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SU‐E‐T‐323: Investigation of the Effect of the Gold‐Tissue Interface on the Radiation Dose Enhancement Due to Gold Nanoparticles
Author(s) -
Paudel N,
Shvydka D,
Parsai E
Publication year - 2011
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3612277
Subject(s) - colloidal gold , dosimetry , photon , nanoparticle , materials science , monte carlo method , radiation , photon energy , molecular physics , nanotechnology , chemistry , optics , physics , nuclear medicine , mathematics , medicine , statistics
Purpose: Injection of gold nanoparticles into a tumor site has been found promising in achieving selective radiation dose enhancement within the tumor due to goldˈs high atomic number Z=79, and favorable biological compatibility. So far the amplitude of the dose enhancement has been modeled in an approximation of average distribution of separate gold atoms rather than nanoparticles, thus neglecting the effect of the gold‐tissue interface. Evaluation of the dose deposition at the interface allowed us to estimate the dose enhancement more adequately. Method and Materials: Monte Carlo N‐Particle radiation transport code version 5 (MCNP5) was used to study the dose enhancement in a 1‐dimensional approximation, with a layer of gold placed within tumor. Dimension of gold along the beam direction was set to 100 nm, while in the transverse directions to 10×10 cm2. Mono‐energetic photon sources, from 20 keV to 4 MeV, were directed onto the tumor, and dose enhancements relative to the uniform all‐tumor case were obtained in the vicinity of the gold layer. Results: The dose deposited in the tumor in the vicinity of the gold layer varies with the energy of the incoming photon beam. The highest enhancement, up to several hundred percents, was obtained for the lowest energy; with much more modest enhancement of 10 to 20% at MeV energies. The region of the dose enhancement fall‐off around the particle extends to ∼3microns, therefore for realistic nanoparticle concentrations ∼1% dose enhancement regions will overlap. Conclusions: Our approach of evaluating the gold‐tissue interface around one particle allowed for a simple way of obtaining dose distributions and more adequate values of dose enhancement factors. Use of gold particles can be justified even for MeV photon therapies where only modest, 10 to 20 % dose enhancement ratios are achieved, if a tumor site is close to a critical structure.