The Institute for Biomedical Imaging (IBI) was founded in 2014 by Tobias Knopp and is a joint research department of the University Medical Center Hamburg-Eppendorf (UKE) and the Hamburg University of Technology (TUHH). Medical imaging is the non-invasive imaging of sections of the human body and plays an important role in the diagnosis, treatment and post-treatment of diseases. Effective, safe and high quality imaging is essential for many medical decisions and can prevent unnecessary medical procedures. Our research interests lie in the field of tomographic imaging, with a focus on Magnetic Resonance Imaging (MRI) and the young imaging technique Magnetic Particle Imaging (MPI). In particular, we are working on the hardware development of MPI systems, the research of new signal processing, image reconstruction and image processing algorithms, and the evaluation of medical applicability. In close cooperation with our clinical partners at the UKE, we also conduct translational research with the goal of bringing state-of-the-art acquisition and reconstruction methods into clinical routine.
Magnetic particle imaging exploits the non-linear magnetization of superparamagnetic iron-oxide particles to generate a tomographic image in a defined field-of-view. For reconstruction of the particle distribution, a time-consuming calibration step is required, in which system matrices get measured using a robot. To achieve artifact-free images, system matrices need to cover not only the field-of-view but also a larger area around it. Especially for large measurements – inevitable for future clinical application – this leads to long calibration time and high consumption of persistent memory. In this work, we analyze the signal in the outer part of the system matrix and motivate the usage of extrapolation methods to computationally expand the system matrix after restricting the calibration to the field-of-view. We propose a suitable extrapolation method and show its applicability on measured 2D and 3D data. In doing so, we achieve a considerable reduction of calibration time and consumption of persistent memory while preserving an artifact-free result.
The entire methodology is described in the paper "Extrapolation of System Matrices in Magnetic Particle Imaging" by Konrad Scheffler, Marija Boberg, and Tobias Knopp, which you can find here.