Nowadays more and more radiotherapy departments use intensity modulated beams for treatment of patients. Intensity modulated radiotherapy (ImRT) is able to modificate intensity of radiation across the iradiated field. In this way it is posible to achieve better dose conformity than in conventional radiotherapy. Implementation of ImRT allows us to escalate dose to target volume with same side effects of organs at risk as in conventional radiotherapy or to reduce normal tissue complication - decrease dose to organ at risk with the same tumour dose. This fact reguires extension of our guality system to all network of delivery dose to patients, inclusive linear accelerator with multileaf collimator, treatment planning system, electronic portal imaging device and so on. Quality assurance is guaranteed both periodical user tests and independent verification of The State Office for Nuclear Safety. The aim of this work is finding the optimal and effective way for the verification treatment plans, determining criteria for evaluation measured results, proposing summary all aspects of radiation protection patients which are treate ionisation beams with intensity modulated radiotherapy. The optimization one of the principles of radiation protection will be provided by routin verification treatment plans.

Electronic Portal Image Devices (EPID) são dispositivos eletrônicos que foram criados originalmente para aquisição de imagens portais. Atualmente eles também têm sido estudados para reconstrução de dose no plano do eixo central (paralelo ao EPID) na modalidade transit (modalidade que considera um material atenuador entre a fonte e o EPID). Neste trabalho foi determinado um algoritmo de reconstrução de dose para relacionar mapas bidimensionais de dose localizados dentro de geometrias que simularam uma situação clínica em radioterapia de forma simplificada. Para tal foram feitas simulações Monte Carlo utilizando o pacote de simulação PENELOPE de maneira que um cubo composto de água representou o corpo do paciente e um paralelepípedo retângulo composto de água representou o EPID. Definiu-se primeiramente a geometria controle e os parâmetros de irradiação controle e então foram feitas simulações para determinar a equação de reconstrução de dose referencial. Uma vez determinada essa equação, foram feitas novas simulações variando o tamanho de campo, espessura do objeto simulador do corpo, distância entre a fonte e a superfície de entrada do objeto simulador do corpo (DFS) e distância entre a superfície de saída do objeto simulador do corpo e o centro do objeto simulador do EPID (DSDE). Os arquivos de saída dessas simulações alimentaram o programa contendo o algoritmo de reconstrução de dose, feito em MATLAB®. Após a aplicação do programa, comparou-se a matriz que representa o mapa bidimensional localizado dentro do objeto simulador do corpo com a matriz localizada no mesmo local, reconstruída a partir da matriz que representa o objeto simulador do EPID. Os resultados encontrados neste trabalho mostram que a equação de reconstrução de dose e o algoritmo de reconstrução de dose propostos são válidos com desvios padrão menor que 1,6%. / Electronic Portal Image Devices (EPID) were originally created to acquire portal images, but they have also been studied for dose reconstruction in the central axis plane (parallel to the EPID) in transit mode (mode which considers an attenuator material between the source and the EPID). In this work we determined a dose reconstruction algorithm that relate two-dimensional dose maps located within geometries that simulated a clinical situation in simplified form. For this, simulations were performed using the simulation package PENELOPE so that a cube composed of water represented the patients body and a rectangle parallelepiped composed of water represented the EPID. We defined a control geometry and control irradiation parameters first, then simulations were performed to determine the referential dose reconstruction equation. Once determined this equation, new simulations were performed varying the field size, the body phantom thickness, the distance between the source and the body phantom entrance surface (DFS) and the distance between the body phantom exit surface and the EPID phantom center. The output files of these simulations fed the program containing the dose reconstruction algorithm, wrote in MATLAB®. After the program application, we compared the matrix that represents the two-dimensional map located within the body phantom with the matrix located at the same site, reconstructed from the matrix that represents the EPID phantom. The results in this work show that the dose reconstruction equation and the dose reconstruction algorithm proposed are valid with less than 1,6% standard deviation.

L’essor des nouvelles techniques de traitement en radiothérapie externe a rendu nécessaire la mise en place de nouveaux contrôles qualité (CQ). Il est en effet capital de s’assurer que la dose délivrée au patient est bien conforme à celle qui lui a été prescrite. Les détecteurs EPID, initialement utilisés pour contrôler l’exactitude du positionnement du patient, sont de plus en plus employés pour vérifier la conformité du traitement. L’image qu’ils enregistrent au cours d’une irradiation peut par exemple être comparée à une image de référence, qui correspond à ce qui aurait été mesuré si le traitement s’était déroulé dans les conditions de sa planification. Le succès de ce CQ repose (1) sur la précision avec laquelle on peut prédire l’image EPID (ou portale) de référence et (2) sur les performances de l’outil de comparaison d’image utilisé. Nous avons étudié au cours de cette thèse ces deux points clés. Nous nous sommes tout d’abord tournés vers une méthode de prédiction d’images EPID haute résolution basée sur le couplage de simulations Monte-Carlo (MC) et de la technique de débruitage DGPLM. Pour la mettre en œuvre, nous avons modélisé un accélérateur linéaire d’électrons à usage médical (linac) dans le code MC PENELOPE et optimisé les paramètres de sa source d’électrons primaires pour des calculs de dose dans l’eau. L’analyse d’un fichier d’espace des phases (PSF) de 71 Go stocké sous le cône égalisateur nous a ensuite permis de développer un modèle de sources virtuelles (MSV) représenté par des histogrammes corrélés (environ 200 Mo). Ce nouveau MSV, plus compact que le PSF, est tout aussi précis pour les calculs de dose dans l’eau si son maillage est déterminé selon une méthode adaptative. La modélisation du détecteur EPID dans PENELOPE suggère que les hypothèses faites sur les propriétés de la tâche focale du linac sont trop simplistes et doivent être reconsidérées. L’évaluation du MSV pour la prédiction d’images EPID haute résolution a quant à elle conduit à d’excellents résultats. Une fois la chaine de prédiction de l’image portale de référence validée, nous l’avons utilisée pour détecter des irrégularités dans les traitements de RCMI. Dans une étude préliminaire, nous avons volontairement introduit des erreurs de traitement dans le calcul d’images EPID (dérive du faisceau d’irradiation, modification de la morphologie ou de la position du patient). Le γ-index traditionnellement utilisé en routine s’est avéré moins performant que le χ-index pour les détecter. Une étude plus approfondie aura pour objet de déterminer des seuils de détection d’erreurs en fonction de leur nature et d’éprouver les performances d’autres tests. / Advanced techniques used in radiotherapy for cancer treatment, such as Intensity-Modulated Radiation Therapy (IMRT), require extensive verification procedures to ensure the correct dose delivery. Electronic Portal Imaging Devices (EPIDs) are widely used for quality assurance in radiotherapy, and also for dosimetric verifications. For this latter application, the images obtained during the treatment session can be compared to a pre-calculated reference image in order to highlight dose delivery errors. The quality control performance depends (1) on the accuracy of the pre-calculated reference image (2) on the ability of the tool used to compare images to detect errors. These two key points were studied during this PhD work. We chose to use a Monte Carlo (MC)-based method developed in the laboratory and based on the DPGLM (Dirichlet process generalized linear model) denoising technique to predict high-resolution reference images. A model of the studied linear accelerator (linac Synergy, Elekta, Crawley, UK) was first developed using the PENELOPE MC codes, and then commissioned using measurements acquired in the Hôpital Nord of Marseille. A 71 Go phase space file (PSF) stored under the flattening filter was then analyzed to build a new kind of virtual source model based on correlated histograms (200 Mo). This new and compact VSM is as much accurate as the PSF to calculate dose distributions in water if histogram sampling is based on adaptive method. The associated EPID modelling in PENELOPE suggests that hypothesis about linac primary source were too simple and should be reconsidered. The use of the VSM to predict high-resolution portal images however led to excellent results. The VSM associated to the linac and EPID MC models were used to detect errors in IMRT treatment plans. A preliminary study was conducted introducing on purpose treatment errors in portal image calculations (primary source parameters, phantom position and morphology changes). The γ-index commonly used in clinical routine appears to be less effective than the χ-index. A future in-depth study will be dedicated to determine error detection threshold according to their nature and to evaluate other comparison test robustness. The developed portal image prediction method associated to robust analysis tools will then constitute an adapted way to assure treatment quality control.

Electronic Portal Image Devices (EPID) são dispositivos eletrônicos que foram criados originalmente para aquisição de imagens portais. Atualmente eles também têm sido estudados para reconstrução de dose no plano do eixo central (paralelo ao EPID) na modalidade transit (modalidade que considera um material atenuador entre a fonte e o EPID). Neste trabalho foi determinado um algoritmo de reconstrução de dose para relacionar mapas bidimensionais de dose localizados dentro de geometrias que simularam uma situação clínica em radioterapia de forma simplificada. Para tal foram feitas simulações Monte Carlo utilizando o pacote de simulação PENELOPE de maneira que um cubo composto de água representou o corpo do paciente e um paralelepípedo retângulo composto de água representou o EPID. Definiu-se primeiramente a geometria controle e os parâmetros de irradiação controle e então foram feitas simulações para determinar a equação de reconstrução de dose referencial. Uma vez determinada essa equação, foram feitas novas simulações variando o tamanho de campo, espessura do objeto simulador do corpo, distância entre a fonte e a superfície de entrada do objeto simulador do corpo (DFS) e distância entre a superfície de saída do objeto simulador do corpo e o centro do objeto simulador do EPID (DSDE). Os arquivos de saída dessas simulações alimentaram o programa contendo o algoritmo de reconstrução de dose, feito em MATLAB®. Após a aplicação do programa, comparou-se a matriz que representa o mapa bidimensional localizado dentro do objeto simulador do corpo com a matriz localizada no mesmo local, reconstruída a partir da matriz que representa o objeto simulador do EPID. Os resultados encontrados neste trabalho mostram que a equação de reconstrução de dose e o algoritmo de reconstrução de dose propostos são válidos com desvios padrão menor que 1,6%. / Electronic Portal Image Devices (EPID) were originally created to acquire portal images, but they have also been studied for dose reconstruction in the central axis plane (parallel to the EPID) in transit mode (mode which considers an attenuator material between the source and the EPID). In this work we determined a dose reconstruction algorithm that relate two-dimensional dose maps located within geometries that simulated a clinical situation in simplified form. For this, simulations were performed using the simulation package PENELOPE so that a cube composed of water represented the patients body and a rectangle parallelepiped composed of water represented the EPID. We defined a control geometry and control irradiation parameters first, then simulations were performed to determine the referential dose reconstruction equation. Once determined this equation, new simulations were performed varying the field size, the body phantom thickness, the distance between the source and the body phantom entrance surface (DFS) and the distance between the body phantom exit surface and the EPID phantom center. The output files of these simulations fed the program containing the dose reconstruction algorithm, wrote in MATLAB®. After the program application, we compared the matrix that represents the two-dimensional map located within the body phantom with the matrix located at the same site, reconstructed from the matrix that represents the EPID phantom. The results in this work show that the dose reconstruction equation and the dose reconstruction algorithm proposed are valid with less than 1,6% standard deviation.

Dose verification is a critical component of adaptive radiotherapy, as it provides a measurement of treatment delivery success. Based on the measured outcome, the plan may be adapted to account for differences between the planned dose and the delivered dose. Although placement of an EPID behind the patient during treatment allows for exit dosimetry which may be used to reconstruct the delivered patient dose via backprojection of the fluence, there have not been any studies examining the basic assumption of backprojection-based dose verification: that deviations between the expected and delivered exit fluences are totally caused by errors in the delivered fluence, and not caused by patient geometry changes. In this dissertation, the validity of this assumption is tested. Exit fluence deviations caused by machine fluence delivery errors are measured as well as those caused by interfractional changes in the patient anatomy. Dose reconstruction errors resulting from the backprojection assumption are assessed. Correlations are examined between exit fluence deviations and patient dose reconstruction deviations. Based on these correlations, a decision tree is proposed detailing when caution should be taken in performing dose reconstruction to achieve delivery verification. Finally, a semi-automated dose verification tool is constructed for both clinical and research purposes.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-05-26T20:02:59Z No. of bitstreams: 1 2016 - Phillipe Bauer de Ara?jo D?ria.pdf: 2728729 bytes, checksum: 9a6172b97d933c398e4d0dd04647cad7 (MD5) / Made available in DSpace on 2017-05-26T20:02:59Z (GMT). No. of bitstreams: 1 2016 - Phillipe Bauer de Ara?jo D?ria.pdf: 2728729 bytes, checksum: 9a6172b97d933c398e4d0dd04647cad7 (MD5) Previous issue date: 2016-02-26 / The current study aims to develop a minimally invasive surgical technique with the use of cryosurgery that provides sterilization of sheep for different purposes. It was used eighteen rams, half blood Santa In?s x Dorper, pubescent, with aged between 8 and 12 months and scrotal circumference greater than or equal to 25 cm, kept in confinement. The animals were weighed, clinical and hematological tests were done. By ultrasonographic, testes, epididymides and spermatic cords were evaluated and was made breeding soundness examination, serum testosterone dosage and libido test. After being considered suitable, were divided into two groups, with nine animals each group: TEST GROUP (TG) and CONTROL GROUP (CG). The surgical technique in TG consisted in the transfixing of the tail of the epididymis in the medial latero direction, with sterile and disposable hypodermic needle of 0.80 x 40mm, 21G x 1 ?, is being coupled to a circuit composed of stainless steel adapter attached to a flexible rubber tube with 15 cm in length, diameter of 7,05mm and 4,50mm of lumen, connected to unit Cryogun CryAc, then receiving the application of two cycles of freeze / thaw, by time of 60 / 45 seconds respectively by repeating the procedure on the contralateral organ. In CG proceeded only epididymis tail transfixion as previously described, without cryosurgery, waiting for the same time interval as in TG. The animals were observed for a period of 33 days, repeating to the end of this stage all tests performed before surgery, followed by orchiectomy to obtain the testis, the epididymides and tunics for macroscopic and histological in stained laminas by hematoxylin and eosin observed in optical microscopy. Semen analysis performed at 33 days revealed azoospermia in six of the nine sheep allocated in TG which was not observed in CG sheep. The statistical analysis showed no significant changes in body weight, scrotal circumference and libido of TG animals. Serum testosterone measurements before and after the procedure in TG were within the curve. Ultrasonography in the TG showed no changes in the testicular parenchyma, however demonstrating changes in the shape and increased epididymal tail dimensions with heterogeneous echo texture and the presence of cystic cavities occupying a large area of the epididymis tail, with hypoechoic homogeneous content inside. Microscopy revealed changes in the testicles of eight TG animals as contracted seminiferous tubules, diffuse vacuolation of germ cells, absence of sperm cells in the lineage, reduction in sperm production and the presence of sperm cells dead. It was noted in the epididymal tail semen extravasation into the interstitial space, with the formation of spermatic granuloma, adjacent fibrosis, and the presence of large vacuoles with stasis of the sperm cells inside and thickening of the coats in some patients. It concludes that the proposed technique in TG is safe, fast, easy to perform, with low cost, minimally invasive and free of the occurrence of postoperative complications, providing sterilization of six of the nine sheep evaluated in the 33-day period. / O presente estudo visa o desenvolvimento de t?cnica cir?rgica minimamente invasiva com o emprego da criocirurgia que proporcione a esteriliza??o de carneiros para diferentes fins. Foram utilizados 18 ovinos, mesti?os Santa In?s x Dorper, machos, inteiros, p?beres, com idade entre 8 e 12 meses e circunfer?ncia escrotal maior ou igual a 25 cm, mantidos em confinamento. Os animais foram submetidos a pesagem, avalia??o cl?nica, hematol?gica, ultrassonografia de test?culo/epid?dimo e cord?o esperm?tico, exame androl?gico, dosagem de testosterona s?rica e teste de libido. Ap?s serem considerados aptos, foram divididos em dois grupos experimentais, com nove animais cada, denominados GRUPO TESTE (GT) e GRUPO CONTROLE (GC). A t?cnica cir?rgica aplicada nos pacientes do (GT) consistiu da transfixa??o da cauda do epid?dimo com agulha hipod?rmica est?ril descart?vel 0,80 x 40mm, 21G x 1 ?, no sentido latero medial, estando esta acoplada a um circuito composto por adaptador de a?o inox ligado um tubo de borracha flex?vel de 15cm de comprimento, 7,05mm de di?metro e l?men de 4,50mm, conectado a aparelho Cryogun CryAc, recebendo ent?o a aplica??o de dois ciclos de congelamento / descongelamento, pelo tempo de 60 segundos / 45 segundos respectivamente, repetindo-se o procedimento no ?rg?o contralateral. No GC procedeu-se apenas a transfixa??o da cauda do epid?dimo conforme descrito previamente, aguardando-se pelo mesmo intervalo de tempo que no GT, sem a realiza??o da criocirurgia. Os animais foram acompanhados por um per?odo de 33 dias, repetindo-se ao final desta etapa todos os exames realizados antes da interven??o cir?rgica, seguidos de orquiectomia para obten??o das pe?as contendo os test?culos, epid?dimos e t?nicas para avalia??o macrosc?pica e posterior an?lise histopatol?gica das l?minas coradas por Hematoxilina e Eosina em microscopia ?ptica. O espermograma realizado aos 33 dias revelou azoospermia em seis dos nove carneiros do GT, n?o tendo sido observado este quadro em nenhum dos ovinos do GC. As analises estat?sticas n?o evidenciaram altera??es significativas para peso corporal, per?metro escrotal e libido dos animais do GT. As dosagens de testosterona s?rica antes e ap?s a realiza??o da t?cnica proposta no GT situaram-se dentro da curva. O exame ultrassonogr?fico do GT n?o evidenciou altera??es no par?nquima testicular, demonstrando por?m altera??es na forma e aumento das dimens?es da cauda do epid?dimo, com ecotextura heterog?nea e a presen?a de cavidades c?sticas ocupando uma grande ?rea da cauda do epididimo, com conte?do homog?neo hipoec?ico em seu interior. A microscopia revelou altera??es nos test?culos em oito animais do GT com t?bulos semin?feros contra?dos, vacuoliza??o difusa de c?lulas germinativas, aus?ncia de c?lulas da linhagem esperm?tica, redu??o na produ??o de espermatozoides e presen?a de espermatozoides mortos, notou-se na cauda do epid?dimo o extravazamento de s?men para o interst?cio, com a forma??o de granuloma esperm?tico, fibrose adjacente, al?m da presen?a de grandes vac?olos com estase de espermatozoides no seu interior e espessamento das t?nicas em alguns pacientes. Conclu?mos que a t?cnica proposta no GT mostrou-se segura, r?pida, de f?cil execu??o, baixo custo, minimamente invasiva e isenta da ocorr?ncia de complica??es p?s-operat?rias, proporcionando a esteriliza??o de seis dos nove carneiros avaliados no per?odo de 33 dias.

<p>A commercially available amorphous silicon electronic portal imaging device (EPID) was studied with regard to its dosimetric properties and to determine its usefulness as a tool for dosimetric pre-treatment verification of radiotherapy treatment fields. The dosimetric properties that were studied include reproducibility over time, linearity with dose, dose rate dependence and ghosting effects. The pre-treatment verification is performed by acquiring dosimetric images with the EPID and comparing these images with predicted images, calculated by the treatment planning system. This method for verification was evaluated. Also, the calibration and configuration of the treatment planning system and of the EPID for dosimetric verification was performed and is presented here.</p><p>The dosimetric properties of the EPID were found to be suitable for the measurements for which it is intended. It is linear with dose and does not show significant dose rate dependence or ghosting effects. As a pre-treatment verification system it is accurate within 3% and 3mm for ~99% of a region around the irradiated area of the image.</p>

A commercially available amorphous silicon electronic portal imaging device (EPID) was studied with regard to its dosimetric properties and to determine its usefulness as a tool for dosimetric pre-treatment verification of radiotherapy treatment fields. The dosimetric properties that were studied include reproducibility over time, linearity with dose, dose rate dependence and ghosting effects. The pre-treatment verification is performed by acquiring dosimetric images with the EPID and comparing these images with predicted images, calculated by the treatment planning system. This method for verification was evaluated. Also, the calibration and configuration of the treatment planning system and of the EPID for dosimetric verification was performed and is presented here. The dosimetric properties of the EPID were found to be suitable for the measurements for which it is intended. It is linear with dose and does not show significant dose rate dependence or ghosting effects. As a pre-treatment verification system it is accurate within 3% and 3mm for ~99% of a region around the irradiated area of the image.

Radiation therapy is continuously increasing in complexity due to technological innovation in delivery techniques, necessitating thorough dosimetric verification. Comparing accurately predicted portal dose images to measured images obtained during patient treatment can determine if a particular treatment was delivered correctly. The goal of this thesis was to create a method to predict portal dose images that was versatile and accurate enough to use in a clinical setting. All measured images in this work were obtained with an amorphous silicon electronic portal imaging device (a-Si EPID), but the technique is applicable to any planar imager. A detailed, physics-motivated fluence model was developed to characterize fluence exiting the linear accelerator head. The model was further refined using results from Monte Carlo simulations and schematics of the linear accelerator. The fluence incident on the EPID was converted to a portal dose image through a superposition of Monte Carlo-generated, monoenergetic dose kernels specific to the a-Si EPID. Predictions of clinical IMRT fields with no patient present agreed with measured portal dose images within 3% and 3 mm. The dose kernels were applied ignoring the geometrically divergent nature of incident fluence on the EPID. A computational investigation into this parallel dose kernel assumption determined its validity under clinically relevant situations. Introducing a patient or phantom into the beam required the portal image prediction algorithm to account for patient scatter and attenuation. Primary fluence was calculated by attenuating raylines cast through the patient CT dataset, while scatter fluence was determined through the superposition of pre-calculated scatter fluence kernels. Total dose in the EPID was calculated by convolving the total predicted incident fluence with the EPID-specific dose kernels. The algorithm was tested on water slabs with square fields, agreeing with measurement within 3% and 3 mm. The method was then applied to five prostate and six head-and-neck IMRT treatment courses (~1900 clinical images). Deviations between the predicted and measured images were quantified. The portal dose image prediction model developed in this thesis work has been shown to be accurate, and it was demonstrated to be able to verify patients’ delivered radiation treatments.

Radiation therapy is continuously increasing in complexity due to technological innovation in delivery techniques, necessitating thorough dosimetric verification. Comparing accurately predicted portal dose images to measured images obtained during patient treatment can determine if a particular treatment was delivered correctly. The goal of this thesis was to create a method to predict portal dose images that was versatile and accurate enough to use in a clinical setting. All measured images in this work were obtained with an amorphous silicon electronic portal imaging device (a-Si EPID), but the technique is applicable to any planar imager. A detailed, physics-motivated fluence model was developed to characterize fluence exiting the linear accelerator head. The model was further refined using results from Monte Carlo simulations and schematics of the linear accelerator. The fluence incident on the EPID was converted to a portal dose image through a superposition of Monte Carlo-generated, monoenergetic dose kernels specific to the a-Si EPID. Predictions of clinical IMRT fields with no patient present agreed with measured portal dose images within 3% and 3 mm. The dose kernels were applied ignoring the geometrically divergent nature of incident fluence on the EPID. A computational investigation into this parallel dose kernel assumption determined its validity under clinically relevant situations. Introducing a patient or phantom into the beam required the portal image prediction algorithm to account for patient scatter and attenuation. Primary fluence was calculated by attenuating raylines cast through the patient CT dataset, while scatter fluence was determined through the superposition of pre-calculated scatter fluence kernels. Total dose in the EPID was calculated by convolving the total predicted incident fluence with the EPID-specific dose kernels. The algorithm was tested on water slabs with square fields, agreeing with measurement within 3% and 3 mm. The method was then applied to five prostate and six head-and-neck IMRT treatment courses (~1900 clinical images). Deviations between the predicted and measured images were quantified. The portal dose image prediction model developed in this thesis work has been shown to be accurate, and it was demonstrated to be able to verify patients’ delivered radiation treatments.