  Purpose: Diffusion Magnetic Resonance Imaging (dMRI) is confounded by its
long acquisition duration, thereby thwarting the detection of rapid
microstructural changes, especially when diffusivity variations are accompanied
by rapid changes in T2. The purpose of the present study is to accelerate dMRI
to a single scan acquisition, and to enable a more accurate estimation of
diffusivity as function of time. Methods: A general methodology termed
Incomplete Initial Nutation Diffusion Imaging (INDI) capturing two diffusion
contrasts in a single shot, is presented. INDI creates a longitudinal
magnetization reservoir that facilitates the successive acquisition of two
images separated by only a few milliseconds. INDI's theory is presented,
followed by proof-of-concept ex- and in-vivo experiments at 16.4 T and 9.4 T.
Results: Mean diffusivities (MDs) extracted from INDI were comparable with
Diffusion Tensor Imaging (DTI) and the two-shot IDE in the water phantom. As
expected in the brain tissues, DTI provided lower MD than UF-IDE and IDE, but
IDE and UF-IDE were in excellent agreement. Simulations are presented for
identifying the regimes where INDI is most beneficial. Conclusions: INDI
accelerates dMRI acquisition to single-shot mode, which can be of great
importance for mapping dynamic microstructural properties in-vivo without T2
bias.
