Diffusion-weighted DESS protocol optimization for simultaneous mapping of the mean diffusivity, proton density and relaxation times at 3 Tesla

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Abstract

Purpose

To design a general framework for the optimization of an MRI protocol based on the the diffusion-weighted dual-echo steady-state (DW-DESS) sequence, enabling quantitative and simultaneous mapping of proton density (PD), relaxation times T1 and T2 and diffusion coefficient D.

Methods

A parameterization of the DW-DESS sequence minimizing the Cramér-Rao lower bound of each parameter estimate was proposed and tested in a phantom experiment. An extension of the protocol was implemented for brain imaging to return the rotationally invariant mean diffusivity (MD).

Results

In an NiCl2-doped agar gel phantom wherein T1/T2 ms, the parameter estimation errors were below 3% for PD and T1 and below 7% for T2 and D while the measured signal-to-noise ratio always exceeded 20. In the human brain, the in vivo parametric maps obtained were overall in reasonable agreement with gold standard measurements, despite a broadening of the distributions due to physiological motion.

Conclusion

Within the optimization framework presented here, DW-DESS images can be quantitatively interpreted to yield four intrinsic parameters of the tissue. Currently, the method is limited by the sensitivity of the DW-DESS sequence in terms of physiological motion. Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine

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