A technique for the in vivo dose verification of intensity modulated radiation therapy (IMRT) has been developed. An electronic portal image, calibrated in terms of absolute dose, is acquired for each radiation field following transmission through the patient at the time of treatment. For an IMRT field, the portal image signal is back-projected through a model of the patient in order to calculate the dose at the isocentric plane perpendicular to the beam central axis. The IMRT in vivo dose verification technique was adapted for volumetric modu- lated arc therapy (VMAT) treatments when a single dosimetric image is acquired over an arc. The patient dose along axis of gantry rotation can be directly related to the signal along the vertical axis of EPIs in integrated mode. In this novel VMAT in vivo dosimetry technique, the portal image signal is back-projected through a rotationally averaged model of the patient to calculate a 1D in vivo dose along the axis of gantry rotation. A research ethics board clinical study was approved and transmission portal images were acquired at regular intervals from human subjects. Portal image-derived isocenter point doses were in good agreement with treatment planning system (TPS) calculations for IMRT (mean difference δ=0.0%, standard deviation of the differences σ=4.3%) and VMAT (δ=1.1%, σ=1.7%). The one-dimensional (VMAT) and two-dimensional (IMRT) reconstructed doses were further analyzed by calculating mean dose differences and γ−evaluation pass-rates, which were also shown to be in good agreement with TPS calculations. The portal image-based in vivo dosimetry techniques were shown to be clinically feasible, with reconstruction times on the order of minutes for the first fraction and less than one minute for each fraction thereafter. / Graduate / 0760 / 0574 / 0760

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-04-04T20:01:36Z No. of bitstreams: 1 RodrigoSerafimDeAraujo_DISSERT.pdf: 1281426 bytes, checksum: 6cdad3aba7595958f61e934a0dd41917 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-04-13T00:16:25Z (GMT) No. of bitstreams: 1 RodrigoSerafimDeAraujo_DISSERT.pdf: 1281426 bytes, checksum: 6cdad3aba7595958f61e934a0dd41917 (MD5) / Made available in DSpace on 2017-04-13T00:16:25Z (GMT). No. of bitstreams: 1 RodrigoSerafimDeAraujo_DISSERT.pdf: 1281426 bytes, checksum: 6cdad3aba7595958f61e934a0dd41917 (MD5) Previous issue date: 2016-12-12 / Considerando-se a import?ncia ecol?gica do morcego Artibeus planirostris e a import?ncia da avalia??o epididim?ria para o entendimento de sua fun??o reprodutiva, objetivou-se compreender os par?metros reprodutivos desta esp?cie a partir da an?lise morfol?gica e morfom?trica do epid?dimo. Foram utilizados 16 animais adultos, coletados durante as esta??es seca (n=08) e chuvosa (n=08) de 2014. As capturas foram realizadas na cidade de Natal-RN (latitude 5?50?33.9?S e longitude 35?12?07.6? W) (autoriza??o SISBIO no 25233-1), utilizando-se redes de neblina. Ap?s anestesia e eutan?sia por perfus?o transcard?aca, foi realizada a coleta dos epid?dimos (autoriza??o CEUA/UFRN no 009/2012), seguido de processamento histol?gico para inclus?o em historesina e an?lises sob microscopia de luz. An?lises morfom?tricas dos componentes do par?nquima epididim?rio foram realizadas a partir da captura de imagens das l?minas histol?gicas, utilizando-se o software Image-Pro Plus. Os resultados foram submetidos ? ANOVA, sendo as m?dias comparadas pelo teste t de Student ao n?vel de signific?ncia de 5%, seguido do p?s-teste de Tukey. Nas duas esta??es analisadas, a avalia??o morfol?gica do epid?dimo revelou que o ?rg?o apresentou-se dividido em 4 regi?es principais: segmento inicial, cabe?a, corpo e cauda. O par?nquima apresentou-se composto predominantemente por t?bulos epididim?rios, sustentados por tecido conjuntivo intertubular. Ao longo das tr?s por??es epididim?rias os t?bulos ocuparam 75,07?2,94% do par?nquima na esta??o chuvosa e 67,23?2,44% na esta??o seca, sendo seus percentuais nas regi?es da cabe?a e corpo significativamente maiores na esta??o chuvosa em rela??o ? esta??o seca. O restante do par?nquima foi representado pela regi?o intertubular, que apresentou redu??o proporcional nas mesmas regi?es entre as esta??es. Os t?bulos foram constitu?dos por epit?lio pseudoestratificado cil?ndrico com estereoc?lios, apoiado sobre uma t?nica pr?pria, e l?men. O epit?lio epididim?rio foi o principal componente do t?bulo epididim?rio, sendo que na regi?o da cauda seu percentual foi maior na esta??o seca (27,58?8,33%) em rela??o ? chuvosa (17,79?4,33%). Este epit?lio apresentou-se composto pelas c?lulas principais (PR), basais (BA), estreitas (ES), halo (HA), claras (CL) e apicais (AP), sendo que a primeira e a ?ltima apresentaram, respectivamente, maior e menor distribui??o em todas as regi?es epididim?rias nas duas esta??es. Tanto na regi?o da cabe?a quanto da cauda, as c?lulas PR foram as mais predominantes no epit?lio epididim?rio na esta??o seca em rela??o ? esta??o chuvosa, enquanto as c?lulas BA foram mais predominantes na esta??o chuvosa, tanto na cabe?a quanto na cauda. As c?lulas AP apresentaram maior distribui??o na cabe?a do epid?dimo durante a esta??o chuvosa, enquanto as c?lulas ES apresentaram maior distribui??o no corpo do epid?dimo na esta??o seca, sendo seu registro nessa por??o epididim?ria constituiu um achado novo. Observou-se aumento gradativo em diversos par?metros da cabe?a em dire??o ? cauda, tais como o di?metro dos t?bulos epididim?rios, do l?men e percentual com espermatozoides e da camada de c?lulas musculares lisas ao redor dos t?bulos epididim?rios, contrastando com a diminui??o na altura do epit?lio. Muitos destes par?metros apresentaram maiores valores na esta??o chuvosa em rela??o ? esta??o seca. Conclui-se que o epid?dimo de A. planirostris apresentou-se, de um modo geral, semelhante ao descrito para outros mam?feros, com destaque para as c?lulas estreitas, registradas pela primeira vez na regi?o do corpo. Foram encontrados espermatozoides no l?men dos t?bulos epididim?rios nas duas esta??es avaliadas, especialmente na regi?o da cauda, mostrando assim um padr?o reprodutivo anual cont?nuo, com picos de reprodu??o na esta??o chuvosa. / Considering the ecological importance of the bat Artibeus planirostris and the importance of the epididymal evaluation for the understanding of its reproductive function, this study aimed to understand the reproductive parameters of this species, from the morphological and morphometric analysis of the epididymis. Sixteen adult animals were collected during the dry season (n = 08) and rainy season (n = 08), in 2014. The captures were taken in the city of Natal-RN (5?50'33.9"S and 35?12'07.6"W) (SISBIO authorization no. 25233-1), using mist nets. After anesthesia and euthanasia by transcardiac perfusion, the epididymis were collected (CEUA/UFRN authorization no. 009/2012), followed by histological processing for embedding in historesin and analysis under light microscopy. Morphometric analyzes of the epididymal parenchyma were performed using images from the histological slides, by the Image-Pro Plus software. The results were submitted to ANOVA, and the means were compared by Student's t-test at a significance level of 5%, followed by Tukey's post-test. At the two analyzed seasons, the morphological evaluation showed that the organ was divided into 4 main regions: initial segment, head, body and tail. The parenchyma was predominantly composed of epididymal tubules, supported by intertubular connective tissue. During the three main epididymal portions, the tubules occupied 75.07 ? 2.94 % of parenchyma in rainy season and 67.23 ? 2.44 % in dry season, and its percentages in the head and body were significantly larger in rainy season compared to dry season. The remaining parenchyma was represented by the intertubular region, which showed proportional reduction in the same regions and seasons. The tubules were composed of cylindrical pseudostratified epithelium with stereocilia, supported by a tunica propria and lumen. The epididymal epithelium was the main component of the epididymal tubule. In the tail region, its percentage was higher in dry season (27.58 ? 8.33%) than in rainy season (17.79 ? 4.33%). This epithelium was composed by main (MA), basal (BA), narrow (NA), halo (HA), clear (CL) and apical (AP) cells. The first and the last ones showed, respectively, the highest and the lowest distributions in all epididymal regions, in both rainy and dry seasons. In the head and tail regions, MA cells were the most predominant in the epididymal epithelium in the dry season in relation to the rainy season, while BA cells were the most predominant in the rainy season, such in head as in tail. AP cells had a higher distribution in epididymis head during the rainy season, while NA cells had a greater distribution in the epididymis body during dry season, being its observation in this epididymal portion a new finding. There was an increase in several morphometrical parameters, from the head to the tail, such as the tubular and luminal diameter and its percentages with spermatozoa, as well the muscle cells surrounding the epididymal tubules, in contrast with a decrease in epithelial high. Several of these parameters showed larger values in the rainy season in relation to the dry season. It can be concluded that the epididymis of A. planirostris was similar to that described for other mammals, and the narrow cells were recorded in the region of the body for the first time. It was found spermatozoa in the lumen of epididymal tubules during the two seasons evaluated, especially in the tail region, showing a continuous annual reproductive pattern, with reproductive peaks in the rainy season.

No description available.

<p>Intensity-Modulated Radiation Treatment (IMRT) requires patient-specific quality assurance measurements, which can benefit from the convenience of using an Electronic Portal Imaging Device (EPID) for dose verification. However, EPIDs have limitations stemming from the non-uniform backscatter due to the support-arm as well as from scatter, glare, and an increased sensitivity to low-energy photons. None of these effects is typically accounted for in a treatment planning system (TPS) model, resulting in errors in calculated EPID response of up to 6%. This work addresses the non-uniform backscatter by directly incorporating a support-arm backscatter region into the TPS geometry. The shape of the backscatter region is adjusted iteratively until the TPS-calculated flood-field planar dose matches the flood-field EPID image The scatter, glare and increased low-energy response are addressed by using a radially-dependent Point-Spread Function (Kernel). The kernel is fitted using a least-squares method so that it best reproduces the EPID-acquired image for a checkerboard field. The backscatter-correction method is implemented for a Varian Clinac equipped with a 40 cm x 30 cm (512 x 384 pixel) EPID and a Pinnacle³ TPS and tested for several rectangular and IMRT fields. The scatter, glare and energy-response correction kernel is implemented and tested for a simulated checkerboard field and a simulated IMRT field. Agreement between the EPID-measured image and TPS-calculated planar dose map is seen to improve from 6% to 2% when the backscatter region is added to the Pinnacle³ model. Agreement between the simulated EPID images and simulated TPS images is improved from 14% to approx. 1% when the radially-dependent kernel is used. Simultaneous application of both the backscatter region and Point-Spread Function is a promising direction for future investigations.</p> / Master of Science (MSc)

Cette thèse a été réalisée dans le cadre de la dosimétrie des faisceaux de haute énergie délivrés au patient pendant un traitement de radiothérapie externe. L'objectif de ce travail est de vérifier que la distribution de dose 3D absorbée dans le patient est conforme au calcul réalisé sur le système de planification de traitement (TPS) à partir de l'imageur portal (en anglais : Electronic Portal Imaging Device, EPID). L'acquisition est réalisée en mode continu avec le détecteur aS-1200 au silicium amorphe embarqué sur la machine TrueBeam STx (VARIAN Medical system, Palo Alto, USA). Les faisceaux ont une énergie de 10 MeV et un débit de 600 UM.min-1. La distance source-détecteur (DSD) est de 150 cm. Après correction des pixels défectueux, une étape d'étalonnage permet de convertir leur signal en dose absorbée dans l'eau via une fonction de réponse. Des kernels de correction sont également utilisés pour prendre en compte la différence de matériaux entre l'EPID et l'eau et pour corriger la pénombre sur les profils de dose. Un premier modèle de calcul a permis ensuite de rétroprojeter la dose portale en milieu homogène en prenant en compte plusieurs phénomènes : les photons diffusés provenant du fantôme et rajoutant un excès de signal sur les images, l'atténuation des faisceaux, la diffusion dans le fantôme, l'effet de build-up et l'effet de durcissement du faisceau avec la profondeur. La dose reconstruite est comparée à celle calculée par le TPS avec une analyse gamma globale (3% du maximum de dose et 3 mm de DTA). L'algorithme a été testé sur un fantôme cylindrique homogène et sur un fantôme de pelvis à partir de champs modulés en intensité (RCMI) et à partir de champs d'arcthérapie volumique modulés, VMAT selon l'acronyme anglais Volumetric Modulated Arc Therapy. Le modèle a ensuite été affiné pour prendre en compte les hétérogénéités traversées dans le milieu au moyen des distances équivalentes eau dans une nouvelle approche de dosimétrie plus connue sous le terme de " in aqua vivo " (1). Il a été testé sur un fantôme thorax et, in vivo sur 10 patients traités pour une tumeur de la prostate à partir de champs VMAT. Pour finir, le modèle in aqua a été testé sur le fantôme thorax avant et après y avoir appliqué certaines modifications afin d'évaluer la possibilité de détection de sources d'erreurs pouvant influencer la bonne délivrance de la dose au patient.[...] / This thesis aims at the dosimetry of high energy photon beams delivered to the patient during an external radiation therapy treatment. The objective of this work is to use EPID the Electronic Portal Imaging Device (EPID) in order to verify that the 3D absorbed dose distribution in the patient is consistent with the calculation performed on the Treatment Planning System (TPS). The acquisition is carried out in continuous mode with the aS-1200 amorphous silicon detector embedded on the TrueBeam STx machine (VARIAN Medical system, Palo Alto, USA) for 10MV photons with a 600 UM.min-1 dose rate. The source-detector distance (SDD) is 150 cm. After correction of the defective pixels, a calibration step is performed to convert the signal into an absorbed dose in water via a response function. Correction kernels are also used to take into account the difference in materials between EPID and water and to correct penumbra. A first model of backprojection was performed to reconstruct the absorbed dose distribution in a homogeneous medium by taking into account several phenomena: the scattered photons coming from the phantom to the EPID, the attenuation of the beams, the diffusion into the phantom, the build-up, and the effect of beam hardening with depth. The reconstructed dose is compared to the one calculated by the TPS with global gamma analysis (3% as the maximum dose difference criteria and 3mm as the distance to agreement criteria). The algorithm was tested on a homogeneous cylindrical phantom and a pelvis phantom for Intensity-Modulated Radiation Therapy (IMRT) and (Volumetric Arc Therapy (VMAT) technics. The model was then refined to take into account the heterogeneities in the medium by using radiological distances in a new dosimetrical approach better known as "in aqua vivo" (1). It has been tested on a thorax phantom and, in vivo on 10 patients treated for a prostate tumor from VMAT fields. Finally, the in aqua model was tested on the thorax phantom before and after making some modifications to evaluate the possibility of detecting errors that could affect the correct delivery of the dose to the patient. [...]

Made available in DSpace on 2014-12-17T15:32:23Z (GMT). No. of bitstreams: 1 AndreiaFC_DISSERT.pdf: 3035785 bytes, checksum: a9769f0a294924c551036d1a098b7d2a (MD5) Previous issue date: 2014-02-12 / A displasia epitelial (DE) oral ? uma desordem potencialmente maligna (DPM), cujo diagn?stico e grada??o histol?gica se baseiam nas suas altera??es arquiteturais e citol?gicas. Para avaliar o risco de transforma??o maligna dessas les?es de forma mais precisa ? fundamental entender e localizar altera??es gen?ticas e epigen?ticas nas c?lulas displ?sicas, as quais podem ajudar a compreender melhor a progress?o para a malignidade. Dessa forma, o presente estudo objetivou avaliar a imunoexpress?o de EGFR e PTEN nas DEs orais e relacionar esse aspecto com as caracter?sticas cl?nicas e grada??o histol?gica pelo sistema bin?rio (baixo e alto risco de transforma??o maligna). Para tanto, foram selecionados 20 casos de DE de alto risco e 20 de baixo risco para serem submetidos ? an?lise imunoistoqu?mica para os biomarcadores supracitados. A imunomarca??o de cada caso foi avaliada semiquantitativamente atrav?s de escores e quanto ? localiza??o nos estratos epiteliais. A an?lise estat?stica foi realizada atrav?s dos testes de Mann-Whitney, Qui-quadrado de Pearson, Exato de Fisher e de correla??o de Spearman com n?vel de signific?ncia estabelecido em 5%. Os resultados mostraram que 57,5% dos pacientes eram do g?nero feminino, a m?dia de idade foi de 57,5 anos, 42,5% foram diagnosticados clinicamente como leucoplasia e a maioria dos casos foi proveniente de les?es localizadas na l?ngua (32,5%). De forma geral, g?nero e idade n?o exerceram influ?ncia na imunoexpress?o do EGFR e PTEN. A express?o do EGFR foi observada em 100% dos casos, nos quais houve predom?nio do escore 3 (75%) e imunoreatividade em todas as camadas epiteliais (55%), independente da grada??o histol?gica (p = 0,453 e p = 0,204, respectivamente). O PTEN revelou positividade de marca??o em 87,5% dos casos, nos quais observou-se predom?nio do escore 0 (55%) e imunoreatividade limitada ? camada basal (40%), por?m sem diferen?as significativas entre os grupos histol?gicos (p = 0,904 e p = 0,915, respectivamente). Por fim, quando analisados, em conjunto, os 40 casos de DEs, foi observada uma fraca correla??o positiva, estatisticamente significativa, entre os padr?es de imunoexpress?o do EGFR e do PTEN (r = 0,317; p = 0,046). Com base nesses resultados, altera??es no padr?o de express?o do EGFR e PTEN sugerem que essas prote?nas participam de processos moleculares relacionados com a carcinog?nese em mucosa oral

Made available in DSpace on 2014-12-17T14:13:43Z (GMT). No. of bitstreams: 1 FranciscoCSJ.pdf: 1235219 bytes, checksum: 99fd9a9cd6382f5c2247c17ecd9cce0b (MD5) Previous issue date: 2009-10-09 / Staphylococcus aureus resistente ? meticilina (MRSA) ? um dos principais agentes de infec??es associadas a servi?os de sa?de em todo o mundo. No Brasil, h? a predomin?ncia de um clone de MRSA multirresistente denominando clone epid?mico brasileiro (CEB). Entretanto, novos clones n?omultirresistentes com alta virul?ncia t?m sido descritos em infec??es comunit?rias e hospitalares. O objetivo desse estudo foi realizar a caracteriza??o fenot?pica e genot?pica de cepas de MRSA isoladas na cidade do Natal/RN. Inicialmente avaliamos 60 amostras de S. aureus quanto a resist?ncia ? meticilina atrav?s de diferentes t?cnicas fenot?picas, utilizando a detec??o do gene mecA por PCR como padr?o. O antibiograma de todas as cepas foi realizado utilizando 12 antimicrobianos conforme descrito pelo CLSI. As cepas de MRSA foram caracterizadas geneticamente atrav?s da tipagem do cassete cromoss?mico estafiloc?cico mec (SCCmec) e da eletroforese em campo el?trico alternado (PFGE). Dos 60 S. aureus estudados, 45 foram resistentes ? meticilina. Observamos que para algumas cepas de MRSA os testes de triagem em ?gar com 6&#956;g/mL de oxacilina e difus?o em meio s?lido com oxacilina-1&#956;g apresentaram dificuldades na sua interpreta??o. No entanto, todas as 45 amostras de MRSA, foram facilmente detectadas pelos testes com o disco de cefoxitina-30&#956;g e pesquisa da PBP2a. A an?lise molecular das cepas de MRSA mostrou 8 padr?es distintos de PFGE (A-H), com predomin?ncia do padr?o A (73%), relacionado ao CEB. Estas carreavam o SCCmec tipo IIIA, e apresentaram uma consider?vel variedade de subtipos (A1-A16). Cinco cepas de MRSA portando SCCmec IV tamb?m foram xiv identificadas, tr?s delas relacionadas geneticamente ao clone USA800 (Padr?o B). Destas cinco, tr?s (2 padr?o F e 1 padr?o B) foram altamente suscept?veis as drogas testadas, entretanto, dois outros isolados, padr?o B, apresentaram multirresist?ncia. As amostras restantes pertenciam a padr?es de PFGE distintos dos clones internacionais predominantes em nosso continente. Para realiza??o deste projeto de pesquisa, a metodologia exigiu a intera??o com pesquisadores de ?reas como: infectologia, microbiologia e biologia molecular. Portanto, esta disserta??o apresentou um car?ter de multidisciplinaridade e transdiciplinaridade no seu desenvolvimento

Made available in DSpace on 2014-12-17T15:15:00Z (GMT). No. of bitstreams: 1 MarceloBS_TESE.pdf: 1282048 bytes, checksum: fb344c5ca563e7fc0032c38d8cab9256 (MD5) Previous issue date: 2013-08-02 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Nos ?ltimos anos, propaga??es epid?micas t?m sido alvo de muitos estudos baseados nos m?todos da F?sica Estat?stica. As din?micas desses processos epid?micos, tipicamente de n?o equil?brio, resultam na competi??o entre indiv?duos infectados (ativos) e indiv?duos saud?veis (inativo). Estes sistemas de n?o-equil?brio possuem um estado ativo estatisticamente estacion?rio, que representa a persist?ncia da epidemia, e um estado absorvente que reflete o fim da epidemia. ? a transi??o entre estes estados (ativo e inativo) que nos permite a an?lise cr?tica desses sistemas. Neste contexto, esta tese investiga dois destes processos, onde o primeiro deles corresponde a uma generaliza??o para o processo de contato em uma cadeia linear. Neste modelo, cada par de s?tios est? conectado com probabilidade P(r) que decai com a dist?ncia entre os s?tios r da forma 1/r&#945;. O modelo permite uma varia??o cont?nua entre a cadeia unidimensional padr?o, caracterizada por liga??es apenas entre primeiros vizinhos (&#945; &#8594; &#8734;), at? uma rede completamente conectada (&#945; = 0) caracterizada por comportamento de campo m?dio. Desenvolvemos an?lise de escala de tamanho finito para obter o ponto cr?tico e o conjunto de expoentes cr?ticos para distintos valores do expoente de liga??o &#945;. Dados do par?metro de ordem colapsam em uma curva universal. Mostramos tamb?m que os expoentes cr?ticos variam continuamente com &#945;. No segundo trabalho, introduzimos o modelo processo epid?mico superdifusivo, onde indiv?duos saud?veis (A) e infectado (B) podem saltar com distintas probabilidades (DA e DB respectivamente) sobre um dist?ncia &#8467; distribu?da de acordo com uma probabilidade tipo lei de pot?ncia P(&#8467;) = 1/ &#8467;?. Para ?&#8805;3 a propaga??o equivale a difus?o normal, e para ?<3 corresponde aos voos de L?vy. No regime de difus?o DA > DB, resultados da teoria de campo tem sugerido transi??o de primeira ordem, conjectura esta n?o endossada por v?rios estudos num?ricos. Realizamos um extensivo estudo num?rico do comportamento cr?tico de ambos os regimes, difusivo (?&#8805;3) e superdifusivo (?<3), para o caso em que DA > DB. Aplicamos an?lise de escala de tamanho finito para obter as propriedades cr?ticas inerentes ao modelo para v?rios valores de ?. A an?lise do modelo indica uma transi??o de fase de segunda ordem com expoentes cr?ticos variando continuamente

At the BC Cancer Agency (BCCA), Vancouver Island Centre (VIC), the clinical verification of Intensity Modulated Radiation Therapy (IMRT) treatment plans involves comparing Portal Image (PI) -based three-dimensionally reconstructed (EPIDose) dose distributions to planned doses calculated using the Pencil Beam Convolution (PBC) algorithm. Discrepancies surpassing established action levels constitute failure. Since 2007, the failure rate of IMRT verification process had been increasing, reaching as high as 18.5% in 2009. A retrospective evaluation of clinical IMRT verification failures was conducted to identify causes and possible resolutions. Thirty clinical verification failures were identified. An equipment malfunction was discovered and subsequently repaired, and several failures were resolved in the process. Statistical uncertainty in measurement outcome was small in comparison to action levels and not considered significant to the production of failures. Still, over 50% of the redelivered plans were shown to consistently fail. A subgroup of consistent verification plans were compared to ion chamber point dose measurements. Relative to ion chamber measurements, EPIDose underestimated the dose while the dose calculation algorithm (PBC, Eclipse version 8.1.18) overestimated the same point dose. Comparisons of individual fields demonstrated that none were identifiably problematic; dose discrepancies were the result of minor but accumulating dose differences. Consistent verification failures were recalculated using two advanced dose calculation engines (the Anisotropic Analytical Algorithm and Monte Carlo). In general, verification metrics improved, and all failures were resolved. Three distinct indices of fluence modulation (or complexity) were shown to correlate with verification metrics. This indicated that deficiencies in both the leaf motion calculator and the PBC (Eclipse version 8.1.18) had likely contributed to the production of failures. In conclusion, clinical verification failures were resolved retrospectively by replacing faulty equipment and using more advanced methods of planned dose calculation, supporting the efficacy and continued use of PI-based three dimensional dose reconstruction for IMRT verification.

Made available in DSpace on 2014-12-17T14:10:19Z (GMT). No. of bitstreams: 1 FredericoLS_DISSERT.pdf: 1177174 bytes, checksum: efe72b5694aaae13f9be30ff705ec1c9 (MD5) Previous issue date: 2010-10-27 / The pair contact process - PCP is a nonequilibrium stochastic model which, like the basic contact process - CP, exhibits a phase transition to an absorbing state. While the absorbing state CP corresponds to a unique configuration (empty lattice), the PCP process infinitely many. Numerical and theoretical studies, nevertheless, indicate that the PCP belongs to the same universality class as the CP (direct percolation class), but with anomalies in the critical spreading dynamics. An infinite number of absorbing configurations arise in the PCP because all process (creation and annihilation) require a nearest-neighbor pair of particles. The diffusive pair contact process - PCPD) was proposed by Grassberger in 1982. But the interest in the problem follows its rediscovery by the Langevin description. On the basis of numerical results and renormalization group arguments, Carlon, Henkel and Schollw?ck (2001), suggested that certain critical exponents in the PCPD had values similar to those of the party-conserving - PC class. On the other hand, Hinrichsen (2001), reported simulation results inconsistent with the PC class, and proposed that the PCPD belongs to a new universality class. The controversy regarding the universality of the PCPD remains unresolved. In the PCPD, a nearest-neighbor pair of particles is necessary for the process of creation and annihilation, but the particles to diffuse individually. In this work we study the PCPD with diffusion of pair, in which isolated particles cannot move; a nearest-neighbor pair diffuses as a unit. Using quasistationary simulation, we determined with good precision the critical point and critical exponents for three values of the diffusive probability: D=0.5 and D=0.1. For D=0.5: PC=0.89007(3), &#946;/v=0.252(9), z=1.573(1), =1.10(2), m=1.1758(24). For D=0.1: PC=0.9172(1), &#946;/v=0.252(9), z=1.579(11), =1.11(4), m=1.173(4) / O processo de contato por par -PCP ? um modelo estoc?stico de n?o equil?brio que se inspira no processo de contato simples -PC e que exibe uma transi??o de fase para um estado absorvente. Embora que o estado absorvente para o PC corresponda a uma ?nica configura??o (estado vazio), o PCP possui infinitas configura??es. No entanto, estudos num?ricos e te?ricos indicam que o PCP pertence a mesma classe de universalidade do PC (classe da percola??o direcionada), mas apresenta uma anomalia na din?mica de propaga??o. Um n?mero infinito de configura??es de estados absorventes surge no PCP, devido a todos os processos de cria??o e aniquila??o que requererem um par de part?culas de vizinhos mais pr?ximos. O processo de contato por par difusivo - PCPD foi proposto por Grassberger em 1982. Por?m, o interesse neste problema segue com a redescoberta por Howard; T?uber (1997), que questionaram a validade da descri??o de Langevin. Com base nos resultados num?ricos e em grupo de renormaliza??o, Carlon; Henkel ; Schollw?ck, (2001), observaram que alguns expoentes cr?ticos no PCPD apresentam valores similares ao da classe PC. Porem, Hinrichsen (2001), mostrou resultados diferentes do caso PCPD, atrav?s da simula??o, para o caso PC, propondo uma nova classe de universalidade. At? hoje existe uma controv?rsia em rela??o a classe de universalidade do PCPD. No PCPD ? necess?rio um par de part?culas vizinhas para os processos de cria??o e aniquila??o, embora as part?culas difundam individualmente. Neste trabalho, estudamos o PCPDP com difus?o de pares, no qual part?culas isoladas n?o podem difundir. Pares vizinhos difundem juntos. Usando simula??o quase-estacion?ria, determinamos com boa precis?o o ponto cr?tico e os expoentes para dois valores da probabilidade de difus?o: D=0.5, e 0.1. Para D=0.5: PC=0.89007(3), &#946;/v=0.252(9), z=1.573(1), =1.10(2), m=1.1758(24). Para D=0.1: PC=0.9172(1), &#946;/v=0.252(9), z=1.579(11), =1.11(4), m=1.173(4)