In order to reduce the side effects generated by the most common cancer treatment therapies, chemo- and radiotherapy, two new approaches are being investigated. These new approaches are magnetic drug targeting (MDT) and magnetic hyperthermia, and are based on the use of magnetic nanoparticles. In the first one, these magnetic nanoparticles are used as drug carriers and the success of the treatment depends on the correct distribution of the drug within the tumour tissue. Computed tomography analysis has been performed on tumour tissue after MDT in order to find out the distribution of the nanoparticles. The measurements have been carried out in two different laboratories, one based on a synchrotron beamline and another one with a cone x-ray source. First results show that the drug carriers form clusters within the tumour tissue.