Dose enhancement in radiotherapy by novel application of gadolinium based MRI contrast agent nanomagnetic particles in gel dosimetry

Abstract

The primary goal of radiotherapy is increasing dose in tumor cells and sparing normal tissues. One of the novel ways to achieve this goal is enhancing tumor dose by high atomic number (z) materials. Using high-z radiosensitizers in tumor cells could increase the effect of radiotherapy treatments through increasing photoelectric cross section and number of auger electrons. Advancements in nanotechnology made it possible to use nanoparticles in cancer imaging and treatments. Although many studies have been done on radiosensitization by different materials, most of them have focused on the dose response in the presence of gold nanoparticles. Of our knowledge there is not any experimental study on the radiosensitizing by gadolinium oxide (Gd2O3) nanomagnetic particles in brachytherapy and megavoltage beam radiotherapy. In this study we evaluate dose enhancement properties of gadolinium nanoparticle which is an MRI contrast agent in complex form. Because of increasing relaxation time and high atomic number (z=64), Gd2O3 can be used in image-guided radiotherapy. In recent studies there was a great interest on MRI guided radiotherapy, so it could be efficient to use an MRI contrast agent simultaneously as radiosensitizer in radiotherapy. Herein, dose enhancement in the presence of gadolinium oxide nanoparticles with 0.1mM concentration in a gel filled phantom was investigated. The results show maximum dose enhancement about 15%±0.01 up to 22%±0.02 in brachytherapy by Iridium-192, however this value is about 3.8%±0.002 in external beam radiotherapy with 6 MV photons. Our study approved radiosensitization property of gadolinium oxide nanoparticles in brachytherapy and external beam radiotherapy.