Dissertations / Theses on the topic 'Intensity modulated radiation therapy'
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Chapman, Alison. "Dosimetric verification of intensity modulated radiation therapy." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20061026.141700/index.html.
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Olofsson, Lennart. "Energy and intensity modulated radiation therapy with electrons." Doctoral thesis, Umeå : Department of Radiation Sciences, Radiation Physics, Umeå University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-491.
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Tangboonduangjit, Puangpen. "Intensity-modulated radiation therapy dose maps the matchline effect /." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060724.095712/index.html.
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Kumar, Arvind. "Novel methods for intensity modulated radiation therapy treatment planning." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011543.
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Dou, Xin Wu Xiaodong. "New algorithms for target delineation and radiation delivery in intensity-modulated radiation therapy." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/354.
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Dou, Xin. "New algorithms for target delineation and radiation delivery in intensity-modulated radiation therapy." Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/354.
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Intensity modulated radiation therapy (IMRT) is a modern cancer therapy technique that aims to deliver a highly conformal radiation dose to a target tumor while sparing the surrounding normal tissues. The prescribed dose is specified by an intensity map (IM) matrix and often delivered by a multileaf collimator (MLC).
In this thesis, we study a set of combinatorial optimization problems arising in the field of IMRT: 1) the auto-contouring problems using region properties, which aim to optimize the intraclass variance of the target objects; 2) the field decomposition problems, whose goal is to decompose a "complex" IM to the sum of two "simpler" sub-IMs such that the two sub-IMs are delivered in orthogonal directions to improve the delivery efficiency; 3) the field splitting problems, which seek to split a large IM that can not be directly delivered by MLC into several separate sub-IMs of size no larger than the given MLC size and the delivery effectiveness is optimized.
Our algorithms are based on combinatorial techniques - mostly graph-based algorithms. We strive to find the globally optimal solution efficiently - in a linear or low polynomial time. In the case that the exact algorithm is not efficient enough, an approximation algorithm is also developed for solving the problem.
We have implemented all the proposed algorithms and experimented on computer-generated phantoms and clinical data. Comparing with results supervised by experts, the auto-contouring algorithms yield highly accurate results for all tested datasets. The field decomposition and field splitting methods produce treatment plans of much better quality while comparing with the state-of-the-art commercial treatment planning system.
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Thompson, Heather K. "Numerically produced compensators for conventional and intensity modulated beam therapy." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30834.
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A study is performed to assess the utility of a computer numerically controlled (CNC) mill to produce missing tissue compensating filters and for the delivery of intensity-modulated beams for inverse treatment planning. A computer aided machining (CAM) software is used to assist in the design and construction of such filters. Geometric measurements of stepped and wedged surfaces are made to examine the accuracy of surface milling. Results show that the deviation of the filter surfaces from design does not exceed 1.5%. Effective attenuation coefficients are measured for CadFree and Cerrobend in a 6 MV photon beam. The ability of the CNC mill to accurately produce surfaces is further verified with dose profile measurements in a 6 MV photon beam. Dose profiles, measured beneath the test phantoms and beneath a flat phantom are compared to those produced by a commercial treatment planning system. Agreement between measured and predicted profiles is within 2%, indicating the viability of the system for filter production.
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Iori, Mauro. "Rotational intensity modulated radiation therapy : dosimetric, treatment planning, and radiobiological aspects." Thesis, University of Liverpool, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569581.
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The introduction in Radiation Oncology of x-ray beams fluence modulation, the treatment technique known as Intensity Modulated Radiation Therapy (IMRT), is leading to the flourishing of new and increasingly sophisticated treatments. It is within this context that delivery systems have been evolving from static to rotational IMRT techniques through which significant advantages have occurred in terms of treatment plan quality, delivery efficiency and accuracy, although paying the price of longer calculation times for the plan optimization. The point has been reached where the perceived advantages of rotational IMRT techniques, for which some companies have marketed therapy systems with different architecture from that of conventional linear accelerators, have led users to question whether the established and more conventional systems are becoming obsolete. However, the newly available methods of delivering Intensity Modulated Arc Therapies (IMAT) using conventional accelerators, an advanced form of rotational IMRT that combines multiple arcs with variable fluence and gantry speed, seem to have provided a preliminary answer to this concern. Although it is difficult to know which of these treatment modalities will be discontinued in the near future, it is clear that the rotational IMR T is expected to become increasingly important. Therefore, the problem of understanding which are the strengths of these techniques, or the most effective methods (forward or inverse-planning based) of their treatment planning procedures, as well as the most robust and effective systems for verifying dosimetrically such rotational deliveries can be considered current research topics. As a results, different aspects of rotational IMRT techniques have been investigated in this work, starting with the pre-clinical dosimetry of IMAT therapies, passing through the planning procedures also in comparison with static IMR T, and advancing to a special application of 'rotational IMRT': the simulation of radiobiologically optimised, voxel-based dose-painting, guided by the metabolic tumour imaging. In particular we have worked on: two methods for the pre-clinical dosimetry of IMA T treatments using a matrix detector of ionization-chambers and an electronic portal imaging device, a forward and an inverse-planning approach for simulating IMAT treatments, a ranking of plans simulated with static and rotational IMRT modalities on prostate tumour. The high conformality achievable by rotational IMRT, as well as its potential to deliver selectively different doses inside a heterogeneous target volume, together with the image guidance capabilities of the newest therapy units, makes arc modulation the most appropriate and suitable instrument for assessing future "dose painting" treatments. In this regard, two radiobiological objective functions for guiding the dose redistribution inside a group of prostate tumours according to their estimated clonogenic density distribution (based on Position Emission Tomography imaging) were developed, compared and analysed.
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Fredriksson, Albin. "Robust optimization of radiation therapy accounting for geometric uncertainty." Doctoral thesis, KTH, Optimeringslära och systemteori, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122262.
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Geometric errors may compromise the quality of radiation therapy treatments. Optimization methods that account for errors can reduce their effects. The first paper of this thesis introduces minimax optimization to account for systematic range and setup errors in intensity-modulated proton therapy. The minimax method optimizes the worst case outcome of the errors within a given set. It is applied to three patient cases and shown to yield improved target coverage robustness and healthy structure sparing compared to conventional methods using margins, uniform beam doses, and density override. Information about the uncertainties enables the optimization to counterbalance the effects of errors. In the second paper, random setup errors of uncertain distribution---in addition to the systematic range and setup errors---are considered in a framework that enables scaling between expected value and minimax optimization. Experiments on a phantom show that the best and mean case tradeoffs between target coverage and critical structure sparing are similar between the methods of the framework, but that the worst case tradeoff improves with conservativeness. Minimax optimization only considers the worst case errors. When the planning criteria cannot be fulfilled for all errors, this may have an adverse effect on the plan quality. The third paper introduces a method for such cases that modifies the set of considered errors to maximize the probability of satisfying the planning criteria. For two cases treated with intensity-modulated photon and proton therapy, the method increased the number of satisfied criteria substantially. Grasping for a little less sometimes yields better plans. In the fourth paper, the theory for multicriteria optimization is extended to incorporate minimax optimization. Minimax optimization is shown to better exploit spatial information than objective-wise worst case optimization, which has previously been used for robust multicriteria optimization. The fifth and sixth papers introduce methods for improving treatment plans: one for deliverable Pareto surface navigation, which improves upon the Pareto set representations of previous methods; and one that minimizes healthy structure doses while constraining the doses of all structures not to deteriorate compared to a reference plan, thereby improving upon plans that have been reached with too weak planning goals.QC 20130516
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Meyer, Jurgen. "Accommodating practical constraints for intensity-modulated radiation therapy by means of compensators." Thesis, Coventry University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369972.
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Fitzgerald, Rhys J. "A comparison of volumetric modulated arc therapy (VMAT), intensity modulated radiation therapy (IMRT) and 3-dimensional conformal radiation therapy (3DCRT) for stereotactic ablative radiation therapy (SABR) for early stage lung cancer." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/99826/4/Rhys_Fitzgerald_Thesis.pdf.
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This thesis is a comparative study looking at different radiation therapy treatment techniques for treating early stage lung cancer. It investigated three different techniques that had differing number of beams and treatment angles. Furthermore, it also look at beams that rotated, against beams that were stationary. It was discovered that multiple beams that continuously rotate around the patient provided optimal dose to the tumour, minimum dose to surrounding healthy tissues and had the quickest delivery time.
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Shin, Naomi. "Modeling secondary cancer risk following paediatric radiotherapy: a comparison of intensity modulated proton therapy and photon therapy." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106431.
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Proton radiotherapy is known to reduce the radiation dose delivered to normal healthy tissue compared to photon techniques. The increase in normal tissue sparing could result in fewer acute and late effects from radiation therapy. In this work proton therapy plans were created for patients previously treated using photon therapy. Intensity modulated proton therapy (IMPT) plans were planned using inverse planning in Varian's Eclipse treatment planning system with a scanning proton beam model to the same relative biological effectiveness (RBE)-weighted prescription dose as the photon plan. Proton and photon plans were compared for target dose conformity and homogeneity, body volumes receiving 2 Gy and 5 Gy, integral dose, dose to normal tissues and second cancer risk. Secondary cancer risk was determined using two methods. The relative risk of secondary cancer was found using the method described by Nguyen et al. by applying a linear relationship between integral dose and relative risk of secondary cancer. The second approach used Schneider et al.'s organ equivalent dose concept to describe the dose in the body and then calculate the excess absolute risk and cumulative risk for solid cancers in the body.IMPT and photon plans had similar target conformity and homogeneity. However IMPT plans had reduced integral dose and volumes of the body receiving low dose. Overall the risk of radiation induced secondary cancer was lower for IMPT plans compared to the corresponding photon plans with a reduction of ~36% using the integral dose model and ~50% using the organ equivalent dose model.Un avantage connu de la radiothérapie par protons est la réduction de la dose reçue par les tissus normaux et sains par rapport aux traitements en photons. Cette réduction de dose peut résulter en une diminution des effets aigus et tardifs de la radiothérapie. Dans cet ouvrage, les plans de protonthérapie ont été créés pour des patients ayant été traités par radiothérapie en photons. Les plans de protonthérapie conformationnelle avec modulation d'intensité (PCMI) ont été conçus par planification inverse dans le système de planification de traitement Eclipse de Varian de façon à ce que le faisceau de protons en balayage produise la même dose de prescription que plan en photons, tout en tenant compte des efficacités biologiques relatives des deux types de radiation. Les plans en photons et en protons ont ensuite été comparés en termes de conformité de la dose, d'homogénéité de la dose, de volumes recevant 2 et 5 Gy, de dose intégrale, de dose aux tissus normaux et de risque de cancer secondaire. Le risque relatif de cancer secondaire a été determiné par la méthode décrite par Nguyen et al. en applicant une relation linéaire entre la dose intégrale et le risque relatif de cancer secondaire. Une deuxième approche employée dans cet ouvrage utilise le concept de dose équivalente à un organe de Schneider et al. pour décrire la dose dans le corps et par la suite calculer l'excès de risque absolu et le risque cumulatif de cancers solides dans le corps. Les traitements comparés, soit en photons et en protons, ont démontré une conformité et une homogénéité de la dose similaires dans le volume cible. Toutefois, les plans de PCMI réduisent la dose intégrale et diminuent les volumes du corps recevant une faible dose. Globalement, le risque d'induction d'un cancer secondaire est plus faible pour les plans de PCMI que pour les plans équivalents en photons avec une réduction de ~36% en utilisant le modèle de dose intégrale et ~50% en utilisant le modèle de dose équivalente à un organe.
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Wake, Giulia M. G. H. "Exact minimisation of treatment time for the delivery of intensity modulated radiation therapy." University of Western Australia. School of Mathematics and Statistics, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0195.
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This thesis investigates the exact minimisation of treatment delivery time for Intensity Modulated Radiation Therapy (IMRT) for the treatment of cancer using Multileaf Collimators (MLC). Although patients are required to remain stationary during the delivery of IMRT, inevitably some patient movement will occur, particularly if treatment times are longer than necessary. Therefore minimising the treatment delivery time of IMRT may result in less patient movement, less inaccuracy in the dosage received and a potentially improved outcome for the patient. When IMRT is delivered using multileaf collimators in 'step and shoot' mode, it consists of a sequence of multileaf collimator configurations, or shape matrices; for each, time is needed to set up the configuration, and in addition the patient is exposed to radiation for a specified time, or beam-on time. The 'step and shoot leaf sequencing' problems for minimising treatment time considered in this thesis are the constant set-up time Total Treatment Time (TTT) problem and the Beam-on Time Constrained Minimum Cardinality (BTCMC) problem. The TTT problem minimises a weighted sum of total beam-on time and total number of shape matrices used, whereas the BTCMC problem lexicographically minimises the total beam-on time then the number of shape matrices used in a solution. The vast majority of approaches to these strongly NP-hard problems are heuristics; of the few exact approaches, the formulations either have excessive computation times or their solution methods do not easily incorporate multileaf collimator mechanical constraints (which are present in most currently used MLC systems). In this thesis, new exact mixed integer and integer programming formulations for solving the TTT and BTCMC problems are developed. The models and solution methods considered can be applied to the unconstrained and constrained versions of the problems, where 'constrained' refers to the modelling of additional MLC mechanical constraints. Within the context of integer programming formulations, new and existing methods for improving the computational efficiency of the models presented are investigated. Numerical results for all variations considered are provided. This thesis demonstrates that significant computational improvement can be achieved for the exact mixed integer and integer programming models investigated, via solution approaches based on an idea of systematically 'stepping-up' through the number of shape matrices used in a formulation, via additional constraints (particularly symmetry breaking constraints) and via the application of improved bounds on variables. This thesis also makes a contribution to the wider field of integer programming through the examination of an interesting substructure of an exact integer programming model. In summary, this thesis presents a thorough analysis of possible integer programming models for the strongly NP-hard 'step and shoot' leaf sequencing problems and investigates and applies methods for improving the computational efficiency of such formulations. In this way, this thesis contributes to the field of leaf sequencing for the application of Intensity Modulated Radiation Therapy using Multileaf Collimators.
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Javedan, Khosrow. "Investigation of Buildup Dose for Therapeutic Intensity Modulated Photon Beams in Radiation Therapy." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3449.
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Buildup dose of Mega Voltage (MV) photon beams can be a limiting factor in intensitymodulated radiation therapy (IMRT) treatments. Excessive doses can cause patient discomfort and treatment interruptions, while underdosing may lead to local failure.
Many factors which contribute to buildup dose, including the photon beam energy spectrum, scattered or contaminant radiation and their angular distribution, are not modeled well in commercial treatment planning systems. The accurate Monte Carlo method was employed in the studies to estimate the doses.
Buildup dose of 6MV photon beams was investigated for three fundamentally different IMRT modalities: between Helical TomoTherapy and traditional opposed tangential beams, solid IMRT and multileaf collimator (MLC)-based IMRT techniques. Solid IMRT, as an alternative to MLC, achieves prescription dose distribution objectives, according to our study.
Measurements and Monte Carlo calculations of buildup dose in chest wall treatment were compared between TomoTherapy IMRT and traditional tangential-beam technique. The effect of bolus in helical delivery was also investigated in this study.
In addition, measurements and Monte Carlo calculations of buildup dose in solid IMRT and MLC based IMRT treatment modalities were compared. A brass step compensator was designed and built for the solid IMRT. Matching MLC step sequences were used for the MLC IMRT.
This dissertation also presents the commissioning of a Monte Carlo code system, BEAMnrc, for a Varian Trilogy linear accelerator (LINAC) and the application in buildup dose calculation. Scattered dose components, MLC component dose and mean spectral energy for the IMRT treatment techniques were analyzed.
The agreement between measured 6MV and calculated depth dose and beam profiles was (± 1% or ±1 mm) for 10x10 and 40x40 cm2 fields. The optimum electron beam energy and its radial distribution incident on tungsten target were found to be 6 MeV and 1 mm respectively.
The helical delivery study concluded that buildup dose is higher with TomoTherapy compared to the opposed tangential technique in chest wall treatment. The solid and MLC IMRT comparison concluded that buildup dose was up to 7% lower for solid IMRT compared to MLC IMRT due to beam hardening of brass.
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Walker, Justin A. "The Use of an On-Board MV Imager for Plan Verification of Intensity Modulated Radiation Therapy and Volumetrically Modulated Arc Therapy." University of Toledo Health Science Campus / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=mco1372701428.
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Milette, Marie-Pierre. "Direct optimization of 3D dose distributions using collimator rotation." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/274.
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The primary goal of this thesis is to improve the precision and efficiency of radiation therapy treatment. This goal is achieved by developing and implementing a direct aperture optimization (DAO) platform where the multileaf collimator (MLC) is rotated between each aperture. The approach is referred to as rotating aperture optimization (RAO).
A series of tests is performed to evaluate how a final optimized plan depends on MLC parameters. Imposing constraints on the leaf
sequence results in increased efficiency and a simplification of the treatment plan without compromising the quality of the dose
distribution. It is also shown that an arrangement of equispaced collimator angles takes full advantage of the flexibility associated with collimator rotation.
A study including ten recurring nasopharynx cancer patients is used to evaluate the capabilities of RAO compared to other optimization techniques. It is shown that RAO plans require significantly less
linac radiation output (monitor units or MU) while maintaining equivalent dose distribution quality compared to plans generated with the conventional fluence based approach. Furthermore with an
improved collimator rotation speed, the RAO plans should be executable in the same or less time than plans generated with the
fluence-based approach. For the second part of the study it is shown that plans generated with RAO are as good as or better than plans generated with standard fixed collimator DAO. Film and ion chamber
measurements indicate that RAO plans can be delivered more accurately than DAO plans.
Additional applications of DAO were investigated through collaboration with two PhD students. First, Monte Carlo was used to
generate pencil beam dose distributions for DAO inverse treatment planning (MC-DAO). The MC-DAO technique correctly models
traditionally difficult treatment geometries such as small fields and tissue inhomogeneities. The MC-DAO also takes advantage of the improved MU efficiency associated with the DAO technique. Secondly
DAO is proposed for adaptive radiation therapy. The results show that plan re-adaptation can be performed more quickly than complete plan regeneration thereby minimizing the time the patient has to
spend in the treatment room and reducing the potential for geometric errors in treatment delivery.
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suh, yelin. "DEVELOPMENT AND INVESTIGATION OF INTENSITY-MODULATED RADIATION THERAPY TREATMENT PLANNING FOR FOUR-DIMENSIONAL ANATOMY." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1827.
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Lung cancer is the leading cause of cancer-related deaths worldwide. Radiotherapy is one of the main treatment modalities of lung cancer. However, the achievable accuracy of radiotherapy treatment is limited for lung-based tumors due to respiratory motion. Four-dimensional radiotherapy explicitly accounts for anatomic motion by characterizing the motion, creating a treatment plan that accounts for this motion, and delivering this plan to the moving anatomy. This thesis focuses on the current problems and solutions throughout the course of four-dimensional radiotherapy. For characterization of respiratory-induced motion, patient tumor motion data were analyzed. It is shown that tumor motion can be significant during radiotherapy treatment, and its extent, direction, and linearity vary considerably between patients, between treatment fractions, and between respiratory cycles. After this, approaches to four-dimensional intensity-modulated radiation therapy treatment planning were developed and investigated. Among the techniques to manage respiratory motion, tumor tracking using a dynamic multileaf collimator delivery technique was chosen as a promising method. A formalism to solve a general four-dimensional intensity-modulated radiation therapy treatment-planning problem was developed. Specific solutions to this problem accounting for tumor motion initially in one dimension and extending this to three dimensions were developed and investigated using four-dimensional computed tomography planning scans of lung cancer patients. For four-dimensional radiotherapy treatment delivery, accuracy of two-dimensional projection imaging methods was investigated. Geometric uncertainty due to the limitation of two-dimensional imaging in monitoring three-dimensional tumor motion during treatment delivery was quantified. This geometric uncertainty can be used to estimate proper margins when a single two-dimensional projection imager is used for four-dimensional treatment delivery. Lastly, tumor-tracking delivery using a moving average algorithm was investigated as an alternative delivery technique that reduces mechanical motion constraints of a multileaf collimator. Moving average tracking provides an approximate solution that can be immediately implemented for delivery of four-dimensional intensity-modulated radiation therapy treatment. The clinical implementation of four-dimensional guidance, intensity-modulated radiation therapy treatment planning, and dynamic multileaf collimator tracking delivery may have a positive impact on the treatment of lung cancer.
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Hack, Joshua. "Development and implementation of quality-assurance standards for external beam intensity modulated radiation therapy." Toledo, Ohio : University of Toledo, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=mco1265034762.
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Zhang, Tianfang. "Direct optimization of dose-volume histogram metrics in intensity modulated radiation therapy treatment planning." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231548.
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In optimization of intensity-modulated radiation therapy treatment plans, dose-volumehistogram (DVH) functions are often used as objective functions to minimize the violationof dose-volume criteria. Neither DVH functions nor dose-volume criteria, however,are ideal for gradient-based optimization as the former are not continuously differentiableand the latter are discontinuous functions of dose, apart from both beingnonconvex. In particular, DVH functions often work poorly when used in constraintsdue to their being identically zero when feasible and having vanishing gradients on theboundary of feasibility.In this work, we present a general mathematical framework allowing for direct optimizationon all DVH-based metrics. By regarding voxel doses as sample realizations ofan auxiliary random variable and using kernel density estimation to obtain explicit formulas,one arrives at formulations of volume-at-dose and dose-at-volume which are infinitelydifferentiable functions of dose. This is extended to DVH functions and so calledvolume-based DVH functions, as well as to min/max-dose functions and mean-tail-dosefunctions. Explicit expressions for evaluation of function values and corresponding gradientsare presented. The proposed framework has the advantages of depending on onlyone smoothness parameter, of approximation errors to conventional counterparts beingnegligible for practical purposes, and of a general consistency between derived functions.Numerical tests, which were performed for illustrative purposes, show that smoothdose-at-volume works better than quadratic penalties when used in constraints and thatsmooth DVH functions in certain cases have significant advantage over conventionalsuch. The results of this work have been successfully applied to lexicographic optimizationin a fluence map optimization setting.Vid optimering av behandlingsplaner i intensitetsmodulerad strålterapi används dosvolym- histogram-funktioner (DVH-funktioner) ofta som målfunktioner för att minimera avståndet till dos-volymkriterier. Varken DVH-funktioner eller dos-volymkriterier är emellertid idealiska för gradientbaserad optimering då de förstnämnda inte är kontinuerligt deriverbara och de sistnämnda är diskontinuerliga funktioner av dos, samtidigt som båda också är ickekonvexa. Speciellt fungerar DVH-funktioner ofta dåligt i bivillkor då de är identiskt noll i tillåtna områden och har försvinnande gradienter på randen till tillåtenhet. I detta arbete presenteras ett generellt matematiskt ramverk som möjliggör direkt optimering på samtliga DVH-baserade mått. Genom att betrakta voxeldoser som stickprovsutfall från en stokastisk hjälpvariabel och använda ickeparametrisk densitetsskattning för att få explicita formler, kan måtten volume-at-dose och dose-at-volume formuleras som oändligt deriverbara funktioner av dos. Detta utökas till DVH-funktioner och så kallade volymbaserade DVH-funktioner, såväl som till mindos- och maxdosfunktioner och medelsvansdos-funktioner. Explicita uttryck för evaluering av funktionsvärden och tillhörande gradienter presenteras. Det föreslagna ramverket har fördelarna av att bero på endast en mjukhetsparameter, av att approximationsfelen till konventionella motsvarigheter är försumbara i praktiska sammanhang, och av en allmän konsistens mellan härledda funktioner. Numeriska tester genomförda i illustrativt syfte visar att slät dose-at-volume fungerar bättre än kvadratiska straff i bivillkor och att släta DVH-funktioner i vissa fall har betydlig fördel över konventionella sådana. Resultaten av detta arbete har med framgång applicerats på lexikografisk optimering inom fluensoptimering.
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Bokrantz, Rasmus. "Multicriteria optimization for managing tradeoffs in radiation therapy treatment planning." Doctoral thesis, KTH, Optimeringslära och systemteori, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122663.
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Treatment planning for radiation therapy inherently involves tradeoffs, such as between tumor control and normal tissue sparing, between time-efficiency and dose quality, and between nominal plan quality and robustness. The purpose of this thesis is to develop methods that can facilitate decision making related to such tradeoffs. The main focus of the thesis is on multicriteria optimization methods where a representative set of treatment plans are first calculated and the most appropriate plan contained in this representation then selected by the treatment planner through continuous interpolation between the precalculated alternatives. These alternatives constitute a subset of the set of Pareto optimal plans, meaning plans such that no criterion can be improved without a sacrifice in another. Approximation of Pareto optimal sets is first studied with respect to fluence map optimization for intensity-modulated radiation therapy. The approximation error of a discrete representation is minimized by calculation of points one at the time at the location where the distance between an inner and outer approximation of the Pareto set currently attains its maximum. A technique for calculating this distance that is orders of magnitude more efficient than the best previous method is presented. A generalization to distributed computational environments is also proposed. Approximation of Pareto optimal sets is also considered with respect to direct machine parameter optimization. Optimization of this form is used to calculate representations where any interpolated treatment plan is directly deliverable. The fact that finite representations of Pareto optimal sets have approximation errors with respect to Pareto optimality is addressed by a technique that removes these errors by a projection onto the exact Pareto set. Projections are also studied subject to constraints that prevent the dose-volume histogram from deteriorating. Multicriteria optimization is extended to treatment planning for volumetric-modulated arc therapy and intensity-modulated proton therapy. Proton therapy plans that are robust against geometric errors are calculated by optimization of the worst case outcome. The theory for multicriteria optimization is extended to accommodate this formulation. Worst case optimization is shown to be preferable to a previous more conservative method that also protects against uncertainties which cannot be realized in practice.En viktig aspekt av planering av strålterapibehandlingar är avvägningar mellan behandlingsmål vilka står i konflikt med varandra. Exempel på sådana avvägningar är mellan tumörkontroll och dos till omkringliggande frisk vävnad, mellan behandlingstid och doskvalitet, och mellan nominell plankvalitet och robusthet med avseende på geometriska fel. Denna avhandling syftar till att utveckla metoder som kan underlätta beslutsfattande kring motstridiga behandlingsmål. Primärt studeras en metod för flermålsoptimering där behandlingsplanen väljs genom kontinuerlig interpolation över ett representativt urval av förberäknade alternativ. De förberäknade behandlingsplanerna utgör en delmängd av de Paretooptimala planerna, det vill säga de planer sådana att en förbättring enligt ett kriterium inte kan ske annat än genom en försämring enligt ett annat. Beräkning av en approximativ representation av mängden av Paretooptimala planer studeras först med avseende på fluensoptimering för intensitetsmodulerad strålterapi. Felet för den approximativa representationen minimeras genom att innesluta mängden av Paretooptimala planer mellan inre och yttre approximationer. Dessa approximationer förfinas iterativt genom att varje ny plan genereras där avståndet mellan approximationerna för tillfället är som störst. En teknik för att beräkna det maximala avståndet mellan approximationerna föreslås vilken är flera storleksordningar snabbare än den bästa tidigare kända metoden. En generalisering till distribuerade beräkningsmiljöer föreslås även. Approximation av mängden av Paretooptimala planer studeras även för direkt maskinparameteroptimering, som används för att beräkna representationer där varje interpolerad behandlingsplan är direkt levererbar. Det faktum att en ändlig representation av mängden av Paretooptimala lösningar har ett approximationsfel till Paretooptimalitet hanteras via en metod där en interpolerad behandlingsplan projiceras på Paretomängden. Projektioner studeras även under bivillkor som förhindrar att den interpolerade planens dos-volym histogram kan försämras. Flermålsoptimering utökas till planering av rotationsterapi och intensitetsmodulerad protonterapi. Protonplaner som är robusta mot geometriska fel beräknas genom optimering med avseende på det värsta möjliga utfallet av de föreliggande osäkerheterna. Flermålsoptimering utökas även teoretiskt till att innefatta denna formulering. Nyttan av värsta fallet-optimering jämfört med tidigare mer konservativa metoder som även skyddar mot osäkerheter som inte kan realiseras i praktiken demonstreras experimentellt.
QC 20130527
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Delage, Patrick. "Radiochromic film dosimetry system: from calibration to in vivo measurements and intensity-modulated radiation therapy quality assurance measurements." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=96676.
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A radiochromic film dosimetry system is presented for the radiochromic filmmodel EBT-2 using a flatbed document scanner, the Epson Expression 10000XLmodel, as a densitometer. The author presents the protocol for radiochromicfilm dose measurements along with the characterization of the radiochromic filmdosimetry system. Results from the measurements taken to characterize thesystem are presented as well as other typical clinical measurements such as qualityassurance measurements and skin dose measurements. Finally intensity modulatedradiation therapy (IMRT) quality assurance measurements are presented andcompared with the MatriXX ionization chamber array system.Un système de dosimétrie de films radiochromiques est présenté pour le modèlede film radiochromique EBT-2 et utilisant un numériseur de photographies, EpsonExpression 10000XL, comme densitomètre. L'auteur présente le protocole pour lesmesures de dose utilisant les films radiochromiques ainsi que la caractérisationdu système de dosimétrie de films radiochromiques. Les résultats des mesurescaractérisant le système sont présentés ainsi que d'autres mesures cliniquestypiques telles que des mesures d'assurance qualité et des mesures de dose lapeau. Enfin des mesures d'assurance qualité pour la radiothérapie par intensitémodulée (IMRT) sont présentées et comparées aux mesures de la matrice dechambre à ionisation MatriXX.
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Wong, Tony Po Yin, and tony wong@swedish org. "Improving Treatment Dose Accuracy in Radiation Therapy." RMIT University. Applied Sciences, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080104.144139.
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The thesis aims to improve treatment dose accuracy in brachytherapy using a high dose rate (HDR) Ir-192 stepping source and in external beam therapy using intensity modulated radiation therapy (IMRT). For HDR brachytherapy, this has been achieved by investigating dose errors in the near field and the transit dose of the HDR brachytherapy stepping source. For IMRT, this study investigates the volume effect of detectors in the dosimetry of small fields, and the clinical implementation and dosimetric verification of a 6MV photon beam for IMRT. For the study of dose errors in the near field of an HDR brachytherapy stepping source, the dose rate at point P at 0.25 cm in water from the transverse bisector of a straight catheter was calculated with Monte Carlo code MCNP 4.A. The Monte Carlo (MC) results were used to compare with the results calculated with the Nucletron Brachytherapy Planning System (BPS) formalism. Using the MC calculated radial dose function and anisotropy function with the BPS formalism, 1% dose calculation accuracy can be achieved even in the near field with negligible extra demand on computation time. A video method was used to analyse the entrance, exit and the inter-dwell transit speed of the HDR stepping source for different path lengths and step sizes ranging from 2.5 mm to 995 mm. The transit speeds were found to be ranging from 54 to 467 mm/s. The results also show that the manufacturer has attempted to compensate for the effects of inter-dwell transit dose by reducing the actual dwell time of the source. A well-type chamber was used to determine the transit doses. Most of the measured dose differences between stationary and stationary plus inter-dwell source movement were within 2%. The small-field dosimetry study investigates the effect of detector size in the dosimetry of small fields and steep dose gradients with a particular emphasis on IMRT measurements. Due to the finite size of the detector, local discrepancies of more than 10 % are found between calculated cross profiles of intensity modulated beams and intensity modulated profiles measured with film. A method to correct for the spatial response of finite sized detectors and to obtain the
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Hynning, Elin. "An Integer Programming Approach to Conversion from Static to Continuous Delivery of Intensity Modulated Radiation Therapy." Thesis, KTH, Optimeringslära och systemteori, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103805.
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The aim of this thesis is to generate a starting guess for volumetric modulated arc therapy (VMAT) plan optimization by using data from an intensity modulated radiation therapy (IMRT) plan. We develop a mixed-binary linear programming model, based on choosing segments among a set of predefined segments. The objective is to deliver intensity modulation as similar as possible to the intensity modulation of the IMRT plan. The quality of the solutions is largely dependent on the quality of the predefined segments. However, the model achieves high similarity in intensity modulation when supplied with suitable segments. Unfortunately, high similarity in intensity modulation does not necessarily imply high similarity in dose distribution. In order for the model to generate VMAT plans with acceptable dose distributions the leaf travel between adjacent control points needs to be kept low. The model shows some promising features, but improvements, especially regarding implementation, need to be made in order for the model to be useful.
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Champion, Heather. "Beam angle and fluence map optimization for PARETO multi-objective intensity modulated radiation therapy treatment planning." Medical Physics, 2011. http://hdl.handle.net/1993/8910.
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In this work we introduce PARETO, a multiobjective optimization tool that simultaneously optimizes beam angles and fluence patterns in intensity-modulated radiation therapy (IMRT) treatment planning using a powerful genetic algorithm. We also investigate various objective functions and compare several parameterizations for modeling beam fluence in terms of fluence map complexity, solution quality, and run efficiency. We have found that the combination of a conformity-based Planning Target Volume (PTV) objective function and a dose-volume histogram or equivalent uniform dose -based objective function for Organs-At-Risk (OARs) produced relatively uniform and conformal PTV doses, with well-spaced beams. For two patient data sets, the linear gradient and beam group fluence parameterizations produced superior solution quality using a moderate and high degree of modulation, respectively, and had comparable run times. PARETO promises to improve the accuracy and efficiency of treatment planning by fully automating the optimization and producing a database of non-dominated solutions for each patient.
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Atwal, Parmveer Singh. "An electronic portal image-based monte carlo approach to in-vivo dosimetry for intensity modulated radiation therapy." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/13711.
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Radical radiotherapy aims to concurrently achieve high tumour control probability and low normal tissue complication probability. Intensity-modulated radiation therapy (IMRT) provides the highly localized radiation dose delivery necessary to reach this goal. As highly conformal techniques become more prevalent, the importance of determining, and accounting for, treatment-planning, patient-setup, and delivery errors, which result in discrepancies between the calculated and actual delivered dose, also increases. Accurate Monte Carlo-based modeling of the equipment overcomes some of these deficiencies. Unfortunately, some sources of delivery errors, such as mis-calibration of the beam-modulating system, cannot be easily incorporated in the model.
Use of the amorphous-silicon detector (or EPID, for Electronic Portal Imaging Device), available on many linear accelerators, provides a solution. We hypothesize that non-transit dose images from the EPID provide us with information regarding certain delivery errors. To obtain this information, we first capture non-transit EPID dose images of the treatment field. Next, removal of intra-EPID scatter via iterative Richardson-Lucy deconvolution converts the dose image to a fluence matrix. Projected back to the height of the beam-modulating system, this matrix can be used to modulate the statistical weight of photons in a phase-space file simulating the linear accelerator from the source to this height. The modulated phase-space can be used to run Monte Carlo calculations through simulated phantoms.
Assumptions regarding the EPID's electromechanical behaviour, as well as regarding beam divergence, were validated. This method was compared and validated against our centre's treatment planning system, for various configurations of the beam-modulating system, in two non-patient phantoms (water and anthropomorphic). The new procedure matched well with film measurements, consistently providing a higher percentage (~10%-15% higher) of pixels with Gamma-Dose (3mm Distance-To-Agreement, 3% Dose-Difference criteria) less than 1, versus the TPS-based dose distributions. This indicates that the EPID-based fluence is more accurate than the TPS-based fluence. This so-called MCEF (Monte Carlo with EPID-based Fluence) procedure can be extended by utilizing Cone-Beam CT (CBCT) to account for any setup errors or physiological changes in the patient. By coupling the EPID-based fluence with CBCT-based phantoms, we believe this method will accurately mimic true 3D in-vivo dosimetry.
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Chytyk-Praznik, Krista. "Dosimetric verification of radiation therapy including intensity modulated treatments, using an amorphous-silicon electronic portal imaging device." American Institute of Physics Publishing, 2006. http://hdl.handle.net/1993/5287.
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Radiation therapy is continuously increasing in complexity due to technological innovation in delivery techniques, necessitating thorough dosimetric verification. Comparing accurately predicted portal dose images to measured images obtained during patient treatment can determine if a particular treatment was delivered correctly. The goal of this thesis was to create a method to predict portal dose images that was versatile and accurate enough to use in a clinical setting. All measured images in this work were obtained with an amorphous silicon electronic portal imaging device (a-Si EPID), but the technique is applicable to any planar imager. A detailed, physics-motivated fluence model was developed to characterize fluence exiting the linear accelerator head. The model was further refined using results from Monte Carlo simulations and schematics of the linear accelerator. The fluence incident on the EPID was converted to a portal dose image through a superposition of Monte Carlo-generated, monoenergetic dose kernels specific to the a-Si EPID. Predictions of clinical IMRT fields with no patient present agreed with measured portal dose images within 3% and 3 mm. The dose kernels were applied ignoring the geometrically divergent nature of incident fluence on the EPID. A computational investigation into this parallel dose kernel assumption determined its validity under clinically relevant situations. Introducing a patient or phantom into the beam required the portal image prediction algorithm to account for patient scatter and attenuation. Primary fluence was calculated by attenuating raylines cast through the patient CT dataset, while scatter fluence was determined through the superposition of pre-calculated scatter fluence kernels. Total dose in the EPID was calculated by convolving the total predicted incident fluence with the EPID-specific dose kernels. The algorithm was tested on water slabs with square fields, agreeing with measurement within 3% and 3 mm. The method was then applied to five prostate and six head-and-neck IMRT treatment courses (~1900 clinical images). Deviations between the predicted and measured images were quantified. The portal dose image prediction model developed in this thesis work has been shown to be accurate, and it was demonstrated to be able to verify patients’ delivered radiation treatments.
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Nakamura, Kiyonao. "A pilot study of highly hypofractionated intensity-modulated radiation therapy over 3 weeks for localized prostate cancer." Kyoto University, 2019. http://hdl.handle.net/2433/242386.
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Massie, Michael Todd. "Respiratory-Gated IMRT Quality Assurance with Motion in Two Dimensions." Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1284726606.
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Stambaugh, Cassandra. "The Evaluation and Study of Modern Radiation Dosimetry Methods as Applied to Advanced Radiation Therapy Treatments Using Intensity Modulated Megavoltage Photon Beams." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5587.
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The purpose of this work is to evaluate quasi-3D arrays for use with intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) and to determine their clinical relevance. This is achieved using a Delta4 from Scandidos and ArcCheck from Sun Nuclear and the associated software. While certain aspects of these devices and software have been previously evaluated, the main goal of this work is to evaluate the new aspects, such as reconstructing dose on a patient CT set, and extending the capabilities. This includes the capability to reconstruct the dose based on a helical delivery as well as studying the dose to a moving target using measurement-guided motion simulations.
It was found that Sun Nuclear's ArcCheck/3DVH system exhibited excellent agreement for dose reconstruction for IMRT/VMAT using a traditional C-arm linear accelerator and stringent 2%/2mm comparison constraints. It also is a powerful tool for measurement-guided dose estimates for moving targets, allowing for many simulations to be performed based on one measurement and the target motion data. For dose reconstruction for a helical delivery, the agreement was not as good for the stringent comparison but was reasonable for the clinically acceptable 3%/3mm comparison. Scandidos' Delta4 shows good agreement with stringent 2%/2mm constraints for its dose reconstruction on the phantom. However, the dose reconstruction on the patient CT set was poor and needs more work.
Overall, it was found that quasi-3D arrays are powerful tools for dose reconstruction and treatment plan comparisons. The ability to reconstruct the dose allows for a dose resolution comparable to the treatment plan, which negates the previous issues with inadequate sampling and resolution issues found when just comparing the diodes. The ability to quickly and accurately compare many plans and target motions with minimum setup makes the quasi-3D array an attractive tool for both commissioning and patient specific quality assurance.
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Lee, Vincent Sung Kin. "The fabrication of an acrylic repositioning stent for use during intensity modulated radiation therapy (IMRT) : a feasibility study." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58841.
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Objectives: Radiation therapy is one of the main treatment modalities for malignant head and neck cancers. To minimize the damage to normal tissues during radiation therapy, various methods of stabilization have been utilized, including thermoplastic facemasks and bite blocks. Our goal is to assess the feasibility of a customized oral repositioning stent and its potential benefits. Methods: Ethics Approval: Approval for this project was obtained through the BC Cancer Agency Research Ethics Board. Participants: 10 consecutive patients scheduled to undergo Intensity Modulated Radiation Therapy (IMRT) for cancers of the maxillary sinus, nasal cavity or oral cavity were recruited and consented to participate in the study. Radiation stent fabrication: Hard baseplate wax was used to create a customized wax pattern of the proposed acrylic stent at chair side and the customized wax pattern was processed in heat-cured clear hard acrylic overnight. Measuring the Stability of the Patient Position: Utilizing data from the daily KeV images, the relative stability of the patient setup was assessed. Monitoring of side effects: Participants completed a questionnaire to evaluate side effects. Assessments were performed at four time points at: baseline; 3 weeks (mid-treatment); last day of radiation (6-weeks); and 3-months post-IMRT. Results: A new workflow protocol has been developed and implemented at the BCCA. Patient stability data demonstrated mean vertical, longitudinal and lateral variations that were not statistically different when compared to two retrospective cohorts. Descriptive analysis of the questionnaire data seems to indicate a similar trend for self-reported oral symptoms as described in the literature. Conclusion: It is possible to fabricate customized repositioning stents for HN cancer patients without affecting their IMRT treatment timeline. In addition, while utilizing the customized repositioning stent we were also able to maintain patient stability comparable to prior protocols and within a range of clinical guidelines as no patients’ treatments were aborted. Acknowledgement: This project was supported by the American College of Prosthodontics’ (ACP) Education Foundation and ACP Research Committee.Dentistry, Faculty of
Graduate
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Wagner, Antoine. "Clinical implementation of a Monte Carlo-based platform for the validation of stereotactic and intensity-modulated radiation therapy." Doctoral thesis, Universite Libre de Bruxelles, 2020. https://dipot.ulb.ac.be/dspace/bitstream/2013/312015/3/ToC.pdf.
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En radiothérapie, le niveau de précision de la dose délivrée au patient au cours de son traitement est d’une importance essentielle dans l’évolution vers une amélioration de la qualité et de la cohérence des données de suivi. L’une des premières étapes vers un système de support à la décision clinique (Clinical-Decision Support System CDSS) est la reconstruction précise de cette dose délivrée, en prenant en compte les nombreux facteurs pouvant générer des déviations significatives entre la dose planifiée visualisée à l’écran par l’utilisateur et la dose réellement accumulée lors des séances de traitement. Ces facteurs incluent les variations de débit de l’accélérateur, les incertitudes d’étalonnage, de calcul de dose, les mouvements du patient et des organes, etc.L’objectif de cette étude est d’implémenter et tester une plate-forme de calcul Monte Carlo pour la validation des systèmes Cyberknife et Tomothérapie installés au Centre Oscar Lambret. L’étude d’un détecteur dédié aux petits faisceaux (la chambre d’ionisation microLion) est également incluse, ce détecteur étant particulièrement adapté aux mesures sur le système Cyberknife.Le contexte et les concepts théoriques sont introduits dans les deux premiers chapitres. Dans le troisième chapitre, la modélisation Monte Carlo du Cyberknife et du détecteur microLion est détaillée. La quatrième partie inclut la description de la plate-forme Moderato et de son module d’évaluation. Dans le dernier chapitre, la modélisation du dernier modèle de Cyberknife (M6) équipé d’un collimateur multi-lames est décrite. Une nouvelle technique est également introduite dans le but d’accélérer la recherche des paramètres du faisceau d’électrons pour un modèle Monte Carlo, permettant une intégration plus simple et automatisée de nouveaux appareils dans Moderato.In radiation therapy, the accuracy of the dose delivered to the patient during the course of treatment is of great importance to progress towards improved quality and coherence of the outcome data. One of the first steps to evolve towards a Clinical-Decision Support System (CDSS) is to be able to accurately reconstruct that delivered dose, taking into account the range of factors that can potentially generate significant differences between the planned dose visualized on the screen of the dosimetrist, and the actually delivered dose accumulated during the treatment sessions. These factors include accelerator output variations, commissioning uncertainties, dose computation errors, patient and organ movement, etc.The objective of this work is to implement and test a Monte Carlo platform for the validation of the Cyberknife and Tomotherapy systems installed at Centre Oscar Lambret. A study of a small field-dedicated detector (the microLion ionization chamber) is also included, this detector being particularly suited for measurements on the Cyberknife system.The context and theoretical concepts are introduced in the first two chapters. In the third chapter, the Monte Carlo modelling of the Cyberknife and microLion detector is detailed. The fourth part includes the description of the Monte Carlo platform Moderato and its evaluation module. In the final chapter, the modelling of the latest MLC-equipped Cyberknife model (the M6) is described. A new technique is also introduced to accelerate the optimization of the beam electron parameters of a Monte Carlo model, thus allowing for an easier and more automated use of the Moderato system.
Doctorat en Sciences biomédicales et pharmaceutiques (Médecine)
info:eu-repo/semantics/nonPublished
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Peet, Samuel. "Out-of-field dosimetry in contemporary radiation therapy." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/234916/1/9325565_samuel_peet_thesis.pdf.
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Radiation therapy is a beneficial treatment for approximately half of all people diagnosed with cancer. This project improved the safety of radiation therapy for several vulnerable cohorts: pregnant patients, patients with electronic implants such as pacemakers, and young people at risk of developing secondary cancers later in life. In doing so, this research furthered equitable access to safe, high-quality health care.
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Ulizio, Vincent Michael. "The Dosimetric Importance of Six Degree of Freedom Couch End to End Quality Assurance for SRS/SBRT Treatments when Comparing Intensity Modulated Radiation Therapy to Volumetric Modulated Arc Therapy." University of Toledo Health Science Campus / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=mco1431091144.
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Carlsson, Fredrik. "Utilizing Problem Structure in Optimization of Radiation Therapy." Doctoral thesis, Stockholm : Matematik, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4689.
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Chiu, Siu-hau, and 招兆厚. "A search for optimal radiation therapy technique for lung tumours stereotactic body radiation therapy (SBRT) : dosimetric comparison of 3D conformal radiotherapy, static gantry intensity modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) with flattening filter (FF) or flattening filter-free (FFF) beams." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/196549.
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Materials/Methods:
Ten patients who underwent thoracic SBRT with primary stage I (T1/2N0) lung cancer or oligometastatic lung lesion, with PTV diameter ≤ 5cm were selected and were immobilized with Easyfoam or Vac-Lock. Planned/treated with inspiratory breath-hold (25 seconds, 70 to 80% of vital capacity) assisted with Active Breathing Control (ABC). Four treatment plans: non-coplanar 3DCRT, coplanar static gantry IMRT, coplanar VMAT (FF) and VMAT (FFF) were generated. Field arrangements, either static fields or partial arcs (duration=20 sec) were used to avoid direct beam entry to contralateral lung. All plans were compared in terms of dosimetric performance included dose to PTV or organs at risk (OAR), high/low dose spillage, integral dose (body and lungs), dose delivery efficiency (MU/Gy) and estimated beam-on time (BOT) with reference to the RTOG 0813 protocol.
Results:
All plans complied with RTOG 0813 protocol. VMAT (FF/ FFF) techniques improved target coverage and dose conformity, with the highest conformity number (CN > 0.91), compared to IMRT (0.88) and 3DCRT (0.85). The control of high dose spillage (NT>105% and CI) for IMRT (3.04% and 1.08) and VMAT (FF/ FFF) (1.08/ 1.06% and 1.03/ 1.04) techniques were comparable (p > 0.05) and significantly better than 3DCRT (4.22% and 1.11, p < 0.005) technique. In addition, VMAT (FF/ FFF) techniques performed the best in controlling low dose spillage (D2cm and R50%) compared with IMRT (reduction: 4.7%, p=0.036 and >5.9%, p = 0.009) and 3DCRT (reduction: > 16.3%, p < 0.001 and > 10%, p = 0.002). Benefits of rapid and isotropic dose fall-off were shown from superior tissue sparing (reduction ranges from 3.2% up to 67%) of ipsilateral brachial plexus, skin (0-5mm), great vessels and ribs. Also lung V10, V12.5, esophagus and heart tend to receive lower dose with VMAT technique. The relatively lower integral dose to whole body (> 3Gy∙L reduction, p < 0.013) and ipsilateral lung (0.65Gy∙L reduction, p = 0.025) compared with 3DCRT, were associated with lower risk of radiation induced cancers. The MU/Gy and BOT were substantial lower for VMAT (FF) (22.4% and 32.4%) compared with IMRT. Apart from higher (7%) maximum skin dose, dosimetric performance for VMAT (FFF) was comparable with VMAT (FF), with advantages of further reduction of MU/Gy (1.8% lesser), partial arc numbers (from 12-14 arcs down to 8 arcs) and BOT (35% shortened), owing to the increased dose output with flattening filter removal.
Conclusions:
VMAT (FF and FFF) plans maintained IMRT equivalent plan qualities, simultaneously enhanced the delivery efficiency with shortened BOT. VMAT (FFF) further reduced the required arcs number and BOT, significantly minimized the intra-fraction motions and more tolerable to patient with long SBRT treatment duration.published_or_final_version
Medicine
Master
Master of Medical Sciences
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Hirata, Kimiko. "Dosimetric evaluation of the Acuros XB algorithm for a 4 MV photon beam in head and neck intensity-modulated radiation therapy." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225473.
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Obata, Yasunori, and Hiroshi Oguchi. "Commissioning of modulator-based IMRT with XiO treatment planning system." AIP Publishing, 2009. http://hdl.handle.net/2237/20613.
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Li, Xing. "Novel brachytherapy techniques for cervical cancer and prostate cancer." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/1682.
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Intensity-modulated brachytherapy techniques, compensator-based intensity modulated brachytherapy (CBT) and interstitial rotating shield brachytherapy (I-RSBT), are two novel conceptual radiation therapies for treating cervical and prostate cancer, respectively. Compared to conventional brachytherapy techniques for treating cervical cancer, CBT can potentially improve the dose conformity to the high-risk clinical target volume (CTV) of the cervix in a less invasive approach. I-RSBT can reduce the dose delivered to the prostate organ at risks (OARs) with the same radiation dose delivered to the prostate CTV. In this work, concepts and prototypes for CBT and I-RSBT were introduced and developed. Preliminary dosimetric measurements were performed for CBT and I-RSBT, respectively.
A CBT prototype system was constructed and experimentally validated. A prototype cylindrical compensator with eight octants, each with different thicknesses, was designed. Direct metal laser sintering (DMLS) was used to construct CoCr and Ti compensator prototypes, and a 4-D milling technique was used to construct a Ti compensator prototype. Gafchromic EBT2 films, held by an acrylic quality assurance (QA) phantom, were irradiated to approximately 125 cGy with an electronic brachytherapy (eBT) source for both shielded and unshielded cases. The dose at each point on the films were calculated using a TG-43 calculation model that was modified to account for the presence of a compensator prototype by ray-tracing.
With I-RSBT, a multi-pass dose delivery mechanism with prototypes was developed. Dosimetric measurements for a Gd-153 radioisotope was performed to demonstrate that using multiple partially shielded Gd-153 sources for I-RSBT is feasible. A treatment planning model was developed for applying I-RSBT clinically. A custom-built, stainless steel encapsulated 150 mCi Gd-153 capsule with an outer length of 12.8 mm, outer diameter of 2.10 mm, active length of 9.98 mm, and active diameter of 1.53 mm was used. A partially shielded catheter was constructed with a 500 micron platinum shield and a 500 micron aluminum emission window, both with 180° azimuthal coverage. An acrylic phantom was constructed to measure the dose distributions from the shielded catheter in the transverse plane using Gafchromic EBT3 films. Film calibration curves were generated from 50, 70, and 100 kVp x-ray beams with NIST-traceable air kerma values to account for energy variation.
In conclusion, CBT, which is a non-invasive alternative to supplementary interstitial brachytherapy, is expected to improve dose conformity to bulky cervical tumors relative to conventional intracavitary brachytherapy. However, at the current stage, it would be time-consuming to construct a patient-specific compensator using DMLS, and the quality assurance of the compensator would be difficult. I-RSBT is a promising approach to reducing radiation dose delivered to prostate OARs. The next step in making Gd-153 based I-RSBT feasible in clinic is developing a Gd-153 source that is small enough such that the source, shield, and catheter all fit within a 16 guage needle, which has a 1.65 mm diameter.
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Inokuchi, Haruo. "Clinical effect of multileaf collimator width on the incidence of late rectal bleeding after high-dose intensity-modulated radiotherapy for localized prostate carcinoma." Kyoto University, 2016. http://hdl.handle.net/2433/215942.
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Aizawa, Rihito. "Increased risk of disease progression in younger men: Analysis of factors predicting biochemical failure and castration-resistant prostate cancer after high-dose intensity-modulated radiation therapy for nonmetastatic prostate cancer." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263542.
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Ono, Tomohiro. "Development of new irradiation techniques using gimbaled x-ray head." Kyoto University, 2016. http://hdl.handle.net/2433/215379.
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Cha, Kyungduck. "Cancer treatment optimization." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22604.
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Thesis (Ph. D.)--Industrial and Systems Engineering, Georgia Institute of Technology, 2008.Committee Chair: Lee, Eva K.; Committee Member: Barnes, Earl; Committee Member: Hertel, Nolan E.; Committee Member: Johnson, Ellis; Committee Member: Monteiro, Renato D.C.
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Chaal, Kahena. "Film dosimetry of intensity modulated beams." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40823.
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ABSTRACT Intensity modulated beams use complicated computerized treatment planning systems; this makes a manual verification of the number of monitor units difficult to perform. Consequently, before treatment, patient-specific quality assurance must be done in order to ensure that the delivery agrees with the plan; this process involves a measurement of 2D dose distribution in a phantom. In this thesis, first, a photostimulable phosphor luminescence device (also referred to as computed radiography or CR) was evaluated for dosimetric purposes. The proposed protocol showed linearity response of the CR, but energy and field size dependence were discovered. Second, two widely used films for IMRT QA were compared: the radiological film, EDR2, and the radiochromic film, EBT, with the use of the scanner EPSON1680 and the software FILMQA. Results showed that in the relative dose mode, EDR2 gives higher number of pixels passing a chosen criterion compared to EBT. This fact is attributed to the highest contrast observed with EDR2; therefore, any change on pixel value due to scanner artifacts will have less impact on dose calculations with EDR2. Finally, the impact of scanner artifacts on dose assessment with EBT films, processed with FILMQA and a program written on MATLAB, was studied. A correction was introduced on MATLAB that proves the importance of taking scanner artifacts into account for the measurements with the scanner EPSON1680 and EBT films digitized in the portrait orientation. Comparison between FILMQA and MATLAB was performed on profile’s measurements and on fifteen head and neck IMRT QA cases. This comparison showed that one case out of fifteen was drastically improved with MATLAB, yet FILMQA gave inaccurate results of profiles compared with the correction applied on MATLAB.ABRÉGÉDélivrer un traitement conforme à la planification est une des responsabilités duphysicien médical; ceci est relativement simple à vérifier en RadiothérapieConformationnelle. Cependant, la complexité des calculs en Radiothérapie avecModulation d’Intensité (RTMI) rend cette vérification moins évidente puisque larelation entre la dose et les unités moniteures est plus difficile à établir. Enconséquence, irradier un fantôme conformément au plan établi pour le patient estune étape effectuée avant chaque traitement. Cette irradiation s’accompagned’une mesure à l’aide d’une chambre d’ionisation et d’une mesure desdistributions de doses à 2D. Dans cette thèse trois points sont soulevés. Lepremier consiste à évaluer le Computed Radiography (CR) en dosimétrie; leprotocole proposé a mené à une réponse linéaire mais dépendante en énergie et enlargeur de champ. En second lieu, une comparaison de deux films (EDR2 et EBT)largement utilisés pour l’assurance qualité en RTMI a été effectuée. L’étude amontré qu’en dose relative, EDR2 donnent de meilleurs résultats que EBT. Ceciest attribuable au fait que le contraste enregistré avec EDR2 rend les artefacts descanners moins importants sur le calcul de dose comparativement à EBT. Latroisième partie de ce travail traite de l’importance des artefacts introduits lors dela lecture des EBT sur le scanner EPSON1680. Une correction de ces artefacts,effectuée sur MATLAB, a prouvé leur importance. Le logiciel FILMQA utilisé enclinique pour le traitement des films a montré une grande erreur sur la mesure desprofils, mais sur 15 plans d’RTMI étudiés, un seul cas a véritablement étéamélioré par la correction effectuée sur MATLAB.
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Ranggård, Nina. "Optimizing Conformity inIntensity Modulated Radiation Therapy." Thesis, KTH, Fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147356.
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Sun, Jidi. "Implementation of 2-Step Intensity Modulated Arc Therapy." Thesis, University of Canterbury. Department of Physics and Astronomy, 2010. http://hdl.handle.net/10092/3844.
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Intensity modulated arc therapy is a novel treatment technique that has shown great potential to be superior to conventional intensity modulated radiotherapy, both in terms of treatment plan quality as well as treatment delivery. Based on previous literature, a simplified technique called two-step intensity modulated arc therapy (2-step IMAT) was implemented into a treatment planning system. In order to automatically generate treatment plans for this technique, a beam portal shaping method was developed to generate beam segments. A sensitivity analysis was carried out on a geometric phantom to determine optimal parameters for the 2-step IMAT implementation for that particular phantom. The segment weights were optimized using the dose-based and dose-volume-based objective functions. The optimal solution search was based on the gradient-descend algorithm. The dose-based objective function was implemented using a so-called lambda-value-dose-based objective function developed in this work in order to increase both speed and flexibility of the optimization. The successful implementation demonstrated the feasibility of automatic 2-step IMAT treatment planning.
A comparison of conventional arc therapy and 2-step IMAT showed improvements in the target dose uniformity by about 50% for both geometric phantom and clinical paraspinal tumor case, whilst also improving the organ sparing. The comparisons between the lambda-value-dose-based and dose-volume-based optimizations showed a speed advantage of the former by a factor of over five in the phantom study.
The current beam portal shaping approach can be improved by optimizing the segment width and including multiple organs-at-risk in the segment generation algorithm. Future work will also include the implementation of a stochastic optimization to minimize the chance of getting trapped in local minima during the segment weight optimization. In summary, the work of this research showed that the automatic 2-step IMAT planning is a viable technique that can result in highly conformal plans while keeping the treatment planning and delivery simple and straightforward.
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Dimitriadis, Doris M. "Construction and dosimetric evaluation of compensators for intensity-modulated beams." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ64343.pdf.
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Pflugfelder, Daniel. "Risk adapted optimization in intensity modulated proton therapy (IMPT)." Saarbrücken VDM Verlag Dr. Müller, 2008. http://d-nb.info/988728478/04.
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Erhart, Kevin. "A DIRECT COMPENSATOR PROFILE OPTIMIZATION APPROACH FOR INTENSITY MODULATED RADIATION TREATMENT PLANNING." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2332.
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Radiation therapy accounts for treatment of over one million cancer patients each year in the United States alone, and its use will continue to grow rapidly in the coming years. Recently, many important advancements have been developed that greatly improve the outcomes and effectiveness of this treatment technique, the most notable being Intensity Modulated Radiation Therapy (IMRT). IMRT is a sophisticated treatment technique where the radiation dose is conformed to the tumor volume, thereby sparing nearby healthy tissue from excessive radiation dose. While IMRT is a valuable tool in the planning of radiation treatments, it is not without its difficulties. This research has created, developed, and tested an innovative approach to IMRT treatment planning, coined Direct Compensator Profile Optimization (DCPO), which is shown to eliminate many of the difficulties typically associated with IMRT planning and delivery using solid compensator based treatment. The major innovation of this technique is that it is a direct delivery parameter optimization approach which has adopted a parameterized surface representation using Non-Uniform Rational B-Splines (NURBs) to replace the conventional beamlet weight optimization approach. This new approach brings with it three key advantages: 1) a reduced number of parameters to optimize, reducing the difficulty of numerical optimization; 2) the ability to ensure complete equivalence of planned and actual manufactured compensators; and 3) direct inclusion of delivery device effects during planning with no performance penalties, eliminating the degrading fluence-to-delivery parameter conversion process. Detailed research into the affects of the DCPO approach on IMRT planning has been completed and a thorough analysis of the developments is provided herein. This research includes a complete description of the DCPO surface representation scheme, inverse planning process, as well as quantification of the manufacturing constraint control procedure. Results are presented which demonstrate the performance and innovation offered by this new approach and show that the resulting compensator shapes can be manufactured to nearly 100 percent of the designed shape.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering PhD
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Wu, Wing-cheung Vincent, and 胡永祥. "Inverse planning in three-dimensional conformal and intensity modulated radiotherapy." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31246163.
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MacKenzie, Marc Alexander. "Intensity modulated arc therapy technique using sliding window dynamic multileaf collimation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0014/NQ59624.pdf.
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