Corpus ID: 61446749

Diffusion imaging with stimulated echoes: signal models and experiment design

  title={Diffusion imaging with stimulated echoes: signal models and experiment design},
  author={Daniel C. Alexander and Tim Bj{\o}rn Dyrby},
  journal={arXiv: Medical Physics},
Purpose: Stimulated echo acquisition mode (STEAM) diffusion MRI can be advantageous over pulsed-gradient spin-echo (PGSE) for diffusion times that are long compared to $\ttwo$. It is important therefore for biomedical diffusion imaging applications at 7T and above where $\ttwo$ is short. [...] Key MethodMethod: We present models for the STEAM signal for free and restricted diffusion that account for crusher and slice-select (butterfly) gradients to avoid such bias.Expand
Stimulated echo diffusion weighted imaging of the liver at 3 Tesla
An optimal stimulated echo acquisition mode (STEAM) diffusion‐weighted imaging (DWI) method dedicated to human liver imaging on 3 Tesla (T) and preliminarily investigate the dependence effect in healthy volunteers are developed. Expand
Brain Microstructure: Impact of the Permeability on Diffusion MRI
Diffusion Magnetic Resonance Imaging (dMRI) enables a non invasive in-vivo characterization of the brain tissue. The disentanglement of each microstructural property reflected on the total dMRIExpand
Does powder averaging remove dispersion bias in diffusion MRI diameter estimates within real 3D axonal architectures?
Through Monte Carlo simulations of diffusion, powder averaging techniques succeed in providing accurate estimates of axon diameter across a range of sequence parameters and diffusion times, even in complex white matter architectures. Expand
Comparison of PGSE and STEAM DTI acquisitions with varying diffusion times for probing anisotropic structures in human kidneys
To evaluate the sensitivity of stimulated‐echo acquisition mode (STEAM) and pulsed‐gradient spin‐echo (PGSE) diffusion tensor imaging (DTI) acquisitions with different diffusion times for measuringExpand
Advanced diffusion MRI for microstructure imaging : theoretical developments
An accurate characterization of tissue features at microscopic level is essential for understanding the brain structure or staging a large variety of diseases, such as Alzheimer’s, multiple sclerosisExpand
Machine learning based compartment models with permeability for white matter microstructure imaging.
A computational model is constructed using Monte Carlo simulations and machine learning in order to learn a mapping between features derived from DW MR signals and ground truth microstructure parameters, and results show that this approach provides a marked improvement over the most widely used mathematical model. Expand
Machine learning based compartment models with permeability for white matter microstructure imaging
A computational model using Monte Carlo simulations and machine learning to estimate microstructure parameters consistent with expectations from the pathology of MS lesions demonstrating the clinical potential of this new technique. Expand
Scan–rescan of axcaliber, macromolecular tissue volume, and g‐ratio in the spinal cord
This work investigated the scan–rescan repeatability of several quantitative MRI techniques in the human spinal cord. Expand
Higher‐order diffusion MRI characterization of mesorectal lymph nodes in rectal cancer
The benefit of higher‐order diffusion MRI models accounting for non‐Gaussian diffusion effects to classify mesorectal lymph nodes both ex vivo at ultrahigh field correlated with histology and in vivo in a clinical scanner upon patient staging is explored. Expand
Ultra-high resolution and multi-shell diffusion MRI of intact ex vivo human brains using kT-dSTEAM at 9.4T
Diffusion MRI (dMRI) in ex vivo human brain specimens is an important research tool for neuroanatomical investigations and the validation of dMRI techniques. Many ex vivo dMRI applications haveExpand


Diffusion imaging using stimulated echoes
The application of stimulated echo acquisition mode (STEAM) sequences for NMR imaging of diffusion is especially suited for spins with T1 ≫ T2 as, e.g., encountered in proton NMR studies ofExpand
Cross-term-compensated pulsed-gradient stimulated echo MR with asymmetric gradient pulse lengths.
In case of asymmetric timing requirements, the generalized MAGSTE sequence with different gradient pulse lengths may help to overcome signal-to-noise limitations in diffusion weighted MR. Expand
Optimal imaging parameters for fiber-orientation estimation in diffusion MRI
Simulations suggest that a ratio of high to low b measurements of 5 to 1 is a good compromise for measuring fiber directions and size and shape indices and that the optimum depends only weakly on the diffusion anisotropy, the maximum gradient strength, and the spin-spin relaxation time. Expand
Pulsed field gradient stimulated echo methods for improved NMR diffusion measurements in heterogeneous systems
Abstract The NMR pulsed magnetic field gradient stimulated echo technique of Tanner is especially useful for measuring the translational diffusion coefficient, D, of the resonant nucleus in materialsExpand
The b matrix in diffusion tensor echo‐planar imaging
The contributions from readout and phase‐encode gradient pulse trains are predicted to have a negligible effect on the echo, but the contributions from other imaging and diffusion gradient pulses applied in both parallel and orthogonal directions are shown to be significant in this sequence. Expand
The matrix formalism for generalised gradients with time-varying orientation in diffusion NMR.
This work shows for primitive geometries (planes, cylinders and spheres), how to express the matrix operators at each time point of the gradient waveform as a linear combination of one or two fundamental matrices and obtains an efficient implementation with both the storage and CPU demands similar to the fixed-orientation case. Expand
Contrast and stability of the axon diameter index from microstructure imaging with diffusion MRI
The results emphasize the key‐role of Gmax for enhancing contrast between axon diameter distributions and are, therefore, relevant in general for microstructure imaging methods and highlight the need for increased Gmax on future commercial systems. Expand
Orientationally invariant indices of axon diameter and density from diffusion MRI
Maps of axon diameter and density indices from the monkey and human data in the corpus callosum and corticospinal tract reflect known trends from histology. Expand
A simple matrix formalism for spin echo analysis of restricted diffusion under generalized gradient waveforms
  • Callaghan
  • Physics, Medicine
  • Journal of magnetic resonance
  • 1997
A simple mathematical formalism is presented which allows closed form expressions for the echo attenuation, E(q), in spin echo diffusion experiments, for practically all gradient waveforms and forExpand
A general framework for experiment design in diffusion MRI and its application in measuring direct tissue‐microstructure features
  • D. Alexander
  • Chemistry, Medicine
  • Magnetic resonance in medicine
  • 2008
This article introduces a new and general framework for optimizing the experiment design for diffusion MRI of samples with unknown orientation. An illustration then uses the framework to study theExpand