E. O. Stejskal

Bio: E. O. Stejskal is an academic researcher. The author has contributed to research in topics: Boundary value problem & Anisotropic diffusion. The author has an hindex of 1, co-authored 1 publications receiving 842 citations.

Use of Spin Echoes in a Pulsed Magnetic‐Field Gradient to Study Anisotropic, Restricted Diffusion and Flow

Abstract: The Bloch—Torrey equations are modified to include the case of anisotropic, restricted diffusion and flow. The problem of solving these modified equations for the amplitude of a spin echo in a time‐dependent magnetic‐field gradient subject to restricting boundary conditions is discussed. This problem is solved for a number of selected cases. In particular, it is found that a magnetic‐field gradient applied in short, intense pulses is effective in defining the time during which nuclear displacements take place. A simplified equation, suitable for the pulsed‐gradient experiment, is presented and solved for two different examples of systems showing restricted diffusion. A procedure for analyzing the data from pulsed‐gradient measurements is suggested, and its merits are discussed. Suggestions are made of systems which may well be expected to show restricted, anisotropic diffusion or interesting flow properties.

Separation of diffusion and perfusion in intravoxel incoherent motion MR imaging.

Abstract: Intravoxel incoherent motion (IVIM) imaging is a method the authors developed to visualize microscopic motions of water. In biologic tissues, these motions include molecular diffusion and microcirculation of blood in the capillary network. IVIM images are quantified by an apparent diffusion coefficient (ADC), which integrates the effects of both diffusion and perfusion. The aim of this work was to demonstrate how much perfusion contributes to the ADC and to present a method for obtaining separate images of diffusion and perfusion. Images were obtained at 0.5 T with high-resolution multisection sequences and without the use of contrast material. Results in a phantom made of resin microspheres demonstrated the ability of the method to separately evaluate diffusion and perfusion. The method was then applied in patients with brain and bone tumors and brain ischemia. Clinical results showed significant promise of the method for tissue characterization by perfusion patterns and for functional studies in the eva...

Use of the Stimulated Echo in NMR Diffusion Studies

Abstract: The stimulated echo in a three‐rf‐pulse experiment is shown to be useful in extending the range of measurement of diffusion coefficients to more viscous substances or the measurement of barrier separations to wider spacings in systems where the diffusing substance has T1 > T2. The spin‐echo attenuation due to self‐diffusion is derived for the general case of a time‐dependent field gradient, and the result is found experimentally to be correct for the special case of a field gradient applied in two equal, square pulses.

Diffusion-tensor MRI: theory, experimental design and data analysis - a technical review.

Abstract: This article treats the theoretical underpinnings of diffusion-tensor magnetic resonance imaging (DT-MRI), as well as experimental design and data analysis issues. We review the mathematical model underlying DT-MRI, discuss the quantitative parameters that are derived from the measured effective diffusion tensor, and describe artifacts that arise in typical DT-MRI acquisitions. We also discuss difficulties in identifying appropriate models to describe water diffusion in heterogeneous tissues, as well as in interpreting experimental data obtained in such issues. Finally, we describe new statistical methods that have been developed to analyse DT-MRI data, and their potential uses in clinical and multi-site studies.