京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22038号 / 医博第4523号 / 新制||医||1038(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 大森 孝一, 教授 松村 由美, 教授 富樫 かおり / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

The aim of this work is primarily to validate the advanced techniques for treatment planning and dosimetric verification for modern megavoltage x-ray radiotherapy. With the advent of modern radiotherapy techniques, there is a great need for assuring quality of the radiation dose distributions generated by the advanced intensity modulated treatments (IMRT/VMAT). This is typically accomplished by the assessment of the treatment plan quality at the planning stage and then verification of the dose distributions through measurements on the phantoms or independent dose calculations prior to the actual delivery of these plans to patients. The major focus of this work is to clinically evaluate the modern 2D and 3D dose verification techniques. The measurement-based dosimetry systems investigated were ArcCHECK/3DVH and SRS MapCHECK. AcrCHECK/3DVH system uses the measurement-guided dose reconstruction algorithm to correct the predicted dose in the patient dataset. The system was intended for VMAT/IMRT QA. SRS MapCHECK was investigated for SRS treatments. The independent dose calculation system was DoseCHECK which employed a GPU-accelerated convolution-superposition of algorithm for 3D dose reconstruction on the patient dataset. Next, a hybrid dose verification system (PerFRACTION) was evaluated, which takes input from both the treatment planning system and the linac EPID and produces a measurement-guided 3D dose distribution for comparison with the plan. This system was investigated for potential QA applications to a modern, efficient SRS technique, involving simultaneously treating multiple targets with a single isocenter. The performance of all dosimetry systems was validated against well-characterized independent dosimeters, such as ion chamber, film and scintillator detectors, or 3D arrays (Delta4), using stringent dose comparison criteria to test their limits for the intended clinical applications. For the initial plan quality evaluation of a novel tool (Feasibility DVH) was investigated. This tool a priori estimates best achievable dose volume histograms for a specific patient, based on the basic physics properties of the megavoltage x-rays, thus helping the planners to guide their efforts. All studied dosimetry systems showed an excellent agreement of the average gamma (a mathematical combination of DD and DTA) passing rates >98% for most of the plans. The 3% DD/2mm DTA criteria were used for extracranial plans and 3%/1mm for intracranial SRS plans. As dictated by the logic of the application, the comparisons were made against TPS calculations, a bi-planar array, or film measurements. Similarly the average percent point dose errors <2% were observed against the ion chambers or film. In the rare instances when the deviations were larger, intuitive explanations were provided, based on either the physics of the plans or inhomogeneous patient anatomy and resulting algorithm limitations. Feasibility DVH was shown to reliably predict the best possible organ sparing for clinical head-and-neck VMAT plans. Overall the investigated dosimetry systems were found reliable and feasible for their intended clinical use.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第21653号 / 医博第4459号 / 新制||医||1035(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 鈴木 実, 教授 富樫 かおり, 教授 森田 智視 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

No description available.

No description available.

Apesar da introdução do controle da qualidade individual nas técnicas complexas de tratamentos, tem-se comprovado que, mesmo assim, é possível a ocorrência de erros na aplicação da dose no momento da aplicação. No entanto, ainda não estão bem estabelecidas as ferramentas de redundância a fim de controlar a dose no momento da terapêutica, além do que, as técnicas mais modernas de tratamento radioterápico desenvolvem as aplicações com feixes rotacionais e os dosímetros tradicionalmente utilizados em controle da qualidade oferecem limitações angulares. Assim, este trabalho vem contribuir para o desenvolvimento de uma metodologia de controle da qualidade de transmissão in vivo utilizando filmes radiocrômicos acoplados ao cabeçote do acelerador linear, durante aplicações radioterápicas nas técnicas de tratamento conformacional e IMRT. A metodologia de controle da qualidade desenvolvida neste trabalho baseia-se na obtenção da distribuição de dose in vivo de tratamentos radioterápicos com um filme radiocrômico EBT2 posicionado em um suporte acrílico, semelhante a uma bandeja, a uma distância fonte-superfície de 56,8 cm, acoplado ao acessório holder do acelerador linear durante a aplicação de todo o tratamento teleterápico. Posteriormente, foi realizada uma análise gama para comparação da distribuição de dose medida pelo filme com a esperada pelo sistema de planejamento, obtida no plano coronal e central de um objeto simulador, com dimensões semelhantes ao suporte acrílico, posicionado à distância de 100 cm, como resultado da transferência do plano em questão. Com os resultados encontrados na seção conformacional, avaliando tanto a simulação Monte Carlo quanto as irradiações, pode-se concluir que a diferença entre a distribuição de dose do sistema de planejamento, na distância foco detector de 100 cm, e do filme, na distância de 56,8 cm, é diminuta e, desta forma, é viável criar uma metodologia para verificação dosimétrica de transmissão utilizando o filme radiocrômico acoplado ao cabeçote do acelerador. O controle da qualidade proposto na técnica de IMRT concordou com o esperado em 24 das 25 situações testadas, apresentando apenas um resultado diferente, ou seja, uma concordância de 96% com o esperado. As avaliações in vivo concordaram com 98% dos controles avaliados. Desta forma, pode-se concluir que a metodologia proposta neste trabalho é factível para o controle da qualidade de transmissão in vivo, em tratamentos radioterápicos que usam a técnica de tratamento conformacional e IMRT e, como ela não oferece dificuldades para o deslocamento angular do gantry, ela poderá ser aplicada em técnicas teleterápicas mais modernas. / Even with the introduction of the individual quality control in the complex techniques of radiation therapy treatments, the occurrence of errors in the release of the dose at the time of application is possible. However, in order to monitor the dose at the time of therapy, redundancy tools are not yet well established, Besides that, the most modern techniques of radiation treatment use rotational beams to deliver the desired dose distributions and the dosimeters traditionally used in quality control of radiation therapy suffer angular limitations. In this way, this work aims to contribute to the development of a methodology of transmission quality control in vivo presenting a dose control technique using radiochromic film coupled to the headstock linear accelerator for radiotherapy applications to monitor conformational techniques and IMRT treatment. The quality control methodology developed in this work is based on obtaining the in vivo dose distribution of radiotherapy treatments with a radiochromic film EBT2, positioned on an acrylic stand, similar to a tray at a source-surface distance of 56.8 cm, coupled to the linear accelerator accessory holder during application of any treatment. It was subsequently performed a gama analysis for comparison of the dose distribution measured by the film with the expected dose distribution by the treatment planning system. The expected dose distribution was obtained in the coronal and central plane of a phantom, with similar dimensions to the acrylic stand and positioned on a source-surface distance of 100 cm as a result of the transfer of the plan in question. Based on the results presented in the conformational section, evaluating both, Monte Carlo simulation and irradiation results, it can be concluded that the difference between the distribution of the dose planning system, focus distance 100 cm detector, and the film, on distance of 56.8 cm, are small, and in this way it is feasible to create a methodology for dosimetry verification using radiochromic film coupled to the head of the accelerator. The proposed quality control in IMRT technique agreed with expected in 24 simulations of the 25 situations tested, showing only one different result, i.e., there was a 96% concordance with the expected. In this way, it can be concluded that the methodology proposed in this work is feasible for the in vivo quality control of radiation therapy treatments that use the conformational and IMRT treatment techniques, and also can be applied to the most modern radiotherapy techniques since, it does not offer difficulties with the angular displacement of the gantry.

Apesar da introdução do controle da qualidade individual nas técnicas complexas de tratamentos, tem-se comprovado que, mesmo assim, é possível a ocorrência de erros na aplicação da dose no momento da aplicação. No entanto, ainda não estão bem estabelecidas as ferramentas de redundância a fim de controlar a dose no momento da terapêutica, além do que, as técnicas mais modernas de tratamento radioterápico desenvolvem as aplicações com feixes rotacionais e os dosímetros tradicionalmente utilizados em controle da qualidade oferecem limitações angulares. Assim, este trabalho vem contribuir para o desenvolvimento de uma metodologia de controle da qualidade de transmissão in vivo utilizando filmes radiocrômicos acoplados ao cabeçote do acelerador linear, durante aplicações radioterápicas nas técnicas de tratamento conformacional e IMRT. A metodologia de controle da qualidade desenvolvida neste trabalho baseia-se na obtenção da distribuição de dose in vivo de tratamentos radioterápicos com um filme radiocrômico EBT2 posicionado em um suporte acrílico, semelhante a uma bandeja, a uma distância fonte-superfície de 56,8 cm, acoplado ao acessório holder do acelerador linear durante a aplicação de todo o tratamento teleterápico. Posteriormente, foi realizada uma análise gama para comparação da distribuição de dose medida pelo filme com a esperada pelo sistema de planejamento, obtida no plano coronal e central de um objeto simulador, com dimensões semelhantes ao suporte acrílico, posicionado à distância de 100 cm, como resultado da transferência do plano em questão. Com os resultados encontrados na seção conformacional, avaliando tanto a simulação Monte Carlo quanto as irradiações, pode-se concluir que a diferença entre a distribuição de dose do sistema de planejamento, na distância foco detector de 100 cm, e do filme, na distância de 56,8 cm, é diminuta e, desta forma, é viável criar uma metodologia para verificação dosimétrica de transmissão utilizando o filme radiocrômico acoplado ao cabeçote do acelerador. O controle da qualidade proposto na técnica de IMRT concordou com o esperado em 24 das 25 situações testadas, apresentando apenas um resultado diferente, ou seja, uma concordância de 96% com o esperado. As avaliações in vivo concordaram com 98% dos controles avaliados. Desta forma, pode-se concluir que a metodologia proposta neste trabalho é factível para o controle da qualidade de transmissão in vivo, em tratamentos radioterápicos que usam a técnica de tratamento conformacional e IMRT e, como ela não oferece dificuldades para o deslocamento angular do gantry, ela poderá ser aplicada em técnicas teleterápicas mais modernas. / Even with the introduction of the individual quality control in the complex techniques of radiation therapy treatments, the occurrence of errors in the release of the dose at the time of application is possible. However, in order to monitor the dose at the time of therapy, redundancy tools are not yet well established, Besides that, the most modern techniques of radiation treatment use rotational beams to deliver the desired dose distributions and the dosimeters traditionally used in quality control of radiation therapy suffer angular limitations. In this way, this work aims to contribute to the development of a methodology of transmission quality control in vivo presenting a dose control technique using radiochromic film coupled to the headstock linear accelerator for radiotherapy applications to monitor conformational techniques and IMRT treatment. The quality control methodology developed in this work is based on obtaining the in vivo dose distribution of radiotherapy treatments with a radiochromic film EBT2, positioned on an acrylic stand, similar to a tray at a source-surface distance of 56.8 cm, coupled to the linear accelerator accessory holder during application of any treatment. It was subsequently performed a gama analysis for comparison of the dose distribution measured by the film with the expected dose distribution by the treatment planning system. The expected dose distribution was obtained in the coronal and central plane of a phantom, with similar dimensions to the acrylic stand and positioned on a source-surface distance of 100 cm as a result of the transfer of the plan in question. Based on the results presented in the conformational section, evaluating both, Monte Carlo simulation and irradiation results, it can be concluded that the difference between the distribution of the dose planning system, focus distance 100 cm detector, and the film, on distance of 56.8 cm, are small, and in this way it is feasible to create a methodology for dosimetry verification using radiochromic film coupled to the head of the accelerator. The proposed quality control in IMRT technique agreed with expected in 24 simulations of the 25 situations tested, showing only one different result, i.e., there was a 96% concordance with the expected. In this way, it can be concluded that the methodology proposed in this work is feasible for the in vivo quality control of radiation therapy treatments that use the conformational and IMRT treatment techniques, and also can be applied to the most modern radiotherapy techniques since, it does not offer difficulties with the angular displacement of the gantry.

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.:Abstract Abbreviation list 1 Introduction 2 Theory 2.1 Linac head configuration 2.2 Flattening fifilter disadvantages 2.3 Flattening fifilter free beams 2.4 Intensity modulated radiation therapy 2.5 Multi leaf collimator 2.6 Step and shoot IMRT 2.7 Dynamic delivery 2.8 Intensity modulated arc therapy 2.9 Modulated arc therapy 2.10 Verification of IMRT and mARC treatment plans 3 Materials and Methods 3.1 Materials 3.1.1 Linear accelerator 3.1.2 Dosimetric tools 3.1.3 Dosimetric verification systems 3.1.4 Treatment planning systems 3.2 Methods 3.2.1 Dosimetric parameters of FF and FFF beams 3.2.2 Comparison of IMRT-FF and IMRT-FFF 3.2.3 mARC planning study 3.2.4 Planning comparison parameters 3.2.5 Dosimetric verification 4 Results 4.1 Dosimetric characteristics of FF and FFF beams 4.1.1 Dose rate 4.1.2 Dose profile 4.1.3 Depth dose curve 4.1.4 Dose in buildup region 4.2 Comparison of IMRT-FF and IMRT-FFF 4.2.1 Plan quality 4.2.2Treatment e ciency 4.3 mARC 4.3.1 Final gantry spacing (F.G.S) 4.3.2 mARC and IMRT 4.3.3 Comparison of mARC 10 MV FF and 11 MV FFF plans 4.3.4 Plan verifications 5 Discussion 5.1 Dosimetric parameters of FF and FFF beams 5.2 IMRT-FF and IMRT-FFF 5.3 mARC Summary Bibliography Selbstandigkeitserklarung Curriculum Vitae Acknowledgement

A radioterapia externa pós-operatória em mulheres diagnosticadas com câncer de mama em estágio inicial é tido como um procedimento padrão, no entanto durante o planejamento para irradiação do volume alvo as possíveis incertezas dosimétricas introduzidas dado o movimento respiratório intrínseco da paciente são desconsideradas. Este estudo avalia não apenas a influência da respiração na distribuição tridimensional da dose, mas como essa distribuição se modifica dado a técnica radioterápica empregada para o tratamento. Três técnicas de planejamento foram analisadas: a radioterapia conformacional tridimensional (3D-RT) com filtros, a radioterapia com intensidade modulada (IMRT) usando planejamento direto e o IMRT inverso. A fim de simular o movimento de contração e expansão da caixa torácica, utilizou-se uma plataforma com amplitudes de oscilação pré-determinadas, sendo a frequência de oscilação provida por uma fonte de tensão variável. Para simular a mama usou-se objetos simuladores semiesféricos preenchidos com gel dosimétrico (MAGIC-f). Os planejamentos para cada técnica foram realizados sobre a mesma tomografia computadorizada (CT) do objeto simulador preenchido com água no modo estático. Foram produzidos três lotes de dosímetro gel para o projeto, cada lote foi irradiado com uma técnica radioterápica diferente, sendo que cada lote inclui cinco objetos simuladores e um conjunto de nove tubos de calibração preenchidos com gel MAGIC-f. O primeiro dos objetos simuladores é utilizado como referência, o segundo é irradiado no modo estático, os demais são irradiados em diferentes amplitudes, respectivamente: 0,34 cm, 0,88 cm e 1,22 cm. A informação volumétrica de dose foi obtida utilizando imagens por ressonância magnética nuclear (IRMN), para cada lote foram adquiridos IRMN com sequência multi spin echo e os mapas de relaxometria, que são associados à dose, foram extraídos em um software desenvolvido e aprimorado pelo nosso grupo de pesquisa. A comparação quantitativa dos mapas de relaxometria dos objetos simuladores em movimento em relação ao modo estático foi realizado pelo índice gamma tridimensional (3% / 3mm / 15% Threshold). Para o 3D-RT a porcentagem de pontos aprovados do objeto estático em relação ao oscilante na amplitude de 0,34 cm foi de 96,44%, para amplitude de 0,88 cm foi de 93,23% e para amplitude de 1,22 cm foi de 91,65%. Para o IMRT direto a porcentagem de pontos aprovados do objeto estático em relação ao oscilante na amplitude de 0,34 cm foi de 98,42%, para amplitude de 0,88 cm foi de 95,66% e para amplitude de 1,22 cm foi de 94,31%. Para o IMRT inverso a porcentagem de pontos aprovados do objeto estático em relação ao oscilante na amplitude de 0,34 cm foi de 94,49%, para amplitude de 0,88 cm foi de 93,51% e para amplitude de 1,22 cm foi de 86,62%. A partir dos resultados, infere-se que a movimentação respiratória de baixa amplitude, para tratamentos de câncer de mama, não é um fator preocupante para a rotina clínica, porém o aumento da amplitude da oscilação aumenta a inomogeneidade de dose e pode afetar os parâmetros dosimétricos da cobertura do volume alvo em relação ao planejamento do tratamento. Observou-se em conjunto que a distribuição de dose se modifica claramente com a técnica em uso e no caso do IMRT inverso para amplitude de oscilação de 1,22 cm a aprovação no índice gamma foi menor que 90% / External postoperative radiotherapy in women diagnosed with early stage breast cancer is considered as a standard procedure, however during planning for target volume irradiation as possible dosimetric uncertainties reabsorption of the patient\'s intrinsic respiratory movement are disregarded. This study evaluates not only the influence of respiration on the three-dimensional distribution of the dose but how this distribution is modified due to the radiotherapy technique used for treatment. Three planning techniques were analyzed: three-dimensional conformational radiotherapy (3D-RT) with filters, intensity-modulated radiotherapy (IMRT) using direct planning and inverse IMRT. In order to simulate the movement of contraction and expansion of the chest wall, a platform with predetermined oscillation amplitudes was used, the oscillation frequency was provided by a variable voltage source. To simulate the breast, semi-spherical simulator objects filled with dosimetric gel (MAGIC-f) were used. The plannnings for each technique were performed on the computerized tomography (CT) of the simulator object filled with water in static mode. Three batches of gel dosimeters were prepared for the project, each batch was irradiated with a different radiothermic technique and comprised five simulator objects and a set of nine calibration tubes filled with MAGIC-f gel. The first simulator objects is used as reference, the second is irradiated in the static mode, the others are irradiated using different amplitudes, respectively: 0,34 cm, 0,88 cm and 1,22 cm. Volumetric dose information was obtained using Nuclear Magnetic Resonance Imaging, each batch was scanned with a multi spin echo sequence and the dose-related relaxometry maps were extracted in a software developed and improved by our Group of research. The quantitative comparison of the relaxometry maps of the moving simulator objects with respect to the static mode was performed by the three-dimensional gamma index (3% / 3mm / 15% threshold). For the 3D-RT, the percentage of approved points of the static object with respect to the oscillator in the amplitude of 0.34 cm was 96.44%, for amplitude of 0.88 cm was 93.23% and for amplitude of 1.22 cm was 91.65%. For the direct IMRT the percentage of approved points of the static object in relation to the oscillator in the amplitude of 0.34 cm was 98.42%, for amplitude of 0.88 cm was 95.66% and for amplitude of 1.22 cm was 94.31%. For the inverse IMRT, the percentage of approved points of the static object in relation to the oscillator in the amplitude of 0.34 cm was 94.49%, for amplitude of 0.88 cm was 93.51% and for amplitude of 1.22 cm was 86.62%. From the results, it is inferred that a low-amplitude respiratory movement, for breast cancer treatments, is not a worrying factor for clinical routine, however, increasing the amplitude of the oscillation increases the inomogeneity of the dose and this affects the dosimetry parameters of the target volume coverage. It was observed that the dose distribution changes with the technique in use and in the case of the inverse IMRT for amplitude of oscillation of 1.22 cm, less than 90% of points were approved in the gamma index evaluation