Quantitative comparison of delta P1 versus optical diffusion approximations for modeling near-infrared gold nanoshell heating.

Laser induced thermal therapy combined with the wavelength dependent optical absorption and heating power of gold-coated silica nanoshells can achieve therapeutic heating localized to a tumor volume. Accurate modeling of the spatiotemperal thermal distribution associated with this heating is essential for accurate thermal therapy treatment planning. The optical diffusion approximation (ODA), used in numerous applications of laser fluence in biology, is compared to the delta P1 optical approximation in phantoms containing different concentrations of nanoshells for several laser powers. Results are compared with temperature maps generated by magnetic resonance temperature imaging techniques and show that the delta P1 approximation is more effective than ODA at modeling the thermal distribution. The discrepancy between the two is especially prominent in phantoms with higher nanoshell concentrations where ODA was shown to give unsatisfactory results.

Laser-induced thermal response and characterization of nanoparticles for cancer treatment using magnetic resonance thermal imaging.

Spherical nanoparticles with a gold outer shell and silica core can be tuned to absorb near-infrared light of a specific wavelength. These nanoparticles have the potential to enhance the treatment efficacy of laser-induced thermal therapy (LITT). In order to enhance both the potential efficacy and safety of such procedures, accurate methods of treatment planning are needed to predict the temperature distribution associated with treatment application. In this work, the standard diffusion approximation was used to model the laser fluence in phantoms containing different concentrations of nanoparticles, and the temperature distribution within the phantom was simulated in three-dimensions using the finite element technique. Magnetic resonance temperature imaging was used to visualize the spatiotemporal distribution of the temperature in the phantoms. In most cases, excellent correlation is demonstrated between the simulations and the experiment (<3.0% mean error observed). This has significant implications for the treatment planning of LITT treatments using gold-silica nanoshells.