Monte Carlo study of the dose enhancement effect of gold
nanoparticles during X-ray therapies and evaluation of the anti-angiogenic
effect on tumour capillary vessels
Affiliations: Section of Radiological Sciences, Department of
Biomedical Sciences and of Morphologic and Functional Imaging, University of
Messina, Messina, Italy | INFN, Istituto Nazionale di Fisica Nucleare, Gruppo
Collegato di Messina, Messina, Italy | Department of Physics and Earth Sciences, University
of Messina, Messina, Italy
Note: [] Corresponding author: Ernesto Amato, PhD, Department of
Biomedical Sciences and of Morphologic and Functional Imaging, University of
Messina, via Consolare Valeria, 1 – Pad. E, I-98125 Messina, Italy. Tel.:
+39 090 2212942; Fax: +39 090 2212843; E-mail: eamato@unime.it
Abstract: Gold nanoparticles (GNPs) are a promising radiosensitizer agent in
radiotherapy. Through a simulation performed with the Geant4 Monte Carlo code,
we evaluated the dose enhancement effect of GNPs during therapies with an x-ray
tube operating at 150 kV (E=55 keV and E_{max}= 150 keV) and
we studied the impact of GNP diffusion out of the tumour vessels, in terms of
antiangiogenic and cytotoxic effects. Firstly, a single x-ray beam was assumed to irradiate a
parallelepiped volume of soft tissue, in which a GNP-doped "target" volume was
placed at different depths. Average dose enhancement factors (DEF) in presence
of GNPs were obtained as a function of the target depth and GNP concentration,
uniformly distributed; values ranging between 1.6 for 10 mg Au/g at 0 cm and
7.2 for 200 mg Au/g at 5 cm were determined. Furtherly, a second geometry was
adopted, in which a blood capillary vessel (10 μm thick and 10 μm of
inner radius) was placed at the centre of a cubic volume of soft tissue; doses
and DEFs to the capillary endothelium as well as to the surrounding viable
tumour were evaluated, for different models of GNP diffusion. Our results indicate that the radial DEF profiles around the vessel
are in close relationship with the radial profiles of GNP concentration
assumed, except for at sharp gradients of concentration. DEFs at the
endothelium ranged from 1.6 to 6.5, for GNP concentrations in the blood of 10
and 200 mg/ml, respectively. These data can be helpful for the development of new and more
specific GNP-based radiosensitizers of potential interest in radiotherapy,
exploiting the combined benefit of anti-angiogenic and cytotoxic dose
enhancement effects.
Keywords: Gold nanoparticle, radiotherapy, radiosensitization, angiogenesis, Monte Carlo simulation
