Technical Note: Taking EGSnrc to new lows: Development of egs++ lattice geometry and testing with microscopic geometries

Martinov, Martin P.; Thomson, Rowan M.

doi:10.1002/mp.14172

Cited by 12 publications

(10 citation statements)

References 28 publications

(63 reference statements)

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“…The lattice was generated using the modified “egs_lattice” module [ 52 ] following the geometry of a hexagonal Hf 6 ‐BDC nMOF with Hf 6 O 4 (OH) 4 SBUs and BDC linkers. Hf 6 ‐BDC was modeled as a 3D spherical lattice with a diameter of 94 nm that was formed by linking spherical HfO 2 ( r = 0.44 nm) clusters in a hexagonal manner.…”

Section: Resultsmentioning

confidence: 99%

Monte Carlo Simulations Reveal New Design Principles for Efficient Nanoradiosensitizers Based on Nanoscale Metal–Organic Frameworks

Mao

et al. 2021

Advanced Materials

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photon-matter interactions, the photoelectric process is more likely to occur on high-Z elements where photoelectrons are ejected following photon absorption. Auger electrons are further generated after the holes are filled by higher-orbital electrons. In addition, inorganic nanoparticles (NPs) usually possess higher densities compared to organic molecules, leading to further enhancement of energy deposition on a per unit space basis. As a result, various studies have explored the potential of high-Z element-based nanoradiosensitizers such as gold nanoparticles (Au NPs) and hafnium oxide nanoparticles (HfO 2 NPs) to amplify the generation of photoelectrons and Auger electrons. Hainfeld et al. reported improved survival of EMT-6 mammary carcinoma-bearing mice by 1 year after treatment with Au NPs and X-rays. [32] Notably, NBTXR3, a 50 nm HfO 2 NP developed by Nanobiotix, received European market approval (CE Mark) as a medical device for the treatment of locally advanced soft tissue sarcoma in 2019. [33,34] The sizes of NPs can impact their radiosensitizing effects. [35] In the study of Au NPs with various sizes, Misawa et al. found that smaller Au NPs showed greater yields of ROS including hydroxyl radical and superoxide, [36] suggesting the positive effects of high surface areas on NP radiosensitization. However, the interplay between a nanoradiosensitizer and a biological system is much more complicated. First, NPs of sizes ranging from 10 to 200 nm can preferentially accumulate in tumor tissues via the enhanced permeability and retention effect. [37] NPs smaller than 10 nm can be easily cleared through renal filtration without significant accumulation in tumors. [38] Second, the sizes of NPs also affect their cellular uptake. [39] Chithrani et al. studied size-dependent Au NPs uptake in mammalian cells and found that 50 nm Au NPs showed higher cellular uptake when compared to 14 and 70 nm Au NPs. [40] Similarly, NBTXR3 was engineered with a size of 50 nm to enhance cancer cell uptake. [41] We recently reported the design of nanoscale metal-organic frameworks (nMOFs) comprising metal-oxo cluster secondary building units (SBUs) and organic bridging ligands and examined their potential use as a novel class of nanoradiosensitizers. [42][43][44][45] We hypothesized that highly porous nMOFs might afford unprecedentedly high radiosensitization with an Nanoscale metal-organic frameworks (nMOFs) have recently been shown to provide better radiosensitization than solid nanoparticles (NPs) when excited with X-rays. Here, a Monte Carlo simulation of different radiosensitization effects by NPs and nMOFs using a lattice model consisting of 3D arrays of nanoscale secondary building units (SBUs) is reported. The simulation results reveal that lattices outperform solid NPs regardless of radiation sources or particle sizes via enhanced scatterings of photons and electrons within the lattices. Optimum dose enhancement can be achieved by tuning SBU size and inter-SBU distance.

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Section: Resultsmentioning

confidence: 99%

Monte Carlo Simulations Reveal New Design Principles for Efficient Nanoradiosensitizers Based on Nanoscale Metal–Organic Frameworks

Mao

et al. 2021

Advanced Materials

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“…Simulating the MOF type of geometries is troublesome in a regular Monte Carlo study due to the heavy memory consumption led by tremendous SBUs inside MOFs. Based on the well-developed EGS lattice, , we built a lattice geometry implementation in Monte Carlo toolkit Geant4 − which is called Geant4-lattice. In the Geant4-lattice navigator, we modified the hexagonal lattice geometry and built a new face-centered cubic lattice geometry.…”

Section: Experimental Methodsmentioning

confidence: 99%

Radiolytic Water Splitting Sensitized by Nanoscale Metal–Organic Frameworks

Cheng

Zhou

et al. 2023

J. Am. Chem. Soc.

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High-energy radiation that is compatible with renewable energy sources enables direct H 2 production from water for fuels; however, the challenge is to convert it as efficiently as possible, and the existing strategies have limited success. Herein, we report the use of Zr/Hf-based nanoscale UiO-66 metal− organic frameworks as highly effective and stable radiation sensitizers for purified and natural water splitting under γ-ray irradiation. Scavenging and pulse radiolysis experiments with Monte Carlo simulations show that the combination of 3D arrays of ultrasmall metal-oxo clusters and high porosity affords unprecedented effective scattering between secondary electrons and confined water, generating increased precursors of solvated electrons and excited states of water, which are the main species responsible for H 2 production enhancement. The use of a small quantity (<80 mmol/L) of UiO-66-Hf-OH can achieve a γ-rays-to-hydrogen conversion efficiency exceeding 10% that significantly outperforms Zr-/Hf-oxide nanoparticles and the existing radiolytic H 2 promoters. Our work highlights the feasibility and merit of MOF-assisted radiolytic water splitting and promises a competitive method for creating a green H 2 economy.

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“…Validation of this geometry was performed by Martinov and Thomson. 13 Application egs_chamber is compiled with the EADL_RELAX macro set to true which ensures atomic relaxations are modeled for all energies and transitions (which is now the default with EGSnrc). Default parameters are used for simulations except as noted here.…”

Section: Monte Carlo Parametersmentioning

confidence: 99%

Multiscale Monte Carlo simulations of gold nanoparticle dose‐enhanced radiotherapy I: Cellular dose enhancement in microscopic models

2023

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Background: The introduction of Gold NanoParticles (GNPs) in radiotherapy treatments necessitates considerations such as GNP size, location, and quantity, as well as patient geometry and beam quality. Physics considerations span length scales across many orders of magnitude (nanometer-to-centimeter), presenting challenges that often limit the scope of dosimetric studies to either micro-or macroscopic scales. Purpose: To investigate GNP dose-enhanced radiation Therapy (GNPT) through Monte Carlo (MC) simulations that bridge micro-to-macroscopic scales. The work is presented in two parts, with Part I (this work) investigating accurate and efficient MC modeling at the single cell level to calculate nucleus and cytoplasm Dose Enhancement Factors (n,cDEFs), considering a broad parameter space including GNP concentration, GNP intracellular distribution, cell size, and incident photon energy. Part II then evaluates cell dose enhancement factors across macroscopic (tumor) length scales. Methods: Different methods of modeling gold within cells are compared, from a contiguous volume of either pure gold or gold-tissue mixture to discrete GNPs in a hexagonal close-packed lattice. MC simulations with EGSnrc are performed to calculate n,cDEF for a cell with radius r cell = 7.35 µm and nucleus r nuc = 5 µm considering 10 to 370 keV incident photons, gold concentrations from 4 to 24 mg Au /g tissue , and three different GNP configurations within the cell: GNPs distributed around the surface of the nucleus (perinuclear) or GNPs packed into one (or four) endosome(s). Select simulations are extended to cells with different cell (and nucleus) sizes: 5 µm (2, 3, and 4 µm), 7.35 µm (4 and 6 µm), and 10 µm (7, 8, and 9 µm). Results: n,cDEFs are sensitive to the method of modeling gold in the cell, with differences of up to 17% observed; the hexagonal lattice of GNPs is chosen (as the most realistic model) for all subsequent simulations. Across cell/nucleus radii, source energies, and gold concentrations, both nDEF and cDEF are highest for GNPs in the perinuclear configuration, compared with GNPs in one (or four) endosome(s). Across all simulations of the (r cell , r nuc ) = (7.35, 5) µm cell, nDEFs and cDEFs range from unity to 6.83 and 3.87, respectively. Including different cell sizes, nDEFs and cDEFs as

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Technical Note: Taking EGSnrc to new lows: Development of egs++ lattice geometry and testing with microscopic geometries

Cited by 12 publications

References 28 publications

Monte Carlo Simulations Reveal New Design Principles for Efficient Nanoradiosensitizers Based on Nanoscale Metal–Organic Frameworks

Monte Carlo Simulations Reveal New Design Principles for Efficient Nanoradiosensitizers Based on Nanoscale Metal–Organic Frameworks

Radiolytic Water Splitting Sensitized by Nanoscale Metal–Organic Frameworks

Multiscale Monte Carlo simulations of gold nanoparticle dose‐enhanced radiotherapy I: Cellular dose enhancement in microscopic models

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