Determination of the magnetic particle distribution in tumour tissue by means of X-ray tomography

In biomedical applications of ferrofluids, the resulting distribution of the magnetic nanoparticles is a crucial parameter for the effect of the therapeutic approach. In order to increase the efficacy of local cancer treatments incorporating ferrofluids likemagnetic drug targeting and hyperthermia, the biodistribution of theses fluids in the respective tissue has to be optimized. Usually, the distribution of particles is determined by histological cuts of the investigated specimen, a technique which provides only local information about the overall distribution of the magnetic material, e. g. in a tumour. Radioscopic techniques based on gamma or x- rays are well established, suitable for in vivo examination and non- destructive, but only provide two- dimensional integral information in the direction of the beam. Here we have used micro- tomography incorporating a conventional x- ray tube as well as monochromatic synchrotron radiation - as a tool for a three- dimensional analysis of the distribution of magnetic nanoparticles in biological applications. Compared to biological matter, the iron- based magnetic nanoparticles provide sufficiently high absorption for x- rays and thus serve as an intrinsic contrast agent for the examinations. The results show the principle feasibility of the method for a quantitative determination of the agglomeration behaviour of the nanoparticles within carcinogenic tissue after intravascular or intratumoural injection.