Dr.-Ing. Matthias Gräser

Universitätsklinikum Hamburg-Eppendorf (UKE)
Sektion für Biomedizinische Bildgebung
Lottestraße 55
2ter Stock, Raum 212
22529 Hamburg

Technische Universität Hamburg (TUHH)
Institut für Biomedizinische Bildgebung
Gebäude E, Raum 4.044
Am Schwarzenberg-Campus 3
21073 Hamburg

Tel.: 040 / 7410 25812
E-Mail: matthias.graeser(at)tuhh.de
E-Mail: ma.graeser(at)uke.de

Research Interests

  • Magnetic Particle Imaging
  • Low Noise Electronics
  • Inductive Sensors
  • Passive Electrical Devices

Curriculum Vitae

Matthias Gräser submitted his Dr.-Ing. thesis in january 2016 at the institute of medical engineering (IMT) at the university of Lübeck and is now working as a Research Scientist at the institute for biomedical imaging (IBI) at the technical university in Hamburg, Germany.  Here he develops concepts for Magnetic-Particle-Imaging (MPI) devices. His main aim is to improve the sensitivity of the imageing devices and improve resolution and application possibilities of MPI technology.

In 2011 Matthias Gräser started to work at the IMT as a Research Associate in the Magnetic Particle Imaging Technology (MAPIT) project. In this project he devolped the analog signal chains for a rabbit sized field free line imager. Additionally he developed a two-dimensional Magnetic-Particle-Spectrometer. This device can apply various field sequences and measure the particle response with a very high signal-to-noise ratio (SNR).

The dynamic behaviour of magnetic nanoparticles is still not fully understood. Matthias Gräser investigated the particle behaviour by modeling the particle behaviour with stochastic differential equations. With this model it is possible to simulate the impact of several particle parameters and field sequences on the particle response .

In 2010 Matthias Gräser finished his diploma at the Karlsruhe Institue of Technology (KIT). His diploma thesis investigated the nerve stimulation of magnetic fields in the range from 4 kHz to 25 kHz.

Journal Publications

[76866]
Title: Dynamic single-domain particle model for magnetite particles with combined crystalline and shape anisotropy.
Written by: M. Graeser, K. Bente, and T. M. Buzug
in: <em>Journal of Physics D: Applied Physics</em>. (2015).
Volume: <strong>48</strong>. Number: (27),
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DOI: 10.1088/0022-3727/48/27/275001
URL: http://iopscience.iop.org/0022-3727/48/27/275001/
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[www] [BibTex]

Note: article, Paper ID: 275001

Abstract: The dynamical behaviour of superparamagnetic iron oxide nanoparticles ({SPIONs}) is not yet fully understood. In magnetic particle imaging ({MPI}) {SPIONs} are used to determine quantitative real-time medical images of a tracer material distribution. For reaching spatial resolution in the sub-millimetre range, {MPI} requires a well engineered instrumentation providing a magnetic field gradient exceeding 2 T m\$\{\}{\textasciicircum}\{-\{1\}\}\$ . However, as the particle performance strongly affects the sensitivity of the imaging process, optimization of the particle parameters is a crucial factor, which is not easy to address. Today most simulations of {MPI} use the Langevin model to describe the particle behaviour. In equilibrium, the model matches the measured data. If alternating fields in the mid {kHz} frequency range are applied, the dynamic behaviour of the particles differs from the Langevin theory due to anisotropy effects, particle–particle-interactions and/or exchange interaction in case of multi-core particles. In this paper a model based on previous work is introduced, which was adopted to include crystal and shape anisotropy of immobilised mono-domain single-core particles. The model is applied to typical {MPI} frequencies and field strengths with different possible superposition of the anisotropy effects, leading to differences in the particle response. It is shown that, despite comparatively high anisotropy constants, the magnetocrystalline anisotropy energy does not quench the signal response for {MPI}. The constructive superposition of shape and crystal anisotropy leads to the best performance in terms of sensitivity and resolution of the associated imaging modality and slightly reduces the energy barriers compared to a sole-shape anisotropy.

Conference Proceedings

[76866]
Title: Dynamic single-domain particle model for magnetite particles with combined crystalline and shape anisotropy.
Written by: M. Graeser, K. Bente, and T. M. Buzug
in: <em>Journal of Physics D: Applied Physics</em>. (2015).
Volume: <strong>48</strong>. Number: (27),
on pages:
Chapter:
Editor:
Publisher:
Series:
Address:
Edition:
ISBN:
how published:
Organization:
School:
Institution:
Type:
DOI: 10.1088/0022-3727/48/27/275001
URL: http://iopscience.iop.org/0022-3727/48/27/275001/
ARXIVID:
PMID:

[www] [BibTex]

Note: article, Paper ID: 275001

Abstract: The dynamical behaviour of superparamagnetic iron oxide nanoparticles ({SPIONs}) is not yet fully understood. In magnetic particle imaging ({MPI}) {SPIONs} are used to determine quantitative real-time medical images of a tracer material distribution. For reaching spatial resolution in the sub-millimetre range, {MPI} requires a well engineered instrumentation providing a magnetic field gradient exceeding 2 T m\$\{\}{\textasciicircum}\{-\{1\}\}\$ . However, as the particle performance strongly affects the sensitivity of the imaging process, optimization of the particle parameters is a crucial factor, which is not easy to address. Today most simulations of {MPI} use the Langevin model to describe the particle behaviour. In equilibrium, the model matches the measured data. If alternating fields in the mid {kHz} frequency range are applied, the dynamic behaviour of the particles differs from the Langevin theory due to anisotropy effects, particle–particle-interactions and/or exchange interaction in case of multi-core particles. In this paper a model based on previous work is introduced, which was adopted to include crystal and shape anisotropy of immobilised mono-domain single-core particles. The model is applied to typical {MPI} frequencies and field strengths with different possible superposition of the anisotropy effects, leading to differences in the particle response. It is shown that, despite comparatively high anisotropy constants, the magnetocrystalline anisotropy energy does not quench the signal response for {MPI}. The constructive superposition of shape and crystal anisotropy leads to the best performance in terms of sensitivity and resolution of the associated imaging modality and slightly reduces the energy barriers compared to a sole-shape anisotropy.