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Pages
- 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.
Show less - 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.
Show less - Date Issued
- 2014
- PURL
- http://purl.flvc.org/fau/fd/FA00005812
- 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, Leventouri, Theodora, Graduate College
- Abstract/Description
-
Purpose: To explore offset values in dose optimization with pencil beam (PB) algorithm to minimize dosimetric differences with plans calculated with Monte Carlo (MC) for lung cancer treatment with Stereotactic Body Radiotherapy (SBRT). Methods: 20 cases of Non-Small Cell Lung Cancer, treated with gated full motion range SBRT were selected. According to the proximity of the Gross Tumor Volume (GTV) to the chest wall, two groups are defined. Treatment plans were created on 4D average intensity...
Show morePurpose: To explore offset values in dose optimization with pencil beam (PB) algorithm to minimize dosimetric differences with plans calculated with Monte Carlo (MC) for lung cancer treatment with Stereotactic Body Radiotherapy (SBRT). Methods: 20 cases of Non-Small Cell Lung Cancer, treated with gated full motion range SBRT were selected. According to the proximity of the Gross Tumor Volume (GTV) to the chest wall, two groups are defined. Treatment plans were created on 4D average intensity projection (AIP) CT set with Brainlab iPlanDose® 4.1.2 planning system. The D97 of PTV was normalized to 50Gy using the fast PB and compared with MC. The optimized plan was then recomputed over each 4D respiratory phase, and compared with MC. Results: The mean difference in the PB and MC D97 of the ITV was 10.5% (±0.8%) of the prescription dose (50Gy). PB algorithm showed 2.3-2.4% less overestimation to the D97 of the ITV, when comparing to MC, in the maximum exhalation phase than in the maximal inhalation phase. Significantly smaller dose difference between PB and MC is also shown in plans for peripheral lesions (7.7 ± 0.7%) versus for central lesions (12.7±0.8%) (p< 0.01). Conclusions: The dosimetric differences between PB and MC can be reasonably predicted depending on the location of lesion in the lung, and may be used as offset value in dose optimization with PB. Caution is suggested when using the maximum inhalation phase for treatment planning.
Show less - Date Issued
- 2014
- PURL
- http://purl.flvc.org/fau/fd/FA00005813
- 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.
Show less - 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.
Show less - 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.
Show less - 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.
Show less - 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.
Show less - 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)
- 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)
- 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.
Show less - Date Issued
- 2000
- PURL
- http://purl.flvc.org/fcla/dt/12718
- Subject Headings
- Rietveld method, Apatite, X-rays--Diffraction
- Format
- Document (PDF)
- 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.
Show less - Date Issued
- 2002
- PURL
- http://purl.flvc.org/fcla/dt/12879
- Subject Headings
- X-rays--Diffraction, Neutrons--Diffraction, Hydroxyapatite, Silicon
- Format
- Document (PDF)
- 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.
Show less - 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
- Dosimetric and radiobiological comparison of CyberKnife M6(TM) InCise multileaf collimator over IRIS(TM) variable collimator in prostate stereotactic body radiation therapy.
- Creator
- Kathriarachchi, Vindu, Shang, Charles, Evans, Grant, Leventouri, Theodora, Kalantzis, Georgios
- Date Issued
- 2016
- PURL
- http://purl.flvc.org/fau/fd/FAUIR000166
- Format
- Citation
