Simultaneous Motion and Distortion Correction Using Dual‐Echo Diffusion‐Weighted MRI

Abstract

Geometric distortions resulting from large pose changes reduce the accuracy of motion measurements and interfere with the ability to generate artifact-free information. Our goal is to develop an algorithm and pulse sequence to enable motion-compensated, geometric distortion compensated diffusion-weighted MRI, and to evaluate its efficacy in correcting for the field inhomogeneity and position changes, induced by large and frequent head motions. METHODS: Dual echo planar imaging (EPI) with a blip-reversed phase encoding distortion correction technique was evaluated in five volunteers in two separate experiments and compared with static field map distortion correction. In the first experiment, dual-echo EPI images were acquired in two head positions designed to induce a large field inhomogeneity change. A field map and a distortion-free structural image were acquired at each position to assess the ability of dual-echo EPI to generate reliable field maps and enable geometric distortion correction in both positions. In the second experiment, volunteers were asked to move to multiple random positions during a diffusion scan. Images were reconstructed using the dual-echo correction and a slice-to-volume registration (SVR) registration algorithm. The accuracy of SVR motion estimates was compared to externally measured ground truth motion parameters. RESULTS:Our results show that dual-echo EPI can produce slice-level field maps with comparable quality to field maps generated by the reference gold standard method. We also show that slice-level distortion correction improves the accuracy of SVR algorithms as slices acquired at different orientations have different levels of distortion, which can create errors in the registration process. CONCLUSIONS: Dual-echo acquisitions with blip-reversed phase encoding can be used to generate slice-level distortion-free images, which is critical for motion-robust slice to volume registration. The distortion corrected images not only result in better motion estimates, but they also enable a more accurate final diffusion image reconstruction.

Manifold‐based respiratory phase estimation enables motion and distortion correction of free‐breathing cardiac diffusion tensor MRI

“…A previous approach that considered motion in DW imaging of children used a dual-echo sequence to acquire 2 readouts in opposite phase-encoding directions for each DW image. [34][35][36] The short time between the dual-echo readouts (~30 ms) allowed the assumption that there is no motion between the 2 images and that standard DisCo techniques could be applied. However, this technique could not be used in cardiac imaging due to the short T 2 decay of the myocardium compared to the long TE for the second readout, which is on the order of ~100 ms.…”

Diffusion‐weighted magnetic resonance imaging in rat kidney using two‐dimensional navigated, interleaved echo‐planar imaging at 7.0 T

“…To compensate for the scan time prolongation, PI techniques can be integrated in ms‐EPI. Furthermore, combining a blip‐up/down acquisition (BUDA) strategy with ms‐EPI has the potential to achieve distortion‐free renal DWI with high resolution 54,55 . Only a half of four shots will be used in BUDA, compared with our four‐shot EPI settings, and thus reduces the scan time by half.…”

Retrospective Distortion and Motion Correction for Free‐Breathing DW‐MRI of the Kidneys Using Dual‐Echo EPI and Slice‐to‐Volume Registration

“…A novel dual‐echo sequence was implemented to acquire two EPI readouts with opposite phase‐encoding directions for each slice and diffusion weighting. The two EPI readouts were introduced to estimate the distortion field at each position and therefore account for the change in distortion field due to motion, eg, when organs are placed at different locations 21,22,27 . Due to the short time between the first and second readout (~30–50 msec), the motion of the kidneys between these two images is negligible.…”

“…In order to compensate for geometric distortion in the presence of motion, a method was recently proposed for DW‐MRI of the brain. In this work, the method was extended and evaluated for application to geometric distortion correction in abdominal DW‐MRI 21,22 …”