Quantification of structural changes in the corpus callosumin children with profound hypoxic-ischaemic brain injury

Background Birth-related acute profound hypoxic–ischaemic brain injury has specific patterns of damage including the paracentral lobules. Objective To test the hypothesis that there is anatomically coherent regional volume loss of the corpus callosum as a result of this hemispheric abnormality. Materials and methods Study subjects included 13 children with proven acute profound hypoxic–ischaemic brain injury and 13 children with developmental delay but no brain abnormalities. A computerised system divided the corpus callosum into 100 segments, measuring each width. Principal component analysis grouped the widths into contiguous anatomical regions. We conducted analysis of variance of corpus callosum widths as well as support vector machine stratification into patient groups. Results There was statistically significant narrowing of the mid–posterior body and genu of the corpus callosum in children with hypoxic–ischaemic brain injury. Support vector machine analysis yielded over 95% accuracy in patient group stratification using the corpus callosum centile widths. Conclusion Focal volume loss is seen in the corpus callosum of children with hypoxic–ischaemic brain injury secondary to loss of commissural fibres arising in the paracentral lobules. Support vector machine stratification into the hypoxic–ischaemic brain injury group or the control group on the basis of corpus callosum width is highly accurate and points towards rapid clinical translation of this technique as a potential biomarker of hypoxic–ischaemic brain injur

Concentration Dependent MPI Tracer Performance

Magnetic Particle Imaging (MPI) and Magnetic Particle Spectroscopy (MPS) usually require a reference sample measurement to provide information about the non-linear dynamic magnetic behavior of a specific magnetic nanoparticle (MNP) type. This reference sample based approach presupposes that this dynamic magnetization behavior of MNP is concentration independent. We investigated Resovist® and its precursor Ferucarbotran at different concentrations to verify this assumption by means of MPS. Remarkably, for Resovist® we found a strong concentration dependence of the MPS signal. Above an iron concentration of about 150 mmol/L the shape of the moment and phase spectra changed with increasing iron concentration. In contrast, for Ferucarbotran we found no concentration dependence of the dynamic magnetic behavior even though at a two?fold higher initial concentration. Our experimental results indicate that the dynamic magnetic behavior of MPI tracers may be altered at higher concentrations and should be studied prior to MPI by MPS experiments

Hyphenation of Field-Flow Fractionation and Magnetic Particle Spectroscopy

Magnetic nanoparticles (MNPs) exhibit unique magnetic properties making them ideally suited for a variety of biomedical applications. Depending on the desired magnetic effect, MNPs must meet special magnetic requirements which are mainly determined by their structural properties (e.g., size distribution). The hyphenation of chromatographic separation techniques with complementary detectors is capable of providing multidimensional information of submicron particles. Although various methods have already been combined for this approach, so far, no detector for the online magnetic analysis was used. Magnetic particle spectroscopy (MPS) has been proven a straightforward technique for specific quantification and characterization of MNPs. It combines high sensitivity with high temporal resolution; both of these are prerequisites for a successful hyphenation with chromatographic separation. We demonstrate the capability of MPS to specifically detect and characterize MNPs under usually applied asymmetric flow field-flow fractionation (A4F) conditions (flow rates, MNP concentration, different MNP types). To this end MPS has been successfully integrated into an A4F multidetector platform including dynamic ligth scattering (DLS), multi-angle light scattering (MALS) and ultraviolet (UV) detection. Our system allows for rapid and comprehensive characterization of typical MNP samples for the systematic investigation of structure-dependent magnetic properties. This has been demonstrated by magnetic analysis of the commercial magnetic resonance imaging (MRI) contrast agent Ferucarbotran (FER) during hydrodynamic A4F fractionation

Influence of magnetic nanoparticles interactions on their magnetic particle imaging performance

Abstract: The here presented study investigated the influence of magnetic particle-particle interactions within the MPI tracer MNP on the imaging performance of the tracers. To realize a proper separation and to increase the distances between the individual tracer MNP (which results in reduced particle-particle interactions), the MNP were diluted by non-magnetic SiO2 spacers in the nanometer range. The obtained MNP/SiO2 mixtures were characterized and used to build up measurement phantoms by embedding the mixture into a long-term stable polymer matrix. In MPS and MPI measurements it was found that reduction of the magnetic interactions encompassed by increasing the MNP distances leads for the tested tracer system to a weaker decrease of higher harmonics in the MPS spectra after immobilization of the particles and thereby, a higher spatial MPI resolution can be achieved

MPS and MRI efficacy of magnetosomes from wild-type and mutant bacterial strains

The future of Magnetic Particle Imaging (MPI), as a tracer-based imaging modality, crucially relies on the development of high-performing tracers. Due to their ideal structural and magnetic properties, biogenic nanoparticles extracted from magnetotactic bacteria are promising candidates for MPI tracer research. In the present study we investigate the potential of bacterial magnetosomes, extracted from wild-type bacteria of the strain Magnetospirillum gryphiswaldense and various mutants thereof, as new tracer materials for MPI. Furthermore, we investigate the structural and magnetic properties of the magnetosomes as well as their suitability as Magnetic Resonance Imaging (MRI) agents in order to explain differences in MPI and MRI efficacies