Temperature dependence in magnetic particle imaging

Abstract

Experimental results are presented demonstrating how temperature can influence the dynamics of magnetic nanoparticles (MNPs) in liquid suspension, when exposed to alternating magnetic fields in the kilohertz frequency range. The measurements used to probe the nanoparticle systems are directly linked to both the emerging biomedical technique of magnetic particle imaging (MPI), and to the recently proposed concept of remote nanoscale thermometry using MNPs under AC field excitation. Here, we report measurements on three common types of MNPs, two of which are currently leading candidates for use as tracers in MPI. Using highly-sensitive magnetic particle spectroscopy (MPS), we demonstrate significant and divergent thermal dependences in several key measures used in the evaluation of MNP dynamics for use in MPI and other applications. The temperature range studied was between 296 and 318 Kelvin, making our findings of particular importance for MPI and other biomedical technologies. Furthermore, we report the detection of the same temperature dependences in measurements conducted using the detection coils within an operational preclinical MPI scanner. This clearly shows the importance of considering temperature during MPI development, and the potential for temperature-resolved MPI using this system. We propose possible physical explanations for the differences in the behaviors observed between the different particle types, and discuss our results in terms of the opportunities and concerns they raise for MPI and other MNP based technologies.

Spatial and Temperature Resolutions of Magnetic Nanoparticle Temperature Imaging with a Scanning Magnetic Particle Spectrometer

“…With increasing temperature, the Brownian relaxation time τ B ( T ) significantly decreases due to a higher thermal energy and a lower viscosity. It means that MNPs can rotate faster to follow the excited AC magnetic field, thus strengthening the MNP magnetization, especially higher harmonics [ 32 , 33 ]. Thus, a higher temperature leads to a higher harmonic ratio, as shown in Figure 2 .…”

In vivo magnetic particle imaging: angiography of inferior vena cava and aorta in rats using newly developed multicore particles

“…Implementation of other commercially available traces with promising MPI characteristics such as perimag 26,27 and synomag-D 28 (micromod Partikeltechnologie GmbH, Rostock, Germany) and comparison with the obtained results would be of interest in future studies. Another general limitation in MPI based on SF is the possible mismatch of the SF-sample used for calibration and the magnetization dynamics of MNP under influence of their specific local environment in vivo [29][30][31][32] , which causes image artifacts and reduced sensitivity of MPI 33 . In a further step, we will investigate to which extent the adaptation of the SF e.g.…”

Lissajous scanning magnetic particle imaging as a multifunctional platform for magnetic hyperthermia therapy

“…27 Temperature dependence of the MPI imaging signal produced by FCT nanoparticles under simple 1D field excitations was previously noted in ref. 28.…”