Helene Rahn

Visualization of superparamagnetic nanoparticles in vascular tissue using XμCT and histology.

In order to increase the dose of antineoplastic agents in the tumor area, the concept of magnetic drug targeting (MDT) has been developed. Magnetic nanoparticles consisting of iron oxide and a biocompatible cover layer suspended in an aqueous solution (ferrofluid) serve as carriers for chemotherapeutics being enriched by an external magnetic field after intra-arterial application in desired body compartments (i.e., tumor). We established an ex vivo model to simulate in vivo conditions in a circulating system consisting of magnetic iron oxide nanoparticles passing an intact bovine artery and being focused by an external magnetic field to study their distribution in the vessel. Micro-computed X-ray tomography (XμCT) and histology can elucidate the arrangement of these particles after application. XμCT-analysis has been performed on arterial sections after MDT in order to determine the distribution of the nanoparticles. These measurements have been carried out with a cone X-ray source and corresponding histological sections were stained with Prussian blue. It could be shown that combining XμCT and histology offers the opportunity for a better understanding of the mechanisms of nanoparticle deposition in the vascular system after MDT.

Tissue Model for the Study of Heat Transition During Magnetic Heating Treatment

Heat can be induced within a tissue enriched with magnetic nanoparticles by exposing it to an alternating magnetic field. In this paper we examine the evaluation of the heat distribution and therefore the temperature development around such a heat source which can be suitable for magnetic heating treatment. We study the heat transfer from tissue enriched with magnetic nanoparticles to regions of no or minor enrichment of nanoparticles, particularly. The evaluation of the temperature distribution took place with the help of a tissue phantom. The phantom is composed of two concentric cylinders. The inner cylinder consists of a defined mixture of polyurethane gel and magnetic fluid. This cylinder represents tissue enriched with nanoparticles. The outer cylinder, which stands for pure tissue consists of polyurethane only. This tissue phantom has been exposed to an alternating magnetic field according to the protocol of the magnetic heating treatment. The temperature measurements were performed by thermocouples which are placed on defined positions. The experimentally obtained temperature data is the basis for a finite element method (FEM) simulation model. The FEM model allows the determination of heat transition from regions enriched with magnetic nanoparticles to regions with no or minor nanoparticle accumulation.

First Results of the DITO-Experiment at the HARWI II Beamline at GKSS/DESY

At the HARWI II beamline at the GKSS outstation at DESY a new experiment for position sensitive diffractometry and tomography called DITO was built and commissioned this year. Due to the available high energy synchrotron radiation with photon energies up to 100 keV it is possible to investigate the bulk of metallic samples of a few mm thickness with both methods. The diffractometry detector allows the investigation of the phase composition as well as phase sensitive determination of residual stresses with a spatial resolution of 6 μm while the tomography detector can either measure a whole tomogram in high resolution mode with a spatial resolution of 2 μm within 3 to 4 hours or in high speed mode recording a whole tomogram within 15 seconds with a spatial resolution of 40 μm.

3D Semi-quantification of Nanoparticle Content in Tissue on Experimental and Commercial μCT-Scanner

X-ray computed tomography is a widely used imaging technique nowadays. Especially in medicine it takes an important role for visualization and diagnostics. Micro-computed tomography (μCT) follows the same principle as conventional medical CT-Scanner. But the objects analyzed are smaller, thus an improvement in spatial resolution down to few micrometers is possible. In the work field of biomedical application of magnetic nanoparticles μCT has been used for the visualization of the nanoparticle accumulations within tumoral regions after magnetic drug targeting. Further on, a calibration procedure has been developed and applied with a μCT-apparatus. The calibration procedure enables a semi-quantification of the nanoparticle content within the tissue samples. The next step stone in visualization process is the observation of the nanoparticle accumulation during the application of magnetic drug targeting in an animal. Thus, we have tested the calibration procedure on a commercial animal scanner. In this paper we compare the semi-quantitative results figured out in two different μCT-equipments.

CANCER THERAPY WITH MAGNETIC NANOPARTICLES VISUALIZED WITH MRI, X-RAY-TOMOGRAPHY, MAGNETORELAXOMETRY AND HISTOLOGY

Magnetic Drug Targeting (MDT) is a new approach for chemotherapy heading for a higher drug amount in the tumor and simultaneously a reduced overall dose. The aim of the present study was to investigate the distribution of the particles with common imaging techniques. Tumor bearing rabbits were examined with a 4.7 Tesla MRI before and after MDT. The biodistribution of magnetic nanoparticles after MDT was investigated with a high resolution 3-dimensional x-ray-tomography (CCD Camera, 1024x1024 pixels) of the extracted tumor with corresponding histological cross sections. Moreover quantitative analysis was performed with a multichannel SQUID system based on magnetrelaxometry. All methods show a significant enrichment of magnetic nanoparticles in the tumor region.