Recent Advancements of Magnetorelaxometry Imaging Towards Human Applications

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Contents of the Talk

Magnetic nanoparticles (MNP) offer a large variety of promising applications in medicine, e.g., magnetic hyperthermia and magnetic drug targeting. In magnetic hyperthermia, MNP injected into a tumor are heated by an alternating magnetic field with the aim of locally ablating tumor tissue. In magnetic drug targeting, MNP are drug loaded and magnetic fields are used to enrich the MNP in a target region, leading to local application of the drug. Quantitative imaging of the MNP distributions is crucial for planning and monitoring of these treatments. A promising method therefor is magnetorelaxometry imaging (MRXI), where the magnetic moments of superparamagnetic MNP are aligned by applying magnetic excitation fields. After rapidly switching off the excitation fields, the relaxation of the MNP’s net magnetic moment is monitored by magnetometers. From the relaxation signals, the MNP can be quantified, and their binding state can be extracted. Additionally, quantitative spatial information about the MNP distribution is obtained by applying spatially different excitation fields and solving an ill-posed inverse problem. MRX imaging has been established employing superconducting magnetometers (SQUIDs) in small volumes. Recent developments in laser physics enabled novel optically pumped magnetometers (OPM) reaching similar sensitivities while offering flexible sensor positioning and the omission of cryogenic cooling, therewith potentially facilitating the translation of MRXI towards clinical applications.

We successfully demonstrated the potential of OPMs for MRXI, including the investigation and optimization of different parameters like dead time, bandwidth, sensitivity and sensor crosstalk. By optimizing both sensor and excitation coil geometry, significant improvements in terms of spatial resolution could be achieved. Recently, we have investigated advancing MRXI to the nonlinear magnetization regime, allowing for higher excitation fields and larger fields of view. Finally, we have developed a human head sized MRXI system, demonstrating the feasibility of detecting and quantifying MNP distributions, e.g. during hyperthermia therapy of glioblastoma. This talk will present the recent advancements and discuss the potential, challenges and limitations of the translation of MRXI towards human applications.

Short CV

Daniel Baumgarten received his master’s and Ph.D. degrees in biomedical engineering from TU Ilmenau, Germany, in 2006 and 2011, respectively. After postdoc appointments at TU Ilmenau and Universiti Teknologie Malaysia, he became a junior professor at TU Ilmenau in 2013. Since 2016, he has been a full professor and head of the Institute of Electrical and Biomedical Engineering at UMIT TIROL – Private University for Health Sciences and Health Technology in Hall in Tirol, Austria. Among others, he is a board member of the Austrian Society for Biomedical Engineering (ÖGBMT), Austrian representative International Federation of Medical & Biological Engineering (IFMBE), member of the Austrian Nano Information Commission and chairman of the technology platform NanoMedicine-Austria. His research interests include the investigation of bioelectric and biomagnetic phenomena, bionanomagnetism as well as biomedical imaging, modeling and simulation.