English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Open

We introduce a structured low rank algorithm for the calibration-freecompensation of field inhomogeneity artifacts in Echo Planar Imaging (EPI) MRIdata. We acquire the data using two EPI readouts that differ in echo-time (TE).Using time segmentation, we reformulate the field inhomogeneity compensationproblem as the recovery of an image time series from highly undersampledFourier measurements. The temporal profile at each pixel is modeled as a singleexponential, which is exploited to fill in the missing entries. We show thatthe exponential behavior at each pixel, along with the spatial smoothness ofthe exponential parameters, can be exploited to derive a 3D annihilationrelation in the Fourier domain. This relation translates to a low rank propertyon a structured multi-fold Toeplitz matrix, whose entries correspond to themeasured k-space samples. We introduce a fast two-step algorithm for thecompletion of the Toeplitz matrix from the available samples. In the firststep, we estimate the null space vectors of the Toeplitz matrix using only itsfully sampled rows. The null space is then used to estimate the signalsubspace, which facilitates the efficient recovery of the time series ofimages. We finally demonstrate the proposed approach on spherical MR phantomdata and human data and show that the artifacts are significantly reduced. Theproposed approach could potentially be used to compensate for time varyingfield map variations in dynamic applications such as functional MRI.

Calibration-free B0 correction of EPI data using structured low rank matrix recovery