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1
Crosbie, Jeffrey. "Synchrotron microbeam radiation therapy". Monash University. Faculty of Science. School of Physics, 2008. http://arrow.monash.edu.au/hdl/1959.1/64948.
Testo completoAbstract (sommario):
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.
2
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.
Testo completoAbstract (sommario):
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.
3
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/.
Testo completo
4
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.
Testo completoAbstract (sommario):
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.
5
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.
Testo completoAbstract (sommario):
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.
6
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.
Testo completoAbstract (sommario):
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
7
Chan, Kin Wa (Karl), University of Western Sydney, of Science Technology and Environment College e 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.
Testo completoAbstract (sommario):
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)
8
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.
Testo completoAbstract (sommario):
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.
9
Ranggård, Nina. "Optimizing Conformity inIntensity Modulated Radiation Therapy". Thesis, KTH, Fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147356.
Testo completo
10
Chan, Timothy Ching-Yee. "Optimization under uncertainty in radiation therapy". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40302.
Testo completoAbstract (sommario):
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.
11
Brauer-Krisch, E. "Experimental dosimetry for Microbeam Radiation Therapy". Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1357933/.
Testo completoAbstract (sommario):
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.
12
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.
Testo completo
13
Dial, Christian W. "Adaptive Radiation Therapy for Lung Cancer". VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3579.
Testo completoAbstract (sommario):
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.
14
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.
Testo completo
15
Mueller, Marco. "Direct tumour tracking during radiation therapy". Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29450.
Testo completoAbstract (sommario):
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.
16
Fan, Qiyong. "Emission guided radiation therapy: a feasibility study". Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37277.
Testo completoAbstract (sommario):
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.
17
Wong, Tony Po Yin, e 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.
Testo completoAbstract (sommario):
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
18
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.
Testo completo
19
Fan, Qiyong. "Emission guided radiation therapy: a feasibility study". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52153.
Testo completoAbstract (sommario):
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.
20
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.
Testo completoAbstract (sommario):
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.
21
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.
Testo completoAbstract (sommario):
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.
22
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.
Testo completoAbstract (sommario):
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.
23
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.
Testo completo
24
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.
Testo completoAbstract (sommario):
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.
25
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.
Testo completo
26
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.
Testo completo
27
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.
Testo completo
28
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.
Testo completoAbstract (sommario):
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.
29
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.
Testo completo
30
Ramakrishnan, Jagdish. "Dynamic optimization of fractionation schedules in radiation therapy". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82181.
Testo completoAbstract (sommario):
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.
31
Watkins, W. Tyler. "Optimization of Radiation Therapy in Time-Dependent Anatomy". VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3069.
Testo completoAbstract (sommario):
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.
32
Zhou, Jining. "ORGAN MOTION AND IMAGE GUIDANCE IN RADIATION THERAPY". VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1681.
Testo completoAbstract (sommario):
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.
33
Shao, Wei. "Improving functional avoidance radiation therapy by image registration". Diss., University of Iowa, 2019. https://ir.uiowa.edu/etd/7031.
Testo completoAbstract (sommario):
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.
34
Reynard, Dimitri. "Development of Accurate Dosimetry for Microbeam Radiation Therapy". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAS038/document.
Testo completoAbstract (sommario):
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
35
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.
Testo completoAbstract (sommario):
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.
36
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.
Testo completoAbstract (sommario):
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.
4
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)
37
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.
Testo completoAbstract (sommario):
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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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.
Testo completo
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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.
Testo completo
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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.
Testo completo
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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.
Testo completoAbstract (sommario):
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
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Wiklund, Kristin. "Modeling of dose and sensitivity heterogeneities in radiation therapy". Doctoral thesis, Stockholms universitet, Fysikum, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-74719.
Testo completoAbstract (sommario):
The increased interest in the use of light ion therapy is due to the high dose conformity to the target and the dense energy deposition along the tracks resulting in increased relative biological effectiveness compared to conventional radiation therapy. In spite of the good clinical experience, fundamental research on the characteristics of the ion beams is still needed in order to be able to fully explore their use. Therefore, a Monte Carlo track structure code, KITrack, simulating the transport of electrons in liquid water, has been developed and used for calculation of parameters of interest for beam characterization. The influence of the choice of the cross sections for the physical processes on the electron tracks has also been explored. As an alternative to Monte Carlo calculations a semi-analytical approach to calculate the radial dose distribution from ions, has been derived and validated. In advanced radiation therapy, accurate characterization of the beams has to be complemented by comprehensive radiobiological models, which relate the dose deposition into the cells to the outcome of the treatment. The second part of the study has therefore explored the influence of heterogeneity in the dose deposition into the cells as well as the heterogeneity in the cells sensitivity to radiation on the probability of controlling the tumor. Analytical expressions for tumor control probability including heterogeneous dose depositions or variation of radiation sensitivity of cells and tumors have been derived and validated with numerical simulations. The more realistic case of a combination of these effects has also been explored through numerical simulations. The MC code KITrack has evolved into an extremely useful tool for beam characterization. The tumor control probability, given by the analytical derived expression, can help improve radiation therapy. A novel anisotropy index has been proposed. It is a measure of the absence of isotropy and provides deeper understanding of the relationship between beam quality and biological effects.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.
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Alrushoud, Abdullah A. "Polymer gel dosimetry in radiation therapy using computed tomography". Thesis, University of Surrey, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616921.
Testo completoAbstract (sommario):
There have been developments in radiation therapy treatment techiques, which lead to an increase in the complexity of these treatments. The aim is to deliver highly conformal three-dimensional (3D) dose distributions, such as stereotactic radiosurgery (SRS). Polymer gel dosimetry offers three-dimensional (3D) dosimetry techniques for dose verification of dose distributions. Nisopropyl- acrylamide (NIP AM) polymer gel was the latest to develop and can be prepared under a normal atmospheric environment and has lower toxicity compared with the highly toxic polymer gels used earlier. NIPAM polymer gel using X-ray computed tomography (CT) was experimentally investigated in terms of its X-ray CT dose response, sensitivity and dose resolution. The effect of radiation beam type, radiation beam energy and radiation beam dose rate on X-ray CT dose response have also been studied. The temporal stability of NIP AM polymer gel has been examined over several days post-irradiation. The change in the polymer gel dosimeter's physical and electron densities as a function of absorbed dose was also investigated. In ,this study two new prototype phantoms were designed and constructed for imaging and irradiation of polymer gel dosimeters to provide simplicity and practicality for clinical dosimetry. The dosimetric and water equivalence properties of four NIP AM based polymer gel dosimeter formulations have been studied by examining their physical properties, interaction probability, radiation transport parameters and performing Monte Carlo modelling of depth doses. NIP AM polymer gel dosimeter irradiated at different doses using 6 Me V photon beam and 400 MU min-1 dose rate were found to have higher CT dose response (up to 37.8% at 10 Gy dose point) than results reported in the literature for NIP AM gel using similar concentration. The CT dose sensitivity of NIPAM polymer gel was found to be 0.405±0.014 H Gi1 , which is 26.2% higher than the reported sensitivity of 0.32l±0.008 H Gy-l with similar NIPAM gel concentration. The maximum change in physical density as a function of absorbed dose for polymer gel dosimeters was found to be up to ~1.0% for an absorbed dose of 20 Gy. 111
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Olsson, Henrik. "Utilizing the Degrees of Freedom in Radiation Therapy Optimization". Thesis, KTH, Optimeringslära och systemteori, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214566.
Testo completoAbstract (sommario):
The development of advanced software for radiation therapy treatment has had a significant role in the last decades’ improvements in cancer treatment. By optimizing the radiation dose given to each patient, the probability of a successful treatment increases. The development of mathematical optimization methods, required to produce as good radiation therapy treatment plans as possible, is therefore of high importance. When producing treatment plans for Volumetric Modulated Arc Therapy (VMAT) today, there are degrees of freedom that are not fully utilized. The possibility of rotating the patient couch and collimator during radiation delivery, to achieve a better dose distribution over the patient, is not taken advantage of. In order to take full advantage of these extra degrees of freedom, methods for predicting how good different arcs will perform during VMAT-delivery need to be developed. Since the number of possible VMAT-arcs is very large, such a method needs to be very time efficient in order to be of conventional use. In this thesis, a heuristic method for finding good VMAT-arcs for patients with multiple brain metastasis is proposed. In the method, the sphere around the patient’s head is discretized into a number of beam directions. From each of these beam directions a projection of the patient’s anatomy is produced, and based on the relative location of the cancer metastasis and the organs desired to protect, a cost is assigned. By linking together adjacent beam direction, VMAT-arcs can be created, and each possible VMATarc is assigned an arc cost depending on the cost of the beam directions it traverses. Such arc cost is used as an indication of how good a VMAT-arc will perform during VMAT-delivery. The heuristic method is tested and evaluated on four different patient cases. In three of the patient cases, the proposed method gives good results. Overall the results indicate that it is possible to predict how good a VMAT-arc will perform during VMAT-delivery, by looking at the relative locations of the target and organ projections in a discrete number of points along the arc. However, since the number of test cases are few, no statistically significant conclusions can be drawn.Utvecklingen av avancerad mjukvara för strålningsterapi är en del av de senaste decenniernas framsteg inom cancerbehandling. Genom att optimera stråldosen som ges till varje patient ökar sannolikheten att behandlingen lyckas. Utvecklingen av matematiska optimeringsmetoder, som används för att producera så bra strålningsplaner som möjligt, är därför av högsta vikt. När man producerar strålningsplaner för VMAT (Volumetric Modulated Arc Therapy) idag, utnyttjas inte alla frihetsgrader. Möjligheten att rotera patientbritsen och kollimatorn för att leverera en bättre strålningsdos till patienten lämnas ute. För att kunna utnyttja dessa frigetsgrader fullt ut krävs utveckling av metoder som kan förutspå hur bra olika strålningstrajektorier är. Då det finns ett väldigt stort antal möjliga strålningstrajektorier måste dessa metoder vara tidseffektiva. Under detta exjobb har en heuristisk metod för att hitta bra VMAT-trajektorier för patienter med flera hjärnmetastaser utvecklats. I metoden discretiseras sfären runt patientens huvud i ett antal strålningsriktningar. Från varje strålningsriktning produceras en projektion av patientens anatomi. Baserat på de relativa positionerna av hjärnmetastaserna och de organ man vill skydda tilldelas varje strålningsriktning ett straff. Genom att binda samman intilliggande strålningsriktningar kan sedan VMAT-trajektorier produceras, och varje VMAT-trajektorie tilldelas ett straff baserat på straffen hos de strålningsriktningar som bundits samman för att bilda trajektorien. Straffet som tilldelats en trajektorie används sedan som en indikator för hur bra trajektorien är för VMAT-behandling. Den heuristiska metoden är testad i fyra olika patientfall. I tre av patientfallen ger metoden bra resultat. I sin helhet tyder resultaten på att det är möjligt att förutsäga hur bra en VMAT-trajektorie är för VMAT-behandling, genom att från ett par punkter längst trajektorien titta på de relativa positionerna av metastaserna och de organ som man vill skydda. Dock gör det låga antalet av testfall att inga statisktiskt säkerställda slutsatser kan dras.
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Schneider, Tim. "Advancing the generation of proton minibeams for radiation therapy". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP069.
Testo completoAbstract (sommario):
Malgré d’importants progrès, la tolérance des tissus sains aux rayonnements demeure un facteur central en radiothérapie, limitant par exemple l’efficacité du traitement des gliomes de haute grade. La proton thérapie avec mini-faisceaux (proton minibeam radiation therapy, pMBRT) est une nouvelle stratégie thérapeutique qui a pour objectif d’améliorer la préservation des tissus sains en combinant les avantages balistiques des protons et le fractionnement spatial de la dose obtenu avec des faisceaux submillimétriques. Dans ce contexte, la pMBRT a déjà démontré sa capacité à augmenter l’index thérapeutique dans le traitement des tumeurs cérébrales de rats. Un défi important est la génération des mini-faisceaux dans un cadre clinique : contrairement à la radiothérapie conventionnelle qui utilise des faisceaux larges (diamètre d’environ 5 mm à plusieurs centimètres), les mini-faisceaux se caractérisent par un diamètre de moins d’un millimètre. Actuellement, la génération des mini-faisceaux de protons est réalisée à l’aide de collimateurs mécaniques (blocs en métal avec plusieurs fentes ou trous) ce qui comporte plusieurs inconvénients (notamment une très faible flexibilité, une réduction importante du débit de dose ainsi que la génération de particules secondaires indésirables). Une solution optimale pourrait être la génération des mini-faisceaux par focalisation magnétique. Il en découle la question principale traitée dans cette thèse : Comment la génération des mini-faisceaux de protons par focalisation magnétique peut-elle être réalisée dans un cadre clinique ? En utilisant le modèle numérique d’un pencil beam scanning nozzle (le "nozzle" est la dernière partie d’une ligne de faisceau clinique), il a été démontré que les nozzles actuels ne sont pas adéquats pour focaliser les faisceaux de protons à la taille requise, les principales raisons étant une distance focale trop grande et une présence d’air excessive. En partant de ces conclusions, un nouveau design de nozzle optimisé a été développé. Ce nouveau modèle est capable de générer des mini-faisceaux de protons par focalisation magnétique dans des conditions réalisables avec les technologies existantes. Une étude Monte Carlo a également été menée afin de comparer et de quantifier les différences entre la génération de mini-faisceaux par collimation mécanique et par focalisation magnétique. Dans un second temps, cette thèse présente une évaluation des ions d’hélium comme alternative aux protons pour la radiothérapie avec mini-faisceaux. Il a pu être démontré que les ions d’hélium peuvent être un bon compromis en offrant certains des avantages dosimétriques observés avec les ions lourds sans les risques de toxicité associésDespite major advances over the last decades, the dose tolerance of normal tissue continues to be a central problem in radiation therapy, limiting for example the effective treatment of hypoxic tumours and high-grade gliomas. Proton minibeam radiation therapy (pMBRT) is a novel therapeutic strategy, combining the improved ballistics of protons with the enhanced tissue sparing potential of submillimetric, spatially fractionated beams (minibeams), that has already demonstrated its ability to significantly improve the therapeutic index for brain cancers in rats. In contrast to conventional proton therapy which uses comparatively large beam diameters of five millimetres to several centimetres, minibeams require beam sizes of less than 1 mm which are challenging to create in a clinical context. So far, every implementation of pMBRT at clinically relevant beam energies could only be achieved with the help of mechanical collimators (metal blocks with thin slits or holes). However, this method is inefficient, inflexible and creates high levels of unwanted secondary particles. The optimal approach may therefore be the generation of minibeams through magnetic focussing.This thesis investigates how magnetically focussed proton minibeams can be realised in a clinical context. Starting from the computer model of a modern pencil beam scanning nozzle (the term "nozzle" describes the final elements of a clinical beamline), it could be shown that current nozzles will not be suitable for this task, since their large dimensions and the presence of too much air in the beam path make it impossible to focus the beam down to the required sizes. Instead, an optimised nozzle design has been developed and evaluated with clinical beam models. It could be demonstrated that this design allows the generation of proton minibeams through magnetic focussing and that the new nozzle can be used with already existing technology. Moreover, a Monte Carlo study was performed to compare and quantify the differences between magnetically focussed minibeams and mechanically collimated minibeams.Finally, as the second aspect of this thesis, helium ions were evaluated as a potential alternative to protons for minibeam radiation therapy. It could be shown that helium ions could present a good compromise exhibiting many of the dosimetric advantages of heavier ions without the risks related to normal tissue toxicities
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Zachariah, Elizabeth. "Spatio-Temporal Modeling Of Anatomic Motion For Radiation Therapy". VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3972.
Testo completoAbstract (sommario):
In radiation therapy, it is imperative to deliver high doses of radiation to the tumor while reducing radiation to the healthy tissue. Respiratory motion is the most significant source of errors during treatment. Therefore, it is essential to accurately model respiratory motion for precise and effective radiation delivery. Many approaches exist to account for respiratory motion, such as controlled breath hold and respiratory gating, and they have been relatively successful. They still present many drawbacks. Thus, research has been expanded to tumor tracking.
The overall goal of 4D-CT is to predict tumor motion in real time, and this work attempts to move in that direction. The following work addresses both the temporal and the spatial aspects of four-dimensional CT reconstruction. The aims of the paper are to (1) estimate the temporal parameters of 4D models for anatomy deformation using a novel neural network approach and (2) to use intelligently chosen non-uniform, non-separable splines to improve the spatial resolution of the deformation models in image registration.
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Polston, Gregory K. "A dosimetric model for small-field electron radiation therapy". Muncie, Ind. : Ball State University, 2008. http://cardinalscholar.bsu.edu/366.
Testo completo
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Kumar, Arvind. "Novel methods for intensity modulated radiation therapy treatment planning". [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011543.
Testo completo
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Zhang, Tianfang. "Machine learning multicriteria optimization in radiation therapy treatment planning". Thesis, KTH, Matematisk statistik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-257509.
Testo completoAbstract (sommario):
In radiation therapy treatment planning, recent works have used machine learning based on historically delivered plans to automate the process of producing clinically acceptable plans. Compared to traditional approaches such as repeated weighted-sum optimization or multicriteria optimization (MCO), automated planning methods have, in general, the benefits of low computational times and minimal user interaction, but on the other hand lack the flexibility associated with general-purpose frameworks such as MCO. Machine learning approaches can be especially sensitive to deviations in their dose prediction due to certain properties of the optimization functions usually used for dose mimicking and, moreover, suffer from the fact that there exists no general causality between prediction accuracy and optimized plan quality.In this thesis, we present a means of unifying ideas from machine learning planning methods with the well-established MCO framework. More precisely, given prior knowledge in the form of either a previously optimized plan or a set of historically delivered clinical plans, we are able to automatically generate Pareto optimal plans spanning a dose region corresponding to plans which are achievable as well as clinically acceptable. For the former case, this is achieved by introducing dose--volume constraints; for the latter case, this is achieved by fitting a weighted-data Gaussian mixture model on pre-defined dose statistics using the expectation--maximization algorithm, modifying it with exponential tilting and using specially developed optimization functions to take into account prediction uncertainties.Numerical results for conceptual demonstration are obtained for a prostate cancer case with treatment delivered by a volumetric-modulated arc therapy technique, where it is shown that the methods developed in the thesis are successful in automatically generating Pareto optimal plans of satisfactory quality and diversity, while excluding clinically irrelevant dose regions. For the case of using historical plans as prior knowledge, the computational times are significantly shorter than those typical of conventional MCO.Inom strålterapiplanering har den senaste forskningen använt maskininlärning baserat på historiskt levererade planer för att automatisera den process i vilken kliniskt acceptabla planer produceras. Jämfört med traditionella angreppssätt, såsom upprepad optimering av en viktad målfunktion eller flermålsoptimering (MCO), har automatiska planeringsmetoder generellt sett fördelarna av lägre beräkningstider och minimal användarinteraktion, men saknar däremot flexibiliteten hos allmänna ramverk som exempelvis MCO. Maskininlärningsmetoder kan vara speciellt känsliga för avvikelser i dosprediktionssteget på grund av särskilda egenskaper hos de optimeringsfunktioner som vanligtvis används för att återskapa dosfördelningar, och lider dessutom av problemet att det inte finns något allmängiltigt orsakssamband mellan prediktionsnoggrannhet och kvalitet hos optimerad plan. I detta arbete presenterar vi ett sätt att förena idéer från maskininlärningsbaserade planeringsmetoder med det väletablerade MCO-ramverket. Mer precist kan vi, givet förkunskaper i form av antingen en tidigare optimerad plan eller en uppsättning av historiskt levererade kliniska planer, automatiskt generera Paretooptimala planer som täcker en dosregion motsvarande uppnåeliga såväl som kliniskt acceptabla planer. I det förra fallet görs detta genom att introducera dos--volym-bivillkor; i det senare fallet görs detta genom att anpassa en gaussisk blandningsmodell med viktade data med förväntning--maximering-algoritmen, modifiera den med exponentiell lutning och sedan använda speciellt utvecklade optimeringsfunktioner för att ta hänsyn till prediktionsosäkerheter.Numeriska resultat för konceptuell demonstration erhålls för ett fall av prostatacancer varvid behandlingen levererades med volymetriskt modulerad bågterapi, där det visas att metoderna utvecklade i detta arbete är framgångsrika i att automatiskt generera Paretooptimala planer med tillfredsställande kvalitet och variation medan kliniskt irrelevanta dosregioner utesluts. I fallet då historiska planer används som förkunskap är beräkningstiderna markant kortare än för konventionell MCO.
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Wadlow, Philip James. "MATERIAL SELECTION AND TESTING FOR A RADIATION THERAPY CATHETER". DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1661.
Testo completoAbstract (sommario):
Three different polymers (a high-density polymer and two other polymers) were tested for use as an x-ray catheter in a radiation therapy application. This report describes the testing of these three materials to determine which material is the best option for a long use catheter. Tests included tensile, simulated clinical life, and other tests. Some testing was performed using nitrogen and an industrial coolant. Testing revealed significant non-circularities for some catheters. With increasing pressure, the circularity of these catheters increased. The tensile tests were performed on samples with varying doses of radiation. Tensile testing showed significant decreases in ultimate tensile strength with increasing radiation dose for both polyurethanes. Other testing was performed on the two polyurethanes to determine their compatibility with the industrial coolant. The test showed good compatibility with the coolant. Simulated clinical life tests were performed on a test fixture and with software to run the radiation source automatically for several hours at a time. Overall, one material was found to have very low ductility, made lower with increasing radiation. The material with the higher ductility was chosen as the better catheter material despite some disadvantages when compared to the stiffer polymer. This report describes necessary tests for thin polymer geometries used in applications where resistance to radiation, mechanical integrity, and coolant compatibility are the main considerations.