Eddy current compensated double diffusion encoded (DDE) MRI

TL;DR

This paper presents a method to reduce eddy current-induced distortions in double diffusion encoding MRI, improving the accuracy of microscopic fractional anisotropy measurements in brain imaging.

Contribution

The study adapts the twice refocused spin echo scheme for DDE MRI and demonstrates the importance of compensating both encodings to minimize artifacts.

Findings

Eddy current compensation reduces signal variation.

Compensation of both encodings is necessary for optimal results.

Improved A measurement accuracy in ventricles and grey matter.

Abstract

Purpose: Eddy currents might lead to image distortions in diffusion weighted echo planar imaging. A method is proposed to reduce their effects on double diffusion encoding (DDE) MRI experiments and the thereby derived microscopic fractional anisotropy (\mu FA) . Methods: The twice refocused spin echo scheme was adapted for DDE measurements. To assess the effect of individual diffusion encodings on the image distortions, measurements of a grid of plastic rods in water were performed. The effect of eddy current compensation on \mu FA measurements was evaluated in the brains of six healthy volunteers. Results: The use of an eddy current compensation reduced the signal variation. As expected, the distortions caused by the second encoding were larger than those of the first encoding entailing a stronger need to compensate for them. For an optimal result, however, both encodings had to be compensated. The artifact reduction strongly improved the measurement of the \mu FA in ventricles and grey matter by reducing the overestimation. An effect of the compensation on absolute \mu FA values in white matter was not observed. Conclusion: It is advisable to compensate both encodings in DDE measurements for eddy currents.