A Monte Carlo study of macroscopic and microscopic dose descriptors for kilovoltage cellular dosimetry

Oliver, Patricia; Thomson, Rowan M.

doi:10.1088/1361-6560/aa5136

Cited by 18 publications

(31 citation statements)

References 61 publications

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“…Nucleus and cytoplasm elemental compositions are based on normal mouse mammary epithelial cells (corresponding to composition “g” in table A1 of Oliver and Thomson). Lipid elemental composition and density are obtained from ICRP publication 89 .…”

Section: Methodsmentioning

confidence: 99%

“…is also considered. Nucleus and cytoplasm elemental compositions based on malignant instead of normal mouse mammary epithelial cells are also considered (corresponding to composition “b” in table A1 of Oliver and Thomson). Based on the limited information available in the published literature for normal human mammary epithelial cells, a smaller mean nuclear radius of 2.8 μm is also considered, in addition to r nuc , epi = 5.8 μm.…”

Section: Methodsmentioning

confidence: 99%

“…12 Recent research considering energy deposition in cellular targets has demonstrated considerable differences between macro-and microscopic dose descriptors: nuclear doses differ from dose-to-medium by up to 32% for kilovoltage photon energies. 13 Given that mammography uses kilovoltage photon sources, these results suggest that there may be considerable differences between macroscopic dose descriptors relevant for mammography (such as the MGD or dose to a glandular tissue voxel), and energy deposition in subcellular targets within the breast. Furthermore, the stochastic nature of radiation transport and energy deposition is a potentially important consideration for low doses ( $ several mGy) and small ( $ lm-sized) target sizes.…”

Section: Introductionmentioning

confidence: 97%

“…Cell nuclei (which contain DNA) are considered important targets for cancer induction . Recent research considering energy deposition in cellular targets has demonstrated considerable differences between macro‐ and microscopic dose descriptors: nuclear doses differ from dose‐to‐medium by up to 32% for kilovoltage photon energies . Given that mammography uses kilovoltage photon sources, these results suggest that there may be considerable differences between macroscopic dose descriptors relevant for mammography (such as the MGD or dose to a glandular tissue voxel), and energy deposition in subcellular targets within the breast.…”

Section: Introductionmentioning

confidence: 99%

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Investigating energy deposition in glandular tissues for mammography using multiscale Monte Carlo simulations

Oliver

Thomson

2019

Medical Physics

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Purpose To investigate energy deposition in glandular tissues of the breast on macro‐ and microscopic length scales in the context of mammography. Methods Multiscale mammography models of breasts are developed, which include segmented, voxelized macroscopic tissue structure as well as nine regions of interest (ROIs) embedded throughout the breast tissue containing explicitly‐modelled cells. Using a 30 kVp Mo/Mo spectrum, Monte Carlo (MC) techniques are used to calculate dose to ∼mm voxels containing glandular and/or adipose tissues, as well as energy deposition on cellular length scales. ROIs consist of at least 1000 mammary epithelial cells and ∼200 adipocytes; specific energy (energy imparted per unit mass; stochastic analogue of the absorbed dose) is calculated within mammary epithelial cell nuclei. Results Macroscopic dose distributions within segmented breast tissue demonstrate considerable variation in energy deposition depending on depth and tissue structure. Doses to voxels containing glandular tissue vary between ∼0.1 and ∼4 times the mean glandular dose (MGD, averaged over the entire breast). Considering microscopic length scales, mean specific energies for mammary epithelial cell nuclei are ∼30% higher than the corresponding glandular voxel dose. Additionally, due to the stochastic nature of radiation, there is considerable variation in energy deposition throughout a cell population within a ROI: for a typical glandular voxel dose of 4 mGy, the standard deviation of the specific energy for mammary epithelial cell nuclei is 85% relative to the mean. Thus, for a glandular voxel dose of 4 mGy at the centre of the breast, corresponding mammary epithelial cell nuclei will receive specific energies up to ∼9 mGy (considering the upper end of the 1σ standard deviation of the specific energy), while a ROI located 2 cm closer to the radiation source will receive specific energies up to ∼40 mGy. Energy deposition within mammary epithelial cell nuclei is sensitive to cell model details including cellular elemental compositions and nucleus size, underlining the importance of realistic cellular models. Conclusions There is considerable variation in energy deposition on both macro‐ and microscopic length scales for mammography, with glandular voxel doses and corresponding cell nuclei specific energies many times higher than the MGD in parts of the breast. These results should be considered for radiation‐induced cancer risk evaluation in mammography which has traditionally focused on a single metric such as the MGD.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Investigating energy deposition in glandular tissues for mammography using multiscale Monte Carlo simulations

Oliver

Thomson

2019

Medical Physics

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“…These authors contributed equally to this work and are co-first authors 2. Correspondence authors: Yang Jiao, email: jiaoyang@suda.edu.cn; Liang Sun, email: slhmz666@suda.edu.cn.…”

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confidence: 99%

Multiple Mesh-type Real Human Cell Models for Dosimetric Application Coupled with Monte Carlo Simulations

et al. 2023

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The mesh-type models are superior to voxel models in cellular dose assessment coupled with Monte Carlo codes. The aim of this study was to expand the micron-scale mesh-type models based on the fluorescence tomography of real human cells, and to investigate the feasibility of these models in the application of various irradiation scenarios and Monte Carlo codes. Six different human cell lines, including pulmonary epithelial BEAS-2B, embryonic kidney 293T, hepatocyte L-02, B-lymphoblastoid HMy2.CIR, Gastric mucosal GES-1, and intestine epithelial FHs74Int, were adopted for single mesh-type models reconstruction and optimization based on laser confocal tomography images. Mesh-type models were transformed into the format of polygon mesh and tetrahedral mesh for the GATE and PHITS Monte Carlo codes, respectively. The effect of model reduction was analyzed by dose assessment and geometry consideration. The cytoplasm and nucleus doses were obtained by designating monoenergetic electrons and protons as external irradiation, and S values with different “target-source” combinations were calculated by assigning radioisotopes as internal exposure. Four kinds of Monte Carlo codes were employed, i.e., GATE with “Livermore,” “Standard” and “Standard and Geant4-DNA mixed” models for electrons and protons, as well as PHITS with “EGS” mode for electrons and radioisotopes. Multiple mesh-type real human cellular models can be applied to Monte Carlo codes directly without voxelization when combined with certain necessary surface reduction. Relative deviations between different cell types were observed among various irradiation scenarios. The relative deviation of nucleus S value reaches up to 85.65% between L-02 and GES-1 cells by 3H for the “nucleus-nucleus” combination, while that of 293T and FHs74Int nucleus dose for external beams at a 5.12 cm depth of water is 106.99%. Nucleus with smaller volume is far more affected by physical codes. There is a considerable deviation for dose within BEAS-2B at the nanoscale. The multiple mesh-type real cell models were more versatile than voxel models and mathematical models. The present study provided several models which can easily be extended to other cell types and irradiation scenarios for RBE estimations and biological effect predictions, including radiation biological experiments, radiotherapy and radiation protection.

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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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A Monte Carlo study of macroscopic and microscopic dose descriptors for kilovoltage cellular dosimetry

Cited by 18 publications

References 61 publications

Investigating energy deposition in glandular tissues for mammography using multiscale Monte Carlo simulations

Investigating energy deposition in glandular tissues for mammography using multiscale Monte Carlo simulations

Multiple Mesh-type Real Human Cell Models for Dosimetric Application Coupled with Monte Carlo Simulations

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

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