31 research outputs found
-Equivariant Networks for Spherical Deconvolution in Diffusion MRI
We present Roto-Translation Equivariant Spherical Deconvolution (RT-ESD), an
equivariant framework for sparse deconvolution of volumes
where each voxel contains a spherical signal. Such 6D data naturally arises in
diffusion MRI (dMRI), a medical imaging modality widely used to measure
microstructure and structural connectivity. As each dMRI voxel is typically a
mixture of various overlapping structures, there is a need for blind
deconvolution to recover crossing anatomical structures such as white matter
tracts. Existing dMRI work takes either an iterative or deep learning approach
to sparse spherical deconvolution, yet it typically does not account for
relationships between neighboring measurements. This work constructs
equivariant deep learning layers which respect to symmetries of spatial
rotations, reflections, and translations, alongside the symmetries of voxelwise
spherical rotations. As a result, RT-ESD improves on previous work across
several tasks including fiber recovery on the DiSCo dataset,
deconvolution-derived partial volume estimation on real-world \textit{in vivo}
human brain dMRI, and improved downstream reconstruction of fiber tractograms
on the Tractometer dataset. Our implementation is available at
https://github.com/AxelElaldi/e3so3_convComment: Accepted to Medical Imaging with Deep Learning (MIDL) 2023. Code
available at https://github.com/AxelElaldi/e3so3_conv . 19 pages with 6
figure
AnyStar: Domain randomized universal star-convex 3D instance segmentation
Star-convex shapes arise across bio-microscopy and radiology in the form of
nuclei, nodules, metastases, and other units. Existing instance segmentation
networks for such structures train on densely labeled instances for each
dataset, which requires substantial and often impractical manual annotation
effort. Further, significant reengineering or finetuning is needed when
presented with new datasets and imaging modalities due to changes in contrast,
shape, orientation, resolution, and density. We present AnyStar, a
domain-randomized generative model that simulates synthetic training data of
blob-like objects with randomized appearance, environments, and imaging physics
to train general-purpose star-convex instance segmentation networks. As a
result, networks trained using our generative model do not require annotated
images from unseen datasets. A single network trained on our synthesized data
accurately 3D segments C. elegans and P. dumerilii nuclei in fluorescence
microscopy, mouse cortical nuclei in micro-CT, zebrafish brain nuclei in EM,
and placental cotyledons in human fetal MRI, all without any retraining,
finetuning, transfer learning, or domain adaptation. Code is available at
https://github.com/neel-dey/AnyStar.Comment: Code available at https://github.com/neel-dey/AnySta
Dynamic Neural Fields for Learning Atlases of 4D Fetal MRI Time-series
We present a method for fast biomedical image atlas construction using neural
fields. Atlases are key to biomedical image analysis tasks, yet conventional
and deep network estimation methods remain time-intensive. In this preliminary
work, we frame subject-specific atlas building as learning a neural field of
deformable spatiotemporal observations. We apply our method to learning
subject-specific atlases and motion stabilization of dynamic BOLD MRI
time-series of fetuses in utero. Our method yields high-quality atlases of
fetal BOLD time-series with 5-7 faster convergence compared to
existing work. While our method slightly underperforms well-tuned baselines in
terms of anatomical overlap, it estimates templates significantly faster, thus
enabling rapid processing and stabilization of large databases of 4D dynamic
MRI acquisitions. Code is available at
https://github.com/Kidrauh/neural-atlasingComment: 6 pages, 2 figures. Accepted by Medical Imaging Meets NeurIPS 202
Effects of Fe2O3 addition and annealing on the mechanical and dissolution properties of MgO- and CaO-containing phosphate glass fibres for bio-applications
This paper investigated the preparation of phosphate glass fibres (PGFs) in the following systems: i) 45P2O5-5B2O3-5Na2O-(29-x)CaO-16MgO-(x)Fe2O3and ii) 45P2O5-5B2O3-5Na2O-24CaO-(21-x)MgO-(x)Fe2O3(where x = 5, 8 and 11 mol%) for biomedical applications. Continuous fibres of 23 ± 1 μm diameter were prepared via a melt-draw spinning process. Compositions with higher Fe2O3content and higher MgO/CaO ratio required higher melting temperature and longer heating time to achieve glass melts for fibre pulling. The effects of Fe2O3 addition and annealing treatment on mechanical properties and degradation behaviours were also investigated. Adding Fe2O3 was found to increase the tensile strength from 523 ± 63 (Ca-Fe5) to 680 ± 75 MPa (Ca-Fe11), improve the tensile modulus from 72 ± 4 (Ca-Fe5) to 78 ± 3 GPa (Ca-Fe11) and decrease the degradation rate from 4.0 (Mg-Fe5) to 1.9 × 10-6kg m-2s-1(Mg-Fe11). The annealing process reduced the fibre tensile strength by 46% (Ca-Fe5), increased the modulus by 19.6% (Ca-Fe8) and decreased the degradation rate by 89.5% (Mg-Fe11) in comparison to the corresponding as-drawn fibres. Additionally, the annealing process also impeded the formation of precipitate shells and revealed coexistence of the precipitation and the pitting corrosion as fibre degradation behaviours