COMPARING MONTE CARLO WITH DISCRETE ORDINATES METHOD FOR SILICA-CORE GOLD NANOSHELLS ASSISTED LASER PHOTOTHERMAL THERAPY

2019 ◽  
Author(s):  
Anderson Nunes Sousa ◽  
Andre Maurente
Keyword(s):  
Monte Carlo ◽  
Photothermal Therapy ◽  
Gold Nanoshells ◽  
Discrete Ordinates ◽  
Discrete Ordinates Method ◽  
Silica Core ◽  
Laser Photothermal Therapy

Experimental and Numerical Studies of Short Pulse Propagation in Model Systems

2002 ◽  
Author(s):  
Sunil Kumar ◽  
Zhixiong Guo ◽  
Janice Aber ◽  
Bruce Garetz
Keyword(s):  
Monte Carlo ◽  
Pulse Propagation ◽  
Short Pulse ◽  
Model Systems ◽  
Discrete Ordinates ◽  
Pulsed Lasers ◽  
Discrete Ordinates Method ◽  
Numerical Studies ◽  
Tissue Phantoms ◽  
Good Agreement

In this paper experimental and numerical studies of the propagation of short-pulsed lasers through scattering and absorbing media are presented. Experimental results of a 60 ps pulse laser transmission in tissue phantoms are obtained and compared with Monte Carlo simulations. Good agreement between the Monte Carlo simulation and experimental measurement is found. Three models are developed for the simulation of short pulse transport. Benchmark comparisons among the Monte Carlo (MC), transient discrete ordinates method (TDOM) and transient radiation element method (TREM) are conducted.

scholarly journals Bifunctional Gold Nanoshells with a Superparamagnetic Iron Oxide−Silica Core Suitable for Both MR Imaging and Photothermal Therapy

2007 ◽  
Vol 111 (17) ◽  
pp. 6245-6251 ◽  
Author(s):  
Xiaojun Ji ◽  
Ruping Shao ◽  
Andrew M. Elliott ◽  
R. Jason Stafford ◽  
Emilio Esparza-Coss ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Mr Imaging ◽  
Photothermal Therapy ◽  
Superparamagnetic Iron Oxide ◽  
Gold Nanoshells ◽  
Silica Core

Computational Simulation of Temperature Elevations in Tumors Using Monte Carlo Method and Comparison to Experimental Measurements in Laser Photothermal Therapy

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Navid Manuchehrabadi ◽  
Yonghui Chen ◽  
Alexander LeBrun ◽  
Ronghui Ma ◽  
Liang Zhu
Keyword(s):  
Monte Carlo ◽  
Optical Properties ◽  
Gold Nanorods ◽  
Photothermal Therapy ◽  
Energy Deposition ◽  
Thermal Damage ◽  
Laser Energy ◽  
Simulated Temperature ◽  
Laser Energy Absorption ◽  
Laser Photothermal Therapy

Accurate simulation of temperature distribution in tumors induced by gold nanorods during laser photothermal therapy relies on precise measurements of thermal, optical, and physiological properties of the tumor with or without nanorods present. In this study, a computational Monte Carlo simulation algorithm is developed to simulate photon propagation in a spherical tumor to calculate laser energy absorption in the tumor and examine the effects of the absorption (μa) and scattering (μs) coefficients of tumors on the generated heating pattern in the tumor. The laser-generated energy deposition distribution is then incorporated into a 3D finite-element model of prostatic tumors embedded in a mouse body to simulate temperature elevations during laser photothermal therapy using gold nanorods. The simulated temperature elevations are compared with measured temperatures in PC3 prostatic tumors in our previous in vivo experimental studies to extract the optical properties of PC3 tumors containing different concentrations of gold nanorods. It has been shown that the total laser energy deposited in the tumor is dominated by μa, while both μa and μs shift the distribution of the energy deposition in the tumor. Three sets of μa and μs are extracted, representing the corresponding optical properties of PC3 tumors containing different concentrations of nanorods to laser irradiance at 808 nm wavelength. With the injection of 0.1 cc of a 250 optical density (OD) nanorod solution, the total laser energy absorption rate is increased by 30% from the case of injecting 0.1 cc of a 50 OD nanorod solution, and by 125% from the control case without nanorod injection. Based on the simulated temperature elevations in the tumor, it is likely that after heating for 15 min, permanent thermal damage occurs in the tumor injected with the 250 OD nanorod solution, while thermal damage to the control tumor and the one injected with the 50 OD nanorod solution may be incomplete.

Angular False Scattering in Radiative Heat Transfer Analysis Using the Discrete-Ordinates Method With Higher-Order Quadrature Sets

2013 ◽  
Author(s):  
Brian Hunter ◽  
Zhixiong Guo
Keyword(s):  
Monte Carlo ◽  
Radiative Transfer ◽  
Phase Function ◽  
Radiative Heat ◽  
Higher Order ◽  
Heat Transfer Analysis ◽  
Discrete Ordinates ◽  
Equal Weight ◽  
Participating Media ◽  
Discrete Ordinates Method

The SN quadrature set for the discrete-ordinates method is limited in overall discrete direction number in order to avoid physically unrealistic negative directional weight factors. Such a limitation can adversely impact radiative transfer predictions. Directional discretization results in errors due to ray effect, as well as angular false scattering error due to distortion of the scattering phase function. The use higher-order quadrature schemes in the discrete-ordinates method allows for improvement in discretization errors without an overall directional limitation. In this analysis, four higher-order quadrature sets (Legendre-Equal Weight, Legendre-Chebyshev, Triangle Tessellation, and Spherical Ring Approximation) are implemented for determination of radiative transfer in a 3-D cubic enclosure containing participating media. Radiative heat fluxes, calculated at low direction number, are compared to the SN quadrature and Monte Carlo predictions to gauge quadrature accuracy. Additionally, investigation into the reduction of angular false scattering with sufficient increase in direction number using higher-order quadrature, including heat flux accuracy with respect to Monte Carlo and computational efficiency, is presented. While higher-order quadrature sets are found to effectively minimize angular false scattering error, it is found to be much more computationally efficient to implement proper phase function normalization for accurate radiative transfer predictions.

Comparing the Monte Carlo Method to the Discrete Ordinates Methods in Fluent for Calculating Radiation Heat Transfer in a Small Particle Receiver

2016 ◽  
Author(s):  
Eugene Cho ◽  
Fletcher Miller
Keyword(s):  
Monte Carlo ◽  
Solar Radiation ◽  
Boundary Conditions ◽  
Fortran Program ◽  
Working Fluid ◽  
Discrete Ordinates ◽  
Ansys Fluent ◽  
Discrete Ordinates Method ◽  
Directional Distribution ◽  
Solar Receiver

The Combustion and Solar Energy Laboratory (C&SEL) at San Diego State University is developing a Small Particle Heat Exchange Receiver (SPHER) to absorb and transfer heat from concentrated solar radiation to a working fluid for a gas turbine. The SPHER is to be used with a Concentrated Solar Power (CSP) system where a heliostat field highly concentrates solar radiation on the optical aperture of the SPHER. The solar radiation is volumetrically absorbed by a unique carbon nanoparticle gas mixture within the cavity of the SPHER. This research focuses on comparing a Computational Fluid Dynamics (CFD) model using the ANSYS FLUENT Discrete Ordinates (DO) Model and a program developed by the C&SEL which uses a Monte Carlo Ray Trace (MCRT) method to calculate the spatial and directional distribution of radiation for an idealized solar receiver geometry. Previous research at the C&SEL has shown successful implementation of the MCRT method to calculate the spatial and directional distribution of radiation for an idealized solar receiver geometry. The MCRT method is highly accurate and will serve as the benchmark solution for this research. However the MCRT code takes several days to run, is inflexible to geometry changes, and is cumbersome to implement as the MCRT code needs to be rewritten for each new receiver geometry being considered. These factors necessitate the need to find an alternate method that accurately calculates the spatial and directional distribution of radiation for a solar receiver and can be efficiently implemented for various receiver geometries being studied. The Discrete Ordinates method is a new method for solving the Radiative Transport Equations (RTE) using a FORTRAN program, developed by the C&SEL, and the ANSYS FLUENT Discrete Ordinates model for calculating the RTE. The FORTRAN program calculates the proper inlet radiation boundary conditions that ANSYS FLUENT uses for calculating the RTE. The methodology used for determining the correct CFD mesh, radiative boundary conditions, optimal number of DO theta and phi discretization, as well as the optical properties of the working fluid will be presented in this paper. The main focus of this research is to compare two different methods for solving the Radiative Transport Equations within the idealized SPHER. The solution data for several cases using the previous coupled MCRT method and the ANSYS FLUENT Discrete Ordinates method is presented for both a collimated and diffuse gray radiation approximation. The case studies focus on researching how the MCRT method and Discrete Ordinates method differ when comparing critical receiver parameters such as the mean outlet temperature, wall temperature profile, outlet tube temperature profile, and total receiver efficiency while keeping the total inlet radiation flux of 5 MW and inlet mass flow rate of 5 kg/s constant. This research also presents a study on the optimal Discrete Ordinates angular discretization, as well as a study to determine the solution’s dependence on the number of inlet boundary conditions imposed on the window.

Theoretical Simulation of Temperature Elevations in Tumors Using Monte Carlo Method and Comparison to Experimental Measurements During Laser Photothermal Therapy

2013 ◽  
Author(s):  
Navid Manuchehrabadi ◽  
Yonghui Chen ◽  
Alexander LeBrun ◽  
Ronghui Ma ◽  
Liang Zhu
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Gold Nanorods ◽  
Photothermal Therapy ◽  
Treatment Protocol ◽  
Gold Nanorod ◽  
Theoretical Simulation ◽  
The Past ◽  
Geometric Ratio ◽  
Laser Photothermal Therapy

Nanotechnology using gold nanoshells or nanorods is a newly developed hyperthermia approach and has been tested in the past several years in cancer treatment.1–2 Gold nanorods have a diameter of ∼10 nm and an aspect ratio of approximately four. By varying the geometric ratio, the nanostructures can be tuned to have strong absorption and scattering to a specific laser wavelength. Designing an optimal treatment protocol of laser photothermal therapy requires understanding of gold nanorod deposition inside the tumor after injection, its resulted specific absorption rate (SAR) distribution, and the ultimate temperature field in the tumor during the treatment. Recent microCT studies by our group have suggested that the gold nanorod solution injected into PC3 prostatic tumors results in an almost uniform distribution of the gold nanorods in the tumors.3 The Monte Carlo method has been used in the past to determine the heating pattern (SAR) of laser-tissue thermal interaction.4 However, the accuracy of the theoretical simulation of the temperature fields in tumors relies on precise measurements of the optical properties of the tumors with nanorods presence.

Temperature Elevations in Implanted Prostatic Tumors During Laser Photothermal Therapy Using Nanorods

2011 ◽  
Author(s):  
L. Zhu ◽  
A. Attaluri ◽  
N. Manuchehrabadi ◽  
H. Cai ◽  
R. Edziah ◽  
...  
Keyword(s):  
Targeted Delivery ◽  
Photothermal Therapy ◽  
Near Infrared ◽  
Laser Energy ◽  
Laser Wavelength ◽  
Gold Nanoshells ◽  
Surrounding Tissue ◽  
Geometric Ratio ◽  
Wide Range ◽  
Laser Photothermal Therapy

Gold nanoshells or nanorods are newly developed nanotechnology in laser photothermal therapy for cancer treatments in recent years [1–10]. Gold nanoshells consists of a solid dielectric nanoparticle core (∼100 nm) coated by a thin gold shell (∼10 nm). Gold nanorods have a diameter of 10 nm and an aspect ratio of approximately four. Nanorods may be taken up by tumors more readily than nanoshells due to nanorods’ smaller size. By varying the geometric ratio, both nanoshells and nanorods can be tuned to have strong absorption and scattering to a specific laser wavelength. Among a wide range of laser wavelengths, the near infrared (NIR) laser at ∼800 nm is most attractive to clinicians due to its deep optical penetration in tissue. Therefore, the tissue would appear almost “transparent” to the 800 nm laser light before the laser reaches the nanoshells or nanorods in tumors, with minimal laser energy wasted by the tissue without the nanostructures. The laser energy absorbed in an area congregating by the nanostructures is transferred to the surrounding tissue by heat conduction. This approach not only achieves targeted delivery of laser energy to the tumor, but also maximally concentrates a majority of the laser energy to the tumor region.

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