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

[76877]
Title: Experimental Validation of the Selection Field of a Rabbit-Sized FFL Scanner.
Written by: A. Bakenecker, T. Friedrich, A. von Gladiss, M. Graeser, J. Stelzner, and T. M. Buzug
in: <em>International Journal on Magnetic Particle Imaging</em>. (2017).
Volume: <strong>3</strong>. Number: (1),
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URL: https://journal.iwmpi.org/index.php/iwmpi/article/view/75
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[www] [BibTex]

Note: article

Abstract: There are two different field topologies in magnetic particle imaging which enable the spatial encoding of the signal. Scanners using a field-free line (FFL) are promising regarding their sensitivity, because the low field volume is larger compared to a field-free point (FFP) and therefore, more particles contribute to the signal. A rabbit-sized FFL scanner with a bore diameter of 173 mm was presented in 2014. After planning and assembling the scanner an experimental validation of the designated field topology of the selection field is presented. With a hall probe the field topologies of the z-gradient coil and the two quadrupoles forming together the selection field of the scanner were investigated. These magnetic field measurements show the expected field topologies: an FFP formed by the z-gradient coil and an FFL parallel to the bore of the scanner formed by each quadrupole. From these measurements the field gradients were calculated and approximated towards the designated currents. The results are in good agreement with the expected field gradients. In order to determine the best suitable frequency for rotating the FFL measurements were done on the power loss in the shielding taking place for higher frequencies. And the power transmission of the transformer, which is problematic for low frequencies. A rotation frequency of 20 Hz is chosen as it represents a compromise between transformer performance and power loss in the shielding.

Conference Proceedings

[76877]
Title: Experimental Validation of the Selection Field of a Rabbit-Sized FFL Scanner.
Written by: A. Bakenecker, T. Friedrich, A. von Gladiss, M. Graeser, J. Stelzner, and T. M. Buzug
in: <em>International Journal on Magnetic Particle Imaging</em>. (2017).
Volume: <strong>3</strong>. Number: (1),
on pages:
Chapter:
Editor:
Publisher:
Series:
Address:
Edition:
ISBN:
how published:
Organization:
School:
Institution:
Type:
DOI:
URL: https://journal.iwmpi.org/index.php/iwmpi/article/view/75
ARXIVID:
PMID:

[www] [BibTex]

Note: article

Abstract: There are two different field topologies in magnetic particle imaging which enable the spatial encoding of the signal. Scanners using a field-free line (FFL) are promising regarding their sensitivity, because the low field volume is larger compared to a field-free point (FFP) and therefore, more particles contribute to the signal. A rabbit-sized FFL scanner with a bore diameter of 173 mm was presented in 2014. After planning and assembling the scanner an experimental validation of the designated field topology of the selection field is presented. With a hall probe the field topologies of the z-gradient coil and the two quadrupoles forming together the selection field of the scanner were investigated. These magnetic field measurements show the expected field topologies: an FFP formed by the z-gradient coil and an FFL parallel to the bore of the scanner formed by each quadrupole. From these measurements the field gradients were calculated and approximated towards the designated currents. The results are in good agreement with the expected field gradients. In order to determine the best suitable frequency for rotating the FFL measurements were done on the power loss in the shielding taking place for higher frequencies. And the power transmission of the transformer, which is problematic for low frequencies. A rotation frequency of 20 Hz is chosen as it represents a compromise between transformer performance and power loss in the shielding.