Tesi: "IMRT" – Grafiati

1

Sheta, Amal. "IMRT and Rotational IMRT (mARC) Using Flat and Unflat Photon Beams". Doctoral thesis, Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-208212.

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For more than 50 years attening filters have been inserted into the beam path oflinacs to produce a uniform energy fluence distribution of the photon beam and make it suitable for clinical use. Recently, linacs without flattening fifilter (Flattening FilterFree - FFF) are increasingly used in radiotherapy because of its benefifits, e.g. high dose rate (2000 MU/min), reduced scattered and leakage radiation. Hypofractionated radiotherapy is interested in the high dose rate of FFF beams to shorten the treatment delivery time (TDT) especially the FFF beams have acceptable flatness at small fifieldsizes. Radiotherapy techniques that deliver intensity-modulated beams (IMBs), e.g.Tomotherapy, intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), deal with the non-uniformity of the FFF beam profifile and produce homogeneous dose to the target as FF beams do. Siemens modified the Artiste linac in order to enable photon beam delivery with and without a flattening fifilter. The VMAT version developed by Siemens for Artiste linacs as a novel radiation technique is a modulated arc therapy (mARC). mARC technique is available with single, double and multiple complete or partial arcs. The aims of the current study were the determination of the main characteristics of 7 MV and 11 MV FFF photon beams in comparison with their corresponding 6 MV and 10 MV FF photon beams from Artiste digital linacs. Furthermore, IMRT planning comparisons using FF and FFF photon beams were performed using an Oncentra planning system. The performance of various mARC techniques were estimated and compared with Step and Shoot (S&S) IMRT by using a RayStation planning system. The mARC plans created by FF and FFF beams were evaluated to know which technique is the best. All the treatment plans were created for simple and complex shaped target volumes. The treatment plans are compared using two parameters - plan quality and treatment effi ciency. In addition to the planning study, the plan quality assurance of IMRT and mARC plans were performed using two difffferent volumetric quality assurance devices, Delta4 and Octavius 4D. Removal of the flattening fifilter causes changes in the dosimetric features of photon beams. IMRT plans with and without flattening fifilter were clinically acceptable where both plans have similar quality. In comparison with IMRT-FF, IMRT-FFF plansrequire more MUs and for some clinical cases require longer TDT. mARC technique can deliver dose distributions that are comparable to S&S-IMRT and could be an alternative with a potential to improve the effi ciency of the IMRT treatment delivery.

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2

Khadija, Murshed. "A Comparative Analysis of Conventional MLC Based IMRT and Solid Compensator Based IMRT Treatment Techniques". University of Toledo Health Science Campus / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=mco1264434257.

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3

Schiefer, Hans. "Kontrollen des Planungs-Bestrahlungsprozesses bei IMRT /". Basel : [s.n.], 2009. http://edoc.unibas.ch/diss/DissB_8781.

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4

Matsushima, Luciana Cardoso. "Determinação das curvas de isodose e confirmação do planejamento em Radioterapia de Intensidade Modulada - IMRT convencional empregando as técnicas de termoluminescência, luminescência opticamente estimulada e detectores semicondutores". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-24042015-095037/.

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A radioterapia é uma das três principais modalidades utilizadas no tratamento de doenças malignas como o câncer; as outras duas são a quimioterapia e a radiocirurgia. Em contraste com outras especialidades médicas que necessitam principalmente do conhecimento clínico e da experiência de especialistas, a radioterapia, com a utilização da radiação ionizante no tratamento do câncer, depende do investimento pesado em tecnologias modernas e dos esforços colaborativos de diversos profissionais, cuja equipe coordenada influencia, sobremaneira, o resultado do tratamento. A Radioterapia de intensidade modulada (IMRT) com o uso de colimadores multilâminas (multileaf collimators MLCs) tem o potencial para alcançar um alto grau de conformidade da dose no alvo (tumor a ser tratado) e ainda promover a proteção de tecidos normais do que a maioria de outras técnicas de tratamento, especialmente para volumes-alvo ou órgãos de risco com formatos complexos. Entretanto, estudos recentes mostraram que baixas doses de radiação podem causar tumores secundários. Esse trabalho tem como objetivo a determinação da distribuição de dose de radiação absorvida em diversas simulações de tratamentos radioterápicos com o uso de dosímetros compostos de LiF:Mg,Ti; CaSO4:Dy e Al2O3:C, utilizando um objeto simulador de polimetilmetacrilato (PMMA) empregando as seguintes técnicas dosimétricas: termoluminescência (TL), luminescência opticamente estimulada (OSL) e detectores semicondutores (diodos).
Radiotherapy is one of three principal treatment modalities used in the treatment of malignant diseases such as cancer; the other two are chemotherapy and radiosurgery. In contrast to other medical specialties that rely mainly on the clinical knowledge and experience of medical specialists, radiotherapy, with its use of ionizing radiation in treatment of cancer, relies heavily on modern technology and the collaborative efforts of several professionals whose coordinated team approach greatly influences the outcome of the treatment. Intensity modulated radiation therapy (IMRT) with the use of multileaf collimators (MLCs) has the potential to achieve a much higher degree of target conformity and normal tissue sparing than most other treatment techniques, especially for target volumes or organs at risk with complex shapes. However, recent studies show that low doses of radiation can cause secondary cancers. This work aims to determine the radiation dose distribution in several radiation therapy treatment simulations with use of LiF:Mg,Ti; CaSO4:Dy and Al2O3:C dosimeters using a PMMA phantom for the following dosimetry techniques: thermoluminescence, optically stimulated luminescence (OSL) and semiconductor detectors.

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5

Barros, Catarina da Silva. "Estudo, avaliação e optimização em radioterapia - IMRT". Master's thesis, Faculdade de Ciências e Tecnologia, 2010. http://hdl.handle.net/10362/4797.

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Mestrado Integrado em Engenharia Biomédica
O cancro continua ser um problema de saúde pública, apesar dos esforços e desenvolvimentos verificados na luta contra o mesmo. Estima-se que em 2030 a incidência do cancro na população mundial duplique, sendo o envelhecimento da população a principal causa apontada pela Organização Mundial de Saúde (WHO, do inglês World Health Organization Desta forma, os avanços tecnológicos na saúde têm sido constantes, trazendo desenvolvimentos essenciais no diagnóstico e tratamento das mais variadas patologias. No que concerne à radioterapia, especialidade terapêutica utilizada em cerca de 50% a 60% dos doentes oncológicos, o seu estado acompanha os panoramas mais vanguardistas. ). A radioterapia de intensidade modelada (IMRT, do inglês Intensity-Modulated Radiation Therapy), resultante da evolução da técnica de radioterapia conformacional tridimensional (3D-CRT, do inglês Three-Dimensional Conformal Radiotherapy), veio a acrescentar à conformação geométrica do feixe de radiação, a capacidade de utilização da modulação da intensidade do mesmo. Desta forma a IMRT permite uma conformação dosimétrica, que salvaguarda ao máximo a integridade das estruturas adjacentes, bem como, o escalonamento de dose, mais eficaz do ponto de vista de controlo tumoral. No entanto, este ganho em saúde faz-se acompanhar, muitas vezes, do aumento de custos. Neste contexto é essencial avaliar e quantificar os custos, e as respectivas consequências/benefícios clínicos inerentes à utilização da tecnologia. Com este projecto, realizado em contexto empresarial, pretendeu-se estudar, avaliar e elaborar propostas de optimização que visem a implementação clínica da IMRT, aplicada a patologias da próstata e mama, num Serviço de Radioterapia de um Prestador de Cuidados de Saúde (PCS) público. Neste prestador, foram analisados todos os procedimentos do workflow de 3D-CRT das patologias da cabeça e pescoço (C&P), mama e da próstata, incluindo a caracterização a nível dos recursos humanos (RH) com a respectiva duração característica de cada tarefa mapeada, quer dos recursos tecnológicos envolvidos. Visto este PCS já ter iniciado a aplicação clínica de IMRT ao cancro de C&P, foram também analisados os procedimentos referentes a esta patologia, de forma a servirem de base para a realização dos modelos de IMRT para a mama e próstata, tal como, para comparar os custos inerentes à realização desta técnica, em relação à técnica conformacional. Por último projectou-se cenários da realização IMRT ao invés da 3D-CRT no PCS em estudo, para a neoplasia que economicamente se mostrou mais favorável.

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6

Garcia, Aaron Nicholas. "Comparative Investigation of Dosimetric Tools in IMRT". Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1187369612.

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7

Cruz, António Manuel Costa. "IMRT beam angle optimization using Tabu search". Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/17714.

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Mestrado em Matemática e Aplicações
O número de pacientes com cancro continua a crescer no mundo e a Organização Mundial da Saúde considerou mesmo esta como uma das principais ameaças para a saúde e o desenvolvimento humano. Dependendo da localização e das especi cidades do tumor, existem muitos tratamentos que podem ser usados, incluindo cirurgia, quimioterapia, imunoterapia e radioterapia. A Radioterapia de Intensidade Modulada (IMRT | Intensity Modulated Radiation Therapy) é uma das modalidades mais avançadas de radioterapia, onde a otimização pode ter um papel importante no que diz respeito à qualidade do tratamento aplicado. Em IMRT, o feixe de radiação pode ser visto como se fosse constituído por vários pequenos feixes, pelo uso de um colimador multifolhas, que permite que a intensidade seja modulada. Este complexo problema de otimização pode ser dividido em três subproblemas, que estão relacionados entre si e que podem ser resolvidos sequencialmente. Para cada paciente, os ângulos de onde a radiação ir a ocorrer têm de ser determinados (problema geométrico | otimização angular). Depois, para cada um desses ângulos, o mapa de intensidades (ou fluências) tem de ser calculado (problema das intensidades | otimização das fluências). Finalmente, e necessário determinar o comportamento do colimador multifolhas, de forma a garantir que as intensidades são, de facto, atribuídas (problema de realiza ção). Em cada um destes problemas de otimização, a qualidade do tratamento atribuído depende dos modelos e algoritmos usados. Neste trabalho, a nossa atenção estará particularmente focada na otimização angular, um problema conhecido por ser altamente não-convexo, com muitos mínimos locais e com uma função objetivo que requer muito tempo de computação para ser calculada. Tal significa, respetivamente, que os algoritmos que sejam baseados no cálculo de gradientes ou que requeiram muitas avaliações da função objetivo podem não ser adequados. Assim, os procedimentos metaheurísticos podem ser uma boa alternativa para abordar este problema, visto que são capazes de escapar de mínimos locais e são conhecidos por conseguirem calcular boas soluções em problemas complexos. Neste trabalho ser a descrita uma aplicação para Pesquisa Tabu. Serão ainda apresentados os testes computacionais realizados, considerando dez casos clínicos de pacientes previamente tratados por radioterapia, pretendendo-se mostrar que a Pesquisa Tabu e capaz de melhorar os resultados obtidos através da solução equidistante, cujo uso e comum na prática clínica.
The number of cancer patients continues to grow worldwide and the World Health Organization has even considered cancer as one of the main threats to human health and development. Depending on the location and speci cities of the tumor, there are many treatments that can be used, including surgery, chemotherapy, immunotherapy and radiation therapy. Intensity Modulated Radiation Therapy (IMRT) is one of the most advanced radiation therapy modalities, and optimization can have a key role in the quality of the treatment delivered. In IMRT, the radiation beam can be thought of as being composed by several small beams, through the use of a multileaf collimator, allowing radiation intensity to be modulated. This complex optimization problem can be divided in three related subproblems that can be solved sequentially. For each patient, the angles from which the radiation will be delivered have to be determined (geometric problem | beam angle optimization). Then, for each of these angles, the radiation intensity map is calculated ( uence or intensity optimization). Finally, it is necessary to determine the behavior of the multileaf collimator that guarantees that the desired radiation intensities are, indeed, delivered (realization problem). In each of these optimization problems, the quality of the treatment delivered depends on the models and algorithms used. In this work the attention will be focused in beam angle optimization, a problem known to be highly non{convex, with many local minima and with an objective function that is time expensive to calculate, which, respectively, means that algorithms that are gradient{based or that require many objective function evaluations will not be adequate. Metaheuristics can be the right tool to tackle this problem, since they are capable of escaping local minima and are known to be able to calculate good solutions for complex problems. In this work, an application of Tabu Search to beam angle optimization is described. Computational results considering ten clinical cases of head{and{neck cancer patients are presented, showing that Tabu Search is capable of improving the equidistant solution usually used in clinical practice.

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8

Markovic, Miljenko. "Comparison of IMRT delivery methods a thesis /". San Antonio : UTHSC, 2008. http://learningobjects.library.uthscsa.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=58&CISOBOX=1&REC=13.

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9

Heeger, Jonas [Verfasser]. "Bestrahlung von Kopf-Hals-Tumoren mit fluenzmodulierter Radiotherapie (IMRT) : Vergleich zweier IMRT-Techniken mit 3D-konformaler Bestrahlung / Jonas Heeger". Köln : Deutsche Zentralbibliothek für Medizin, 2013. http://d-nb.info/1042333823/34.

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10

Flosi, Adriana Aparecida. "Desenvolvimento de cálculo de unidades monitoras para IMRT". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-03042012-092734/.

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A verificação de forma independente do cálculo de dose e de unidades monitoras num plano de tratamento de IMRT é um passo importante nos procedimentos de garantia de qualidade da técnica em questão. Atualmente este verificação é baseada apenas em medidas experimentais demoradas e trabalhosas. Neste trabalho foi desenvolvido uma metodologia de cálculo de unidades monitoras de forma independente como uma nova ferramenta para garantir a qualidade e exatidão dos tratamentos de IMRT. Os valores encontrados se aproximam bastante dos valores calculados pelo sistema de planejamento utilizado, de forma que o algoritmo de cálculo desenvolvido apresentou uma concordância dentro de ± 1,8 % para uma geometria simples. Após diversos testes e com os níveis de ação devidamente estabelecidos, a verificação independente da unidade monitora para planos de tratamento de IMRT se tornará uma ferramenta efetiva e eficiente no controle de qualidade que ajuda a identificar e reduzir possíveis erros de tratamento em radioterapia. Como contribuição original deste trabalho, assegura-se aos serviços de Radioterapia a utilização da metodologia desenvolvida como ferramenta de controle de qualidade em tratamentos com IMRT. Em especial aos serviços que não dispõem de recursos econômicos para adquirirem softwares comercialmente disponíveis para o cálculo independente da unidade monitora.
Independent verification of dose calculations and monitor units settings of IMRT treatment plans is an important step in the quality assurance procedure for IMRT technique. At present, the verification is mainly based on experimental measurements, which are time consuming and laborious. In this work an independent methodology of monitor units calculation was developed as a new tool for IMRT treatments quality and precision assurance. The values found are near those calculated by the treatment planning system used, in a manner that the calculation algorithm demonstrated ± 1,8 % concordance in a simple geometry with the system. After several tests and the levels of action well established, the independent monitor units verification for IMRT treatment plans will become an effective and efficient tool in quality assurance, helping identification and the reduction of possible mistakes in radiotherapy treatments. To radiotherapy services is assured the use of the developed methodology as a tool of quality control in IMRT treatments as an original contribution of this work, specially those that do not dispose financial resources to acquire commercially available independent monitor unit calculus software.

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FLOSI, ADRIANA A. "Desenvolvimento de cálculos de unidades monitoras para IMRT". reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10087.

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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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12

Borges, Leandro Federiche. "Validação da metodologia de controle da qualidade in vivo com auxílio de filme radiocrômico, aplicados à teleterapia". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/17/17159/tde-04012017-155803/.

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A aferição da dose por técnica de dosimetria in vivo garante que a dose calculada pelo sistema de planejamento seja àquela entregue pelo acelerador linear (AL) durante a radioterapia, garantindo assim os processos de controle de qualidade. O objetivo deste trabalho foi validar a técnica de controle de qualidade em IMRT utilizando filme radiocrômico. Foram analisados 47 planejamentos de IMRT de três regiões: próstata, cabeça e pescoço e crânio. Para cada planejamento utilizouse um filme radiocrômico EBT2 acoplado ao cabeçote do acelerador linear através de uma bandeja preparada para o filme. A leitura e posterior análise da dose pontual e distribuição de dose após 24 horas, foi realizada em sofware desenvolvido em MatLab. O índice de aprovação foi de 92%. Quatro planos foram reprovados em pelo menos 1 critério, sendo 3 de cabeça e pescoço e 1 de crânio. Os resultados da dosimetria in vivo com filme radiocrômico foi validada, podendo ser considerada uma técnica confiável e prática na aferição da dose em radioterapia.
The measurement of dose, using the in vivo technique dosimetry, ensures that the dose calculated by the planning system is exactly the same as the dose delivered in linear accelerator, this ensures quality assurance in radiotherapy. The objective of this study was to evaluate the quality control techinique of IMRT treatments using radiochromic film. We analyzed 47 IMRT plans, which divided into three regions: Prostate, head and neck, and skull. For each plan, we used a radiochromic film coupled in linear accelerator head by a tray prepared to film placement. The film was stored for 24 hours after irradiation. Reading and analysis of point dose and 2D dose distribution were performed after this period. ll plans analyzed, the approval rating was 92%, and the others were flunked at least one criterion. Based on the results obtained in vivo dosimetry with radiochromic film was validated. This technique is reliable and practical to measure the dose delivered by linear accelerator.

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13

Haukås, Solveig. ""Optimalisering av IMRT-planar for øyre-nase-hals-kreft"". Thesis, Norwegian University of Science and Technology, Department of Physics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-6259.

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In the dose planning system Oncentra MasterPlan there is a module for IMRT planning (IMRT - Intensity modulated radiation therapy). This module optimizes the plan based on given requirements for doses given to target volumes and organs at risk. The new enhanced algorithm (PBE), which is implemented in MasterPlan, is supposed to make the IMRT planning more exact and effcient. A cylindrical shaped target volume, with an organ at risk inside, was defined in MasterPlan to evaluate the dose distribution modeled by the PBE algorithm. A uniform dose of 2 Gy for the target volume and a maximum dose of 0.5 Gy for the organ at risk were set for the optimization. The plans were optimized with different angles of the collimator system, and film measurements were done according to the plans. It was found that the PBE algorithm gives a good description of the dose distribution, “tongue and groove" included, for IMRT optimization.

The principle of IMRT is to treat the patient with non-uniform beams from different directions around the patient. The beams are being optimized to give a high dose to the target volume and an acceptable low dose to the normal tissue and the organs at risk. An !IMRT value" is given as a measure of the quality of the optimization in MasterPlan. This value is used to compare treatment plans, to evaluate the quality of the optimization for different parameters.

The parameters which were examined were the angle of the collimator system, the number of beams given, number of segments, minimum number of MU per segment and minimum field size per segment. It was of interest to see how the parameters affect the IMRT optimization in MasterPlan. 11 patient plans were therefore replanned by varying these parameters. The “IMRT values" for the optimized plans were compared with the one-way ANOVA test Tukey HSD.

No significant differences were shown between the “IMRT values" of the plans with different angles of the collimator system. Nor were any significant differences shown between plans with 5, 7 or 9 beams equally spaced around the patient. Treatment plans containing beams equally spaced were significantly better than plans containing beams given only in front of the patient. The treatment plans containing 30 segments were significantly worse than the plans containing 50, 70 or 150 segments, according to the Tukey test. Although there was no porvable significant difference between the “IMRT values" for 50 and 70 segments, all the tested patients had a lower value (indicating better optimization) for plans containing 70 segments. The improvement of the optimization of plans with more than 70 segments was found to be small. There was no significant difference between the optimization of plans with 2 or 4 MU.

In addition to optimize the weight and fluence of the beams, MasterPlan can also optimize the gantry angles. This has been done for plans of 5 beams and with two different set of initial angles. Gantry optimizations were performed with initial angles formed as a fan in front of the patient and with angles equally spaced around the patient. It was found that in MasterPlan, different angles are found to be optimal depending on the initial angles.

One often wants to give a small part of the target volume a higher dose than the rest of the target, in treatment of head and neck cancer. This can be done in two ways. A boost plan can be made in addition to the original plan without boost, where a small part of the target volume is given a higher dose. This involves optimization and treatment of two plans. Another way is to integrate the boost plan in the original plan, and in this way make one plan. To see if it is possible to achieve more conform dose distributions for treatment with simultaneous integrated boost (SIB) than with the additional plan, 9 of the patients were planned with both methods. It was found that SIB enables more sparing of the organs at risk. A lower dose, closer to the predefined dose criterias of the target volume outside the boost volume is also achieved.

Planleggingsprogrammet Oncentra MasterPlan har ein modul for IMRT-planlegging (IMRT - Intensity modulated radiation therapy). Denne modulen optimaliserer planar på bakgrunn av førehandsgjevne dosekrav til målvolum og risikoorgan. Den nye ”enhanced"-algoritmen (PBE) som no er implementert i MasterPlan skal gjere IMRT-planlegginga meir korrekt og effektiv. For å sjekke kor bra dosefordelingane er modellert av PBE-algoritmen vart det definert eit sylinderforma, holt målvolum med eit risikoorgan inni. Det vart sett krav om uniform dose på 2 Gy for målvolumet og maks 0,5 Gy for risikoorganet. Planar vart optimalisert med omsyn til desse krava og med ulike vinklar på kollimatorsystemet. Deretter vart det bestrålt filmar i samsvar med planane, og desse vart samanlikna med dosefordelinga i planane. Det vart funne at PBE-algoritmen gjev ei svært bra beskriving av dosefordelingar med ”tongue and groove"-effektar ved IMRT-optimalisering.

Prinsippet bak IMRT er å behandle ein pasient med ikkje-uniforme felt frå ulike retningar rundt pasienten. Desse felta har blitt optimalisert for å gje høg dose til målvolumet og akseptabel låg dose til det omkringliggjande normalvevet og risikoorgana. I MasterPlan vert det oppgjeve ein IMRT-verdi som er eit mål på kor god optimaliseringa er i forhold til dei gjevne dosekrava. Denne IMRT-verdien er nytta ved samanliking av planar, for å finne ut kor god plan ein kan oppnå ved bruk av ulike parametrar under optimaliseringa.

Parametrar som vart undersøkt var vinkel på kollimatorsystemet, tal på felt, feltretning, tal på segment, minimum MU per segment og minimum feltstorleik per segment. For å sjå korleis valet av desse parametrane påverkar IMRT-optimaliseringa i MasterPlan, vart 11 pasientplanar replanlagt ved å variere parametrane. IMRTverdien til dei optimaliserte planane vart deretter samanlikna ved hjelp av one-way ANOVA-testen Tukey HSD.

Tukey-testen viste at det ikkje var nokon signifkant forskjell mellom IMRTverdiane til planane med ulike kollimatorvinklar. Det vart heller ikkje vist nokon signifkant forskjell mellom planar med 5, 7 og 9 felt jamt fordelt rundt pasienten. Planar med felt jamt fordelt rundt pasienten vart påvist å vere signifikant betre enn felt i vifteform framføre pasienten. I følgje Tukey-testen er planen med 30 segment signifikant dårlegare enn planane med 50, 70 og 150 segment. Det vart òg sett at optimaliseringa vart betre med 70 segment enn med 50 segment for alle dei testa pasientane. Ved å bruke fleire enn 70 segment vart det lita forbetring av optimaliseringa. For dei 11 pasientane vart det ikkje funne nokon signifikant forskjell for optimaliseringa av planar med 2 og 4 MU.

I tillegg til å optimalisere vektinga og intensiteten til felta, er det i MasterPlan mogleg å optimalisere gantryvinklane som felta vert gjevne frå. Dette vart forsøkt for planar med 5 felt og med to ulike sett av gjevne startvinklar. Det vart gjort gantryoptimalisering med startvinklar i vifteformasjon framføre pasienten og med startvinklar jamt fordelt rundt pasienten. Det viste seg at MasterPlan kom fram til forskjellige optimale vinklar avhengig av startvinklane.

I behandling av øyre-nase-hals-kreft er det ofte ynskjeleg å gje ein liten del av målvolumet høgare dose enn resten av volumet. Dette kan gjerast på to måatar. Ein kan lage ein boostplan i tillegg til den vanlege planen, der ein mindre del av målvolumet får høgare dose. I dette tilfellet må ein optimalisere to planar og behandle i samsvar med begge planane. Alternativt kan ein integrere boostplanen i den opphavlege planen slik at berre ein plan vert laga. For å sjå om ein kan oppnå meir konforme planar ved samstundes integrert boost (SIB) enn ved tilleggsboost, vart 9 av pasientane planlagt på begge desse måtane. Det vart funne at SIB gjev moglegheit for meir sparing av risikoorgan og at ein får jamt over ein lågare dose, som er meir i samsvar med krava, til målvolumet utanfor boostvolumet for desse planane.

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14

Xian, Zheng. "Dose verification of a stereotactic IMRT treatment planning system". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/23810.

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In this project, ion chamber measurement and film dosimetry were used to verify dose distributions for a new stereotactic IMRT (Intensity Modulated Radiation Therapy) treatment planning system. This technique combines the principles of stereotactic radiosurgery and IMRT to significantly increase the positioning accuracy compared with conventional IMRT . Ion chamber measurements reveal that the discrepancy between the measured and the calculated dose at the isocenter can be up to 2%. Angular dependence of ion chamber sensitivity and the tissue equivalence of the phantom material were determined to be the main sources of this discrepancy. Radiochromic film was used as the film dosimeter in the project. A set of performance tests of Gafchromic EBT film indicated that the uncertainty in Gafchromic EBT film dosimety was expected to be 2.5%. However, the discrepancies we found in measurements of clinical cases using the film were much larger than this. And further investigation into this discrepancy was beyond the scope of this thesis.

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15

Fraser, Danielle J. "Characterizing ionization chamber dosimetry in inverse planned IMRT fields". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84031.

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It is standard practice in radiation therapy to have two independent calculations for the number of monitor units used in patient treatment plans. The relationship between monitor units and absorbed dose to water is sophisticated for MLC-based IMRT. Verification measurements of absorbed dose to water with ionization chambers in MLC-based IMRT fields remains uncertain and the accuracy of computer modeling is limited by the physics assumptions used. In this thesis, point dose measurements from three cylindrical ionization chambers of different collecting volumes are evaluated against the CORVUS (NOMOS Corporation, Cranberry, PA) finite-size pencil beam algorithm and the PEREGRINE (NOMOS Corporation, Cranberry, PA) Monte Carlo calculation engine. After establishing the characteristics of the chambers and treatment planning system under various beam geometries, dynamic and step and shoot MLC deliveries were evaluated. Between detectors, the smallest volume chamber measured the greatest dose. Compared to measurements, CORVUS and PEREGRINE both underestimated the dose in IMRT fields by approximately 5%. On average PEREGRINE yielded better agreement than CORVUS by 2%.

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16

Boudreau, Chantal. "The use of inhomogeneity corrections for inverse planned IMRT /". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81268.

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In this thesis, the use of inhomogeneity corrections in intensity modulated radiotherapy (IMRT) inverse treatment planning is investigated. Firstly, the dosimetric consequences of CT beam hardening artifacts present on images used for treatment planning are estimated and found to be of little clinical significance (<1% dose difference). Secondly, experiments to evaluate the PEREGRINE Monte Carlo system (Nomos, Cranberry, PA) are undertaken for a 6 MV photon beam. The use of inhomogeneity corrections in clinical treatment planning is assessed for five clinical head and neck cancer cases. The cases are planned with the CORVUS optimization module and the dose distributions are then calculated with CORVUS and PEREGRINE in order to compare the two calculation techniques with emphasis on how each method handles tissue inhomogeneities. The plans are assessed in terms of dose, dose-volume distributions and the biological indices of TCP and NTCP. On average, PEREGRINE calculates a 1% lower mean dose to the GTV and a 2% lower mean dose to the CTV compared to the CORVUS calculations with EPL inhomogeneity corrections. In the last part of this work, quality assurance (QA) measurements are performed for a clinical case to investigate how the CORVUS and PEREGRINE calculations agree with the dose measurements on a QA phantom.

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17

Anderson, J. W. "The Design and Optimisation of Novel Collimators for IMRT". Thesis, Institute of Cancer Research (University Of London), 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516269.

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18

Osewski, Wojciech. "Rekonstrukcja rozkładu dawki w technikach dynamicznych : IMRT i VMAT". Doctoral thesis, Katowice : Uniwersytet Śląski, 2013. http://hdl.handle.net/20.500.12128/5389.

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Abstract (sommario):

Techniki dynamiczne IMRT i VMAT umożliwiają bardzo precyzyjne modulowanie rozkładu dawki w objętości guza nowotworowego przy jednoczesnym oszczędzaniu tkanek zdrowych - struktur krytycznych. Z jednej strony dysponujemy bardzo precyzyjnym systemem planowania rozkładu dawki, z drugiej za realizację planu odpowiada aparat terapeutyczny, który „obarczony” jest tolerancją działania: mechaniczną i elektroniczną. Konieczna jest zatem weryfikacja zgodności rozkładu dawki zaplanowanego ze zrealizowanym - rzeczywistym. W radioterapii każdy plan leczenia musi być zweryfikowany, czy to przed realizacją czy w trakcie terapii. Dlatego, konieczne jest sprawdzenie czy techniki dynamiczne realizowane są poprawnie, zgodnie z obliczonymi wartościami. W systemie planowania Eclipse - firmy Varian Medical Systems, w procesie planowania leczenia w technice dynamicznej generowane są mapy fluencji, na podstawie których wyliczany jest trójwymiarowy rozkład dawki oraz przeliczane są one na ruch listków kolimatora wielolistkowego. Złożenie map fluencji, a co za tym idzie również ruchów listków kolimatora, generuje trójwymiarowy rozkład dawki w ciele pacjenta. Listki kolimatora wielolistkowego poruszają się z pewną tolerancją. W przypadku, gdy taka tolerancja zostaje przekroczona promieniowanie jest wstrzymywane. Interesujące jest to, co dzieje się gdy błąd ruchu listków jest mniejszy od zakresu tolerancji. Jeżeli zaplanowany ruch listków kolimatora różni się od rzeczywistego, wówczas rzeczywisty rozkład dawki musi różnić się od zaplanowanego. Pytanie o ile? Czy można to wyliczyć?

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19

Sheta, Amal [Verfasser], Ulrich [Akademischer Betreuer] Wolf, Thomas [Akademischer Betreuer] Kuhnt, Rolf-Dieter [Gutachter] Kortmann e Tilo [Gutachter] Wiezorek. "IMRT and Rotational IMRT (mARC) Using Flat and Unflat Photon Beams / Amal Sheta ; Gutachter: Rolf-Dieter Kortmann, Tilo Wiezorek ; Ulrich Wolf, Thomas Kuhnt". Leipzig : Universitätsbibliothek Leipzig, 2016. http://d-nb.info/1240627637/34.

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20

Watanabe, Érika Yumi. "Avaliação do dispositivo eletrônico de imagem portal \"Portal Dosimetry\" no controle de qualidade de radioterapia de intensidade modulada". Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-08082011-110213/.

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No presente trabalho serão apresentados testes de comissionamento e de avaliação da utilização do portal dosimetry, da Varian, no controle de qualidade dos planejamentos de radioterapia de intensidade modulada. Os testes de comissionamento foram realizados para caracterizar o portal dosimetry em termos dosimétricos e para avaliar a sua possível aplicação em radioterapia. Esses testes demonstraram que o portal dosimetry possui todas as características necessárias para ser utilizado em dosimetria na radioterapia tais como linearidade da resposta com a dose, independência com a taxa de dose, reprodutibilidade, dentre outras. A avaliação da utilização do portal dosimetry no controle de qualidade de IMRT foi realizada em duas etapas: avaliação da capacidade do dispositivo em detectar erros propositalmente introduzidos em fluências simples e em fluências complexas. Foram introduzidos erros de magnitude conhecida em áreas determinadas das fluências e foi realizado o controle de qualidade dessas fluências com o portal dosimetry e com mais três sistemas dosimétricos: câmara de ionização, filme e matriz de câmaras de ionização. Os dados obtidos com o portal foram comparados com os dos outros dispositivos e todos foram capazes de identificar os erros introduzidos de maneira satisfatória, sendo os valores, normalizados para a fluência original, obtidos com o dosímetro portal indênticos aos da câmara de ionização e aos da matriz de câmaras de ionização (seven29) e diferindo em até 2% dos valores obtidos com os filmes. As fluências medidas com o portal dosimetry foram avaliadas em termos quantitativos e qualitativos. Os índices da função gama fornecidos pelo software de análise do portal dosimetry não apresentaram regras definidas de comportamento em relação aos erros introduzidos e por essa razão a análise qualitativa se mostrou indispensável nos casos avaliados.
In this paper we present commissioning testing and evaluation of the use of Varians portal dosimetry in the quality assurance of intensity-modulated radiotherapy. The commissioning tests were performed to characterize the portal dosimetry in terms dosimetric and to assess the its possible application in radiotherapy. These tests demonstrated that portal dosimetry has all the characteristics to be used for dosimetry in radiotherapy such as linear response with dose, the independence of dose rate, reproducibility, and others. The evaluation of the use of portal dosimetry in quality control of IMRT was performed in two steps: assessing the ability of the device to detect errors deliberately introduced in simple and complex fluences. Errors of known magnitude were introduced in certain areas of fluences and was carried out quality control of these fluences with portal dosimetry and three dosimetric systems: ionization chamber, film and array of ionization chambers. The data obtained from the portal were compared with those of other devices and all were able to identify errors introduced satisfactorily, the values, normalized to the original fluence, obtained with the portal dosimetry were similar to the ionization chamber and the array of ion chambers (seven29) and differing in up to 2% of the values obtained with the films. The fluences measured with the portal dosimetry were evaluated both quantitatively and qualitatively. The index of the gamma function provided by software analysis of portal dosimetry showed no defined rules of behavior in relation to the errors introduced and for this reason the qualitative analysis has proved indispensable in cases evaluated.

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21

Obata, Yasunori, e 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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22

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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23

Hofmann, Tobias. "Evaluation der intensitätsmodulierten Bestrahlungstechnik für die stereotaktische Strahlentherapie im kraniellen Bereich". Master's thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1234514545566-63458.

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Die fraktionierte stereotaktisch geführte Radiotherapie stellt eine Möglichkeit der Behandlung intrakranieller Tumoren dar, bei denen eine chirurgische Resektion nicht oder nicht vollständig möglich ist. Ziel dieser Arbeit war der Vergleich der Dosisverteilung von Bestrahlungsplänen, die mittels fluenzmodulierter (IMRT) und 3D konformaler stereotaktisch geführter Bestrahlungstechnik (conformal beam) für Hypophysenadenome und petroclivale Meningeome erstellt wurden. Auf Basis des CT-Datensatzes eines Alderson-Phantoms erfolgten zunächst die systematische Untersuchung der IMRT Eingabeparameter und die Definition von Dosis-Volumen-Constraints für beide Tumorentitäten. Im Anschluss wurden die gewonnenen Erkenntnisse bei der fluenzmodulierten Bestrahlungsplanung von 10 realen Patienten, 5 je Tumorentität, angewendet. Zusätzlich wurde für jeden dieser Patienten ein 3D konformaler Bestrahlungsplan erstellt. Die Evaluation der Bestrahlungspläne erfolgte durch verschiedene quantitativer Parameter unter Einbeziehung der subjektiven Beurteilung der Dosisverteilung. Bei beiden Tumorentitäten lieferte in je 4 von 5 Fällen die IMRT einen Vorteil gegenüber der conformal beam Bestrahlung, der vor allem auf der besseren Erfassung, Dosishomogenität und höheren Median-Dosis im bestrahlten Zielvolumen (PTV) beruhte. Komplex geformte Zielvolumina profitierten dabei besonders von der Fluenzmodulation. Dem stand jedoch in einigen Fälle eine stärke Belastung der Risikoorgane (OAR) mit einer höheren Dosis und die generell höhere Anzahl notwendiger Monitoreinheiten gegenüber. Zuletzt wurde auf Basis von MatLAB eine Software entwickelt, welche die Verifikation von stereotaktisch geführten IMRT-Bestrahlungen und die Analyse von Winston-Lutz-Tests ermöglicht.

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24

Andræ, Nils. "Commissioning and validation of small subfields in Step-and-shoot IMRT". Thesis, Stockholm University, Medical Radiation Physics (together with KI), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8316.

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One of the most used irradiation techniques in modern radiation therapy is step-and-shoot IMRT. The accuracy of this technique when delivering complex dose distributions strongly depends on the size of the subfields. The aims of this study is to determine the minimum size of subfields that can be used efficiently in Step-and-Shoot IMRT, to investigate the validation process for beam delivery and treatment planning dose calculations, and to find recommendations for practical clinical implementations.

Two different detectors, a CC04 ion chamber and a SFD stereotactic diode, have been used for measuring head scatter factors in air (Sc), total output factors (Scp) and dose profiles in water for a wide range of field sizes. The measurements were compared to calculations done with a pre-release version of the Nucletron MasterPlanTM v 3.1 treatment planning system that employs a novel, high resolution fluence modelling for both its pencil beam and collapsed cone dose calculation algorithms. Collimator settings were explicitly checked using FWHM film measurements with a build-up sheet of tungsten placed close to the treatment head to reduce the influence from lateral electron transport and geometrical penumbra. An analysis of the influence and sensitivity of Scp for small fields with respect to the linear accelerator source size and shape was also made.

The measurements with the ionization chamber and the stereotactic diode showed good agreements with each other and with the treatment planning system calculations for field sizes larger than 2×2 cm2. For small field sizes, measurements with different detectors yielded different results. Calculations showed agreements with measurements with the smallest detector, provided careful field size calibration and commissioning of calculation parameters. Uncertainties in collimator settings and source characteristics were shown to yield large uncertainties in Scp for fields smaller than 2×2 cm2.

The treatment planning system was found to properly handle small subfields but results were very sensitive to uncertainties in source size, as well as calibration and reproducibility of the collimator settings. Therefore if subfields smaller than 2×2 cm2 are to be used in IMRT extra care should be taken to determine the source characteristics and to calibrate the collimators. The volume of the detectors used for validation of such small fields and the loss of charged particle equilibrium conditions also have to be taken into consideration.

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25

Sample, Scott Alexander. "Evaluation of Beam Angle Scoring Using MCNP and Applied to IMRT". Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14570.

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Equispaced beam arrangements are typically used for IMRT plans. This beam arrangement provides adequate dose coverage to the target while sparing dose to other structures. However, an equispaced beam arrangement may not provide the best dose coverage to the target while sparing dose to the other structures. Beam angle optimization attempts to optimize the beam directions to produce a better IMRT plan; this is achieved by increasing dose to the target while minimizing dose to the remaining structures. Most methods of beam angle optimization attempt to optimize the beam angles and the beam intensity profiles to find an optimal set of beam angles. This thesis attempts to optimize the beam angles without determining the beam intensity profiles. An MCNP simulation is run to score the beam directions; the simulation is run as an adjoint problem to reduce simulation time, with the target as the source and the detectors scoring the dose for the gantry angles of the beam. Then, an optimization algorithm is run to select a set of beam angles for an optimized IMRT plan. The optimized IMRT plan is compared to an equispaced IMRT plan on a commercial treatment planning system to determine if this method of beam angle optimization is better than using an equispaced beam arrangement. The results of this thesis indicate that the coupling of an MCNP simulation for scoring with an optimization algorithm to select beam angles will produce a better IMRT plan than an equispaced IMRT plan. Three different geometries were used and for all geometries, the optimized IMRT plan had a higher average dose to the target while maintaining or increasing dose sparing to the critical structure and normal tissue.

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26

Bragg, Christopher Mark. "Implementation of IMRT Methods including the assessment of a new calculation algorithm". Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490192.

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The implementation of IMRT methods including the assessment of a new calculation algorithm The development of intensity modulated radiotherapy (IMRT) planning techniques has introduced new possibilities for improving the treatment of cancer. However, as just one step in the radiotherapy process its potential cannot be fully realised without the continuing development of other steps such as dose calculation accuracy and imaging. The aims of this were threefold. The first aim was to investigate the use ofIMRT in the treatment of tumours of the parotid and non-small cell lung cancer (NSCLC). Secondly, the potential for improving the planning of IMRT NSCLC treatments through the incorporation of lung function information derived from hyperpolarised 3-helium magnetic resonance imaging eHe-MRI) was .studied. The final aim was to investigate the impact of a new convolution-superposition dose calculation algorithm, the Analytical Anisotropic Algorithm (AAA), on the planning and pretreatment verification ofIMRT treatments for a range of sites. Class solutions were developed for the IMRT treatment of parotid and NSCLC. Improved sparing of normal lung tissue was found to be possible by the inclusion oflung ventilation information from 3He-MRI in the IMRT planning process, without detriment to target coverage. A detailed dosimetric assessment of the performance of the AAA in less challenging situations than those posed by IMRT showed its accuracy to be excellent in situations ranging from heterogeneous phantoms to simulated treatment plans. AAA calculations of IMRT plans agreed with measurement generally to within 3% or 3mm distance to agreement, an improvement in accuracy over the previous pencil beam algorithm, particularly in regions of low density. Reassessment of NSCLC plan acceptance criteria is necessary in the light of this.

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27

Sonier, Marcus. "IMRT treatment planning for arteriovenous malformations : patient stratification and dosimetric quality assurance". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/43782.

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Stereotactic Radiosurgery is a treatment of choice for Arteriovenous Malformations (AVMs) in anatomical locations associated with a risk of surgical complications. However, SRS has a risk of toxicity due to radiation injury to brain tissue. Therefore, use of intensity-modulated radiotherapy (IMRT) has been advocated because, compared to 3D Conformal Radiotherapy (3DCRT), it leads to improved PTV conformity and Normal Tissue (NT) sparing. The aim of this study was: 1) to develop stratification rules for AVM patients based on benefits they receive from IMRT; 2) to assess optimized dose distributions against prospectively collected data for symptomatic radiation injury; 3) to test and benchmark IMRT QA procedures for patient applications with the iPlan system. Thirty-one AVM patients previously treated with 3DCRT were replanned using static gantry IMRT for BrainLab microMLC using the iPlan system, with the 3DCRT plans as a reference. First, PTV constraints were applied and the conformity of the prescription dose to the PTV was compared between the treatment techniques. Next, NT constraints were introduced into the IMRT plans at the 7 and 12Gy isodoses. These constraints were manipulated to achieve maximum NT sparing while maintaining PTV coverage. Then, NT volumes receiving 7 and 12Gy were compared between the plan types. Finally, ion chamber and film dose verification were performed to scrutinize the accuracy of the IMRT improvements and determine the clinical validity of each plan. Examination of conformity index, NT max dose, and 7 and 12Gy isodose volumes showed a separation of patients into those who did and did not benefit from IMRT for two plan types: PTV Only and OAR Low. For PTV Only, each subset of patients received improvements of 0.10-0.68, 4.0-12.3%, 0-7.072cc, and 0.5-4.496cc, respectively, while, for OAR Low, patients received improvements of 0.10-0.58, 0-6.5%, 1.0-7.952cc, and 0.5-3.704cc, respectively. The 12Gy volume results translated to a decrease in the probability of symptomatic injury by 0.3-11.2% and 0.3-9.3% for PTV Only and OAR Low IMRT. In conclusion, this work indicates the potential for significant patient improvements when treating AVMs and provides rules to predict which patients are likely to benefit from IMRT.

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Ho, Kean Fatt. "Optimising dose escalated intensity modulated radiotherapy (IMRT) in head and neck cancer". Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508596.

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29

Lavor, Milton. "Avaliação das ferramentas de controle de qualidade para pacientes submetidos ao IMRT". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-16062011-161534/.

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Atualmente a radioterapia de intensidade modulada (IMRT) está sendo implementada em um número crescente de centros no Brasil. Como conseqüência disto, muitas instituições estão enfrentando o problema de executar um programa de controle de qualidade antes e durante a execução do IMRT na prática da rotina clínica. O objetivo deste trabalho é avaliar e propor uma metodologia para o controle de qualidade de tratamentos com IMRT. Uma câmara de ionização e um detector bidimensional foram utilizados para avaliar a dose absoluta total de todos os campos em um determinado ponto. A distribuição de dose relativa total de todos os campos foi medida com filmes radiocrômicos e um detector bidimensional em uma profundidade no objeto simulador. Uma comparação entre as distribuições de dose medidas e calculadas foi realizada usando o método do índice gama, avaliando o percentual de pontos que satisfazem os critérios de diferença dose de ±3% e distância de concordância de ±3 mm. Como resultado da dosimetria absoluta de 113 feixes de IMRT medidos com uma câmara de ionização e 81 feixes usando o detector bidimensional, foi proposto um nível de ação de cerca de ± 5% em relação ao sistema de planejamento e de tratamento para a verificação da dose em um único ponto na região de baixo gradiente de dose. A análise das medições com o detector bidimensional mostrou que o valor da função gama foi <1 para 97,7% dos dados e, para o filme, o valor da função gama foi <1 para 96,6% dos dados. Neste trabalho pode-se concluir que para uma entrega exata de dose em IMRT sliding-window com um colimador micro multilâminas, os parâmetros de dose total absoluta e distribuição de dose total relativa devem ser verificados por dosimetria absoluta e relativa respectivamente.
Intensity modulated radiation therapy (IMRT) is currently been implemented in a rapidly growing number of centers in Brazil. As consequence many institutions are now facing the problem of performing a comprehensive quality control program before and during the implementation of IMRT in the clinical routine practice. The aim of this work is to evaluate and propose a methodology for quality assurance in IMRT treatments. An ionization chamber and a two-dimensional array detector were performed to assess the absolute value of the total dose of all fields in one specific point. The relative total dose distribution of all fields was measured with a radiochromic film and a two-dimensional array at one depth in a phantom. A comparison between measured and calculated dose distributions was performed using the gamma-index method, assessing the percentage of points that meet the criteria of ±3% dose difference and ±3 mm distance to agreement. As a result of 113 tested IMRT beams using ionization chamber and 81 using two-dimensional array, the proposal was to take an action level of about ± 5% compared to the treatment planning systems and measurements, for the verification of the dose in a single point at the low gradient dose region. Analysis of the two-dimensional array measurements showed that the gamma value was <1 for 97.7% of the data and for the film the gamma value was <1 for 96.6% of the data. This can be concluded that for an accurate delivery of dose in sliding-window IMRT with micro multileaf collimator, the absolute value of the total dose and the relative total dose distribution should be checked by absolute and relative dosimetry respectively.

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30

Soh, Hwee Shin. "Quantitative metrics for assessing IMRT plan quality : comparing planning conformity and complexity". Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/51364/.

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Intensity Modulated Radiation Therapy (IMRT) is a complex form of radiation delivery for the treatment of malignant tumours and other diseases. In IMRT treatment planning, quantitative assessment is crucial to measure and improve the plan quality and treatment delivery. The search for simple and universal quantitative metrics to assess IMRT treatment plan quality has been identified as important but as yet not entirely successful. The aim of this thesis was to assess the IMRT treatment plan quality by establishing quantitative metrics for planning conformity and complexity. The metrics proposed in this work were simple, reproducible and universally applicable to all IMRT techniques, which included step-and-shoot IMRT (SSIMRT), volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT). Two metrics, conformity index (CI) and conformation number (CN) were adopted to quantify the plan conformity. The data used for CI and CN calculations were easily retrieved from dose volume histogram (DVH). By reporting both of these metrics, comprehensive information on target coverage and irradiation of normal tissues could be provided. For the quantification of planning complexity, a new and novel spatial complexity matrix (SCM) was introduced to measure the average dose gradient of a dose profile. In addition, the spatial frequency ratio (SFR) was established to explore the proportion of rapidly varying dose with distance in a treatment plan by using one-dimensional power spectral density (1D PSD). Virtual phantoms were developed for the initial quantitative assessment, in order to form a basis for treatment plan inter-comparisons amongst the different IMRT techniques. A series of multi organs at risk (OARs) phantoms was developed to simulate the planning target volume (PTV) and OARs for different configurations. A virtual prostate phantom was also designed to include a unique shape of PTV and the OAR in close proximity to PTV, in order to mimic clinical prostate case. Quantitative assessments were undertaken on all the IMRT plans generated using the virtual phantoms. The results of these phantom studies have shown for the first time, the feasibility of the developed quantitative metrics for assessing plan quality. Following the successful application of SCM and SFR on the phantom plans, verification work was undertaken to demonstrate the clinical relevance of these self-developed complexity metrics. A retrospective study was carried out to assess the complexity of plans for the treatment of prostate and head and neck tumours. The information contained in DICOM-RT objects were utilised to acquire dose data from the corresponding dose plane. A qualitative survey on plan complexity was also conducted amongst treatment planners, to demonstrate the correlation between the qualitative and quantitative results. These preliminary studies demonstrated the successful application of the self-developed complexity metrics on clinical IMRT treatment plans. In conclusion, the work in this thesis has demonstrated the successful establishment of quantitative metrics for assessing plan conformity and complexity of different IMRT techniques. These metrics were considered as universal tools for the inter-comparison of plan quality for different IMRT techniques and were successfully applied and translated from phantom studies to the clinical setting. Whilst the judgment and experience of the treatment planner undoubtedly remains paramount for making a final decision on the best plan in the interest of the patient, it is expected that the use of quantitative metrics will provide an effective means of benchmarking performance, minimising treatment plan variability and enhancing the quality of IMRT treatment planning.

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Tzec, Quiñones Irving Ubaldo, e Cortes Jeanette Rodríguez. "Control de calidad en tratamientos de IMRT con película radiocrómica Gafchromic EBT3". Tesis de maestría, Universidad Autónoma del Estado de México, 2017. http://hdl.handle.net/20.500.11799/66163.

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Resumen En la actualidad, la IMRT gana cada vez mayor aceptación y difusión para el tratamiento de cáncer, debido a las ventajas respecto a otras técnicas de tratamiento, como aumento de la dosis absorbida al tejido a irradiar y menor dosis al tejido circundante y órganos de riesgo. Sin embargo, debido a la naturaleza de la conformación de la dosis total, es común la formación de zonas de alto gradiente, por lo que es importante asegurar que el plan de tratamiento realizado con el sistema de planeación sea suministrado al paciente con la exactitud y precisión necesarias para cumplir con los parámetros de dosis absorbida y protección al tejido sano. En este trabajo se evaluó la película radiocrómica EBT3 con miras a su utilización para el aseguramiento de la calidad en los tratamientos de radioterapia con la técnica IMRT en el Hospital General de México. Para esto se compararon las distribuciones de dosis en un plano medidas con estas películas y con las películas radiográficas EDR2, con los datos calculados por el sistema de planeación, utilizando el índice gamma como criterio de evaluación. Se estudiaron los planes de nueve pacientes, para lo cual se caracterizaron las curvas de calibración correspondientes a cada tipo de película, se realizaron mediciones de dosis puntuales con cámara de ionización, y se realizó el análisis gamma con criterios de 3%/3 mm, 4%/3 mm y 5%/3 mm para la diferencia de dosis y la distancia en concordancia. El 100% de las distribuciones medidas con las películas radiocrómicas tuvieron un porcentaje de puntos con γ<1 mayor al 90% con el criterio de 3%/3 mm, mientras que dos tercios de los planes analizados con las películas radiográficas cumplieron con esta restricción. Las mediciones con cámara de ionización mostraron una diferencia entre la dosis medida y calculada menor al 3% en ocho de los nueve planes analizados. Los resultados indican que las películas radiocrómicas EBT3 son adecuadas para el análisis de distribución de dosis en el control de calidad paciente especifico en tratamientos de IMRT en la institución.

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32

LAVOR, MILTON. "Avaliação das ferramentas de controle de qualidade para pacientes submetidos ao IMRT". reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9971.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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33

Jadon, Rashmi. "Adaptive image-guided radiotherapy strategies for implementation of IMRT in gynaecological malignancies". Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/98750/.

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Intensity-modulated radiotherapy (IMRT) for gynaecological malignancies aims to reduce toxicity and improve tumour control. However, there are several barriers to its uptake in clinical practice. Amongst these are that of pelvic organ motion, whereby due to motion of the target organs on treatment there is a risk of geographical miss with IMRT. Secondly, although new IMRT techniques may improve bowel toxicity there is limited knowledge about dose-volume constraints for bowel, making it difficult to assess whether new techniques are likely to translate into clinical improvements. The purpose of this thesis is to address these problems. Methods Dose-volume constraints for late bowel toxicity are investigated initially through systematic review, followed by a dose-volume study based on toxicity data from pelvic radiotherapy patients. Pelvic organ motion is assessed in a systematic review examining organ motion patterns and potential strategies to account for this. Population-based and adaptive margin strategies are investigated in modelling studies for both definitive cervical cancer patients and post-hysterectomy patients. Results Initial systematic review of the literature, followed by the analysis of the toxicity and dosevolume data of 203 pelvic radiotherapy patients highlighted anal canal, bowel loops, bowel bag, sigmoid and large bowel as important organs at risk (OARs) for bowel toxicity. Dosevolume constraints were derived for these organs. Pelvic organ motion was found to be a significant problem for gynaecological IMRT. Adaptive margin strategies, such as plan-of-the-day, were demonstrated to achieve both CTV coverage whilst reducing dose to the OARs compared to standard margins and population-based margins. Conclusions Dose-volume constraints derived for late bowel toxicity, if validated with independent data, may be used to reduce bowel toxicity in future patients, and as a benchmark to assess the efficacy of new IMRT techniques. Adaptive strategies for gynaecological cancers appear a promising solution for organ motion management.

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34

Pichler, Joseph Alan. "IMRT Plan Delivery Verification Utilizing a Spiral Phantom with Radiochromic Film Dosimetry". University of Toledo Health Science Campus / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=mco1288963613.

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35

Pfeiffer, Marie-Luise [Verfasser]. "Dosisvergleich von Bestrahlungsplänen bei HNO-Tumoren für IMRT-Techniken / Marie-Luise Pfeiffer". Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1155165918/34.

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36

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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37

Morlotti, Marcelo Scolaro. "Verificação de tratamentos radioterápicos diversos com dosimetria termoluminescente". Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-09052007-195209/.

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As técnicas radioterápicas evoluíram muito nas últimas décadas, destacando-se a utilização de feixes segmentados por colimadores de multifolhas, os quais permitem entregar maior quantidade de dose com maior precisão espacial. Os sistemas de planejamento em radioterapia (TPS), entretanto, são em grande parte fechados, com acesso restrito aos parâmetros de cálculo de dose. Desta forma, o presente trabalho teve como principal objetivo comparar valores de dose envolvidas em tratamentos radioterápicos, medidos com a técnica de dosimetria termoluminescente (TL), usando um objeto simulador antropomórfico (Alderson Rando Phantom - ARP) como paciente, com valores de referência extraídos dos TPS em simulações realistas de tratamento. O objeto simulador continha dosímetros TL de LiF (TLD100) posicionados na pelve, no tórax, na cabeça e no pescoço, a fim de que fossem monitoradas regiões com dose homogênea (como no volume alvo planejado - PTV), regiões com gradiente de dose e regiões afastadas do PTV. As irradiações foram feitas usando técnicas de radioterapia conformacional 3D e radioterapia por modulação da intensidade do feixe (IMRT). Quatro TPS foram utilizados: CadPlan, ECLIPSE, Helax-TMS e KonRad. Em algumas situações utilizaram-se algoritmos de cálculo implementados pelos fabricantes nos TPS; dois deles baseados em correção de heterogeneidades (Batho e pencil beam) e um deles baseado em convolução e superposição de feixes simulados (collapsed cone). Nos casos de irradiações com IMRT os algoritmos foram sempre usados. Paralelamente ao uso do ARP, utilizou-se um objeto simulador com água com objetivo de verificar o comportamento dos dosímetros TL expostos a feixes de fótons de alta energia, em comparação com câmaras de ionização cilíndricas do tipo Farmer (volume interno de 0,6 cm3). Além disso, esse objeto simulador possibilitou garantir a qualidade de suportes desenvolvidos para a câmara e para os dosímetros, nos casos de medidas em água. A irradiação da pelve do objeto simulador ARP, região com poucas heterogeneidades, revelou que o comportamento do material que o constitui é equivalente ao da água e, por isso, pode ser usado na simulação de tecido humano em feixes de radioterapia. Simulações de tratamentos revelaram compatibilidade entre valores medidos e planejados no interior do PTV, com discrepâncias menores que 2%; valores que estão dentro dos limites estabelecidos pelo ICRU62 (+7%/-5%, 2?). Nas regiões afastadas do PTV, todos os códigos de planejamento apresentaram discrepâncias relativamente grandes, evidenciando limitações no cálculo de componentes secondárias. Apesar dos algoritmos de cálculo aumentarem a concordância entre doses medidas e planejadas, não foi possível identificar diferenças entre os algoritmos pencil beam e collapsed cone. Em regiões onde havia alto gradiente de dose, as discrepâncias se tornam maiores devido à dificuldade em posicionar os dosímetros no mesmo ponto em que o cálculo é feito. Sistematicamente, observou-se que a técnica para radioterapia 3D apresenta valores de dose dentro dos limites preestabelecidos, enquanto IMRT mostra valores com maior exatidão.
The last decades noticed a massive improvement in radiotherapy techniques and the use of segmented beams produced by multileaf collimators. However, the dose radiation therapy planning systems (TPS) in use are characterized by the restriction of access to the calculation algorithms. The aim of this work was to compare dose values measured in an anthropomorphic phantom (Alderson Rando Phantom - ARP) to the reference dose values obtained from the TPS in real case simulations of radiotherapy treatments. Thermoluminescent dosimetry (TLD) technique was used to evaluate the doses. LiF dosimeters (TLD100) were positioned on the phantom pelvis, thorax, head and neck at homogeneous dose regions, as the Planned Target Volume (PTV), gradient dose regions, and areas far from PTV. The doses were delivered using two techniques, 3D conformal radiotherapy and Intensity Modulated Radiation Therapy (IMRT). Four TPS were used: CadPlan, ECLIPSE, Helax-TMS and KonRad. In several situations, calculation algorithms implemented in these planning systems were employed to take heterogeneities into account: two of them were correction-based algorithms (Batho and Pencil Beam) and one of them based in beam convolution-superposition (Collapsed Cone). Furthermore, a liquid water phantom was used to compare the TLD behavior to the Farmer thimble chamber (0,6 cc internal volume) results when exposed to high-energy photon beams. It was also possible to verify the quality of the PMMA supports that wer used in the calibration of the dosimeters on clinical beam, obtaining reliable results. Both the ARP pelvis and a water phantom showed similar behavior under irradiation, indicating that, in highly homogenous regions, the ARP material can be used to simulate human soft tissues under radiotherapy treatment. Inside the PTV, the dosimetry performed in the ARP, showed compatibility between measured and planned dose values, with discrepancies smaller than 2%, which are within the ICRU62 fixed limits (+7%/-5%, 2?). When the algorithms were used, a better agreement between the experimental and planned doses was achieved, but it was not possible to discriminate the Pencil Beam and Collapsed Cone algorithms. In regions with large dose gradients, the discrepancies between experimental and planned dose values are higher as the difficulties the position of the dosimeters are more critical. The measured doses, when the 3D radiotherapy technique was used, were within the ICRU62 pre-established limits whereas the IMRT technique provider more accurate values.

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38

Al-Roumi, Moh'd. "Verification of patient position during intensity modulated radiotherapy by electronic portal imaging devices using Monte Carlo techniques". Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/116175/1/Moh%27d_Al-Roumi_Thesis.pdf.

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This study generated Monte Carlo (MC) Intensity modulated radiotherapy images to be used as reference images (after calibration) in the verification process of patient set-up errors during radiotherapy treatment. A proposed imaging procedure was developed to estimate the set-up errors during treatment. These developments will improve the accuracy of radiotherapy treatment that is a crucial component of many advanced cancer treatments.

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39

Tsugawa, Takahiko, Masahiro Hagiwara, Hisato Nakazawa, Tatsuya Kobayashi, Yuta Shibamoto, Chisa Hashizume e Yoshimasa Mori. "STEREOTACTIC RADIOTHERAPY FOR SPINAL INTRADURAL METASTASES DEVELOPING WITHIN OR ADJACENT TO THE PREVIOUS IRRADIATION FIELD : REPORT OF THREE CASES". Nagoya University School of Medicine, 2013. http://hdl.handle.net/2237/18476.

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40

Mathayomchan, Boonyanit. "MULTIOBJECTIVE APPROACH TO MORPHOLOGICAL BASED RADIATION TREATMENT PLANNING". Case Western Reserve University School of Graduate Studies / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=case1131365356.

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41

Studer, Gabriela Monika. "Intensitäts-modulierte Radiotherapie (IMRT) maligner Kopf-Hals-Tumoren : Resultate bestätigen die entwickelten Konzepte /". Zürich, 2007. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000253372.

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42

Brodeur, Marylène. "Verification of IMRT beam delivery with a ferrous sulfate gel dosimeter and MRI". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=78331.

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Intensity modulated photon beam radiation therapy often results in dynamically delivered beams with small field sizes and steep dose gradients. This defines a need for an integrating, tissue-equivalent, high resolution dosimeter. 3D ferrous sulfate gel based dosimetry involves the use of magnetic resonance (MR) images of radiosensitive paramagnetic gels. The goal of this work is to create a patient specific quality assurance (QA) procedure that links measured dosimetnc information to clinical goals.
The gel dosimeter system is tested through a set of simple experiments which characterize and confirm the system as a valid QA tool for conformal and intensity modulated radiation therapy.
For this work, dynamic photon beams are created on a commercially available inverse treatment planning system and the treatment is delivered to a gel filled acrylic mold. Software has been developed to quantify dose from the QA MR images, and to register this information to the planning computed tomography (CT) scan. The software displays the measured dose on the planning CT, and calculates dose-volume histograms for the registered measured data and contoured patient structures. This work reveals good agreement between planned and measured dose distributions, with less than 5% difference in the mean doses of the contoured patient structures.

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43

Altenstein, Georg [Verfasser], e Uwe [Akademischer Betreuer] Oelfke. "A Novel Collimator Concept for Fast Rotational IMRT / Georg Altenstein ; Betreuer: Uwe Oelfke". Heidelberg : Universitätsbibliothek Heidelberg, 2014. http://d-nb.info/1180300637/34.

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44

Tang, Nin-fai Francis. "Monte Carlo dose calculations in quality assurance for IMRT of head and neck cancers". Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/b40203797.

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45

Tang, Nin-fai Francis, e 鄧年輝. "Monte Carlo dose calculations in quality assurance for IMRT of head and neck cancers". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40203797.

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46

Linnebach, Julian [Verfasser], e Uwe [Akademischer Betreuer] Haverkamp. "Einsatz der intensitätsmodulierten Radiotherapie (IMRT) beim mediastinalen Hodgkin-Lymphom / Julian Linnebach ; Betreuer: Uwe Haverkamp". Münster : Universitäts- und Landesbibliothek Münster, 2014. http://d-nb.info/1138280976/34.

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47

Williams, Matthew John Physics Faculty of Science UNSW. "Investigations into static multileaf collimator based intensity modulated radiotherapy". Awarded by:University of New South Wales. Physics, 2005. http://handle.unsw.edu.au/1959.4/20577.

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Intensity Modulated Radiation Therapy (IMRT) is a modern radiotherapy treatment technique used to obtain highly conformal dose distributions. The delivery of IMRT is commonly achieved through the use of a multileaf collimator (MLC). One of the hindrances at present to the widespread use of IMRT is the increased time required for its planning, delivery and verification. In this thesis one particular method of MLC based IMRT, known as Static Multileaf Collimator based IMRT (SMLC-IMRT), has been studied along with methods for improving it???s delivery efficiency. The properties of an MLC commonly used in SMLC-IMRT have been characterised. The potential ramifications of these properties on the dosimetric accuracy of the delivered IMRT field were also investigated. An Interactive Leaf Sequencing (ILS) program was developed that allowed for the manipulation and processing of intensity maps using a variety of methods. The objective of each method was to improve the delivery efficiency whilst maintaining the dosimetric quality of the IMRT treatment. The different methods investigated were collimator angle optimisation, filtration, and intensity level optimisation. The collimator was optimised by identifying the angle at which the minimum monitor unit???s (MU???s) were required when using a sliding-window delivery method. A Savitzky-Golay filter was applied to random intensity maps and suitable filtration parameters identified for filtering clinical IMRT fields, and the intensity levels were optimised based on a deviation threshold. The deviation threshold identified the acceptable level of difference tolerable between the original and modified intensity map. Several IMRT cases were investigated and the impact of each the methods on MU???s, segments and dose distribution observed. As the complexity of IMRT fields increases the dosimetric impact of the MLC properties increases. Complex SMLC-IMRT fields require longer delivery times due to the increased number of MU???s and segments. Collimator optimisation was shown to be a fast and effective means of improving delivery efficiency with negligible dosimetric change to the optimised plan. Modifying intensity maps by applying a filter and optimising the intensity levels did reduce the complexity and improve the delivery efficiency, but also required a dosimetric compromise of the optimised plan.

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48

Yin, Lingshu. "Dose painting to combat tumor hypoxia while sparing urethra in prostate IMRT: a biologically based adaptive approach accounting for setup uncertainties and organ motion". Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2524.

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Enhanced resistance to radiation could be caused by both chronic hypoxia and acute hypoxic which has been reported in prostate cancer in various studies. Therefore currently used dose prescriptions (70Gy in 35 fractions) for external beam radiation therapy (EBRT) of prostate cancer has been suggested insufficient to provide optimum clinical outcome. In this study, we propose a Biologically Guided Radiation Therapy approach to boost dose in hypoxic prostate tumor regions while sparing the urethra. A previously proposed hypoxia model was modified for prostate cancer and incorporated into treatment plan optimization. The concept of equivalent uniform dose (EUD) was used in the optimization and evaluation of results. CT data from 25 prostate cancer patients who recently received EBRT at the British Columbia Cancer Agency (BCCA) and hypothetical hypoxic regions manually drawn on these CT scans were selected for this study. The results show that our methods could boost dose in target volume to substantially higher levels. EUD of planning target volume increased to more than 80Gy, despite accounting for effects of hypoxia. This increase was achieved with only minor changes in dose in normal tissues, typically less than 5Gy. Notably, urethra sparing was excellent with a EUD around 64Gy. Robustness of the proposed approach is verified against various hypoxic settings. EUD comparison between RT plans in biological guided and conventional approaches using the same RT technique (Volumetric Modulated Arc Therapy) also suggests that biologically guided radiation therapy (BGRT) approach is more suitable for dose painting purposes with the advantage of delivering sufficient dose to hypoxia region in different scenarios and sparing normal tissue better. Furthermore, we also investigated the impact of inter-fraction patient set-up error and intra-fraction organ motion on the high dose gradients achieved with this proposed dose painting method and explored the feasibility of adapting geometrical uncertainties (represented as systematic error and random error) into treatment planning. Image error obtained from EPID images are used to derive systematic uncertainty and random uncertainty. During the geometrical uncertainty adapted optimization, dose matrix in PTV is shifted based on systematic error and convolved with a Gaussian kernel which is pre-calculated using random error. CT sets and organ contours from five patients who enrolled in the previous dose painting i study are selected. For each of them, seven plans are generated using cumulated uncertainty data which was collected after every five fractions. We also present the outcome in terms of equivalent uniform dose (EUD). For four of the patients, EUD history of all seven plans suggests using the proposed optimization method with uncertainty data from the first five fractions, it is possible to achieve the same target coverage of static treatment plans (difference in EUD less than 1Gy). Meanwhile, the elimination of PTV margin also leads to a significant dose reduction (more than 15Gy) in rectum.

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49

Silva, Luis Felipe Oliveira e. "Desenvolvimento e avaliação de um sistema de cálculo de dose independente para controle de qualidade de IMRT do tipo jaws-only". reponame:Repositório Institucional da UnB, 2015. http://dx.doi.org/10.26512/2015.10.D.20724.

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Dissertação (mestrado)—Universidade de Brasília, Faculdade Gama, Programa de Pós-Graduação em Engenharia Biomédica, 2015.
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A radioterapia de intensidade modulada (IMRT, do inglês intensitymodulatedradiotherapy) proporciona distribuições de dose bastante complexas, com regiões de alto gradiente de dose. Essa complexidade representa um desafio maior no controle de qualidade (CQ) quando se compara a IMRT com a radioterapia convencional. O objetivo do presente trabalho foi desenvolver e avaliar um sistema de cálculo de dose independente, chamado SCI, para o controle de qualidade da IMRT do tipojawsonly. O software desenvolvido utiliza um algoritmo de cálculo de dose baseado em correções realizadas no fator de calibração do acelerador linear, por meio de fatores tabelados, derivados de medições e calculados a partir de simples modelagem. Os próprios dados gerados no comissionamento são usados para alimentar o algoritmo.Os cálculos são realizados em um plano de um fantoma retangular. Para validar o SCI, comparações entre as previsões dosimétricas do sistema e outras referências foram realizadas. Foram comparados: doses pontuais no centro de campos assimétricos medidos com câmara de ionização; perfis de campos medidos com filme radiocrômico e com câmara de ionização; distribuições planares de dose de cinco casos de câncer de próstata e cinco de cabeça e pescoço medidas com um arranjo bidimensional de câmaras de ionização e calculadas pelo sistema de planejamento de tratamento (SPT). A avaliação foi realizada utilizando diferenças percentuais de dose, a menor diferença de posição em que se encontra o mesmo valor de dose (DTA, do inglês distancetoagreement) e a avaliação gama com critérios: (i) diferença máxima de dose de 3%, DTA de 3 mm; (ii) diferença máxima de dose 5%, DTA de 3 mm; e (iii) diferença máxima de dose 5%, DTA de 5 mm. As diferenças encontradas nas comparações entre as doses obtidas no centro de campos assimétricos foram menores do que 2,5%.As diferenças nos perfis dos campos quadrados menores do que 30x30 cm2 foram menores do que 2% ou 2mm. Os campos menores, medidos com filme, apresentaram diferenças mais consideráveis (DTAs de até 5 mm foram observadas). Esse resultado já era esperado devido à maior resolução espacial do filme quando comparada à da câmara de ionização (volume sensível de 0,125 cc). As avaliações gama usando tanto as medições quanto o SPT como referência sugerem que o SCI representa a distribuição de dose real segundo o critério de 5% de diferença máxima de dose e 5 mm de DTA, uma vez que a média de pontos aprovados foi superior a 96,5% (p<0,001) em todos os casos quando esse critério foi utilizado. O sistema também apresenta um boa representação segundo o critério de 5% de diferença máxima de dose e 3 mm de DTA (média de pontos aprovados superior a 92,0%; p<0,01). As médias de pontos aprovados com esses dois critérios estão, portanto, de acordo com os valores tipicamente usados como referência por profissionais da área de radioterapia. Desta forma, o sistema desenvolvido no presente trabalho está pronto para ser utilizado para o CQ de IMRT do tipo jawsonly sem custo adicional em relação aos equipamentos já utilizados, reduzindo o fluxo de trabalho comparado a métodos mais tradicionais e sem ocupação adicional da máquina de tratamento.
Intensity modulated radiation therapy (IMRT) provides complex dose distributions with high dose gradient regions. This complexity is a major challenge for quality assurance (QA), specially when comparing IMRT with conventional radiotherapy. In this research, I propose, develop, and evaluate an independent dose calculation system for QA of jaws only IMRT (JOIMRT). The developed software uses a dose calculation algorithm based on corrections performed over the linear accelerator (linac) calibration factor. In order to perform this corrections I used tabulated factors derived from measurements and calculated from simple modeling. Also, I used the linac's commissioning data as input to the algorithm.The developed system then performs the main computations over a rectangular phantom plan. To validate the proposed system, I compared the predictions of the dosimetric system with references that are commonly used in the literature. Specifically, I compared: point doses in the center of asymmetric field measured with an ionization chamber; dose profiles measured with radiochromic film and an ionization chamber; planar dose distributions of five of prostate and five head and neck cases measured with a two-dimensional array of ionization chambers and calculated by the treatment planning system (TPS). The evaluation was performed using percentage dose differences, distance to agreement (DTA) and gamma evaluation with tree criterions: (i) maximum difference dose of 3% and 3 mm DTA, (ii) maximum difference dose of 5% and 3 mm DTA, and (iii) maximum difference dose of 5% and 5 mm DTA. The differences in the comparisons between the doses obtained in the center of asymmetric fields were smaller than 2.5%. Differences in the profiles of square fields up to 30x30 cm2 were smaller than 2% or 2 mm. Smaller fields measured with film showed more significant differences (I measured DTAs up to 5 mm). This result was expected because of the higher spatial resolution of the film, as compared to the ionization chamber that provided the measurements used as inputs to the calculation algorithm (sensitive volume of 0.125 cc). The point approval ratings using both measurements and the TPS as a reference suggest that the independent dose calculation system represents the actual dose distribution according to the criterion of 5 % maximum dose difference and 5 mm DTA, since the average was approved points above 96.5% (<0,001) in all cases when this criterion was used. The system also features a good representation according to the criterion of 5% maximal dose difference and 3 mm DTA (average of approved points above 92.0%; p <0.01). Therefore, the average of approved points obtained with those two criteria satisfies the values typically used as references by radiotherapy professionals. In this way, the system I developed is ready to be used for the JOIMRT QA with no additional cost with respect to equipment already used, reducing the workload compared to more traditional methods and without additional treatment machine occupation.

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50

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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Abstract (sommario):

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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Tesi sul tema "IMRT"

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