160 research outputs found
Interferon lambda protects the female reproductive tract against Zika virus infection
Zika virus infections can cause devastating congenital birth defects but the underlying interactions with the host immune system are not well understood. Here, the authors examine the immune basis of vaginal protection and susceptibility to Zika viral infection, and identify a hormonal dependent role for interferon-lambda-mediated protection against disease
Prediction of motion induced magnetic fields for human brain MRI at 3T
Objective Maps of B0 field inhomogeneities are often used to improve MRI
image quality, even in a retrospective fashion. These field inhomogeneities
depend on the exact head position within the static field but acquiring field
maps (FM) at every position is time consuming. Here we explore different ways
to obtain B0 predictions at different head positions. Methods FM were predicted
from iterative simulations with four field factors: 1) sample induced B0 field,
2) system's spherical harmonic shim field, 3) perturbing field originating
outside the field of view, 4) sequence phase errors. The simulation was
improved by including local susceptibility sources estimated from UTE scans and
position-specific masks. The estimation performance of the simulated FMs and a
transformed FM, obtained from the measured reference FM, were compared with the
actual FM at different head positions. Results The transformed FM provided
inconsistent results for large head movements (>5 degree rotation), while the
simulation strategy had a superior prediction accuracy for all positions. The
simulated FM was used to optimize B0 shims with up to 22.2% improvement with
respect to the transformed FM approach. Conclusion The proposed simulation
strategy is able to predict movement induced B0 field inhomogeneities yielding
more precise estimates of the ground truth field homogeneity than the
transformed FM
Practical considerations for in vivo MRI with higher dimensional spatial encoding
Object: This work seeks to examine practical aspects of in vivo imaging when spatial encoding is performed with three or more encoding channels for a 2D image. Materials and methods: The recently developed 4-Dimensional Radial In/Out (4D-RIO) trajectory is compared in simulations to an alternative higher-order encoding scheme referred to as O-space imaging. Direct comparison of local k-space representations leads to the proposal of a modification to the O-space imaging trajectory based on a scheme of prephasing to improve the reconstructed image quality. Data were collected using a 4D-RIO acquisition in vivo in the human brain and several image reconstructions were compared, exploiting the property that the dense encoding matrix, after a 1D or 2D Fourier transform, can be approximated by a sparse matrix by discarding entries below a chosen magnitude. Results: The proposed prephasing scheme for the O-space trajectory shows a marked improvement in quality in the simulated image reconstruction. In experiments, 4D-RIO data acquired in vivo in the human brain can be reconstructed to a reasonable quality using only 5% of the encoding matrix—massively reducing computer memory requirements for a practical reconstruction. Conclusion: Trajectory design and reconstruction techniques such as these may prove especially useful when extending generalized higher-order encoding methods to 3D image
Implementation and Application of PSF-Based EPI Distortion Correction to High Field Animal Imaging
The purpose of this work is to demonstrate the functionality and performance of a PSF-based geometric distortion correction for high-field functional animal EPI. The EPI method was extended to measure the PSF and a postprocessing chain was implemented in Matlab for offline distortion correction. The correction procedure was applied to phantom and in vivo imaging of mice and rats at 9.4T using different SE-EPI and DWI-EPI protocols. Results show the significant improvement in image quality for single- and multishot EPI. Using a reduced FOV in the PSF encoding direction clearly reduced the acquisition time for PSF data by an acceleration factor of 2 or 4, without affecting the correction quality
Toxoplasma gondii infection drives conversion of NK cells into ILC1-like cells
Innate lymphoid cells (ILCs) were originally classified based on their cytokine profiles, placing natural killer (NK) cells and ILC1s together, but recent studies support their separation into different lineages at steady-state. However, tumors may induce NK cell conversion into ILC1-like cells that are limited to the tumor microenvironment and whether this conversion occurs beyond this environment remains unknown. Here, we describ
Pulseq: A rapid and hardwareâ independent pulse sequence prototyping framework
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136354/1/mrm26235.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136354/2/mrm26235_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136354/3/mrm26235-sup-0001-suppinfo.pd
- …