Magnetic Resonance

| Spatially localized MR spectroscopy and spectroscopic imaging for biomedical applications | | Nuclear hyperpolarization of noble gases for NMR measurements | | Generation of temporally and spatially defined magnetic fields | | Measurement of electric, magnetic and ion fields | | Inverse and optimization problems | | Information physics | | Software for license |

The activity of the NMR Group is oriented, above all, to the development of measurement methods and technologies for biomedical and technological applications of nuclear magnetic resonance. The current research is focused on

spectroscopic imaging (MRSI) and spatially localized MR spectroscopy (MRS), primarily of the human brain,
nuclear hyperpolarization of noble gases and their application in NMR measurements,
material analysis:

MR compatibility of materials used in medicine (dental implants et sim.),
application of NMR for the characterization of porous materials.

Instrumentally, this research is based on the Institute’s 4.7 Tesla NMR system with maximum sample diameter of 6 cm, as well as systems of collaborating institutions, most notably the 1.5 Tesla clinical scanner Siemens Symphonyinstalled in the St. Anne University Hospital in Brno. The research in nuclear hyperpolarization is carried out in cooperation with the Coherence Optics Department of the Institute.

Further research topics are a continuation of the primary NMR competence of the Group:

generation of temporally and spatially defined magnetic fields,
measurement of electric, magnetic, and ion fields,
inverse and optimization problems,
information physics.

Research topics

Spatially localized MR spectroscopy and spectroscopic imaging for biomedical applications

Methods for the acquisition of NMR spectra that are spatially localized in living organisms or tissues (most notably, the human brain) are being developed and optimized. The research goal is to improve the quality of such NMR spectra and their quantification and, thereby, to improve the conditions for a successful application of these techniques in medical research and clinical practice.
The attention is focused, above all, on the acquisition of high quality 1H NMR spectra of all available and diagnostically relevant low-molecular-weight metabolites (N-acetyl aspartate, creatine, choline, inositol, glutamine, glutamate etc.). Specific research topics:

pulse sequences and RF pulses for spatial and/or spectral selection,
minimization of the contamination of the metabolite measured spectra by signals of water and lipids generated outside of the region of interst,
highly efficient suppression of the strong water and lipid signals,
elimination of undesirable spectral distortions,
efficient differentiation of signal from low-molecular weight metabolites and macromolecules and lipids,
application of 2D and editing techniques in in vivo MR spectroscopy,
effects of magnetization transfer on the metabolite signal intensity,
optimization of the excitation techniques for achieving the maximum signal-to-noise ratio,
accelerated and fast spectroscopic imaging.

Substantial elements of this research are

computer simulation of NMR experiments,
implementation of theoretically optimized methods,
data analysis.

Computer simulation of NMR experiments is an area where the Group’s activity is focused on the development of mathematical models and the simulation of experiments including spatial and/or spatial localization, i.e. experiments utilizing frequency selective radio-frequency (RF] pulses and/or magnetic field gradients. The software developed is used for the design and optimization of selective RF pulses and pulse sequences.
Method implementation consists in the development of system-specific software that controls the target NMR system. Currently, the group is oriented to systems by Siemens, MR Solutions and Bruker.
In close collaboration with IBD NRC Canada the members of the Group have developed a program system for the processing and visualization of multidimensional NMR data from various NMR sources on a PC. The software is dedicated to research use and numerous variants of 2- and 3-dimensional MR imaging and spectroscopic imaging. Its modularity makes it possible to input NMR data in various proprietary formats, process and visualize them in a unified form and expand the functionality by customized modules. The current development is focused on the development of special functions for quantitative evaluation of spectroscopic and imaging data.

Nuclear hyperpolarization of noble gases for NMR measurements

Nuclear hyperpolarization, i.e. boosting the magnetization of atomic nuclei above the value corresponding to the Boltzmann thermodynamic equilibrium, is a prospective area for many applications of NMR. The current work is directed to the development of the technology for efficient hyperpolarization of xenon-129 by means of spin exchange with laser-polarized rubidium vapour. In this process, the goal is to ensure an efficient transfer of the angular momentum of circularly polarized photons generated by a titanium-sapphire of diode laser to the rubidium atom electron and later on to the nuclei of xenon. This method will be applicable also for the hyperpolarization of helium-3. Hyperpolarized noble gas can be applied in biological (body cavities – lungs, colon, gas exchange) as well as material studies (porous materials).

Generation of temporally and spatially defined magnetic fields

The subject of interest are methods of designing coils generating spatially defined magnetic fields (gradient and shim coils, shim optimization) and methods of generating temporally defined fields (preemphasis for a defined ramps and shaping gradient field pulses, eliminating the impact of eddy currents in systems with or without active shielding).

Measurement of electric, magnetic and ion fields

This complementary programme is devoted to the measurement of feeble magnetic and electric fields. It further includes the measurement of ion “fields” (i.e., spatial distribution of ions). For increasing the accuracy of the measurements, special filtering techniques (adaptive and wavelet filtration) are being developed. The development of the methods of measurement of electric, magnetic and ion fields in natural and residential environment should enable the study the impact of these fields on the human organism and, subsequently, its optimization, for instance for therapeutic purposes.

Inverse and optimization problems

The interest in inverse and optimization problems is motivated by the frequent needs of solving optimization problems (development of robust and efficient methods of nuclear spin system excitation, NMR data analysis, coils and preemphasis for magnetic field generation). A specific research subject was, e.g., Bayesian-entropic theory of evolutionary processes, combining the inference from incomplete information and hierarchical adaptible structure.

Information physics

The connection between physics and the information theory is most noticeable in the area of quantum mechanics, which is the basic theory on which the physics of NMR is built. However metaphysical this area may seem, it is an interesting and developing area, which, however, still offers more questions than answers:

What is the relationship between the laws of physics and the information theory?
Why do so many analogies between the information theory and physical laws exist?
Which inner principles induce the very laws of the information theory and probability theory?
Is it possible to unify the concept of probabilities in the classical, statistical and quantum physics?
What are general relationships between the macroscopic and microscopic levels of description?
What does the information physics offer for non-paradoxical interpretations of quantum phenomena?
What is the link between the principles of symmetries, conservation laws, and probability theory?
What might the information physics tell us about some puzzling "coincidencies" and exceptional structures, which are being discovered at the crossroads between geometry, algebra, topology, and modern theories of particles physics?
How was the concept of probability and the maximum entropy principle understood by the classics of theoretical physics, and what are some vital implications for current research?
What is the role of the maximum entropy principle in understanding complex nonlinear systems?

Some questions are directly related to NMR:

Bayesian-entropic quantification of highly non-ideal signals and spectra, incorporating contextual information and uncertainty analysis.
Generalized NMR-spectroscopy as a unifying view of various data representations and RF-excitations.
How to eliminate contradictions between the standard sensitivity theory of Fourier-Transform NMR and the Second Law of Thermodynamics?
What is the probabilistic and entropic meaning of the theorems of Fourier spectral analysis?
Which structure is adequate for representing the concept of "spin" and, more generaly, the concept of "particle parameters"?
Is the project of "Quantum NMR Computer" being based on a mere interpretation artifact?

Software for license

NMRScope-B
NMRScope-B is a plugin for program jMRUI version 4.0 (http http://www.mrui.uab.es/mrui/) or later. The plugin provides the functionality useful for the simulation of coupled spin systems during the NMR experiment. In the simulation, such properties as chemical shifts, spin-spin coupling, relaxation, spatial and/or spectral excitation selectivity, and customized pulse sequences are accounted for. The primary target is to support the simulation of NMR signals a spectra of biomedically interesting metabolites, as needed for spectroscopic quantitation, but many functions are provided to support the development of methods for in vivo MR spectroscopy and spectroscopic imaging.
The software is provided under the program jMRUI license, which is provided free of charge for non-profit use. More information, the manual and the software are available upon request from jana@isibrno.cz.
The software has been developed by Institute of Scientific Instruments of the ASCR, v.v.i., Brno, Czech Republic, utilizing the support of the jMRUI kernel and of the jMRUI software development team. The development was financially supported by grants FAST “Advanced Signal-Processing for Ultra-Fast Magnetic Resonance, and Training“ (MRTN-CT-2006-035801), GA102/09/1861 and AV0 Z20650511.