diffusivity was shown to be stable. Thus, a new range of tissue conditions in which the intrinsic diffusivity is known to be affected, e.g. stroke, can be accurately characterised.

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