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 Title
 MCNP5 Monte Carlo based dosimetry for the Nucletron Iridium192 high doserate brachytherapy source with tissue heterogeneity corrections.
 Creator
 Herrera, Ramses, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

A Monte Carlo model has been developed using MCNP5 to simulate the Nucletron Ir192 HDR source in order to investigate the influence of tissue heterogeneities on dose calculations compared to the dose in homogeneous water media, as it is typically calculated by brachytherapy Treatment Planning Systems (TPS). Validity of the simulation was verified in water medium in comparison with peer reviewed results using the dosimetric parameters recommended by AAPM, Task Group43. The doserates in...
Show moreA Monte Carlo model has been developed using MCNP5 to simulate the Nucletron Ir192 HDR source in order to investigate the influence of tissue heterogeneities on dose calculations compared to the dose in homogeneous water media, as it is typically calculated by brachytherapy Treatment Planning Systems (TPS). Validity of the simulation was verified in water medium in comparison with peer reviewed results using the dosimetric parameters recommended by AAPM, Task Group43. The doserates in simulated prostate, bladder and rectum were compared to those obtained in the homogeneous water phantom. Based on the resulting dose differences, it is inferred that TPS algorithms for brachytherapy dose calculations overestimate the dose to tissues like prostate and bladder by up to 49%. A clinically relevant dose underestimation of 5.5% to the rectum was also found. We recommend that further investigation using actual patient CT data as input to the Monte Carlo simulation be performed.
Show less  Date Issued
 2012
 PURL
 http://purl.flvc.org/FAU/3355564
 Subject Headings
 Medical physics, Iridium, Therapeutic use, Imaging systems in medicine, Radioisotope brachytherapy
 Format
 Document (PDF)
 Title
 Simplicial matter in discrete and quantum spacetimes.
 Creator
 McDonald, Jonathan Ryan., Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

A discrete formalism for General Relativity was introduced in 1961 by Tulio Regge in the form of a piecewiselinear manifold as an approximation to (pseudo)Riemannian manifolds. This formalism, known as Regge Calculus, has primarily been used to study vacuum spacetimes as both an approximation for classical General Relativity and as a framework for quantum gravity. However, there has been no consistent effort to include arbitrary nongravitational sources into Regge Calculus or examine the...
Show moreA discrete formalism for General Relativity was introduced in 1961 by Tulio Regge in the form of a piecewiselinear manifold as an approximation to (pseudo)Riemannian manifolds. This formalism, known as Regge Calculus, has primarily been used to study vacuum spacetimes as both an approximation for classical General Relativity and as a framework for quantum gravity. However, there has been no consistent effort to include arbitrary nongravitational sources into Regge Calculus or examine the structural details of how this is done. This manuscript explores the underlying framework of Regge Calculus in an effort elucidate the structural properties of the lattice geometry most useful for incorporating particles and fields. Correspondingly, we first derive the contracted Bianchi identity as a guide towards understanding how particles and fields can be coupled to the lattice so as to automatically ensure conservation of source. In doing so, we derive a Kirchhofflike conservation principle that identifies the flow of energy and momentum as a flux through the circumcentric dual boundaries. This circuit construction arises naturally from the topological structure suggested by the contracted Bianchi identity. Using the results of the contracted Bianchi identity we explore the generic properties of the local topology in Regge Calculus for arbitrary triangulations and suggest a firstprinciples definition that is consistent with the inclusion of source. This prescription for extending vacuum Regge Calculus is sufficiently general to be applicable to other approaches to discrete quantum gravity. We discuss how these findings bear on a quantized theory of gravity in which the coupling to source provides a physical interpretation for the approximate invariance principles of the discrete theory.
Show less  Date Issued
 2009
 PURL
 http://purl.flvc.org/FAU/186691
 Subject Headings
 Special relativity (Physics), Space and time, Distribution (Probability theory), Global differential geometry, Quantum field theory, Mathematical physics
 Format
 Document (PDF)
 Title
 Simultaneous xray and neutron diffraction Rietveld refinements of nanophase Fe substituted hydroxyapatite.
 Creator
 Kyriacou, Andreas, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The effect of Fe substitution on the crystal structure of hydroxyapatite (HAp) is studied by applying simultaneous Rietveld refinements of powder xray and neutron diffraction patterns. Fe is one of the trace elements replacing Ca in HAp, which is the major mineral phase in bones and teeth. The morphology and magnetic properties of the FeHAp system are also studied by transmission electron microscopy and magnetization measurements. Samples of Ca(5x)Fex(PO4)3OH with 0
Show moreThe effect of Fe substitution on the crystal structure of hydroxyapatite (HAp) is studied by applying simultaneous Rietveld refinements of powder xray and neutron diffraction patterns. Fe is one of the trace elements replacing Ca in HAp, which is the major mineral phase in bones and teeth. The morphology and magnetic properties of the FeHAp system are also studied by transmission electron microscopy and magnetization measurements. Samples of Ca(5x)Fex(PO4)3OH with 0< x < 0.3 were prepared. Single phase HAp was identified in xray diffraction patterns (XRD) of samples with x < 0.1 inferring that the solubility limits are less than 0.1. Hematite ((Sa(BFe2O3) is identified as a secondary phase for higher Fe content. The refined parameters show that Fe is incorporated in the HAp structure by replacing Ca in the two crystallographic sites with a preference at the Ca2 site. This preference explains the small effect of the Fe substitution on the lattice constants of HAp. The overall decrease of the lattice constants is explained by the ionic vi size difference of Ca and Fe. The increasing trend of the alattice constant with x in the Fe substituted samples is attributed to a lattice relaxation caused by the substitution of the 4 and 6fold Fe at the 7 and 9fold Ca1 and Ca2 sites. This Ca local geometry reduction is indicated by a slight increase of the Ca1O3 and Ca2O1 bond lengths. Above the solubility limit x = 0.05, the Fe is partitioned in and out of the HAp structure with increasing nominal Fe content x. The excess Fe is oxidized to hematite. The TEM analysis and magnetic measurements support the results of the simultaneous Rietveld refinements. The TEM images show no significant effect on the morphology and size of the HAp particles upon Fe incorporation. The particles are either spheres or short rods of dimensions 2060 nm. Hematite particles are imaged in the samples with x exceeding the solubility limit. These particles
Show less  Date Issued
 Florida Atlantic University
 PURL
 http://purl.flvc.org/FAU/3342204
 Subject Headings
 Xrays, Diffraction, Rietveld method, Nanostructured materials, Biomedical materials
 Format
 Document (PDF)
 Title
 Stochastic processes in the social sciences: markets, prices and wealth distributions.
 Creator
 Romero, Natalia E., Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The present work uses statistical mechanics tools to investigate the dynamics of markets, prices, trades and wealth distribution. We studied the evolution of market dynamics in different stages of historical development by analyzing commodity prices from two distinct periods : ancient Babylon, and medieval and early modern England. We find that the firstdigit distributrions of both Babylon and England commodity prices follow Benford's Law, indicating that the data represent empirical...
Show moreThe present work uses statistical mechanics tools to investigate the dynamics of markets, prices, trades and wealth distribution. We studied the evolution of market dynamics in different stages of historical development by analyzing commodity prices from two distinct periods : ancient Babylon, and medieval and early modern England. We find that the firstdigit distributrions of both Babylon and England commodity prices follow Benford's Law, indicating that the data represent empirical observations typically arising from a free market. Further, we find that the normalized prices of both Babylon and England agricultural commodities are characterized by stretched exponential distributions, and exhibit persistent correlations of a power law type over long periods of up to several centuries, in contrast to contemporary markets. Our findings suggest that similar market interactions may underlie the dynamics of ancient agricultural commodity prices, and that these interactions may remain stable across centuries. To further investigate the dynamics of markets, we present the analogy between transfers of money between individuals and the transfer of energy through particle collisions by means of the kinetic theory of gases. We introduce a theoretical framework of how micro rules of trading lead to the emergence of income and wealth distribution. Particularly, we study the effects of different types of distribution of savings/investments among individuals in a society and different welfare/subsidies redistribution policies. Results show that while considering savings propensities, the models approach empirical distributions of wealth quite well. The effect of redistribution better captures specific features of the distributions which earlier models failed to do. Moreover, the models still preserve the exponential decay observed in empirical income distributions reported by tax data and surveys.
Show less  Date Issued
 2012
 PURL
 http://purl.flvc.org/FAU/3352825
 Subject Headings
 Stochastic processes, Mathematical models, Consumption (Economics), Mathematical models, Business cycles, Mathematical models, Statics and dynamics (Social sciences), Mathematical models
 Format
 Document (PDF)
 Title
 A dosimetric study of a heterogeneous phantom for lung stereotactic body radiation therapy comparing Monte Carlo and pencil beam calculations to dose distributions measured with a 2d diode array.
 Creator
 Curley, Casey Michael, Ouhib, Zoubir, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Monte Carlo (MC) and Pencil Beam (PB) calculations are compared to their measured planar dose distributions using a 2D diode array for lung Stereotactic Body Radiation Therapy (SBRT). The planar dose distributions were studied for two different phantom types: an inhouse heterogeneous phantom and a homogeneous phantom. The motivation is to mimic the human anatomy during a lung SBRT treatment and incorporate heterogeneities into the pretreatment Quality Assurance process, where measured and...
Show moreMonte Carlo (MC) and Pencil Beam (PB) calculations are compared to their measured planar dose distributions using a 2D diode array for lung Stereotactic Body Radiation Therapy (SBRT). The planar dose distributions were studied for two different phantom types: an inhouse heterogeneous phantom and a homogeneous phantom. The motivation is to mimic the human anatomy during a lung SBRT treatment and incorporate heterogeneities into the pretreatment Quality Assurance process, where measured and calculated planar dose distributions are compared before the radiation treatment. Individual and combined field dosimetry has been performed for both fixed gantry angle (anterior to posterior) and planned gantry angle delivery. A gamma analysis has been performed for all beam arrangements. The measurements were obtained using the 2D diode array MapCHECK 2™.
Show less  Date Issued
 2015
 PURL
 http://purl.flvc.org/fau/fd/FA00004360
 Subject Headings
 Cancer  Radiotherapy, Drug development  Computer simulation, Image guided radiation therapy, Ion bombardment, Lung cancer  Treatment, Medical physics, Monte Carlo method, Proton beams
 Format
 Document (PDF)
 Title
 COMMISSIONING AND ACCEPTANCE TESTING OF A TRUEBEAM LINEAR ACCELERATOR.
 Creator
 Dumitru, Nicolae, Pella, Silvia, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Due to the difficulty of a complex commissioning technique for a multi energetic, multimodality linear accelerator, I perform all the commissioning and acceptance testing for a TrueBeam linear accelerator with 4 megavoltage (MV) energies of which 2 are flattening filterfree (FFF) and 6 electron energies varying from 6 MeV to 20 MeV. A 2 dimensional (2D) water tank was used for scanning all the required field sizes for all the energies. The one dimensional (1D) water tank was used to collect...
Show moreDue to the difficulty of a complex commissioning technique for a multi energetic, multimodality linear accelerator, I perform all the commissioning and acceptance testing for a TrueBeam linear accelerator with 4 megavoltage (MV) energies of which 2 are flattening filterfree (FFF) and 6 electron energies varying from 6 MeV to 20 MeV. A 2 dimensional (2D) water tank was used for scanning all the required field sizes for all the energies. The one dimensional (1D) water tank was used to collect all the output factors for all the photon fields sizes small to medium electron field sizes. For the large electron fields sizes, we had to use the 2D water tank. All the collected data was converted into a file type accepted by the planning system (Eclipse) and subsequently imported there. Treatment plans were generated using multiple forms of planning to verify the viability and quality of the beam data commissioned.
Show less  Date Issued
 2019
 PURL
 http://purl.flvc.org/fau/fd/FA00013301
 Subject Headings
 Linear accelerators, CancerTreatment, Radiation dosimetry
 Format
 Document (PDF)
 Title
 Binary neutron star mergeres: simulations with arbitrarily spinning stars.
 Creator
 Tsatsin, Petr, Marronetti, Pedro, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The starting point of any general relativistic numerical simulation is a solution of the Hamiltonian and momentum constraints that (ideally) represents an astrophysically realistic scenario. This dissertation presents a new method to produce initial data sets for binary neutron stars with arbitrary spins and orbital eccentricities. The method only provides approximate solutions to the constraints. However, it was shown that the corresponding constraint violations subside after a few orbits,...
Show moreThe starting point of any general relativistic numerical simulation is a solution of the Hamiltonian and momentum constraints that (ideally) represents an astrophysically realistic scenario. This dissertation presents a new method to produce initial data sets for binary neutron stars with arbitrary spins and orbital eccentricities. The method only provides approximate solutions to the constraints. However, it was shown that the corresponding constraint violations subside after a few orbits, becoming comparable to those found in evolutions of standard conformally flat, helically symmetric binary initial data. This dissertation presents the first spinning neutron star binary simulations in circular orbits with a orbital eccentricity less then 0.01. The initial data sets corresponding to binaries with spins aligned, zero and antialigned with the orbital angular momentum were evolved in time. These simulations show the orbital “hangup” effect previously seen in binary black holes. Additionally, they show orbital eccentricities that can be up to one order of magnitude smaller than those found in helically symmetric initial sets evolutions.
Show less  Date Issued
 2013
 PURL
 http://purl.flvc.org/fau/fd/FA0004067
 Subject Headings
 Astrophysics, Black holes (Astronomy), General relativity (Physics), Gravitational waves, Neutron stars, Particles (Nuclear physics)
 Format
 Document (PDF)
 Title
 Empirical beam angle optimization for lung cancer intensity modulated radiation therapy.
 Creator
 Doozan, Brian, Pella, Silvia, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Empirical methods of beam angle optimization (BAO) are tested against the BAO that is currently employed in Eclipse treatment planning software. Creating an improved BAO can decrease the amount of time a dosimetrist spends on making a treatment plan, improve the treatment quality and enhance the tools an inexperienced dosimetrist can use to develop planning techniques. Using empirical data created by experienced dosimetrists from 69 patients treated for lung cancer, the most frequently used...
Show moreEmpirical methods of beam angle optimization (BAO) are tested against the BAO that is currently employed in Eclipse treatment planning software. Creating an improved BAO can decrease the amount of time a dosimetrist spends on making a treatment plan, improve the treatment quality and enhance the tools an inexperienced dosimetrist can use to develop planning techniques. Using empirical data created by experienced dosimetrists from 69 patients treated for lung cancer, the most frequently used gantry angles were applied to four different regions in each lung to gather an optimal set of fields that could be used to treat future lung cancer patients. This method, given the moniker FAU BAO, is compared in 7 plans created with the Eclipse BAO choosing 5 fields and 9 fields. The results show that the conformality index improved by 30% or 3% when using the 5 and 9 fields. The conformation number was better by 12% from the 5 fields and 9% from the 9 fields. The organs at risk (OAR) were overall more protected to produce fewer nonstochastic effects from the radiation treatment with the FAU BAO.
Show less  Date Issued
 2014
 PURL
 http://purl.flvc.org/fau/fd/FA00004280, http://purl.flvc.org/fau/fd/FA00004280
 Subject Headings
 Cancer  Radiotherapy, Image guided radiation therapy, Lung cancer  Treatment, Medical physics, Medical radiology  Data processing, Medicine  Mathematical models
 Format
 Document (PDF)
 Title
 DIFFEOMORPHISM INVARIANT COSMOLOGICAL SECTOR IN LOOP QUANTUM GRAVITY.
 Creator
 Mendonca, Phillip, Engle, Jonathan, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

1In this dissertation we work out in detail a new proposal to define rigorously a sector of loop quantum gravity at the diffeomorphism invariant level corresponding to homogeneous and isotropic cosmologies, and propose how to compare in detail the physics of this sector with that of loop quantum cosmology. The key technical steps we have completed are (a) to formulate conditions for homogeneity and isotropy in a diffeomorphism covariant way on the classical phase space of general relativity,...
Show more1In this dissertation we work out in detail a new proposal to define rigorously a sector of loop quantum gravity at the diffeomorphism invariant level corresponding to homogeneous and isotropic cosmologies, and propose how to compare in detail the physics of this sector with that of loop quantum cosmology. The key technical steps we have completed are (a) to formulate conditions for homogeneity and isotropy in a diffeomorphism covariant way on the classical phase space of general relativity, and (b) to translate these conditions consistently using wellunderstood techniques to loop quantum gravity. To impose the symmetry at the quantum level, on both the connection and its conjugate momentum, the method used necessarily has similiarities to the GuptaBleuler method of quantizing the electromagnetic field. Lastly, a strategy for embedding states of loop quantum cosmology into this new homogeneous isotropic sector, and using this embedding to compare the physics, is presented.
Show less  Date Issued
 2019
 PURL
 http://purl.flvc.org/fau/fd/FA00013334
 Subject Headings
 Diffeomorphisms, Quantum gravity, Quantum cosmology, Invariants, Isotropy
 Format
 Document (PDF)
 Title
 Dosimetric comparison of inverse planning by simulated annealing (IPSA) and dose points optimized treatment plans in high dose rate (HDR) brachytherapy of skin lesions using Freiburg flap applicator.
 Creator
 Ghebremichael, Bereket Tewolde, Ouhib, Zoubir, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

A detailed dosimetric comparison between Inverse Planning by Simulated Annealing (IPSA) and Dose Points (DP) optimized treatment plans has been performed for High Dose Rate (HDR) brachytherapy of skin lesions using Freiburg Flap applicator in order to find out whether or not IPSA offers better clinical dosimetric outcomes for lesions categorized into four different curvatures. Without compromising target coverage, IPSA reduced the volume of Planning Target Volume (lesion) that received at...
Show moreA detailed dosimetric comparison between Inverse Planning by Simulated Annealing (IPSA) and Dose Points (DP) optimized treatment plans has been performed for High Dose Rate (HDR) brachytherapy of skin lesions using Freiburg Flap applicator in order to find out whether or not IPSA offers better clinical dosimetric outcomes for lesions categorized into four different curvatures. Without compromising target coverage, IPSA reduced the volume of Planning Target Volume (lesion) that received at least 125% of the prescription dose on average by 41%. It also reduced the volume of the healthy skin surrounding the lesion that receives at least 100% of the prescription dose on average by 42%. IPSA did not show any advantage over DP in sparing normal structures underlying the lesions treated. Although DP optimization algorithm has been regularly used at Lynn Cancer Institute for HDR brachytherapy of skin lesions, recent upgrades in IPSA software have made IPSA more amenable to rapid treatment planning and therefore IPSA can be used either in place of DP or as its alternative.
Show less  Date Issued
 2014
 PURL
 http://purl.flvc.org/fau/fd/FA00004285
 Subject Headings
 Artificial intelligence  Medical applications, Cancer  Treatment, Computational intellingence, Imaging systems in medicine, Medical physics
 Format
 Document (PDF)
 Title
 Dosimetry comparison between treatment plans computed with Finite size pencil beam algorithm and Monte Carlo algorithm using InCise™ Multileaf collimator equipped CyberKnife® System.
 Creator
 Galpayage Dona, Kalpani Nisansala Udeni, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Since the release of the Cyberknife Multileaf Collimator (CKMLC), it has been a constant concern on the realistic dose differences computed with its earlyavailable Finite Size Pencil Beam algorithm (FSPB) from those computed by using industry wellaccepted algorithms such as the Monte Carlo (MC) dose algorithm. In this study dose disparities between FSPB and MC dose calculation algorithms for selected CKMLC treatment plans were quantified. The dosimetry for planning target volume (PTV) and...
Show moreSince the release of the Cyberknife Multileaf Collimator (CKMLC), it has been a constant concern on the realistic dose differences computed with its earlyavailable Finite Size Pencil Beam algorithm (FSPB) from those computed by using industry wellaccepted algorithms such as the Monte Carlo (MC) dose algorithm. In this study dose disparities between FSPB and MC dose calculation algorithms for selected CKMLC treatment plans were quantified. The dosimetry for planning target volume (PTV) and major organs at risks (OAR) was compared by calculating normalized percentage deviations (Ndev) between the two algorithms. It is found that the FSPB algorithm overestimates D95 of PTV when compared with the MC algorithm by averaging 24.0% in detached lung cases, and 15.0% in nondetached lung cases which is attributed to the absence of heterogeneity correction in the FSPB algorithm. Average dose differences are 0.3% in intracranial and 0.9% in pancreas cases. Ndev for the D95 of PTV range from 8.8% to 14.1% for the CKMLC lung treatment plans with small field (SF ≤ 2x2cm2). Ndev is ranged from 0.57.0% for OARs.
Show less  Date Issued
 2018
 PURL
 http://purl.flvc.org/fau/fd/FA00013123
 Subject Headings
 Radiosurgery, Radiation dosimetry, Monte Carlo method, Algorithms, Lung Neoplasmsradiotherapy
 Format
 Document (PDF)
 Title
 Efficient Machine Learning Algorithms for Identifying Risk Factors of Prostate and Breast Cancers among Males and Females.
 Creator
 Rikhtehgaran, Samaneh, Muhammad, Wazir, Florida Atlantic University, Department of Physics, Charles E. Schmidt College of Science
 Abstract/Description

One of the most common types of cancer among women is breast cancer. It represents one of the diseases leading to a high number of mortalities among women. On the other hand, prostate cancer is the second most frequent malignancy in men worldwide. The early detection of prostate cancer is fundamental to reduce mortality and increase the survival rate. A comparison between six types of machine learning models as Logistic Regression, Decision Tree, Random Forest, Gradient Boosting, k Nearest...
Show moreOne of the most common types of cancer among women is breast cancer. It represents one of the diseases leading to a high number of mortalities among women. On the other hand, prostate cancer is the second most frequent malignancy in men worldwide. The early detection of prostate cancer is fundamental to reduce mortality and increase the survival rate. A comparison between six types of machine learning models as Logistic Regression, Decision Tree, Random Forest, Gradient Boosting, k Nearest Neighbors, and Naïve Bayes has been performed. This research aims to identify the most efficient machine learning algorithms for identifying the most significant risk factors of prostate and breast cancers. For this reason, National Health Interview Survey (NHIS) and Prostate, Lung, Colorectal, and Ovarian (PLCO) datasets are used. A comprehensive comparison of risk factors leading to these two crucial cancers can significantly impact early detection and progressive improvement in survival.
Show less  Date Issued
 2021
 PURL
 http://purl.flvc.org/fau/fd/FA00013755
 Subject Headings
 Machine learning, Algorithms, CancerRisk factors, BreastCancer, ProstateCancer
 Format
 Document (PDF)
 Title
 Firstprinciples study of metastable phases and structural anomalies of Fe, Al, Zn, and Cd under pressure.
 Creator
 Apostol, Florin., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Stable and metastable phases of Fe and Al and structural anomalies of Zn and Cd have been studied by epitaxial Bain path (EBP) and minimum path (MNP) firstprinciples procedures, based on finding equilibrium structures from minimizing the Gibbs free energy G with respect to structure at a given hydrostatic pressure p and temperature T . The main accomplishments are as follows. (1) This dissertation illustrates the effectiveness of the MNP procedure for finding stable and metastable phases of...
Show moreStable and metastable phases of Fe and Al and structural anomalies of Zn and Cd have been studied by epitaxial Bain path (EBP) and minimum path (MNP) firstprinciples procedures, based on finding equilibrium structures from minimizing the Gibbs free energy G with respect to structure at a given hydrostatic pressure p and temperature T . The main accomplishments are as follows. (1) This dissertation illustrates the effectiveness of the MNP procedure for finding stable and metastable phases of an element by studying four Bravais phases of Fe including bodycentered tetragonal (bct), bodycentered cubic (bcc), facecentered cubic (fcc) and rhombohedral (rh) phases. The determination of absolute stability using MNP is new; MNP finds all the elastic constants cjj of a given state and the eigenvalues of the elastic constants matrix, which determine the absolute stability of the state., (2) We have extended our search for stable and metastable phases from zero temperature to finite temperature, which requires the calculations of the Debye temperature Od from cjj in the case of no symmetry. The Debye theory is modified by introducing a parameter B2 that gives the fraction of the full Debye zeropoint energy possessed by the actual dispersive mode frequencies. The value of the lattice parameter of fcc Al at low temperatures,a(T) , is shown to be accurately determined by the modified Debye theory of lattice vibrations and firstprinciples total energy band calculations with the MNP procedure. (3) The existence of structural anomalies in hcp Zn and Cd has been shown from firstprinciples totalenergy calculations using WIEN2k with the EBP procedure., Evaluation of the pressure dependence of various elastic quantities which are much more sensitive to the anomaly shows that the anomalies in hcp Zn and hcp Cd exist over a considerable range of pressure; several abrupt changes in the electron distribution are thereby indicated in that pressure range. (4) Calculations on the zonecenter transverse optical phonon frequencies Vto(p) of hcp Zn, which found oscillatory behavior of Vto(p) in the pressure range of the anomalies, support the conclusions made in (3) on the structural anomalies. Based on this dissertation research four papers have been published in refereed journals.
Show less  Date Issued
 2008
 PURL
 http://purl.flvc.org/FAU/186334
 Subject Headings
 Epitaxy, Mathematical physics, Metals, Electric properties, Phase transformation (Statistical physics)
 Format
 Document (PDF)
 Title
 Comparison of treatment plans calculated using ray tracing and Monte Carlo algorithms for lung cancer patients having undergone radiotherapy with cyberknife.
 Creator
 Pennington, Andreea, Selvaraj, Raj, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The purpose of this research is to determine the feasibility of introducing the Monte Carlo (MC) dose calculation algorithm into the clinical practice. Unlike the Ray Tracing (RT) algorithm, the MC algorithm is not affected by the tissue inhomogeneities, which are significant inside the chest cavity. A retrospective study was completed for 102 plans calculated using both the RT and MC algorithms. The D95 of the PTV was 26% lower for the MC calculation. The first parameter of conformality, as...
Show moreThe purpose of this research is to determine the feasibility of introducing the Monte Carlo (MC) dose calculation algorithm into the clinical practice. Unlike the Ray Tracing (RT) algorithm, the MC algorithm is not affected by the tissue inhomogeneities, which are significant inside the chest cavity. A retrospective study was completed for 102 plans calculated using both the RT and MC algorithms. The D95 of the PTV was 26% lower for the MC calculation. The first parameter of conformality, as defined as the ratio of the Prescription Isodose Volume to the PTV Volume was on average 1.27 for RT and 0.67 for MC. The results confirm that the RT algorithm significantly overestimates the dosages delivered confirming previous analyses. Correlations indicate that these overestimates are largest for small PTV and/or when the ratio of the volume of lung tissue to the PTV approaches 1.
Show less  Date Issued
 2014
 PURL
 http://purl.flvc.org/fau/fd/FA00004316
 Subject Headings
 Computer graphics, Diagnostic imaging, Image guided radiation therapy, Lung cancer  Treatment, Lungs  Cancer  Radiotherapy, Monte Carlo method
 Format
 Document (PDF)
 Title
 Comparison of Measured and Computed Lateral Penumbra for a ProteusPlus Pencil Beam Scanning Proton Therapy System.
 Creator
 Leyva, Michael, Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The lateral penumbra of a proton pencil beam scanning system (PBS) is of great importance in sparing of organs at risk and normal tissue when treating patients. The purpose of this current work is to measure the lateral penumbra of the Ion Beam Applications (Ion Beam Applications, Louvain‐la‐Neuve, Belgium) ProteusPLUS PBS Proton Therapy System and compare the measurements with the computed results from the RayStation proton treatment planning system. The lateral penumbra (80%20%) was...
Show moreThe lateral penumbra of a proton pencil beam scanning system (PBS) is of great importance in sparing of organs at risk and normal tissue when treating patients. The purpose of this current work is to measure the lateral penumbra of the Ion Beam Applications (Ion Beam Applications, Louvain‐la‐Neuve, Belgium) ProteusPLUS PBS Proton Therapy System and compare the measurements with the computed results from the RayStation proton treatment planning system. The lateral penumbra (80%20%) was measured using EBT3 Gafchromic film in the water tank. The lateral penumbra was studied for various parameters such as range, depth, and air gap. The computed lateral penumbra was found to be higher than the measured lateral penumbra by up to 2.3 mm in the case of depth dependency at 30 cm, and lower by up to 1.18 mm in the case of an air gap of 15 cm.
Show less  Date Issued
 2019
 PURL
 http://purl.flvc.org/fau/fd/FA00013229
 Subject Headings
 Proton Therapy, RadiotherapyMeasurement, Radiotherapy Planning, ComputerAssisted
 Format
 Document (PDF)
 Title
 Effect of Processing Temperature on the Properties of Nanophase Fesubstituted Hydroxypatite.
 Creator
 Kathriarachchi, Vindu, Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The effect of processing temperature on the crystal structure properties of the Fesubstituted Hydroxyapatite (FeHAp) was studied by using the Rietveld refinement method of powder xray (XRD) and neutron diffraction (NPD) patterns. Superconducting QUantum Interference Device (SQUID) magnetometry, transmission electron microscopy (TEM) and xray fluorescence spectroscopy (XRF) were used to study the magnetic properties, particle morphology and chemical composition of the prepared samples. Two...
Show moreThe effect of processing temperature on the crystal structure properties of the Fesubstituted Hydroxyapatite (FeHAp) was studied by using the Rietveld refinement method of powder xray (XRD) and neutron diffraction (NPD) patterns. Superconducting QUantum Interference Device (SQUID) magnetometry, transmission electron microscopy (TEM) and xray fluorescence spectroscopy (XRF) were used to study the magnetic properties, particle morphology and chemical composition of the prepared samples. Two sets of samples of chemical formula Ca5xFex(PO4)3OH were prepared with x = 0, 0.05, 0.1, 0.2 and 0.3 by using processing temperatures of 37°C and 80°C, following a twostep coprecipitation method. A single phase HAp was identified in samples with x = 0 and 0.05. Processing temperature affects the type and percentage of secondary phases: hematite was detected in samples prepared at 37°C with x ≥ 0.1, hematite and maghemite were detected in samples prepared at 80°C with x = 0.2 and 0.3. Rietveld refinements of NPD and XRD patterns showed that the a lattice constants are greater in Fesubstituted samples prepared at 37°C, whereas the c lattice constants are greater in the 80°C samples for x ≥ 0.05. Fe preferentially substitutes at the Ca2 site in the 80°C samples, whereas Ca1 is the preferred substitution site in the 37°C samples. Fe substitution results to a decrease of the lattice constants at both preparation temperatures. The ratios Fe/(Fe + Ca) of the refined atomic fractions of the samples prepared at 80°C are greater than those of the 37°C samples. Further, more secondary phases form in samples prepared at 37°C compared to 80°C samples. The magnetic measurements reveal that pure HAp is diamagnetic, whereas samples with x = 0.05 and 0.1 are paramagnetic. Samples with x = 0.3 showed superparamagnetic behavior based on ZFC and FC measurements. Similar hysteresis loops in samples x = 0.2 and 0.3 indicate that the samples with x = 0.2 may show superparamagnetic properties. For x = 0.2 and 0.3, the samples prepared at 80°C showed higher magnetization compared to the 37°C samples, because of the maghemite secondary phase. Based on the TEM images, Fe substituted HAp nanoparticles prepared at 37°C are mainly spherically shaped, and the 80°C particles are mainly elongated. Increase of the Fe concentration favors formation of elongated particles and larger spherical particles. The XRF measurements confirm the Fe for Ca substitution in the HAp structure based on the decrease of the Ca/P and the increase of the Fe/(Fe + Ca) atomic ratios with the Fe concentration.
Show less  Date Issued
 2015
 PURL
 http://purl.flvc.org/fau/fd/FA00004512, http://purl.flvc.org/fau/fd/FA00004512
 Subject Headings
 Biomedical materials, Nanostructured materials  Environmental aspects, Nanostructured materials  Mechanical properties, Pharmaceutical biotechnology, Rietveld method
 Format
 Document (PDF)
 Title
 General relativistic quasilocal angular momentum continuity and the stability of strongly elliptic eigenvalue problems.
 Creator
 Wilder, Shawn M., Beetle, Christopher, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

In general relativity, angular momentum of the gravitational field in some volume bounded by an axially symmetric sphere is welldefined as a boundary integral. The definition relies on the symmetry generating vector field, a Killing field, of the boundary. When no such symmetry exists, one defines angular momentum using an approximate Killing field. Contained in the literature are various approximations that capture certain properties of metric preserving vector fields. We explore the...
Show moreIn general relativity, angular momentum of the gravitational field in some volume bounded by an axially symmetric sphere is welldefined as a boundary integral. The definition relies on the symmetry generating vector field, a Killing field, of the boundary. When no such symmetry exists, one defines angular momentum using an approximate Killing field. Contained in the literature are various approximations that capture certain properties of metric preserving vector fields. We explore the continuity of an angular momentum definition that employs an approximate Killing field that is an eigenvector of a particular secondorder differential operator. We find that the eigenvector varies continuously in Hilbert space under smooth perturbations of a smooth boundary geometry. Furthermore, we find that not only is the approximate Killing field continuous but that the eigenvalue problem which defines it is stable in the sense that all of its eigenvalues and eigenvectors are continuous in Hilbert space. We conclude that the stability follows because the eigenvalue problem is strongly elliptic. Additionally, we provide a practical introduction to the mathematical theory of strongly elliptic operators and generalize the above stability results for a large class of such operators.
Show less  Date Issued
 2014
 PURL
 http://purl.flvc.org/fau/fd/FA00004235
 Subject Headings
 Boundary element methods, Boundary value problems, Differential equations, Elliptic  Numerical solutions, Differential equations, Partial  Numerical solutions, Eigenvalues, Spectral theory (Mathematics)
 Format
 Document (PDF)
 Title
 Exploring appropriate offset values for pencil beam and Monte Carlo dose optimization in lung stereotactic body radiotherapy encompassing the effects of respiration and tumor location.
 Creator
 Evans, Grant, Shang, Charles, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Evaluation of dose optimization using the Pencil Beam (PB) and Monte Carlo (MC) algorithms may allow physicists to apply dosimetric offsets to account for inaccuracies of the PB algorithm for lung cancer treatment with Stereotactic Body Radiotherapy (SBRT). 20 cases of NonSmall Cell Lung Cancer (NSCLC) were selected. Treatment plans were created with Brainlab iPlanDose® 4.1.2. The D97 of the Planning Target Volume (PTV) was normalized to 50 Gy on the Average Intensity Projection (AIP) using...
Show moreEvaluation of dose optimization using the Pencil Beam (PB) and Monte Carlo (MC) algorithms may allow physicists to apply dosimetric offsets to account for inaccuracies of the PB algorithm for lung cancer treatment with Stereotactic Body Radiotherapy (SBRT). 20 cases of NonSmall Cell Lung Cancer (NSCLC) were selected. Treatment plans were created with Brainlab iPlanDose® 4.1.2. The D97 of the Planning Target Volume (PTV) was normalized to 50 Gy on the Average Intensity Projection (AIP) using the fast PB and compared with MC. This exact plan with the same beam Monitor Units (MUs) was recalculated over each respiratory phase. The results show that the PB algorithm has a 2.32.4% less overestimation at the maximum exhalation phase than the maximum inhalation phase when compared to MC. Significantly smaller dose difference between PB and MC is also shown in plans for peripheral lesions (7.7 ± 0.7%) versus central lesions (12.7±0.8%)(p< 0.01).
Show less  Date Issued
 2014
 PURL
 http://purl.flvc.org/fau/fd/FA00004105, http://purl.flvc.org/fau/fd/FA00004105
 Subject Headings
 Drug development  Computer simulation, Image guided radiation therapy, Lung cancer  Treatment, Monte Carlo method, Proton beams, Transport theory
 Format
 Document (PDF)
 Title
 A Dosimetric Comparison of 3DCRT, IMRT, and SAVI HDR via NTCP/TCP and DVH Analysis of Critical Organs for Breast Cancer.
 Creator
 Wisnoskie, Sarah, Pella, Silvia, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Accelerated Partial Breast Irradiation (APBI) is a common treatment of breast cancer with many modalities including 3D Conformal Radiation Therapy (3DCRT), Intensity Modulated Radiation Therapy (IMRT), and High Dose Rate Brachytherapy (HDR). In this research, a retrospective analysis of patient’s data was performed to analyze the NTCP/TCP (Normal Tissue Complication Probability/Tumor Control Probability) and Dose Volume Histogram (DVH) parameters for HDR with SAVI, 3D, and IMRT and compare...
Show moreAccelerated Partial Breast Irradiation (APBI) is a common treatment of breast cancer with many modalities including 3D Conformal Radiation Therapy (3DCRT), Intensity Modulated Radiation Therapy (IMRT), and High Dose Rate Brachytherapy (HDR). In this research, a retrospective analysis of patient’s data was performed to analyze the NTCP/TCP (Normal Tissue Complication Probability/Tumor Control Probability) and Dose Volume Histogram (DVH) parameters for HDR with SAVI, 3D, and IMRT and compare them focusing on critical organs such as the heart, ipsilateral lung, chest wall, ribs, and skin. TCP was 90.275%, 55.948%, and 53.369% for HDR, 3D, and IMRT respectively. The ribs were the most sensitive critical organ for all 3 modalities with a mean NTCP of 8%, 15%, and 8% for HDR, 3D, and IMRT respectively. DVH analysis showed HDR spares critical organs more than EBRT except for 2 patients receiving high doses to the ribs and chest wall.
Show less  Date Issued
 2019
 PURL
 http://purl.flvc.org/fau/fd/FA00013281
 Subject Headings
 Radiation dosimetryEvaluation, BreastCancerTreatment, Organs, TissuesEffect of radiation on
 Format
 Document (PDF)
 Title
 A GPU BASED SIMULATED ANNEALING ALGORITHM FOR INTENSITYMODULATED RADIATION THERAPY.
 Creator
 Galanakou, Panagiota, Leventouri, Theodora, Florida Atlantic University, Department of Physics, Charles E. Schmidt College of Science
 Abstract/Description

Simulating Annealing Algorithm (SAA) has been proposed for optimization of the IntensityModulated Radiation Therapy (IMRT). Despite the advantage of the SAA to be a global optimizer, the SAA optimization of IMRT is an extensive computational task due to the large scale of the optimization variables, and therefore it requires significant computational resources. In this research we introduce a parallel graphics processing unit (GPU)based SAA developed in MATLAB platform and compliant with...
Show moreSimulating Annealing Algorithm (SAA) has been proposed for optimization of the IntensityModulated Radiation Therapy (IMRT). Despite the advantage of the SAA to be a global optimizer, the SAA optimization of IMRT is an extensive computational task due to the large scale of the optimization variables, and therefore it requires significant computational resources. In this research we introduce a parallel graphics processing unit (GPU)based SAA developed in MATLAB platform and compliant with the computational environment for radiotherapy research (CERR) for IMRT treatment planning in order elucidate the performance improvement of the SAA in IMRT optimization. First, we identify the “bottlenecks” of our code, and then we parallelize those on the GPU accordingly. Performance tests were conducted on four different GPU cards in comparison to a serial version of the algorithm executed on a CPU. A gradual increase of the speedup factor as a function of the number of beamlets was found for all four GPUs. A maximum speedup factor of 33.48 was achieved for a prostate case, and 30.51 for a lung cancer case when the K40m card and the maximum number of beams was utilized for each case. At the same time, the two optimized IMRT plans that were created (prostate and lung cancer plans) were met the IMRT optimization goals.
Show less  Date Issued
 2019
 PURL
 http://purl.flvc.org/fau/fd/FA00013372
 Subject Headings
 Radiotherapy, IntensityModulated, Annealing algorithm, Simulated annealing (Mathematics), Graphics processing units
 Format
 Document (PDF)