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Title: Optimization algorithms for intensity modulated radiation treatment.
Creator: Doozan, Brian, Leventouri, Theodora, Graduate College
Date Issued: 2013-04-12
PURL: http://purl.flvc.org/fcla/dt/3361926
Subject Headings: Radiotherapy, Radiation dosimetry, Algorithms
Format: Document (PDF)

Title: Preparation and characterization of fSWCNT/HAp-nylon hybridized composite biomaterial and mechanical testing.
Creator: Khanal, Suraj P., Leventouri, Theodora, Graduate College
Abstract/Description: Synthetic hydroxyapatite HAp bears poor mechanical properties that limit its applicability in orthopedics. We study the possibility of overcoming such limitations by incorporating functionalized single walled carbon nanotube fSWCNT and polymerized є- caprolactam. Sonication method was used to disperse fSWCNT in the HAp. A simple hot blending method was used to incorporate HAp/fSWCNT powder with melted polymerized є-caprolactam. The fracture toughness of the composite material was tested in...
Show moreSynthetic hydroxyapatite HAp bears poor mechanical properties that limit its applicability in orthopedics. We study the possibility of overcoming such limitations by incorporating functionalized single walled carbon nanotube fSWCNT and polymerized є- caprolactam. Sonication method was used to disperse fSWCNT in the HAp. A simple hot blending method was used to incorporate HAp/fSWCNT powder with melted polymerized є-caprolactam. The fracture toughness of the composite material was tested in compliance with ASTM D-5045 standard. A critical stress intensity factor K1C of the composite material was found to be 3.55 MPa.m1/2, which is a value comparable to the one for cortical bone.
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Date Issued: 2014
PURL: http://purl.flvc.org/fau/fd/FA00005828
Format: Document (PDF)

Title: Comparison study between BrainLab and Eclipse for small cancer lesions.
Creator: Doozan, Brian, Leventouri, Theodora, Pella, Silvia, Graduate College
Abstract/Description: There are many available options today for treating small lesion cancer cells. Two of the most used options are the planning systems BrainLab and Eclipse. The main difference between the two is the algorithms that are used to calculate the dose distribution of external beam radiation therapy. BrainLab offers a Monte Carlo based algorithm while Eclipse utilizes the Anisotropic Analytical Algorithm. An investigative study on the quality of the planning system is done for cases in lung, head and...
Show moreThere are many available options today for treating small lesion cancer cells. Two of the most used options are the planning systems BrainLab and Eclipse. The main difference between the two is the algorithms that are used to calculate the dose distribution of external beam radiation therapy. BrainLab offers a Monte Carlo based algorithm while Eclipse utilizes the Anisotropic Analytical Algorithm. An investigative study on the quality of the planning system is done for cases in lung, head and neck and prostate. In particular, lung cases are highly heterogeneous which can lead to problems in the calculation. The ability to be able to plan on the best system for individual cases can lead to better and more consistent treatments for cancer patients.
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Date Issued: 2014
PURL: http://purl.flvc.org/fau/fd/FA00005812
Format: Document (PDF)

Title: Dosimetric Consequences From Minimal Displacements In Abpi With Savi Applicators.
Creator: Chandrasekara, Shereen, Pella, Silvia, Leventouri, Theodora, Graduate College
Abstract/Description: Purpose: To highlight the importance of provide proper solid immobilization initially and in every treatment in ABPI with brachytherapy. Materials and Methods: 100 patients receiving brachytherapy treatments in ABPI using the Savi applicators were considered for the study. The CT scans used in the initial plan was compared with every scan obtained before each treatment. Each of these scans were exported in the planning system and registered with the initial plan. Dosimetric evaluations were...
Show morePurpose: To highlight the importance of provide proper solid immobilization initially and in every treatment in ABPI with brachytherapy. Materials and Methods: 100 patients receiving brachytherapy treatments in ABPI using the Savi applicators were considered for the study. The CT scans used in the initial plan was compared with every scan obtained before each treatment. Each of these scans were exported in the planning system and registered with the initial plan. Dosimetric evaluations were performed with their consequences to the ribs and the skin surface. Results: Making the dosimetric comparison for the critical points on the ribs and skin due to very small changes in the interfractionation position revealed dramatic differences in the maximum dose to these critical organs. The cavity's volume manifested changes between fractions as well as the distances to the two critical organs. Therefore the maximum dose manifested variance between 10 and 32 in both of the sites Conclusions: This study demonstrates that using CT scan before each treatment will minimize the risk of delivering undesired high doses to the critical organs. This reveals the urgent need of increasing and improving the immobilization methods when treating ABPI with Savi. In 30 of the cases re-planning was necessary between fractions therefore we conclude that in each case the treatment and planning teams must be prepared for re-plan as needed.
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Date Issued: 2015
PURL: http://purl.flvc.org/fau/fd/FA00005872
Format: Document (PDF)

Title: Motion challenges in high dose rate (HDR) brachytherapy.
Creator: Curley, Casey Michael, Pella, Silvia, Leventouri, Theodora, Graduate College
Date Issued: 2013-04-12
PURL: http://purl.flvc.org/fcla/dt/3361287
Subject Headings: Brachytherapy, Leipzig, Immobilization
Format: Document (PDF)

Title: Should we use RapidArc (VMAT) for breast radiotherapy? A Dosimetric comparison of IMRT versus VMAT optimization.
Creator: Moshiri Sedeh, Nader, Pella, Silvia, Leventouri, Theodora, Graduate College
Abstract/Description: Purpose: The purpose of this study is to compare the dose-volumetric results of intensity modulated radiation therapy (IMRT) with RapidArc (RA Varian Medical Systems, Palo Alto, CA) for whole breast irradiation. Methods: 25 patients previously treated for whole left breast (either RapidArc plan or IMRT) were the subjects of this planning study. Eclipse v 11.0.47 was used to make all retrospective plans using the same contours, energy, machine and normalization. Prescription dose to the...
Show morePurpose: The purpose of this study is to compare the dose-volumetric results of intensity modulated radiation therapy (IMRT) with RapidArc (RA Varian Medical Systems, Palo Alto, CA) for whole breast irradiation. Methods: 25 patients previously treated for whole left breast (either RapidArc plan or IMRT) were the subjects of this planning study. Eclipse v 11.0.47 was used to make all retrospective plans using the same contours, energy, machine and normalization. Prescription dose to the planning target volume was 5000 Gy in 25 fractions. All plans were normalized such that 100% covered 95% of planning target volume (PTV). Results: V10, V20 and Dmean Gy of left lung significantly differed between the two plans (p-value <0.0001, =0.0473 and <0.0001 respectively), but V30 Gy did not (p-value 0.463). V25, D33 and Dmean Gy of heart significantly differed between the two plans (p-value =0.034, <0.0001 and 0.01 respectively), but V10 Gy did not (p-value 0.058). V5 of both right breast and right lung significantly differed between the two plans (p-value <0.0007 and =0.0112, respectively). Also Dmean of both right breast and right lung significantly differed between the two plans (p-value <0.0001 for both). The mean conformity index did not significantly differ, p-value 0.142. There was a significant difference between the mean MUs of the two plans as well, p-value <0.0001.
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Date Issued: 2015
PURL: http://purl.flvc.org/fau/fd/FA00005901
Format: Document (PDF)

Title: Evaluation of surface dose outside the treatment area for breast cancer irradiation modalities using thermoluminescence dosimeters (TLDs).
Creator: Khanal, Suraj P., Ouhib, Zoubir, Leventouri, Theodora, Graduate College
Date Issued: 2013-04-12
PURL: http://purl.flvc.org/fcla/dt/3361319
Subject Headings: Thermoluminescence dosimetry, Breast--Cancer--Treatment
Format: Document (PDF)

Title: Effect of preparation temperature on crystal structure and magnetic properties of nanophase Fe-substituted hydroxyapatite.
Creator: Kathriarachchi, Vindu, Leventouri, Theodora, Sorge, Korey D., Graduate College
Date Issued: 2013-04-12
PURL: http://purl.flvc.org/fcla/dt/3361934
Subject Headings: Hydroxyapatite, Magnetic properties, Crystals--Structure, Temperature
Format: Document (PDF)

Title: Effect of Preparation Temperature on Crystal Structure and Magnetic Properties of Nanophase Fe-Substituted Hydroxyapatite.
Creator: Kathriarachchi, Vindu, Sorge, Korey D., Leventouri, Theodora, Graduate College
Abstract/Description: The purpose of the study is to investigate the effect of preparation temperature on the crystal structure and magnetic properties of nanophase Fe-substituted Hydroxyapatite. Multisubstituted Hydroxyapatite (HAp), Ca5(PO4)3OH, is the main mineral phase in physiological apatite, ~70 wt% in bones and dentin, and ~96 wt% in enamel. Iron is one of the minor substitution elements (0.01-0.1 wt% in bone and 0.003 wt% in enamel) replacing Ca in the HAp structure. Research interest on Fe-HAp is related...
Show moreThe purpose of the study is to investigate the effect of preparation temperature on the crystal structure and magnetic properties of nanophase Fe-substituted Hydroxyapatite. Multisubstituted Hydroxyapatite (HAp), Ca5(PO4)3OH, is the main mineral phase in physiological apatite, ~70 wt% in bones and dentin, and ~96 wt% in enamel. Iron is one of the minor substitution elements (0.01-0.1 wt% in bone and 0.003 wt% in enamel) replacing Ca in the HAp structure. Research interest on Fe-HAp is related to the fact that Fe for Ca substitution reduces the solubility of HAp therefore it functions as a cavities preventive agent. In contrast, Fe overload causes a decrease in bone mechanical strength. Furthermore, Fe-HAp can find applications in hyperthermia based anti-cancer treatments and in magnetic resonance imaging (MRI) contrast agents. Two sets of Ca5-xFex(PO4)3OH samples (x=0,0.05,0.1,0.2,0.3) were synthesized by a chemical precipitation method at physiological temperature (370C) and 800C. The samples were calcinated at 6500C and deuterated at 6000C. The samples were characterized by x-ray powder diffraction (XRD), neutron powder diffraction (NPD) and SQUID Magnetometry. A single-phase system was detected for nominal iron content x≤0.1 by XRD phase identification in both sets of samples, while hematite (α-Fe2O3) and/or maghemite (γ- Fe2O3) develops starting at x=0.1. According to the magnetic measurements, sample with x=0 showed diamagnetic behavior while samples with Fe showed paramagnetic behavior. Combined Rietveld refinements of XRD and NPD patterns will provide accurate information on the effect of processing temperature on the crystallographic parameters of the nano-materials.
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Date Issued: 2014
PURL: http://purl.flvc.org/fau/fd/FA00005825
Format: Document (PDF)

Title: Dosimetric Influence of Dose due to the PTV Dose Uniformity on the Critical Organs.
Creator: Yigit, Erdem, Pella, Silvia, Theodora Leventouri, Theodora Leventouri,, Florida Atlantic University, Department of Physics, Charles E. Schmidt College of Science
Abstract/Description: Dose uniformity in the Planning Target Volume (PTV) can induce a higher-than-expected dose distribution in the nearby critical organs. The goal of this study is to evaluate the influence of the Planning Target volume dose uniformity on the surrounding critical organs (OAR). Ten cases of anonymized patients’ data were selected for our study including: Breast cancer, Brain cancer, Head and Neck cancer, Lung and Prostate calculations of Conformity indices, Biological Effective Doses (BED), Tumor...
Show moreDose uniformity in the Planning Target Volume (PTV) can induce a higher-than-expected dose distribution in the nearby critical organs. The goal of this study is to evaluate the influence of the Planning Target volume dose uniformity on the surrounding critical organs (OAR). Ten cases of anonymized patients’ data were selected for our study including: Breast cancer, Brain cancer, Head and Neck cancer, Lung and Prostate calculations of Conformity indices, Biological Effective Doses (BED), Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) were used to calculate the dose distribution in PTV as well as the dose delivered to the surrounding critical organs of each PTV. We assume that the tumors PTVs have homogeneous density as well as the surrounding normal tissue. Conformity indices (CI) for Breast (PTV) are between 1.8 – 1.9, for Brain (PTV) are between 1.6 – 2.0, for Lungs are 1.5 – 1.6, for Prostate are between 0.4 – 0.5, for Head and Neck are 0.3 – 0.4. Dose uniformity in all the PTVs is 1.089 which is a good indication of the quality of treatment delivered to the tumor. TCP is averaging of value of 87.94 and NTCP is 3.4445.
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Date Issued: 2023
PURL: http://purl.flvc.org/fau/fd/FA00014339
Subject Headings: Radiation dosimetry, Biophysics, Cancer
Format: Document (PDF)

Title: Comparison of Treatment Plans Calculated using Ray Tracing (RT) and Monte Carlo (MC) Algorithms for Lung Cancer Patients Having Undergone Radiotherapy with Cyberknife.
Creator: Pennington, Andreea, Selvaraj, Raj, Graduate College, Leventouri, Theodora, Kirkpatrick, Steven, Oliveira, Silvana
Abstract/Description: Purpose/ Objectives: The latest publications indicate that the Ray Tracing algorithm significantly overestimates the dose delivered as compared to the Monte Carlo MC algorithm. The purpose of this study is to quantify this overestimation and to identify significant correlations between the RT and MC calculated dose distributions.
Materials/Methods: Preliminary results are based on 50 preexisting RT algorithm dose optimization and calculation treatment plans prepared on the Multiplan treatment...
Show morePurpose/ Objectives: The latest publications indicate that the Ray Tracing algorithm significantly overestimates the dose delivered as compared to the Monte Carlo MC algorithm. The purpose of this study is to quantify this overestimation and to identify significant correlations between the RT and MC calculated dose distributions.
Materials/Methods: Preliminary results are based on 50 preexisting RT algorithm dose optimization and calculation treatment plans prepared on the Multiplan treatment planning system Accuray Inc., Sunnyvale, CA. The analysis will be expanded to include 100 plans. These plans are recalculated using the MC algorithm, with high resolution and 1 uncertainty. The geometry and number of beams for a given plan, as well as the number of monitor units, is constant for the calculations for both algorithms and normalized differences are compared.

Results: MC calculated doses were significantly smaller than RT doses. The D95 of the PTV was 27 lower for the MC calculation. The GTV and PTV mean coverage were 13 and 39 less for MC calculation. The first parameter of conformality, as defined as the ratio of the Prescription Isodose Volume to the PTV Volume was on average 1.18 for RT and 0.62 for MC. Maximum doses delivered to OARs was reduced in the MC plans. The correlation of the ratio of air in PTV to the PTV with the difference in PTV coverage had a coefficient of -0.54.

Conclusions: The preliminary results confirm that the RT algorithm significantly overestimates the dosages delivered confirming previous analyses.
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Date Issued: 2014
PURL: http://purl.flvc.org/fau/fd/FA00005162
Format: Document (PDF)

Title: A Computational Study on different penalty approaches for constrained optimization in radiation therapy treatment planning with a simulated annealing algorithm.
Creator: Mohammadi Khoroushadi, Mohammad Sadegh, Shang, Charles, Ouhib, Zoubir, Graduate College, Leventouri, Theodora, Kalantzis, Georgios
Abstract/Description: Simulated Annealing algorithm is utilized for Intensity Modulated Radiation Therapy IMRT optimization. The goal in IMRT is to give the prescribed radiation dose to the tumor while minimizing the dose given to normal organs.
Date Issued: 2015
PURL: http://purl.flvc.org/fau/fd/FA00005891
Format: Document (PDF)

Title: Effect of preparation temperature on crystal structure properties on nanophase Fe-substituted hydroxyapatite.
Creator: Kathriarachchi, Vindu, Kyriacou, Andreas, Khanal, Suraj P., Leventouri, Theodora, Graduate College
Date Issued: 2012-03-30
PURL: http://purl.flvc.org/fcla/dt/3342385
Format: Document (PDF)

$Crystal structure studies of cone snail shells by powder x-ray diffraction$

Title: Crystal structure studies of cone snail shells by powder x-ray diffraction.
Creator: Khanal, Suraj P., Kathriarachchi, Vindu, Kyriacou, Andreas, Leventouri, Theodora, Graduate College
Date Issued: 2011-04-08
PURL: http://purl.flvc.org/fcla/dt/3165805
Subject Headings: Snails, Shells, X-rays --Diffraction
Format: Document (PDF)

$Rietveld analysis of powder diffraction data from a carbonate fluorapatite$

Title: Rietveld analysis of powder diffraction data from a carbonate fluorapatite.
Creator: Moghaddam, Hadi Yazdani, Florida Atlantic University, Leventouri, Theodora
Abstract/Description: The mechanism of the carbonate substitution in the apatite structure is unraveled through analysis of Rietveld refinements of powder diffraction data from a single-phase natural carbonate fluorapatite (francolite). The refined values of the P-O bond lengths give a ~1.6% distortion of the phosphate tetrahedron caused by the carbonate substitution. The two bond lengths P-O1 and P-O2 and their corresponding angles on the mirror plane of the phosphate tetrahedron are mainly disturbed by this...
Show moreThe mechanism of the carbonate substitution in the apatite structure is unraveled through analysis of Rietveld refinements of powder diffraction data from a single-phase natural carbonate fluorapatite (francolite). The refined values of the P-O bond lengths give a ~1.6% distortion of the phosphate tetrahedron caused by the carbonate substitution. The two bond lengths P-O1 and P-O2 and their corresponding angles on the mirror plane of the phosphate tetrahedron are mainly disturbed by this substitution. A static positional disorder, mainly of the atoms at the tetrahedral sites, is revealed from the temperature dependence of the atomic anisotropic displacement parameters. A model for the mechanism of the carbonate entrance in the apatite structure is proposed.
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Date Issued: 2000
PURL: http://purl.flvc.org/fcla/dt/12718
Subject Headings: Rietveld method, Apatite, X-rays--Diffraction
Format: Document (PDF)

$X-ray and neutron diffraction studies of a silicon-substituted bioapatite$

Title: X-ray and neutron diffraction studies of a silicon-substituted bioapatite.
Creator: Bunaciu, Camelia Emanuela., Florida Atlantic University, Leventouri, Theodora
Abstract/Description: The effect of silicon (Si) substitution on the structural properties of hydroxyapatite (HAp) is investigated with powder x-ray and neutron diffraction methods. For this purpose, a series of samples of pure hydroxyapatite and 0.4 wt % Si substituted hydroxyapatite were prepared following a precipitation method. Phase identification from x-ray powder diffraction measurements showed a single hydroxyapatite phase in all the samples. Powder neutron diffraction patterns from room temperature down...
Show moreThe effect of silicon (Si) substitution on the structural properties of hydroxyapatite (HAp) is investigated with powder x-ray and neutron diffraction methods. For this purpose, a series of samples of pure hydroxyapatite and 0.4 wt % Si substituted hydroxyapatite were prepared following a precipitation method. Phase identification from x-ray powder diffraction measurements showed a single hydroxyapatite phase in all the samples. Powder neutron diffraction patterns from room temperature down to 15 K are analyzed using the Rietveld method. The refined lattice constants, interatomic distances and isotropic atomic displacement parameters as a function of temperature for the pure and substituted hydroxyapatite are compared.
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Date Issued: 2002
PURL: http://purl.flvc.org/fcla/dt/12879
Subject Headings: X-rays--Diffraction, Neutrons--Diffraction, Hydroxyapatite, Silicon
Format: Document (PDF)

$X-ray and neutron powder diffraction studies of a biocompatible apatite$

Title: X-ray and neutron powder diffraction studies of a biocompatible apatite.
Creator: Papanearchou, Nearchos I., Florida Atlantic University, Leventouri, Theodora
Abstract/Description: The problem of the carbonate substitution in bioapatites is studied via x-ray and neutron powder diffraction. A series of samples of low temperature carbonate hydroxyapatites with varying carbonate content was synthesized. The carbonate solubility in the hydroxyapatite system was studied with x-ray diffraction. The detailed crystal structure parameters of the synthetic carbonate hydroxyapatites were studied as a function of temperature and carbonate content from the analysis of Rietveld...
Show moreThe problem of the carbonate substitution in bioapatites is studied via x-ray and neutron powder diffraction. A series of samples of low temperature carbonate hydroxyapatites with varying carbonate content was synthesized. The carbonate solubility in the hydroxyapatite system was studied with x-ray diffraction. The detailed crystal structure parameters of the synthetic carbonate hydroxyapatites were studied as a function of temperature and carbonate content from the analysis of Rietveld refinements of neutron powder diffraction data. The phosphate tetrahedron is distorted by the carbonate substitution. The tetrahedral bond lengths P-O1 and P-O2 decrease by 2--3%. The atomic displacement parameters (ADPs) of the tetrahedral P, O1, O2, and O3 sites reveal a static disorder in the carbonate hydroxyapatite specimens. The results of the present comparison are consistent with the mechanism of carbonate substitution on the mirror plane of the phosphate tetrahedron.
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Date Issued: 2000
PURL: http://purl.flvc.org/fcla/dt/12719
Subject Headings: Apatite, X-rays--Diffraction, Neutrons--Diffraction
Format: Document (PDF)

Title: Accurate verification of balloon rotation correction for the contura® multi-lumen device for accelerated partial breast irradiation.
Creator: Kyriacou, Andreas, Benda, R., Vargas, C., Lyden, M., Vicini , F., Leventouri, Theodora, Graduate College, Kasper, M.
Date Issued: 2011-04-08
PURL: http://purl.flvc.org/fcla/dt/3171046
Subject Headings: Breast --Cancer --Radiotherapy, Brachytherapy, Breast Neoplasms --surgery
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 EBT-3 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.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013229
Subject Headings: Proton Therapy, Radiotherapy--Measurement, Radiotherapy Planning, Computer-Assisted
Format: Document (PDF)

Title: Effect of Processing Temperature on the Properties of Nanophase Fe-substituted 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 Fe-substituted Hydroxyapatite (Fe-HAp) was studied by using the Rietveld refinement method of powder x-ray (XRD) and neutron diffraction (NPD) patterns. Superconducting QUantum Interference Device (SQUID) magnetometry, transmission electron microscopy (TEM) and x-ray 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 Fe-substituted Hydroxyapatite (Fe-HAp) was studied by using the Rietveld refinement method of powder x-ray (XRD) and neutron diffraction (NPD) patterns. Superconducting QUantum Interference Device (SQUID) magnetometry, transmission electron microscopy (TEM) and x-ray 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 Ca5-xFex(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 two-step co-precipitation 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 Fe-substituted 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.
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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)

FAU Theses and Dissertations (25)	+ -
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