33 research outputs found
Rapid dynamic speech imaging at 3 Tesla using combination of a custom vocal tract coil, variable density spirals and manifold regularization
Purpose: To improve dynamic speech imaging at 3 Tesla.
Methods: A novel scheme combining a 16-channel vocal tract coil, variable
density spirals (VDS), and manifold regularization was developed. Short readout
duration spirals (1.3 ms long) were used to minimize sensitivity to
off-resonance. The manifold model leveraged similarities between frames sharing
similar vocal tract postures without explicit motion binning. Reconstruction
was posed as a SENSE-based non-local soft weighted temporal regularization
scheme. The self-navigating capability of VDS was leveraged to learn the
structure of the manifold. Our approach was compared against low-rank and
finite difference reconstruction constraints on two volunteers performing
repetitive and arbitrary speaking tasks. Blinded image quality evaluation in
the categories of alias artifacts, spatial blurring, and temporal blurring were
performed by three experts in voice research.
Results: We achieved a spatial resolution of 2.4mm2/pixel and a temporal
resolution of 17.4 ms/frame for single slice imaging, and 52.2 ms/frame for
concurrent 3-slice imaging. Implicit motion binning of the manifold scheme for
both repetitive and fluent speaking tasks was demonstrated. The manifold scheme
provided superior fidelity in modeling articulatory motion compared to low rank
and temporal finite difference schemes. This was reflected by higher image
quality scores in spatial and temporal blurring categories. Our technique
exhibited faint alias artifacts, but offered a reduced interquartile range of
scores compared to other methods in alias artifact category.
Conclusion: Synergistic combination of a custom vocal-tract coil, variable
density spirals and manifold regularization enables robust dynamic speech
imaging at 3 Tesla.Comment: 30 pages, 10 figure
Robust Depth Linear Error Decomposition with Double Total Variation and Nuclear Norm for Dynamic MRI Reconstruction
Compressed Sensing (CS) significantly speeds up Magnetic Resonance Image
(MRI) processing and achieves accurate MRI reconstruction from under-sampled
k-space data. According to the current research, there are still several
problems with dynamic MRI k-space reconstruction based on CS. 1) There are
differences between the Fourier domain and the Image domain, and the
differences between MRI processing of different domains need to be considered.
2) As three-dimensional data, dynamic MRI has its spatial-temporal
characteristics, which need to calculate the difference and consistency of
surface textures while preserving structural integrity and uniqueness. 3)
Dynamic MRI reconstruction is time-consuming and computationally
resource-dependent. In this paper, we propose a novel robust low-rank dynamic
MRI reconstruction optimization model via highly under-sampled and Discrete
Fourier Transform (DFT) called the Robust Depth Linear Error Decomposition
Model (RDLEDM). Our method mainly includes linear decomposition, double Total
Variation (TV), and double Nuclear Norm (NN) regularizations. By adding linear
image domain error analysis, the noise is reduced after under-sampled and DFT
processing, and the anti-interference ability of the algorithm is enhanced.
Double TV and NN regularizations can utilize both spatial-temporal
characteristics and explore the complementary relationship between different
dimensions in dynamic MRI sequences. In addition, Due to the non-smoothness and
non-convexity of TV and NN terms, it is difficult to optimize the unified
objective model. To address this issue, we utilize a fast algorithm by solving
a primal-dual form of the original problem. Compared with five state-of-the-art
methods, extensive experiments on dynamic MRI data demonstrate the superior
performance of the proposed method in terms of both reconstruction accuracy and
time complexity
ICoNIK: Generating Respiratory-Resolved Abdominal MR Reconstructions Using Neural Implicit Representations in k-Space
Motion-resolved reconstruction for abdominal magnetic resonance imaging (MRI)
remains a challenge due to the trade-off between residual motion blurring
caused by discretized motion states and undersampling artefacts. In this work,
we propose to generate blurring-free motion-resolved abdominal reconstructions
by learning a neural implicit representation directly in k-space (NIK). Using
measured sampling points and a data-derived respiratory navigator signal, we
train a network to generate continuous signal values. To aid the regularization
of sparsely sampled regions, we introduce an additional informed correction
layer (ICo), which leverages information from neighboring regions to correct
NIK's prediction. Our proposed generative reconstruction methods, NIK and
ICoNIK, outperform standard motion-resolved reconstruction techniques and
provide a promising solution to address motion artefacts in abdominal MRI