Magnetic nanoparticles as markers for biomedical analysis

Magnetic nanoparticles are tiny magnets of the size of large molecules. These nanoparticles can be used as markers for biomedical analysis with remarkable properties. By homogenous magnetic fields they can be rotated and by gradient fields they can be steered with magnetic forces. By antibody functionalization of their surface other proteins can be coupled to the nanoparticles. This way the mobility of the nanoparticle is changed, which can be detected macroscopically by the modified response to external magnetic fields. Protein interaction can help to deliver drugs and to localize infections or inflammations for diagnostic or therapeutic purposes by magnetic particle imaging (MPI)

Single Harmonic-based Narrowband Magnetic Particle Imaging

Visualization of the in vivo spatial distribution of superparamagnetic iron oxide nanoparticles (SPIONs) is crucial to biomedicine. Magnetic particle imaging (MPI) is one of the most promising approaches for direct measurements of the SPION distribution. In this paper, we systematically investigate a single-harmonic-based narrowband MPI approach. Herein, only the 3rd harmonic at 15 kHz of the SPION signal induced in an excitation magnetic field of 5 kHz is measured via a narrowband detection system for imaging during scanning a field-free-point in a field of view. Experiments on spot and line phantoms are performed to evaluate the spatial distribution by the assessment of the full width at half maximum and modulation transfer function at different excitation magnetic fields from 4 to 10 mT. Experimental results demonstrate that reconstructed images have a spatial resolution of 1.6 and 1.5 mm for a gradient field of 2.2 T/m and 4.4 T/m in x- and z-direction, respectively, at an excitation magnetic field of 4 mT. In terms of line gap, two lines with a gap of 0.5 mm are resolved. With increasing the excitation magnetic field to 10 mT, the spatial resolution gets worse to 2.4 and 2.0 mm in x- and z-direction, respectively. Moreover, the custom-built MPI scanner allows a limit of detection of 53 microgram (Fe)/mL (500 ng Fe weight) using perimag SPIONs. In addition, the excellent performance is demonstrated by imaging experiments on an "emg" logo phantom. We believe that the proposed narrowband MPI approach is a promising approach for SPION imaging

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

This paper quantitatively investigates the spatial and temperature resolutions of magnetic nanoparticle (MNP) temperature imaging with a multiline phantom filled with MNPs. The multiline phantom in total consists of seven lines with different distances between two adjacent lines. A scanning magnetic particle spectrometer is used to measure the spatial distributions of the MNP harmonics for MNP concentration and temperature imaging, whereas an iterative deconvolution method is used to improve the spatial resolution. A modulation transfer function calculated from the MNP concentration image is used to quantitatively present the spatial resolution, whereas the standard deviation of the measured temperatures is used to quantitatively present the temperature resolution. The spatial resolution is about 4 mm while the temperature resolution is about 1.0 K without deconvolution. With increasing the number of the iterative loops in the deconvolution, the spatial resolution is improved to 2 mm while the temperature resolution is worsened to about 9.6 K due to deconvolution-based oscillation

Simultaneous imaging of magnetic nanoparticle concentration, temperature and viscosity with a scanning magnetic particle spectrometer

A new approach of simultaneous imaging of magnetic nanoparticle (MNP) concentration, temperature and viscosity with a custom-built scanning magnetic particle spectrometer (SMPS) is presented. The fundamental f0 and the 3f0 and 5f0 harmonics of the MNPs dominated by Brownian relaxation are measured with the SMPS. The effects of viscosity and temperature on the harmonics are studied in ac magnetic fields with different frequencies and amplitudes. Afterwards, phantom experiments are performed on the MNP samples with different spatial distributions of viscosity and temperature, which demonstrates the feasibility of the proposed approach for simultaneous imaging of MNP concentration, temperature and viscosity imaging

Noise properties of textile, capacitive EEG electrodes

The rigid surface of the conventional PCB-based capacitive electrode produces an undefined distance between the skin and the electrode surface. Therefore, the capacitance introduced by them is uncertain and can vary from electrode to electrode due to their different positions on the scalp. However, textile electrodes which use conductive fabric as electrode surfaces, are bendable over the scalp. Therefore, it provides a certain value of the capacitance which is predictable and calculable accurately if the effective distance to the scalp surface can be determined. In this paper noise characteristics of textile electrodes with different fabric sizes as electrode’s surface and capacity calculations related to each size are presented to determine the effective distances for each electrode size

Measurements of dimensional standards and etalons with feature size from tens of micrometres to millimetres by using sensor strengthened nanomeasuring machine

A laser focus sensor and a contact inductive sensor have been coupled to an ultra high precision positioning stage, referred to as a nanomeasuring machine (NMM), for measurements of dimensional standards with a large measurement volume of 25 mm x 25 mm x 5 mm. Control and measurement software have been designed and complemented. The measurement uncertainty of strengthened NMM has been analyzed and discussed. Groove depth and step height standards with feature heights of tens of micrometres to millimetres as well as aspherical surface etalons are calibrated by nanomeasuring machine. The paper also introduces a method for characterising the measured aspheric surface by least square fitting the measured data to a quadratic paraboloid function. The obtained quadratic coefficients are compared to that measured by a conventional coordinate measuring machine (CMM) and a stylus profiler, showing a good agreement