Tomographic imaging has become a mandatory tool for the diagnosis of a majority of diseases in clinical routine. Since each method has its pros and cons, a variety of them is regularly used in clinics to satisfy all application needs. Magnetic particle imaging (MPI) is a relatively new tomographic imaging technique that images magnetic nanoparticles with a high spatiotemporal resolution in a quantitative way, and in turn is highly suited for vascular and targeted imaging. MPI was introduced in 2005 and now enters the preclinical research phase, where medical researchers get access to this new technology and exploit its potential under physiological conditions. Within this paper, we review the development of MPI since its introduction in 2005. Besides an in-depth description of the basic principles, we provide detailed discussions on imaging sequences, reconstruction algorithms, scanner instrumentation and potential medical applications.

https://iopscience.iop.org/article/10.1088/1361-6560/aa6c99/pdf

Magnetic particle imaging: from proof of principle to preclinical applications

Magnetic fluid hyperthermia (MFH) treatment makes use of a suspension of superparamagnetic iron oxide nanoparticles, administered systemically or locally, in combination with an externally applied alternating magnetic field, to ablate target tissue by generating heat through a process called induction. The heat generated above the mammalian euthermic temperature of 37°C induces apoptotic cell death and/or enhances the susceptibility of the target tissue to other therapies such as radiation and chemotherapy. While most hyperthermia techniques currently in development are targeted towards cancer treatment, hyperthermia is also used to treat restenosis, to remove plaques, to ablate nerves and to alleviate pain by increasing regional blood flow. While RF hyperthermia can be directed invasively towards the site of treatment, non-invasive localization of heat through induction is challenging. In this review, we discuss recent progress in the field of RF magnetic fluid hyperthermia and introduce a new diagnostic imaging modality called magnetic particle imaging that allows for a focused theranostic approach encompassing treatment planning, treatment monitoring and spatially localized inductive heating.

Using magnetic particle imaging systems to localize and guide magnetic hyperthermia treatment: tracers, hardware, and future medical applications

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), is a threat to the global healthcare system and economic security. As of Ju...

Magnetic Nanosensor-Based Virus and Pathogen Detection Strategies Before and During COVID-19

https://iopscience.iop.org/article/10.1088/1361-6463/ab03c0/pdf

Magnetic particle spectroscopy-based bioassays: methods, applications, advances, and future opportunities

Magnetic particle spectroscopy (MPS), also called magnetization response spectroscopy (MRS), is a versatile measurement tool derived from magnetic particle imaging (MPI). It can be interpreted as a...

Magnetic Particle Spectroscopy: A Short Review of Applications Using Magnetic Nanoparticles

The non-linear signal generation in Magnetic Particle Imaging (MPI) using magnetic nanoparticles as tracer materials is still not fully explained and a far-reaching research area. Magnetic Particle Spectroscopy (MPS) was developed to investigate the particle behavior in high externally applied magnetic field strengths and to derive mathematical models which describe the physical processes in MPI in detail. A new MPS setup was built which allows measurements between -13 °C and +114 °C in order to investigate the temperature dependence of the harmonics spectra. Temperature-dependent MPS measurements of diluted FeraSpinTM XL, either as suspension or freeze-dried in a mannitol matrix, using the new setup are shown and exemplarily discussed.

https://www.journal.iwmpi.org/index.php/iwmpi/article/download/66/93

Temperature-dependent MPS measurements

Multi-spectral Magnetic Particle Spectroscopy for the investigation of particle mixtures

Magnetic nanoparticles (MNPs) are used as therapeutic and diagnostic agents for local delivery of heat and image contrast enhancement in diseased tissue. Besides magnetization, the most important parameter that determines their performance for these applications is their magnetic relaxation, which can be affected when MNPs immobilize and agglomerate inside tissues. In this letter, we investigate different MNP agglomeration states for their magnetic relaxation properties under excitation in alternating fields and relate this to their heating efficiency and imaging properties. With focus on magnetic fluid hyperthermia, two different trends in MNP heating efficiency are measured: an increase by up to 23% for agglomerated MNP in suspension and a decrease by up to 28% for mixed states of agglomerated and immobilized MNP, which indicates that immobilization is the dominant effect. The same comparatively moderate effects are obtained for the signal amplitude in magnetic particle spectroscopy.

Magnetic Relaxation of Agglomerated and Immobilized Iron Oxide Nanoparticles for Hyperthermia and Imaging Applications

Magnetic hyperthermia is a technique that describes the heating of material through an external magnetic field. Classic hyperthermia is a medical condition where the human body overheats, being usually triggered by a heat stroke, which can lead to severe damage to organs and tissue due to the denaturation of cells. In modern medicine, hyperthermia can be deliberately induced to specified parts of the body to destroy malignant cells. Magnetic hyperthermia describes the way that this overheating is induced and it has the inherent advantage of being a minimal invasive method when compared to traditional surgery methods. This work presents a particle system that offers huge potential for hyperthermia treatments, given its good loss value, i.e., the particles dissipate a lot of heat to their surroundings when treated with an ac magnetic field. The measurements were performed in a low-cost custom hyperthermia setup. Additional toxicity assessments on Jurkat cells show a very low short-term toxicity on the particles and a moderate low toxicity after two days due to the prevalent health concerns towards nanoparticles in organisms.

Sebastian Draack

Papers

Temperature-dependent MPS measurements

Multi-spectral Magnetic Particle Spectroscopy for the investigation of particle mixtures

Magnetic Relaxation of Agglomerated and Immobilized Iron Oxide Nanoparticles for Hyperthermia and Imaging Applications

Biophysical Characterization of (Silica-coated) Cobalt Ferrite Nanoparticles for Hyperthermia Treatment

Dependence of biomolecule detection on magnetic nanoparticle concentration