Quantification of Proton Dose Enhancement Resulting From Gold Nanoparticles
J Schuemann*, S Dowdell, G Barbone, H Paganetti, Massachusetts General Hospital, Boston, MASU-E-T-404 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
To quantify the proton dose enhancement from different sizes, shapes and distributions of gold nanoparticles (GNP). The high uptake of GNPs in tumors as compared to normal tissue provides the basis for GNP enhanced proton therapy.
Monte Carlo (MC) simulations were performed using TOPAS, which is based on Geant4. The Penelope physics package was instantiated for low energy electromagnetic physics.
We calculated dose distributions of proton beams of energies ranging from 10-150 MeV incident upon a cube of liquid water containing a single GNP of a particular shape (spherical, cylindrical, cubic) and size (1-100nm). Dose enhancement distributions were analyzed in a scoring grid around the GNPs with a resolution of 10x10x10 nm3. The configuration yielding the highest dose enhancement was then used to study the overall dose enhancement for a variety of GNP concentrations (0-100 mg/ml) for homogeneous and clustered GNP distributions.
GNPs increase the dose delivered to a small volume (1x1x1 μm3) by up to 5%. Based on the diminishing return of dose enhancement with size for spherical GNPs we selected GNPs of 50 nm diameter as reference. GNP enhancement is proportional to the concentration in the concentrations investigated, a saturation is expected at very high concentrations.
These results show that the use of GNPs is a promising approach to increase the ratio of tumor and normal tissue in proton therapy. Further investigation is required to determine the optimal specifications for GNPs to yield maximum benefit.
The absorbed dose increases by 5% using GNPs of 50 nm diameter and is nearly independent of the proton energy. The upper limit of GNP concentration has to be established in future biological studies.