Characterization and correction of eddy-current artifacts in unipolar and bipolar diffusion sequences using magnetic field monitoring

Rachel W Chan,Constantin Von Deuster,Daniel Giese,Christian T Stoeck,Jack Harmer,Andrew P Aitken,David Atkinson,Sebastian Kozerke

doi:10.1016/j.jmr.2014.04.018

Rachel W Chan, Constantin Von Deuster + Show 6 more

Open Access

https://doi.org/10.1016/j.jmr.2014.04.018

Copy DOI

Abstract

Diffusion tensor imaging (DTI) of moving organs is gaining increasing attention but robust performance requires sequence modifications and dedicated correction methods to account for system imperfections. In this study, eddy currents in the “unipolar” Stejskal-Tanner and the velocity-compensated “bipolar” spin-echo diffusion sequences were investigated and corrected for using a magnetic field monitoring approach in combination with higher-order image reconstruction. From the field-camera measurements, increased levels of second-order eddy currents were quantified in the unipolar sequence relative to the bipolar diffusion sequence while zeroth and linear orders were found to be similar between both sequences. Second-order image reconstruction based on field-monitoring data resulted in reduced spatial misalignment artifacts and residual displacements of less than 0.43mm and 0.29mm (in the unipolar and bipolar sequences, respectively) after second-order eddy-current correction. Results demonstrate the need for second-order correction in unipolar encoding schemes but also show that bipolar sequences benefit from second-order reconstruction to correct for incomplete intrinsic cancellation of eddy-currents.

Highlights

Diffusion-weighted imaging (DWI) and diffusion-tensor imaging (DTI) are non-invasive MRI techniques with broad clinical applications
While many clinical applications of diffusion imaging are in the brain, there is an increasing number of DWI and DTI studies in other organs [1], including the spinal cord [2], breast [3], prostate [4], liver [5], kidney [6], pancreas [7] and in the heart [8,9]
This has been alleviated by technical advances including the use of cardiac/respiratory navigator techniques, single-shot echo planar imaging (EPI) readouts, and sequence modifications that reduce the effects of any motion that occurs during the diffusion gradients

Summary

Introduction

Diffusion-weighted imaging (DWI) and diffusion-tensor imaging (DTI) are non-invasive MRI techniques with broad clinical applications. Bulk physiological motion has initially been a barrier to performing diffusion imaging in organs affected by motion. In cardiac diffusion, this has been alleviated by technical advances including the use of cardiac/respiratory navigator techniques, single-shot echo planar imaging (EPI) readouts, and sequence modifications that reduce the effects of any motion that occurs during the diffusion gradients. This has been alleviated by technical advances including the use of cardiac/respiratory navigator techniques, single-shot echo planar imaging (EPI) readouts, and sequence modifications that reduce the effects of any motion that occurs during the diffusion gradients Such techniques have improved the robustness and reproducibility of diffusion-imaging applications in moving organs such as cardiac DTI [8,9].

Objectives

Methods

Results

Discussion

Conclusion