Matthias Gräser

Lübeck Germany

matthias@graeser.biz

Matthias Gräser was born in Neuwied in Germany. He completed his studies in mechatronics with a specialization in biomedical engineering in 2010 as a graduate engineer at the Karlsruhe Institute of Technology. In 2016, he received his PhD in medical engineering from the University of Lübeck. His research focused on scientific instrumentation for magnetic imaging and measurement systems especially in magnetic particle imaging.

In 2017, he moved to the Bridge Institute for Biomedical Imaging at the Technical University of Hamburg and the University Medical Center Hamburg Eppendorf as group leader for hardware development. There he developed a human-sized magnetic particle imaging system for stroke detection within the intensive care unit. His work was awarded a special prize for health care research by the Münch Foundation. In addition, he worked on numerous preclinical application studies together with UKE clinicians and on signal processing and calibration strategies for magnetic measurement systems.

In 2021, he was appointed to the professorship of Instrumentation of Imaging at the Institute of Medical Engineering at the University of Lübeck. At the same time, he took over as department head of the Diagnostics Department at Fraunhofer Research Institution for Individualized and Cellbased Medical Engineering (IMTE).

In 2024 he accepted the call for professorship of Metrology at the University of Rostock (W3).

selected publications

2022

System Matrix based Reconstruction for Pulsed Sequences in Magnetic Particle Imaging

Fabian Mohn, and 5 more authors

IEEE Transactions on Medical Imaging, 2022

10.1109/tmi.2022.3149583

2020

Design of a head coil for high resolution mouse brain perfusion imaging using magnetic particle imaging

Matthias Graeser, and 8 more authors

Physics in Medicine & Biology, 2020

Publisher: IOP Publishing

Abs 10.1088/1361-6560/abc09e

Magnetic particle imaging (MPI) is a novel and versatile imaging modality developing toward human application. When up-scaling to human size, the sensitivity of the systems naturally drops as the coil sensitivity depends on the bore diameter. Thus, new methods to push the sensitivity limit further have to be investigated to cope for this loss. In this paper a dedicated surface coil for mice is developed, improving the sensitivity in cerebral imaging applications. Similar to magnetic resonance imaging the developed surface coil improves the sensitivity due to the closer vicinity to the region of interest. With the developed surface coil presented in this work, it is possible to image tracer samples containing only 896 pgfe and detect even small vessels and anatomical structures within a wild type mouse model. As current sensitivity measures require a tracer system a new method for determining a sensitivity measure without this requirement is presented and verified to enable comparison between MPI receiver systems.

2019

Human-sized Magnetic Particle Imaging for Brain Applications

Matthias Graeser, and 13 more authors

Nature Communications, 2019

10.1038/s41467-019-09704-x

2017

Magnetic Particle Imaging for Real-Time Perfusion Imaging in Acute Stroke

Peter Ludewig, and 16 more authors

ACS Nano, 2017

PMID: 28976180

10.1021/acsnano.7b05784
Towards picogram detection of superparamagnetic iron-oxide particles using a gradiometric receive coil

Matthias Graeser, and 9 more authors

Scientific reports, 2017

10.1038/s41598-017-06992-5
Hybrid system calibration for multidimensional magnetic particle imaging

A Gladiss^∗, and 4 more authors

Physics in Medicine and Biology, 2017

10.1088/1361-6560/aa5340

2015

Dynamic single-domain particle model for magnetite particles with combined crystalline and shape anisotropy

Matthias Graeser, and 2 more authors

Journal of Physics D: Applied Physics, 2015

Abs 10.1088/0022-3727/48/27/275001

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\{}^{-{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.
Trajectory dependent particle response for anisotropic mono domain particles in magnetic particle imaging

Matthias Graeser, and 3 more authors

Journal of Physics D: Applied Physics, 2015

Paper ID: 045007

10.1088/0022-3727/49/4/045007
Electronic field free line rotation and relaxation deconvolution in Magnetic Particle Imaging

K. Bente, and 5 more authors

IEEE Transactions on Medical Imaging,, 2015

Abs 10.1109/TMI.2014.2364891

It has been shown that magnetic particle imaging (MPI), an imaging method suggested in 2005, is capable of measuring the spatial distribution of magnetic nanoparticles. Since the particles can be administered as biocompatible suspensions, this method promises to perform well as a tracer-based medical imaging technique. It is capable of generating real-time images, which will be useful in interventional procedures, without utilizing any harmful radiation. To obtain a signal from the administered superparamagnetic iron oxide (SPIO) particles, a sinusoidal changing external homogeneous magnetic field is applied. To achieve spatial encoding, a gradient field is superimposed. Conventional MPI works with a spatial encoding field that features a field free point (FFP). To increase sensitivity, an improved spatial encoding field, featuring a field free line (FFL) can be used. Previous FFL scanners, featuring a 1-D excitation, could demonstrate the feasibility of the FFL-based MPI imaging process. In this work, an FFL-based MPI scanner is presented that features a 2-D excitation field and, for the first time, an electronic rotation of the spatial encoding field. Furthermore, the role of relaxation effects in MPI is starting to move to the center of interest. Nevertheless, no reconstruction schemes presented thus far include a dynamical particle model for image reconstruction. A first application of a model that accounts for relaxation effects in the reconstruction of MPI images is presented here in the form of a simplified, but well performing strategy for signal deconvolution. The results demonstrate the high impact of relaxation deconvolution on the MPI imaging process.