Dissertations / Theses on the topic 'Radiation theray'
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PISANO, FRANCESCA. "The role of the cystectomy and minimally invasive surgery in the complex patient with bladder cancer." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2895636.
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Crosbie, Jeffrey. "Synchrotron microbeam radiation therapy." Monash University. Faculty of Science. School of Physics, 2008. http://arrow.monash.edu.au/hdl/1959.1/64948.
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This thesis presents interdisciplinary, collaborative research in the field of synchrotron microbeam radiation therapy (MRT). Synchrotron MRT is an experimental radiotherapy technique under consideration for clinical use, following demonstration of efficacy in tumour-bearing rodent models with remarkable sparing of normal tissue. A high flux, X-ray beam from a synchrotron is segmented into micro-planar arrays of narrow beams, typically 25 μm wide and with peak-to-peak separations of 200 μm. The radiobiological effect of MRT and the underlying cellular mechanisms are poorly understood. The ratio between dose in the ‘peaks’of the microbeams to the dose in the ‘valleys’, between the microbeams, has strong biological significance. However, there are difficulties in accurately measuring the dose distribution for MRT. The aim of this thesis is to address elements of both the dosimetric and radiobiological gaps that exist in the field of synchrotron MRT. A method of film dosimetry and microdensitometry was adapted in order to measure the peak-to-valley dose ratios for synchrotron MRT. Two types of radiochromic film were irradiated in a phantom and also flush against a microbeam collimator on beamline BL28B2 at the SPring-8 synchrotron. The HD-810 and EBT varieties of radiochromic film were used to record peak dose and valley dose respectively. In other experiments, a dose build-up effect was investigated and the half value layer of the beam with and without the microbeam collimator was measured to investigate the effect of the collimator on the beam quality. The valley dose obtained for films placed flush against the collimator was approximately 0.25% of the peak dose. Within the water phantom, the valley dose had increased to between 0.7–1.8% of the peak dose, depending on the depth in the phantom. We also demonstrated, experimentally and by Monte Carlo simulation, that the dose is not maximal on the surface and that there is a dose build-up effect. The microbeam collimator did not make an appreciable difference to the beam quality. The measured values of peak-to-valley dose ratio were higher than those predicted by previously published Monte Carlo simulation papers. For the radiobiological studies, planar (560 Gy) or cross-planar (2 x 280 Gy or 2 x 560 Gy) irradiations were delivered to mice inoculated with mammary tumours in their leg, on beamline BL28B2 at the SPring-8 synchrotron. Immunohistochemical staining for DNA double strand breaks, proliferation and apoptosis was performed on irradiated tissue sections. The MRT response was compared to conventional radiotherapy at 11, 22 or 44 Gy. The results of the study provides the first evidence for a differential tissue response at a cellular level between normal and tumour tissues following synchrotron MRT. Within 24 hours of MRT to tumour, obvious cell migration had occurred into and out of irradiated zones. MRT-irradiated tumours showed significantly less proliferative capacity by 24 hours post-irradiation (P = 0.002). Median survival times for EMT-6.5 and 67NR tumour-bearing mice following MRT (2 x 560 Gy) and conventional radiotherapy (22 Gy) increased significantly compared to unirradiated controls (P < 0.0005). However, there was markedly less normal tissue damage from MRT than from conventional radiotherapy. MRT-treated normal skin mounts a more coordinated repair response than tumours. Cell-cell communication of death signals from directly irradiated, migrating cells, may explain why tumours are less resistant to high dose MRT than normal tissue.
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Skiöld, Sara. "Radiation induced biomarkers of individual sensitivity to radiation therapy." Doctoral thesis, Stockholms universitet, Institutionen för molekylär biovetenskap, Wenner-Grens institut, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-97123.
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Fifty percent of solid cancers are treated with radiation therapy (RT). The dose used in RT is adjusted to the most sensitive individuals so that not more than 5% of the patients will have severe adverse healthy tissue effects. As a consequence, the majority of the patients will receive a suboptimal dose, as they would have tolerated a higher total dose and received a better tumor control. Thus, if RT could be individualized based on radiation sensitivity (RS), more patients would be cured and the most severe adverse reactions could be avoided. At present the mechanisms behind RS are not known. The long term aim of this thesis was to develop diagnostic tools to assess the individual RS of breast cancer patients and to better understand the mechanisms behind the RS and radiation effects after low dose exposures. The approach was based on the hypothesis that biomarkers of individual RS, in terms of acute adverse skin reactions after breast cancer RT, can be found in whole blood that has been stressed by low doses of ionizing radiation (IR). To reach this goal two different approaches to identify biomarkers of RS have been investigated. A protocol for the analysis of differential protein expression in response to low dose in vitro irradiated whole blood was developed (paper I). This protocol was then used to investigate the proteomic profile of radiation sensitive and normo-sensitive patients, using isotope-coded protein labeled proteomics (ICPL). The results from the ICPL study (paper III) show that the two patient groups have different protein expression profiles both at the basal level and after IR. In paper II the potential biomarker 8-oxo-dG was investigated in serum after IR. The relative levels of IR induced 8-oxo-dG from radiation sensitive patients differ significantly from normo-sensitive patients. This indicates that the sensitive patients differ in their cellular response to IR and that 8-oxo-dG is a potential biomarker for RS.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.
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Fu, Ceji. "Radiative Properties of Emerging Materials and Radiation Heat Transfer at the Nanoscale." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4941.
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A negative index material (NIM), which possesses simultaneously negative permittivity and permeability, is an emerging material that has caught many researchers attention after it was first demonstrated in 2001. It has been shown that electromagnetic waves propagating in NIMs have some remarkable properties such as negative phase velocities and negative refraction and hold enormous promise for applications in imaging and optical communications. This dissertation is centered on investigating the unique aspects of the radiative properties of NIMs. Photon tunneling, which relies on evanescent waves to transfer radiative energy, has important applications in thin-film structures, microscale thermophotovoltaic devices, and scanning thermal microscopes. With multilayer thin-film structures, photon tunneling is shown to be greatly enhanced using NIM layers. The enhancement is attributed to the excitation of surface or bulk polaritons, and depends on the thicknesses of the NIM layers according to the phase matching condition. A new coherent thermal emission source is proposed by pairing a negative permittivity (but positive permeability) layer with a negative permeability (but positive permittivity) layer. The merits of such a coherent thermal emission source are that coherent thermal emission occurs for both s- and p-polarizations, without use of grating structures. Zero power reflectance from an NIM for both polarizations indicates the existence of the Brewster angles for both polarizations under certain conditions. The criteria for the Brewster angle are determined analytically and presented in a regime map. The findings on the unique radiative properties of NIMs may help develop advanced energy conversion devices. Motivated by the recent advancement in scanning probe microscopy, the last part of this dissertation focuses on prediction of the radiation heat transfer between two closely spaced semi-infinite media. The objective is to investigate the dopant concentration of silicon on the near-field radiation heat transfer. It is found that the radiative energy flux can be significantly augmented by using heavily doped silicon for the two media separated at nanometric distances. Large enhancement of radiation heat transfer at the nanoscale may have an impact on the development of near-field thermal probing and nanomanufacturing techniques.
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Bergh, Alphonsus Cornelis Maria van den. "Radiation therapy in pituitary adenomas." [S.l. : [Groningen : s.n.] ; University of Groningen] [Host], 2008. http://irs.ub.rug.nl/ppn/.
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Flejmer, Anna M. "Radiation burden from modern radiation therapy techniques including proton therapy for breast cancer treatment - clinical implications." Doctoral thesis, Linköpings universitet, Avdelningen för kliniska vetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-127370.
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The purpose of this thesis was to study the clinical implications of modern radiotherapy techniques for breast cancer treatment. This was investigated in several individual studies. Study I investigated the implications of using the analytical anisotropic algorithm (AAA) from the perspective of clinical recommendations for breast cancer radiotherapy. Pencil beam convolution plans of 40 breast cancer patients were recalculated with AAA. The latter plans had a significantly worse coverage of the planning target volume (PTV) with the 93% isodose, higher maximum dose in hotspots, higher volumes of the ipsilateral lung receiving doses below 25 Gy and smaller volumes with doses above 25 Gy. AAA also predicted lower doses to the heart. Study II investigated the implications of using the irregular surface compensator (ISC), an electronic compensation algorithm, in comparison to three‐dimensional conformal radiotherapy (3D‐CRT) for breast cancer treatment. Ten breast cancer patients were planned with both techniques. The ISC technique led to better coverage of the clinical target volume of the tumour bed (CTV‐T) and PTV in almost all patients with significant improvement in homogeneity. Study III investigated the feasibility of using scanning pencil beam proton therapy for regional and loco‐regional breast cancer with comparison of ISC photon planning. Ten patients were included in the study, all with dose heterogeneity in the target and/or hotspots in the normal tissues outside the PTV. The proton plans showed comparable or better CTV‐T and PTV coverage, with large reductions in the mean doses to the heart and the ipsilateral lung. Study IV investigated the added value of enhanced inspiration gating (EIG) for proton therapy. Twenty patients were planned on CT datasets acquired during EIG and freebreathing (FB) using photon 3D‐CRT and scanning proton therapy. Proton spot scanning has a high potential to reduce the irradiation of organs‐at‐risk for most patients, beyond what could be achieved with EIG and photon therapy, especially in terms of mean doses to the heart and the left anterior descending artery. Study V investigated the impact of physiological breathing motion during proton radiotherapy for breast cancer. Twelve thoracic patients were planned on CT datasets during breath‐hold at inhalation phase and breath‐hold at exhalation phase. Between inhalation and exhalation phase there were very small differences in dose delivered to the target and cardiovascular structures, with very small clinical implication. The results of these studies showed the potential of various radiotherapy techniques to improve the quality of life for breast cancer patients by limiting the dose burden for normal tissues.
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Francoeur, Mathieu. "NEAR-FIELD RADIATIVE TRANSFER: THERMAL RADIATION, THERMOPHOTOVOLTAIC POWER GENERATION AND OPTICAL CHARACTERIZATION." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/58.
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This dissertation focuses on near-field radiative transfer, which can be defined as the discipline concerned with energy transfer via electromagnetic waves at sub-wavelength distances. Three specific subjects related to this discipline are investigated, namely nearfield thermal radiation, nanoscale-gap thermophotovoltaic (nano-TPV) power generation and optical characterization. An algorithm for the solution of near-field thermal radiation problems in one-dimensional layered media is developed, and several tests are performed showing the accuracy, consistency and versatility of the procedure. The possibility of tuning near-field radiative heat transfer via thin films supporting surface phononpolaritons (SPhPs) in the infrared is afterwards investigated via the computation of the local density of electromagnetic states and the radiative heat flux between two films. Results reveal that due to SPhP coupling, fine tuning of near-field radiative heat transfer is possible by solely varying the structure of the system, the structure being the film thicknesses and their distance of separation. The coexistence of two regimes of near-field thermal radiation between two thin films of silicon carbide is demonstrated via numerical simulations and an asymptotic analysis of the radiative heat transfer coefficient. The impacts of thermal effects on the performances of nano-TPV power generators are investigated via the solution of the coupled near-field thermal radiation, charge and heat transport problem. The viability of nano-TPV devices proposed so far in the literature, based on a tungsten radiator at 2000 K and indium gallium antimonide cell, is questioned due to excessive heating of the junction converting thermal radiation into electricity. Using a convective thermal management system, a heat transfer coefficient as high as 105 Wm-2K-1 is required to maintain the junction at room temperature. The possibility of characterizing non-intrusively, and potentially in real-time, nanoparticles from 5 nm to 100 nm in size via scattered surface wave is explored. The feasibility of the characterization framework is theoretically demonstrated via a sensitivity analysis of the scattering matrix elements. Measurements of the scattering matrix elements for 200 nm and 50 nm gold spherical particles show the great sensitivity of the characterization tool, although an ultimate calibration is difficult with the current version of the experimental set-up.
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Engelbeen, Céline. "The segmentation problem in radiation therapy." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210107.
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The segmentation problem arises in the elaboration of a radiation therapy plan. After the cancer has been diagnosed and the radiation therapy sessions have been prescribed, the physician has to locate the tumor as well as the organs situated in the radiation field, called the organs at risk. The physician also has to determine the different dosage he wants to deliver in each of them and has to define a lower bound on the dosage for the tumor (which represents the minimum amount of radiation that is needed to have a sufficient control of the tumor) and an upper bound for each organ at risk (which represents the maximum amount of radiation that an organ can receive without damaging). Designing a radiation therapy plan that respects these different bounds of dosage is a complex optimization problem that is usually tackled in three steps. The segmentation problem is one of them.Mathematically, the segmentation problem amounts to decomposing a given nonnegative integer matrix A into a nonnegative integer linear combination of some binary matrices. These matrices have to respect the consecutive ones property. In clinical applications several constraints may arise that reduce the set of binary matrices which respect the consecutive ones property that we can use. We study some of them, as the interleaf distance constraint, the interleaf motion constraint, the tongue-and-groove constraint and the minimum separation constraint.
We consider here different versions of the segmentation problem with different objective functions. Hence we deal with the beam-on time problem in order to minimize the total time during which the patient is irradiated. We study this problem under the interleaf distance and the interleaf motion constraints. We consider as well this last problem under the tongue-and-groove constraint in the binary case. We also take into account the cardinality and the lex-min problem. Finally, we present some results for the approximation problem.
/Le problème de segmentation intervient lors de l'élaboration d'un plan de radiothérapie. Après que le médecin ait localisé la tumeur ainsi que les organes se situant à proximité de celle-ci, il doit aussi déterminer les différents dosages qui devront être délivrés. Il détermine alors une borne inférieure sur le dosage que doit recevoir la tumeur afin d'en avoir un contrôle satisfaisant, et des bornes supérieures sur les dosages des différents organes situés dans le champ. Afin de respecter au mieux ces bornes, le plan de radiothérapie doit être préparé de manière minutieuse. Nous nous intéressons à l'une des étapes à réaliser lors de la détermination de ce plan: l'étape de segmentation.
Mathématiquement, cette étape consiste à décomposer une matrice entière et positive donnée en une combinaison positive entière linéaire de certaines matrices binaires. Ces matrices binaires doivent satisfaire la contrainte des uns consécutifs (cette contrainte impose que les uns de ces matrices soient regroupés en un seul bloc sur chaque ligne). Dans les applications cliniques, certaines contraintes supplémentaires peuvent restreindre l'ensemble des matrices binaires ayant les uns consécutifs (matrices 1C) que l'on peut utiliser. Nous en avons étudié certaines d'entre elles comme celle de la contrainte de chariots, la contrainte d'interdiciton de chevauchements, la contrainte tongue-and-groove et la contrainte de séparation minimum.
Le premier problème auquel nous nous intéressons est de trouver une décomposition de la matrice donnée qui minimise la somme des coefficients des matrices binaires. Nous avons développé des algorithmes polynomiaux qui résolvent ce problème sous la contrainte de chariots et/ou la contrainte d'interdiction de chevauchements. De plus, nous avons pu déterminer que, si la matrice donnée est une matrice binaire, on peut trouver en temps polynomial une telle décomposition sous la contrainte tongue-and-groove.
Afin de diminuer le temps de la séance de radiothérapie, il peut être désirable de minimiser le nombre de matrices 1C utilisées dans la décomposition (en ayant pris soin de préalablement minimiser la somme des coefficients ou non). Nous faisons une étude de ce problème dans différents cas particuliers (la matrice donnée n'est constituée que d'une colonne, ou d'une ligne, ou la plus grande entrée de celle-ci est bornée par une constante). Nous présentons de nouvelles bornes inférieures sur le nombre de matrices 1C ainsi que de nouvelles heuristiques.
Finalement, nous terminons par étudier le cas où l'ensemble des matrices 1C ne nous permet pas de décomposer exactement la matrice donnée. Le but est alors de touver une matrice décomposable qui soit aussi proche que possible de la matrice donnée. Après avoir examiné certains cas polynomiaux nous prouvons que le cas général est difficile à approximer avec une erreur additive de O(mn) où m et n représentent les dimensions de la matrice donnée.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Chan, Kin Wa (Karl), University of Western Sydney, of Science Technology and Environment College, and School of Computing and Information Technology. "Lateral electron disequilibrium in radiation therapy." THESIS_CSTE_CIT_Chan_K.xml, 2002. http://handle.uws.edu.au:8081/1959.7/538.
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The radiation dose in radiation therapy is mainly measured by ion chamber. The ion chamber measurement will not be accurate if there is not enough phantom material surrounding the ion chamber to provide the electron equilibrium condition. The lack of electron equilibrium will cause a reduction of dose. This may introduce problems in treatment planning. Because some planning algorithms cannot predict the reduction, they over estimate the dose in the region. Electron disequilibrium will happen when the radiation field size is too small or the density of irradiated material is too low to provide sufficient electrons going into the dose volume. The amount of tissue required to provide electron equilibrium in a 6MV photon beam by three methods: direct calculation from Klein-Nisina equation, measurement in low density material phantom and a Monte Carlo simulation is done to compare with the measurement, an indirect method from a planning algorithm which does not provide an accurate result under lateral electron disequilibrium. When the error starts to happen in such planning algorithm, we know that the electron equilibrium conditions does not exist. Only the 6MV photon beam is investigated. This is because in most cases, a 6MV small fields are used for head and neck (larynx cavity) and 6MV fields are commonly used for lung to minimise uncertainity due to lateral electron at higher energies.Master of Science (Hons)
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Chan, Kin Wa. "Lateral electron disequilibrium in radiation therapy /." View thesis, 2002. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20040507.164802/index.html.
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Thesis (M.Sc.) (Hons)-- University of Western Sydney, 2002."A thesis submitted in fulfillment of the requirements for the Degree of Master of Science (Honours) in Physics at the University of Western Sydney" "September 2002" "Kin Wa (Karl) Chan of Medical Physics Department of Westmead Hospital and the University of Western Sydney"-- t.p. Bibliography: leaves 100-105.
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Ranggård, Nina. "Optimizing Conformity inIntensity Modulated Radiation Therapy." Thesis, KTH, Fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147356.
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Chan, Timothy Ching-Yee. "Optimization under uncertainty in radiation therapy." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40302.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 175-182).
In the context of patient care for life-threatening illnesses, the presence of uncertainty may compromise the quality of a treatment. In this thesis, we investigate robust approaches to managing uncertainty in radiation therapy treatments for cancer. In the first part of the thesis, we study the effect of breathing motion uncertainty on intensity-modulated radiation therapy treatments of a lung tumor. We construct a robust framework that generalizes current mathematical programming formulations that account for motion. This framework gives insight into the trade-off between sparing the healthy tissues and ensuring that the tumor receives sufficient dose. With this trade-off in mind, we show that our robust solution outperforms a nominal (no uncertainty) solution and a margin (worst-case) solution on a clinical case. Next, we perform an in-depth study into the structure of different intensity maps that were witnessed in the first part of the thesis. We consider parameterized intensity maps and investigate their ability to deliver a sufficient dose to the tumor in the presence of motion that follows a Gaussian distribution. We characterize the structure of optimal intensity maps in terms of certain conditions on the problem parameters.
(cont.) Finally, in the last part of the thesis, we study intensity-modulated proton therapy under uncertainty in the location of maximum dose deposited by the beamlets of radiation. We provide a robust formulation for the optimization of proton-based treatments and show that it outperforms traditional formulations in the face of uncertainty. In our computational experiments, we see evidence that optimal robust solutions use the physical characteristics of the proton beam to create dose distributions that are far less sensitive to the underlying uncertainty.
by Timothy Ching-Yee Chan.
Ph.D.
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Brauer-Krisch, E. "Experimental dosimetry for Microbeam Radiation Therapy." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1357933/.
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The thesis gives an overview on the preclinical results in Microbeam Radiation Therapy (MRT), a novel radiation therapy using microscopically small beams. In the first chapter preclinical results and biological observations after Microbeam Radiation Therapy are presented, in particular the normal tissue tolerance is highlighted. A chapter based on theoretical Monte Carlo dose calculations is summarizing a set of data on peak to valley dose ratios (PVDR) and relative dose distributions for various parameter settings, providing some guideline for preclinical studies. The main part of the thesis is focusing on the experimental dosimetry, on one side to measure the high dose rate in the homogenous field proposing the necessary corrections to be applied for absolute dose measurements and on the other side, to measure peak and valley dose. For the high resolution dose measurements of the spatially fractionated beam, results using several types of detectors are presented and discussed. Various results using Gafchromic film dosimetry in combination with a microdensitometer show slightly higher (~10-15 %) valley dose than the MC calculated values. Results of theoretical calculations of output factors and their experimental verification are in very good agreement. The great potential of interlaced Microbeams in an anthropomorphic phantom with one single high dose delivery is discussed, including the technical challenges to be mastered in the future.
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Balsells, Alex T. "Computational Methods for Radiation Therapy Planning." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1557844457085534.
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Dial, Christian W. "Adaptive Radiation Therapy for Lung Cancer." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3579.
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Prognosis for lung cancer patients remains poor. For those receiving radiation therapy, local control and survival have been shown to improve with increased doses; however, deliverable dose is often limited by associated toxicity. Therefore, methods that reduce dose to normal tissues and allow isotoxic escalation are desirable. Adaptive radiation therapy seeks to improve treatment by modifying the initial plan throughout delivery, and has been shown to decrease normal tissue dose. Studies to date suggest a trend of increasing benefit with increases in replanning frequency; however, replanning is costly in terms of workload and past studies implement at most weekly adaptation. The purpose of this thesis is to quantify the benefit associated with daily replanning and characterize the tradeoff between replanning frequency and adaptive benefit. A software tool is developed to facilitate planning studies and to introduce complimentary methods for evaluating adaptive treatments. Synthetic images and contours are xii generated for each fraction of a typical fractionation schedule using principal component analysis and a novel method of sampling coefficients that preserves temporal trends in the data (e.g. tumor regression). Using the synthetic datasets, a series of adaptive schedules ranging from no adaption to daily replanning are simulated and compared to quantify adaptive benefits and characterize tradeoffs with frequency. Daily replanning resulted in significant reductions in all normal tissue planning metrics when compared to no adaptation, and incremental reductions were observed with each increase in replanning frequency while the magnitude of average reductions decreased with each step. Modest correlation between absolute change in planning target volume over the course of treatment and reductions in both mean lung dose and mean esophageal dose were observed.
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Scott, Susan Lynne Pipes. "Enhancing radiation therapy for prostate cancer /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
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Mueller, Marco. "Direct tumour tracking during radiation therapy." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29450.
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Lung cancer stereotactic ablative body radiation therapy is one of the cancer treatment success
stories. However, treatment outcomes and efficacy are limited by the fact that patients move,
breathe, and their hearts beat, causing tumour and healthy tissue motion during imaging and radiation
treatment.
Direct tumour tracking is a novel method to visualise tumours during radiation therapy to improve
treatment accuracy and healthy tissue sparing in the presence of internal anatomic motion. Direct
tumour tracking is an affordable technology that is compatible with 95% of existing radiation therapy
systems and can improve the outcomes of cancer patients globally. Avoiding the cost and risk of
surgically inserted fiducial markers, direct tumour tracking provides the ability to track tumour motion
on a conventional linear accelerator at the time that is needed most – in real-time during radiation
treatment delivery.
This work removes several barriers to widespread clinical implementation of direct tumour tracking
by addressing and delivering solutions for four research topics: (i) the development of a clinically
feasible approach for direct tumour tracking using intra-fraction kilovoltage projections, (ii) the
integration into the lung cancer radiation therapy workflow on a conventional linear accelerator and
the preparation for deployment in clinical trials, (iii) the proof of feasibility to track tumour and organsat-
risk simultaneously and (iv) the benchmarking of the global direct tumour tracking landscape to
enable the placement of new technologies and further assist the safe clinical implementation of direct
tumour tracking globally. This work paves the way for the widespread clinical use of image-guided
radiation therapy on conventional linear accelerators.
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Fitzgerald, Rhys J. "A comparison of volumetric modulated arc therapy (VMAT), intensity modulated radiation therapy (IMRT) and 3-dimensional conformal radiation therapy (3DCRT) for stereotactic ablative radiation therapy (SABR) for early stage lung cancer." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/99826/4/Rhys_Fitzgerald_Thesis.pdf.
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This thesis is a comparative study looking at different radiation therapy treatment techniques for treating early stage lung cancer. It investigated three different techniques that had differing number of beams and treatment angles. Furthermore, it also look at beams that rotated, against beams that were stationary. It was discovered that multiple beams that continuously rotate around the patient provided optimal dose to the tumour, minimum dose to surrounding healthy tissues and had the quickest delivery time.
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Fan, Qiyong. "Emission guided radiation therapy: a feasibility study." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37277.
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Accurate tumor tracking remains as a major challenge in radiation therapy. Large margins are added to the clinical target volume (CTV) to ensure the treatment of tumor in presence of patient setup uncertainty and that caused by intra-motion. Fiducial seeds and calypso markers are commonly implanted into the disease sites to further reduce the dose delivery error due to tumor motion. For more accurate dose delivery and improved patient comfort, the use of radioactive tracers in positron emission tomography (PET) as non-invasive tumor markers has been proposed - a concept called emission-guided radiation therapy (EGRT). Instead of using images obtained from a stand-alone PET scanner for treatment guidance, we mount a positron imaging system on a radiation therapy machine. Such an EGRT system is able to track the tumor in real time based on the lines of response (LOR) of the tumor positron events, and perform radiation therapy simultaneously. In this work, we illustrate the EGRT concept using computer simulations and propose a typical treatment scheme. EGRT's advantage on increased dose delivery accuracy is demonstrated using a pancreas tumor case and a lung tumor case without the setup margin and motion margin. The emission process is simulated by Geant4 Application for Tomographic Emission package and Linac dose delivery is simulated using a voxel-based Monte Carlo algorithm. The tumor tracking error can be controlled within 2 mm which indicates margins can be significantly reduced. The dose distributions show that the proposed EGRT can accurately deliver the prescribed dose to the CTV with much less margins. Although still in a preliminary research stage, EGRT has the potential to substantially reduce tumor location uncertainties and to greatly increase the performance of current radiation therapy.
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Wong, Tony Po Yin, and tony wong@swedish org. "Improving Treatment Dose Accuracy in Radiation Therapy." RMIT University. Applied Sciences, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080104.144139.
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The thesis aims to improve treatment dose accuracy in brachytherapy using a high dose rate (HDR) Ir-192 stepping source and in external beam therapy using intensity modulated radiation therapy (IMRT). For HDR brachytherapy, this has been achieved by investigating dose errors in the near field and the transit dose of the HDR brachytherapy stepping source. For IMRT, this study investigates the volume effect of detectors in the dosimetry of small fields, and the clinical implementation and dosimetric verification of a 6MV photon beam for IMRT. For the study of dose errors in the near field of an HDR brachytherapy stepping source, the dose rate at point P at 0.25 cm in water from the transverse bisector of a straight catheter was calculated with Monte Carlo code MCNP 4.A. The Monte Carlo (MC) results were used to compare with the results calculated with the Nucletron Brachytherapy Planning System (BPS) formalism. Using the MC calculated radial dose function and anisotropy function with the BPS formalism, 1% dose calculation accuracy can be achieved even in the near field with negligible extra demand on computation time. A video method was used to analyse the entrance, exit and the inter-dwell transit speed of the HDR stepping source for different path lengths and step sizes ranging from 2.5 mm to 995 mm. The transit speeds were found to be ranging from 54 to 467 mm/s. The results also show that the manufacturer has attempted to compensate for the effects of inter-dwell transit dose by reducing the actual dwell time of the source. A well-type chamber was used to determine the transit doses. Most of the measured dose differences between stationary and stationary plus inter-dwell source movement were within 2%. The small-field dosimetry study investigates the effect of detector size in the dosimetry of small fields and steep dose gradients with a particular emphasis on IMRT measurements. Due to the finite size of the detector, local discrepancies of more than 10 % are found between calculated cross profiles of intensity modulated beams and intensity modulated profiles measured with film. A method to correct for the spatial response of finite sized detectors and to obtain the
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Chapman, Alison. "Dosimetric verification of intensity modulated radiation therapy." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20061026.141700/index.html.
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Fan, Qiyong. "Emission guided radiation therapy: a feasibility study." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52153.
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The effectiveness of cancer treatment is compromised by the need to reduce the uncertainties originating from a variety of factors including tumor volume delineation, patient setup, and irregular physiologic motion. In particular, effective yet practical tumor motion management remains a major challenge in current external beam radiation therapy. Many strategies such as motion encompassment, breath-hold techniques, and respiratory gating have been proposed in the literature and implemented clinically. These methods have shown success in certain situations with different limitations. With the advent of image guided radiation therapy, real-time tumor tracking methods have become popular in clinics to proactively address the challenge with on-board tumor localization. Nevertheless, such techniques rely on surrogate signals and have been reported vulnerable to errors. In this dissertation, EGRT is proposed as a new modality for effective and practical management strategy of cancer treatment uncertainties. One implementation of EGRT is to use PET emissions in real-time for direct tumor tracking during radiation delivery. Radiation beamlets are delivered along PET lines of response by a fast rotating ring therapy unit consisting of a linear accelerator and PET detectors. A complete treatment scheme with capabilities of accurate tumor tracking and dose planning is proposed to implement this EGRT concept. Simulation studies with physical phantom, 4D digital patient model, and clinical patient datasets are carefully designed to evaluate the feasibility and performance of EGRT. We show that with the capabilities of achieving both tumor tracking and sophisticated intensity modulation, EGRT has the potential to enable an effective implementation of 4D radiation therapy with true biological targeting and other advantages.
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Cutter, David J. "Radiation-related cardiovascular disease following cancer therapy." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:3f02ca87-530d-4ee7-9382-4b457bec62b5.
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Introduction: Some cancer survivors are known to have an elevated risk of morbidity and mortality from cardiovascular disease. An important cause of this elevated risk is recognised to be irradiation of normal tissues during radiotherapy received as part of cancer therapy. There are substantial difficulties in studying radiation-related cardiovascular disease (RRCD). The reasons for this include the complexities of measuring radiation normal tissue doses retrospectively and the prolonged latencies of many of the cardiovascular endpoints. A variety of complimentary research methodologies can help provide additional knowledge to guide the appropriate management of patients treated in the past and of new patients in the future. Methods: 1) A cohort study of mortality from circulatory disease in the nationwide British Childhood Cancer Survivor Study (BCCSS). 2) A case-control study of valvular heart disease (VHD) in Dutch Hodgkin lymphoma (HL) survivors, including retrospective radiation dosimetry to estimate the radiation dose to heart valves. 3) A dosimetric study of cardiovascular radiation doses in patients entered into the UK NCRI Lymphoma Study Group RAPID trial, including predictions of 15-year cardiac mortality using innovative methods. 4) A modelling study to predict mean whole heart dose (MWHD) from involved field radiotherapy (IFRT) for HL using anatomical measures. 5) A prospective study using cardiovascular magnetic resonance (CMR) imaging to characterise the heart in women receiving radiotherapy for breast cancer. Results: 1) The risks of all types of circulatory mortality are elevated in survivors of childhood cancer. The absolute excess risks continue to increase 40+ years following diagnosis. The risk of death from cardiomyopathy and heart failure increased substantially with the introduction of anthracycline chemotherapy. There is no evidence of a reduction in risk of circulatory mortality in more recent eras of diagnosis. 2) There is a strong relationship between estimated radiation dose to the affected heart valve and the risk of subsequent VHD (p<0.001). This effect was modelled to allow prediction of the risk of VHD. 3) A proportion of patients treated with IFRT received a substantial cardiac radiation dose (MWHD = 8.8 Gy, SD = 5.6) but, on average, the predicted 15-year cardiac mortality following treatment is low (absolute risk 0.2%, range 0.0 to 2.7%). 4) It is possible to estimate the mean whole heart dose from IFRT prior to detailed radiotherapy planning based on pre-treatment diagnostic imaging to an accuracy of 5-6% of the prescribed dose. 5) Although women received low cardiac doses (MWHD = 1.5 Gy, SD = 0.8) and have a low predicted risk of cardiac radiation-related morbidity and mortality, there is some evidence of subclinical effects on strain and strain rate imaging of the anterior portions of the left ventricle that receive the highest radiation dose. Conclusions: Using a variety of methods these studies have all succeeded in adding to knowledge about the nature, magnitude and timing of RRCD. This knowledge can be used to help the future management of cancer patients. In addition, each of the studies has natural and planned extensions and will continue to contribute further knowledge into the future.
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Andersson, Björn. "Mathematical Optimization of Radiation Therapy Goal Fulfillment." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-325396.
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Cancer is one of the deadliest diseases today, and with increasingly larger and older populations, cancer constitutes an enormous contemporary and future challenge. Luckily, advances in technology and medicine are continuously contributing to a decrease in cancer mortality, and to the reduction of treatment side effects. The aim of this Master's thesis is to be a part of these advances, thereby increasing the survival chances and well-being of future cancer patients. The thesis regards specifically the improvement of radiation therapy, a form of treatment utilized in both curative and palliative cancer care. In radiation therapy, ionizing radiation is directed at cancerous cells in the body. The radiation prevents the further proliferation of malignant cells by damaging their DNA. However, the radiation is also harmful to healthy cells. It is therefore of utmost importance that the irradiation of the patient is done in such a way to spare the critical organs in the vicinity of the tumor. To obtain the best possible treatment, mathematical optimization algorithms are utilized. Using physical models of how radiation travels in the body, it is possible to calculate what effect the irradiation of the patient will have. To quantify the quality of the treatment, mathematical functions are used, which evaluate the radiation dose under certain criteria. Once these functions are defined, algorithms can be applied that find the optimal treatment with regard to the given criteria. The formulation of these functions and their properties is the main focus of this thesis. Using clinical evaluation criteria previously used to assess treatments, a framework for optimizing functions that directly correlate to the clinical goals is constructed. The framework is examined and used to generate radiation therapy plans for three cancer patients. In each of the cases, the constructed treatment plans demonstrate high quality, often better than or comparable to the plans created by experienced dose planners using existing tools. A particularly interesting application of the developed framework is the automatic generation of treatments. This relies on the clinician giving the clinical goals as input to the algorithm. A plan is then generated with maximal goal fulfillment. This eliminates the tedious and time consuming process of parameter tuning to achieve a satisfactory plan. Several studies have demonstrated the ability of automatic planning to retain the plan quality while substantially improving planning efficiency.
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Dou, Xin Wu Xiaodong. "New algorithms for target delineation and radiation delivery in intensity-modulated radiation therapy." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/354.
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Dou, Xin. "New algorithms for target delineation and radiation delivery in intensity-modulated radiation therapy." Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/354.
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Intensity modulated radiation therapy (IMRT) is a modern cancer therapy technique that aims to deliver a highly conformal radiation dose to a target tumor while sparing the surrounding normal tissues. The prescribed dose is specified by an intensity map (IM) matrix and often delivered by a multileaf collimator (MLC).
In this thesis, we study a set of combinatorial optimization problems arising in the field of IMRT: 1) the auto-contouring problems using region properties, which aim to optimize the intraclass variance of the target objects; 2) the field decomposition problems, whose goal is to decompose a "complex" IM to the sum of two "simpler" sub-IMs such that the two sub-IMs are delivered in orthogonal directions to improve the delivery efficiency; 3) the field splitting problems, which seek to split a large IM that can not be directly delivered by MLC into several separate sub-IMs of size no larger than the given MLC size and the delivery effectiveness is optimized.
Our algorithms are based on combinatorial techniques - mostly graph-based algorithms. We strive to find the globally optimal solution efficiently - in a linear or low polynomial time. In the case that the exact algorithm is not efficient enough, an approximation algorithm is also developed for solving the problem.
We have implemented all the proposed algorithms and experimented on computer-generated phantoms and clinical data. Comparing with results supervised by experts, the auto-contouring algorithms yield highly accurate results for all tested datasets. The field decomposition and field splitting methods produce treatment plans of much better quality while comparing with the state-of-the-art commercial treatment planning system.
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Anstett, Anne. "Approach of combined cancer gene therapy and radiation : Response of promoters to ionizing radiation." Université Louis Pasteur (Strasbourg) (1971-2008), 2005. https://publication-theses.unistra.fr/public/theses_doctorat/2005/ANSTETT_Anne_2005.pdf.
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La thérapie génique est un moyen de traitement du cancer. Cette étude s'intéresse au développement d'un système de thérapie génique induit par les radiations ionisantes (RI) dans le but de radiosensibiliser les cellules vasculaires. Un système d'expression basé sur l'utilisation de promoteurs induits par les irradiations va permettre l'expression de gènes anti-tumoraux dans le réseau vasculaire tumoral. Le développement des tumeurs solides est dépendant de l'angiogénèse, un processus dans lequel de nouveaux vaisseaux sanguins sont générés à partir d'une vascularisation pré-existante. De part leur stabilité génétique, les cellules endothéliales représentent une cible efficace pour l'introduction de tels vecteurs géniques thérapeutiques. L'identification de promoteurs induits par les RI, endogènes aux cellules endothéliales, a été menée suite à une étude des profils d'expression utilisant la technologie des puces à ADN. Les gènes modulés par des doses cliniques de RI ont été décrits. L'utilisation de fortes doses de RI a pour but d'étudier l'effet d'une dose totale de RI délivrée dans les tumeurs. La radio-induction de gènes sélectionnés pour l'étude de promoteurs a été confirmée par RT-PCR. Cette étude a montré que des promoteurs natifs clonés dans des plasmides rapporteurs ne sont pas utilisables en tant que tels en thérapie génique du cancer, limités par leur trop faibles inductions en réponses aux RI. A l'opposé, des promoteurs synthétiques contenant des sites répétés spécifiques pour la fixation de facteurs de transcriptions tels que NF-κB sont de bons candidats en vue d'une utilisation en thérapie génique. L'activité de cinq éléments TGGGGACTTTCCGC placés en tandem a été augmentée d'une manière dose-dépendente. De plus, la réponse à de faibles doses thérapeutiques fractionnées a été augmentée en comparaison à une même dose unique. Une application du promoteur synthétique de fixation pour NF-κB est envisageable dans le traitement radio-thérapeutique du cancerGene therapy is an emerging cancer treatment modality. We are interested in developing a radiation-inducible gene therapy system to sensitize the tumor vasculature to the effects of ionizing radiation (IR) treatment. An expression system based on irradiation-inducible promoters will drive the expression of anti-tumor genes in the tumor vasculature. Solid tumors are dependent on angiogenesis, a process in which new blood vessels are formed from the pre-existing vasculature. Vascular endothelial cells are untransformed and genetically stable, thus avoiding the problem of resistance to the treatments. Vascular endothelial cells may therefore represent a suitable target for this therapeutic gene therapy strategy. The identification of IR-inducible promoters native to endothelial cells was performed by gene expression profiling using cDNA microarray technology. We describe the genes modified by clinically relevant doses of IR. The extension to high doses aimed at studying the effects of total radiation delivery to the tumor. The radio-inducibility of the genes selected for promoter study was confirmed by RT-PCR. Analysis of the activity of promoters in response to IR was also assessed in a reporter plasmid. We found that authentic promoters cloned onto a plasmid are not suitable for cancer gene therapy due to their low induction after IR. In contrast, synthetic promoters containing repeated sequence-specific binding sites for IR-activated transcription factors such as NF-κB are potential candidates for gene therapy. The activity of five tandemly repeated TGGGGACTTTCCGC elements for NF-κB binding in a luciferase reporter was increased in a dose-dependent manner. Interestingly, the response to fractionated low doses was improved in comparison to the total single dose. Thus, we put present evidence that a synthetic promoter for NF-κB specific binding may have application in the radio-therapeutic treatment of cancer
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Tanny, Sean M. "Investigation of Radiation Protection Methodologies for Radiation Therapy Shielding Using Monte Carlo Simulation and Measurement." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1449853114.
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Shin, Naomi. "Modeling secondary cancer risk following paediatric radiotherapy: a comparison of intensity modulated proton therapy and photon therapy." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106431.
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Proton radiotherapy is known to reduce the radiation dose delivered to normal healthy tissue compared to photon techniques. The increase in normal tissue sparing could result in fewer acute and late effects from radiation therapy. In this work proton therapy plans were created for patients previously treated using photon therapy. Intensity modulated proton therapy (IMPT) plans were planned using inverse planning in Varian's Eclipse treatment planning system with a scanning proton beam model to the same relative biological effectiveness (RBE)-weighted prescription dose as the photon plan. Proton and photon plans were compared for target dose conformity and homogeneity, body volumes receiving 2 Gy and 5 Gy, integral dose, dose to normal tissues and second cancer risk. Secondary cancer risk was determined using two methods. The relative risk of secondary cancer was found using the method described by Nguyen et al. by applying a linear relationship between integral dose and relative risk of secondary cancer. The second approach used Schneider et al.'s organ equivalent dose concept to describe the dose in the body and then calculate the excess absolute risk and cumulative risk for solid cancers in the body.IMPT and photon plans had similar target conformity and homogeneity. However IMPT plans had reduced integral dose and volumes of the body receiving low dose. Overall the risk of radiation induced secondary cancer was lower for IMPT plans compared to the corresponding photon plans with a reduction of ~36% using the integral dose model and ~50% using the organ equivalent dose model.Un avantage connu de la radiothérapie par protons est la réduction de la dose reçue par les tissus normaux et sains par rapport aux traitements en photons. Cette réduction de dose peut résulter en une diminution des effets aigus et tardifs de la radiothérapie. Dans cet ouvrage, les plans de protonthérapie ont été créés pour des patients ayant été traités par radiothérapie en photons. Les plans de protonthérapie conformationnelle avec modulation d'intensité (PCMI) ont été conçus par planification inverse dans le système de planification de traitement Eclipse de Varian de façon à ce que le faisceau de protons en balayage produise la même dose de prescription que plan en photons, tout en tenant compte des efficacités biologiques relatives des deux types de radiation. Les plans en photons et en protons ont ensuite été comparés en termes de conformité de la dose, d'homogénéité de la dose, de volumes recevant 2 et 5 Gy, de dose intégrale, de dose aux tissus normaux et de risque de cancer secondaire. Le risque relatif de cancer secondaire a été determiné par la méthode décrite par Nguyen et al. en applicant une relation linéaire entre la dose intégrale et le risque relatif de cancer secondaire. Une deuxième approche employée dans cet ouvrage utilise le concept de dose équivalente à un organe de Schneider et al. pour décrire la dose dans le corps et par la suite calculer l'excès de risque absolu et le risque cumulatif de cancers solides dans le corps. Les traitements comparés, soit en photons et en protons, ont démontré une conformité et une homogénéité de la dose similaires dans le volume cible. Toutefois, les plans de PCMI réduisent la dose intégrale et diminuent les volumes du corps recevant une faible dose. Globalement, le risque d'induction d'un cancer secondaire est plus faible pour les plans de PCMI que pour les plans équivalents en photons avec une réduction de ~36% en utilisant le modèle de dose intégrale et ~50% en utilisant le modèle de dose équivalente à un organe.
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Bäck, Sven Å J. "Implementation of MRI gel dosimetry in radiation therapy." Malmö : Lund : Malmö University Hospital ; Lund University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/68945079.html.
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Olofsson, Lennart. "Energy and intensity modulated radiation therapy with electrons." Doctoral thesis, Umeå : Department of Radiation Sciences, Radiation Physics, Umeå University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-491.
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Carlsson, Fredrik. "Utilizing Problem Structure in Optimization of Radiation Therapy." Doctoral thesis, Stockholm : Matematik, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4689.
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Testa, Mauro. "Charged particle therapy, ion range verification, prompt radiation." Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00566188.
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This PhD thesis reports on the experimental investigation of the prompt photons created during the fragmentation of the carbon beam used in particle therapy. Two series of experiments have been performed at the GANIL and GSI facilities with 95 MeV/u and 305 MeV/u 12C6+ ion beams stopped in PMMA and water phantoms. In both experiments a clear correlation was obtained between the C-ion range and the prompt photon profile. A major issue of these measurements is the discrimination between the prompt photon signal (which is correlated with the ion path) and a vast neutron background uncorrelated with the Bragg-Peak position. Two techniques are employed to allow for this photon-neutron discrimination: the time-of-flight (TOF) and the pulse-shape-discrimination (PSD). The TOF technique allowed demonstrating the correlation of the prompt photon production and the primary ion path while the PSD technique brought great insights to better understand the photon and neutron contribution in TOF spectra. In this work we demonstrated that a collimated set-up detecting prompt photons by means of TOF measurements, could allow real-time control of the longitudinal position of the Bragg-peak under clinical conditions. In the second part of the PhD thesis a simulation study was performed with Geant4 Monte Carlo code to assess the influence of the main design parameters on the efficiency and spatial resolution achievable with a multidetector and multi-collimated Prompt Gamma Camera. Several geometrical configurations for both collimators and stack of detectors have been systematically studied and the considerations on the main design constraints are reported.
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Jain, Suneil. "Gold nanoparticles as novel sensitisers for radiation therapy." Thesis, Queen's University Belfast, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534722.
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Ramakrishnan, Jagdish. "Dynamic optimization of fractionation schedules in radiation therapy." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82181.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 145-156).
In this thesis, we investigate the improvement in treatment effectiveness when dynamically optimizing the fractionation scheme in radiation therapy. In the first part of the thesis, we consider delivering a different dose each day depending on the observed patient anatomy. Given that a fixed prescribed dose must be delivered to the tumor over the course of the treatment, such an approach results in a lower cumulative dose to a radio-sensitive organ-at-risk when compared to that resulting from standard fractionation. We use the dynamic programming algorithm to solve the problem exactly. Next, we suggest an approach which optimizes the fraction size and selects a treatment plan from a plan library. Computational results from patient datasets indicate this approach is beneficial. In the second part of the thesis, we analyze the effect of repopulation on the optimal fractionation scheme. A dynamic programming framework is developed to determine an optimal fractionation scheme based on a model of cell kill due to radiation and tumor growth in between treatment days. We prove that the optimal dose fractions are increasing over time. We find that the presence of accelerated tumor repopulation suggests larger dose fractions later in the treatment to compensate for the increased tumor proliferation.
by Jagdish Ramakrishnan.
Ph.D.
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Watkins, W. Tyler. "Optimization of Radiation Therapy in Time-Dependent Anatomy." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3069.
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The objective of this dissertation is to develop treatment planning techniques that have the potential to improve radiation therapy of time-dependent (4D) anatomy. Specifically, this study examines dose estimation, dose evaluation, and decision making in the context of optimizing lung cancer radiation therapy. Two methods of dose estimation are compared in patients with locally advanced and early stage lung cancer: dose computed on a single image (3D-dose) and deformably registered, accumulated dose (or 4D-dose). The results indicate that differences between 3D- and 4D- dose are not significant in organs at risk (OARs), however, 4D-dose to a moving lung cancer target can deviate from 3D-dose. These differences imply that optimization of the 4D-dose through multiple-anatomy optimization (MAO) can improve radiation therapy in 4D-anatomy. MAO incorporates time-dependent target and OAR geometry while enabling a simple, clinically realizable delivery. MAO has the potential to enhance the therapeutic ratio in terms of target coverage and OAR sparing in 4D-anatomy. In dose evaluation within 4D-anatomy; dose-to-mass is a more intuitive and precise metric in estimating the effects of radiation in tissues. Assuming physical density is proportional to functional tissue density, dose-to-mass has a 1-1 correspondence with radiation damage. Dose-to-mass optimization boosts dose in massive regions of lung cancer targets and can reduce integral dose to lung by preferentially treating through regions of low-density lung tissue. Finally, multi-criteria optimization (MCO) is implemented in order to clarify decision making during plan design for lung cancer treatment. An MCO basis set establishes a patient-specific decision space which reveals trade-offs in OAR-dose at a fixed, constrained target dose. By interpolating the MCO basis set and evaluating the plan on 4D-anatomy, patient- and organ- specific conservatism in plan design can be expressed in real time. Through improved methods of dose estimation, dose evaluation, and decision making, this dissertation will positively impact radiation therapy of time-dependent anatomy.
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Zhou, Jining. "ORGAN MOTION AND IMAGE GUIDANCE IN RADIATION THERAPY." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1681.
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Organ motion and inaccurate patient positioning may compromise radiation therapy outcome. With the aid of image guidance, it is possible to allow for a more accurate organ motion and motion control study, which could lead to the reduction of irradiated healthy tissues and possible dose escalation to the target volume to achieve better treatment results. The studies on the organ motion and image guidance were divided into the following four sections. The first, the interfractional setup uncertainties from day-to-day treatment and intrafractional internal organ motion within the daily treatment from five different anatomic sites were studied with Helical TomoTherapy unit. The pre-treatment mega voltage computed tomography (MVCT) provided the real-time tumor and organ shift coordinates, and can be used to improve the accuracy of patient positioning. The interfractional system errors and random errors were analyzed and the suggested margins for HN, brain, prostate, abdomen and lung were derived. The second, lung stereotactic body radiation therapy using the MIDCO BodyLoc whole body stereotactic localizer combined with TomoTherapy MVCT image guidance were investigated for the possible target and organ motion reduction. The comparison of 3D displacement with and without BodyLoc immobilization showed that, suppression of internal organ motion was improved by using BodyLoc in this study. The third, respiration related tumor motion was accurately studied with the four dimensional computed tomography (4DCT). Deformable registration between different breathing phases was performed to estimate the motion trajectory for lung tumor. Optimization is performed by minimizing the mean squared difference in intensity, and is implemented with a multi-resolution, gradient descent procedure. The fourth, lung tumor mobility and dosimetric benefits were compared with different PTV obtained from 3DCT and 4DCT. The results illustrated that the PTV3D not only included excess normal tissues but also might result in missed target tissue. The normal tissue complication probability (NTCP) from 4D plan was statistically significant smaller than 3D plan for both ipsilateral lung and heart.
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Shao, Wei. "Improving functional avoidance radiation therapy by image registration." Diss., University of Iowa, 2019. https://ir.uiowa.edu/etd/7031.
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Radiation therapy (RT) is commonly used to treat patients with lung cancer. One of the limitations of RT is that irradiation of the surrounding healthy lung tissues during RT may cause damage to the lungs. Radiation-induced pulmonary toxicity may be mitigated by minimizing doses to high-function lung tissues, which we refer to as functional avoidance RT. Lung function can be computed by image registration of treatment planning four-dimensional computed tomography (4DCT), which we refer to as CT ventilation imaging. However, the accuracy of functional avoidance RT is limited by lung function imaging accuracy and artifacts in 4DCT. The goal of this dissertation is to improve the accuracy of functional avoidance RT by overcoming those two limitations.
A common method for estimating lung ventilation uses image registration to align the peak exhale and inhale 3DCT images. This approach called the 2-phase local expansion ratio is limited because it assumes no out-of-phase lung ventilation and may underestimate local lung ventilation. Out-of-phase ventilation occurs when regions of the lung reach their maximum (minimum) local volume in a phase other than the peak of inhalation (end of exhalation). This dissertation presents a new method called the N-phase local expansion ratio for detecting and characterizing locations of the lung that experience out-of-phase ventilation. The N-phase LER measure uses all 4DCT phases instead of two peak phases to estimate lung ventilation. Results show that out-of-phase breathing was common in the lungs and that the spatial distribution of out-of-phase ventilation varied from subject to subject. On average, 49% of the out-of-phase regions were mislabeled as low-function by the 2-phase LER. 4DCT and Xenon-enhanced CT (Xe-CT) of four sheep were used to evaluate the accuracy of 2-phase LER and N-phase LER. Results show that the N-phase LER measure was more correlated with the Xe-CT than the 2-phase LER measure. These results suggest that it may be better to use all 4DCT phases instead of the two peak phases to estimate lung function.
The accuracy of functional avoidance RT may also be improved by reducing the impact of artifacts in 4DCT. In this dissertation, we propose a a geodesic density regression (GDR) algorithm to correct artifacts in one breathing phase by using artifact-free data in corresponding regions of the other breathing phases. Local tissue density change associated with CT intensity change during respiration is accommodated in the GDR algorithm. Binary artifact masks are used to exclude regions of artifacts from the regression, i.e., the GDR algorithm only uses artifact-free data. The GDR algorithm estimates an artifact-free CT template image and its time flow through a respiratory cycle. Evaluation of the GDR algorithm was performed using both 2D CT time-series images with simulated known motion artifacts and treatment planning 4DCT with real motion artifacts. The 2D results show that there is no significant difference (p-value = 0.95) between GDR regression of artifact data using artifact masks and regression of artifact-free data. In contrast, significant errors (p-value = 0.005) were present in the estimated Jacobian images when artifact masks were not used. We also demonstrated the effectiveness of the GDR algorithm for removing real duplication, misalignment, and interpolation artifacts in 4DCT.
Overall this dissertation proposes methods that have the potential to improve functional avoidance RT by accommodating out-of-phase ventilation, and removing motion artifacts in 4DCT using geodesic image regression.
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Reynard, Dimitri. "Development of Accurate Dosimetry for Microbeam Radiation Therapy." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAS038/document.
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L’utilisation de petits champs dans les techniques de radiothérapie a considérablement augmenté, en particulier dans les traitements stéréotaxiques et les grands champs uniformes ou non uniformes qui sont composés de petits champs tels que la radiothérapie à modulation d’intensité (IMRT) ou la radiothérapie par microfaisceaux. Pour ces champs d’irradiation, les erreurs dosimétriques ont augmenté par rapport aux faisceaux conventionnels. La raison principale en est qu’il n’existe pas de protocole dosimétrique standard. Dans le cas de la MRT, un protocole dédié a été développé sur la base d’une mesure de faisceau large avec une chambre d’ionisation PinPoint combinée à la multiplication avec un OF pour prédire la dose dans le pic. Ce protocole est pratique en ce sens qu’il permet de surmonter le manque de résolution spatiale du détecteur et de toute façon d’aller de l’avant avec les procédures pré-cliniques en permettant le calcul de la dose pic. La dose dans la vallée est ensuite récupérée à l’aide du PVDR, également basé sur des calculs MC.Au cours de la dernière décennie, des détecteurs à haute résolution spatiale permettant des mesures à l’échelle du micron sont devenus disponibles. Parmi eux, le détecteur de microdiamants PTW, les films HDV2 combinés avec le système de lecture approprié et le FNTD. Les mesures effectuées sur la ligne de lumière biomédical ID 17 avec ces trois dosimètres ont mis en évidence des divergences entre les valeurs simulées MC de OF et PVDR et les données expérimentales qui traitent d’un problème concernant la validité du protocole de dosimétrie actuel. En outre, il a été souligné que les valeurs OF et PVDR différent entre les différents codes MC, ce qui représente un problème lorsque ces valeurs sont associé au protocole de dosimétrie. Obtenir des valeurs fiables d’OF et de PVDR pour les mesures expérimentales et numériques représente le défi de ce travail.Dans ce travail, les écarts entre les simulations MC et les données mesurées sont attribués à un manque de détails dans les simulations MC et au fait que les caractéristiques spécifiques du détecteur peuvent influencer la mesure. Une série de simulations MC est mise au point pour quantifier chacun de ces effets. Le principal inconvénient d'une telle étude est le temps de simulation, de sorte que des astuces sont utilisées pour accélérer le calcul et néanmoins garder les résultats aussi précis que possibleThe use of small fields in radiotherapy techniques has increased substantially, in particular in stereotactic treatments and large uniform or nonuniform fields that are composed of small fields such as for intensity modulated radiation therapy (IMRT) or Microbeam Radiation Therapy. For these irradiation fields, dosimetric errors have increased compared to conventional beams. The main reason for this is that no standard dosimetric protocol exists. In the case of MRT, a dedicated protocol has been developed based on a broad beam measurement with a PinPoint chamber combined with the multiplication with an OF to predict the peak dose. This protocol is handy in the sense that it allows to overcome the lack of spatial resolution of the detector and anyway move forward with pre-clinical procedures by enabling the calculation of the peak dose. The valley dose is then retrieved using the PVDR also based on MC calculations.Over the last decade, detectors with high spatial resolution allowing measurements at the micron scale became available. Among them, the PTW microDiamond detector, HDV2 films combined with the appropriate read-out system and FNTD. Measurements performed at the ID 17 biomedical beamline with these three dosimeters highlighted discrepancies between the MC simulated values of OF and PVDR and experimental data which addresses an issue regarding the validity of the current dosimetry protocol. Moreover, it has been highlighted that OF and PVDR values differ between the different MC codes which represents a problem when associated with the dosimetry protocol. Obtaining reliable values of OF and PVDR for both experimental and numerical measurement represents the challenge of this work.In this work, the discrepancies between the MC simulations and measured datas are assigned to a lack of details in the MC simulations and to the fact that detector specific characteristics can influence the measurement. A series of MC simulation is developed to quantify each of these effects. The major drawback of such study is the simulation time, so tricks are used to speed up the calculation and nevertheless keep the results as accurate as possible
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Peet, Samuel. "Out-of-field dosimetry in contemporary radiation therapy." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/234916/1/9325565_samuel_peet_thesis.pdf.
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Radiation therapy is a beneficial treatment for approximately half of all people diagnosed with cancer. This project improved the safety of radiation therapy for several vulnerable cohorts: pregnant patients, patients with electronic implants such as pacemakers, and young people at risk of developing secondary cancers later in life. In doing so, this research furthered equitable access to safe, high-quality health care.
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Capuccini, Jenny <1976>. "Short course accelerated radiation therapy in palliative care." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amsdottorato.unibo.it/8411/1/CAPUCCINI_JENNY_TESI.pdf.
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Palliative radiotherapy is a key resource for symptoms control and improvement patient's life
expectancy in advanced stage of illness. The most common symptoms that afflict this type of
patients are pain, bleeding, dysphagia, obstruction, vomiting, nausea. Most of these can benefit
from a hypo-fractionated radiation treatment with a good percentage of complete responses,
variable depending on the symptom considered, but on average 56-70%.
Normally a hypo-fractionated treatment, excluding uncomplicated bone metastases where the single
fraction (800 cGy in 1 fraction) is the standard, provides for 30 Gy delivered in 10 fractions (1
fraction / day) or 20 Gy in 5 fractions (1 fraction / day).
SHARON Project (Short Course Accelerated Radiation Therapy), based on dose-escalation Phase
I-II studies that defined the MDT (maximum tolerated dose), is made up of 7 randomized Phase III
trials (1:1 on Simon's design) that aim to compare the effectiveness on the symptom control of a
conventional hypo-fractionationated radiotherapy compared with an accelerated hypofractionationated
treatment.
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Specifically, the fractionation we propose provides the delivery of 4.5-5 Gy twice a day at a
distance of 6-8 hours for two consecutive days.
GTV will be identified by macroscopic lesion (detailed in the single protocol), CTV by GTV + a
margin of 2 cm and the PTV from CTV + 1 cm of isotropic margin.
There will be described the results of the Sharon-Bone Phase I-II trial, Sharon Head and Neck
Phase I-II trial and Sharone Elderly (pooled analysis phase I-II trials) and the seven randomized
Phase III trials for all the described body regions (Abdomen RT 15-01, Brain RT 15-02, Thorax RT
15-03, Pelvis RT 15-04, H&N RT 15-05, Bone RT 15-06, Esophagus RT 15-07)
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Kutlakhmedov, Yuriy Alekseevich, Anastasiya Georgievna Salivon, Svetlana Anatolyevna Phelovskya, Victor Vladimirovich Rodyna, Irina Valeryevna Matveeva, and Valentina Pavlovna Petrusenko. "Theory of Reliability in Radiation Ecology." Thesis, Industrial Engineering and Management Department SCE - Shamoon College of Engineering Beer Sheva (Israel), 2010. http://er.nau.edu.ua/handle/NAU/23676.
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Proceedings of the international symposium on stochastic models in reliability engineering, life science and operations managementFor twenty years after Chernobyl catastrophe, we studied capability of plants of different kinds to store and retain the radionuclide tracer 137Cs as the measure of stability and reliability of the ecosystem biota exposed to gamma-radiation and chemical pollutants. We introduced two parameters to quantify the ecosystem reliability. First, radiocapacity is defined as the upper level of radionuclide contamination, above which the ecosystem biota species begin to manifest depression and/or suppression of growth. Then, the factor of radiocapacity is defined as probability of the biota constituents to retain the radionuclide tracer. The more is the factor of radiocapacity the higher is reliability of the relevant biota components. With knowledge of the ecosystem structure and these parameters, it is possible to estimate ability of ecosystems to provide the proper distribution and redistribution of the tracer. In particular, we showed that ecosystems of the serious type of organization, like slope and mining ones that are incapable to provide the proper pollutant migration, exhibit low radiocapacity and, thus, low reliability. Using this approach along with the data of geoinformational analysis, we can predict the principal seats of location of pollutants in specific ecosystems and estimate appropriate dose loads and risks.
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Lane, Dana E. "Stochastic theory and cloud-radiation interactions /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p3035916.
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Nilsson, Johan. "Accurate description of heterogeneous tumors for biologically optimized radiation therapy." Doctoral thesis, Stockholm : Division of medical radiation physics, Department of oncology-pathology, Stockholm University and Karolinska Institutet, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-311.
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Lillhök, Jan Erik. "The microdosimetric variance-covariance method used for beam quality characterization in radiation protection and radiation therapy." Doctoral thesis, Stockholm University, Medical Radiation Physics (together with KI), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-6687.
Full textAbstract:
Radiation quality is described by the RBE (relative biological effectiveness) that varies with the ionizing ability of the radiation. Microdosimetric quantities describe distributions of energy imparted to small volumes and can be related to RBE. This has made microdosimetry a powerful tool for radiation quality determinations in both radiation protection and radiation therapy. The variance-covariance method determines the dose-average of the distributions and has traditionally been used with two detectors to correct for beam intensity variations. Methods to separate dose components in mixed radiation fields and to correct for beam variations using only one detector have been developed in this thesis. Quality factor relations have been optimized for different neutron energies, and a new algorithm that takes single energy deposition events from densely ionizing radiation into account has been formulated. The variance-covariance technique and the new methodology have been shown to work well in the cosmic radiation field onboard aircraft, in the mixed photon and neutron fields in the nuclear industry and in pulsed fields around accelerators.
The method has also been used for radiation quality characterization in therapy beams. The biological damage is related to track-structure and ionization clusters and requires descriptions of the energy depositions in nanometre sized volumes. It was shown that both measurements and Monte Carlo simulation (condensed history and track-structure) are needed for a reliable nanodosimetric beam characterization. The combined experimental and simulated results indicate that the dose-mean of the energy imparted to an object in the nanometre region is related to the clinical RBE in neutron, proton and photon beams. The results suggest that the variance-covariance technique and the dose-average of the microdosimetric quantities could be well suited for describing radiation quality also in therapy beams.
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Lillhök, Jan Erik. "The microdosimetric variance-covariance method used for beam quality characterization in radiation protection and radiation therapy /." Stockholm : Medical Radiation Physics, Stockholm University and Karolinska Institutet, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-6687.
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Mestrovic, Ante. "Integration of daily imaging, plan adaptation and radiation delivery for near real-time adaptive radiation therapy." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/3990.
Full textAbstract:
The primary objective of this research was to develop and implement a new approach to on-line adaptive radiation therapy (ART) in which daily imaging, plan adaptation and radiation delivery are temporally integrated and performed concurrently. The advantages of this approach are: reduction of treatment time compared to conventional on-line ART; ability to perform a complete plan re-optimization with minimal extension of treatment time; ability to detect and correct for intra-fractional patient motion.
This work was motivated by an initial study which compared four radiosurgery techniques. This study was the first quantitative analysis of the correlation between patient anatomy and the quality of treatment plans produced by different radiosurgery techniques. A number of different relationships, both qualitative and quantitative, were discovered between patient anatomy and dosimetric parameters for different techniques. The results were used to successfully predetermine the optimal radiosurgery technique based on patient anatomy.
The first step in developing a new approach to on-line ART involved accelerating plan adaptation (re-optimization) using direct aperture optimization (DAO). A series of techniques for adapting the original treatment plan to correct for the deterioration of dose distribution quality caused by the anatomical deformations were investigated. Through modification of the DAO algorithm the optimization search space was reduced and the plan adaptation was significantly accelerated. Next, a new approach to on-line ART was proposed and investigated, in which accelerated plan adaptation and radiation delivery were integrated together and performed concurrently. A fundamental advantage of this approach is that most of the plan re-optimization was performed during radiation delivery, so the time spent adapting the original plan did not significantly increase the overall treatment time. Finally, daily imaging, accelerated plan adaptation and radiation delivery were all temporally integrated using an integrated Linac/Cone Beam CT system. Intra-fractional patient images were used to successfully re-optimize the original treatment plan in near real-time to account for anatomy deformations.
This thesis concludes that integration of daily imaging, plan adaptation and radiation delivery for near real-time ART is both feasible and advantageous. With further advances in related technologies, it promises to become a part of clinical practice in the near future.
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Bogue, Jonathan Nelson. "Evaluation of Patient-Scatter Factors for Radiation Therapy ShieldingUsing Physical Measurement in a "Good" Geometry." University of Toledo Health Science Campus / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=mco1525447575821026.
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Tangboonduangjit, Puangpen. "Intensity-modulated radiation therapy dose maps the matchline effect /." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060724.095712/index.html.
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Fredriksson, Albin. "Robust optimization of radiation therapy accounting for geometric uncertainty." Doctoral thesis, KTH, Optimeringslära och systemteori, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122262.
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Geometric errors may compromise the quality of radiation therapy treatments. Optimization methods that account for errors can reduce their effects. The first paper of this thesis introduces minimax optimization to account for systematic range and setup errors in intensity-modulated proton therapy. The minimax method optimizes the worst case outcome of the errors within a given set. It is applied to three patient cases and shown to yield improved target coverage robustness and healthy structure sparing compared to conventional methods using margins, uniform beam doses, and density override. Information about the uncertainties enables the optimization to counterbalance the effects of errors. In the second paper, random setup errors of uncertain distribution---in addition to the systematic range and setup errors---are considered in a framework that enables scaling between expected value and minimax optimization. Experiments on a phantom show that the best and mean case tradeoffs between target coverage and critical structure sparing are similar between the methods of the framework, but that the worst case tradeoff improves with conservativeness. Minimax optimization only considers the worst case errors. When the planning criteria cannot be fulfilled for all errors, this may have an adverse effect on the plan quality. The third paper introduces a method for such cases that modifies the set of considered errors to maximize the probability of satisfying the planning criteria. For two cases treated with intensity-modulated photon and proton therapy, the method increased the number of satisfied criteria substantially. Grasping for a little less sometimes yields better plans. In the fourth paper, the theory for multicriteria optimization is extended to incorporate minimax optimization. Minimax optimization is shown to better exploit spatial information than objective-wise worst case optimization, which has previously been used for robust multicriteria optimization. The fifth and sixth papers introduce methods for improving treatment plans: one for deliverable Pareto surface navigation, which improves upon the Pareto set representations of previous methods; and one that minimizes healthy structure doses while constraining the doses of all structures not to deteriorate compared to a reference plan, thereby improving upon plans that have been reached with too weak planning goals.QC 20130516