Esta pesquisa foi realizada para verificar se o padrão morfogenético da base craniana é determinante das dimensões transversais da maxila e mandíbula e se tal influência também se estende à porção alveolar das bases apicais. Complementarmente buscou-se avaliar as inclinações vestíbulo-linguais dos dentes posteriores com intuito de verificar se tais inclinações são padronizadas, independente das larguras das bases alveolares, ou se existem variações significativas. A amostra foi composta por 30 indivíduos adultos jovens, brasileiros, leucodermas com perfis faciais equilibrados e neutro-oclusão. Dividiu-se em dois grupos de acordo com a dimensão transversal da base anterior do crânio, definida pela distância entre os pontos esfenóide direito e esquerdo, sendo o grupo G1 composto pelos indivíduos apresentando valores menores que a mediana, e o grupo G2 com indivíduos apresentando valores maiores ou iguais a mediana. Foi realizada correlação intraclasse para avaliar o erro do método; média, mediana e desvio padrão para descrever o grupo amostral; teste t-Student para comparar os grupos G1 e G2; teste exato de Fischer para avaliar associação entre base do crânio e gêneros e Teste de Correlação Linear de Pearson. As medidas apresentaram alta reprodutibilidade. Indivíduos do grupo G2 apresentaram maior largura de mandíbula e maior espessura alveolar dos primeiros molares e primeiros pré-molares superiores. Não houve associação entre largura de base do crânio e gêneros. A largura basal da mandíbula apresentou correlação estatisticamente significante com a largura da base do crânio, assim como a largura alveolar maxilar na região de prémolares e molares superiores em relação à largura basal da maxila. As conclusões foram: a largura da base craniana apresenta correlação com a largura da mandíbula; a largura da maxila varia em consonância com a largura da mandíbula; a largura alveolar da maxila na região de primeiros pré-molares e molares superiores apresenta correlação com largura basal da maxila; a largura basal mandibular apresenta correlação com a largura alveolar da mandíbula na região dos primeiros pré-molares; as inclinações vestíbulo-linguais dos primeiros molares e primeiros prémolares são constantes, independentes das larguras basais e alveolares de suas respectivas bases ósseas. / This research intended to check if the morphogenetic pattern of cranial base determines transverse dimensions of upper and lower face and if it extends to alveolar portion basis. In addition evaluated buccal-lingual inclinations of posterior teeth to examine if they are standardized, regardless of the widths of the alveolar bases, or whether there are significant variations. The sample comprised 30 young adults, Caucasian Brazilian facial profiles with balanced and neutral occlusion. Divided into two groups according to the transverse dimension of the anterior skull base, defined by the distance between right and left sphenoid´s points, the G1 made of individuals with lower values than the median, and G2 with individuals with values greater or equal to median. Intraclass correlation was performed to evaluate the method error, mean, median and standard deviation to describe the sample group, Student t test to compare the groups G1 and G2, Fisher exact test to access the relation between skull base and genres and Test Linear correlation of Pearson. Measurements showed high reproducibility. G2 individuals showed greater mandible width and greater thickness of alveolar bone on upper first molars and first premolars. There was no association between width of skull base and genres. The width of the mandible showed a statistically significant correlation with the width of the skull base and maxillary alveolar width in premolars and molars in relation to basal width of jaw. Conclusions: the width of cranial base is correlated with width of jaw; jaw width varies in line with jaw width and width of maxillary alveolar region of first premolars and molars is correlated with basal width jaw, the basal mandibular width correlates with width of jaw in alveolar region first premolars; the buccolingual inclinations of the first molars and first premolars are constant, independent of basal width and alveolar bone of their respective bases.

Orientador: Francisco Haiter Neto / Texto em português e inglês / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-24T17:16:38Z (GMT). No. of bitstreams: 1 Visconti_MariaAugustaPortellaGuedes_D.pdf: 2357684 bytes, checksum: ed042e1f5da51d27eae5691a052e4cc3 (MD5) Previous issue date: 2014 / Resumo: O presente estudo propôs-se validar os materiais água e acrílico como simuladores de tecidos moles em um estudo in vitro realizado com tomografia computadorizada de feixe cônico (TCFC). Para isso foram utilizadas três cabeças humanas, com tecidos moles intactos, para determinação do padrão-ouro. Essas cabeças foram submetidas a exames de TCFC e posteriormente descarnadas e tomografadas novamente, agora com diferentes tipos de simuladores de tecido mole, seguindo o mesmo protocolo de aquisição. Para simulação dos tecidos moles foram confeccionadas três caixas de acrílico com diferentes dimensões e espessuras. Estas caixas foram utilizadas isoladamente, conjugadas entre si e em combinação com a água, totalizando dez diferentes tipos de simuladores. Um único avaliador experiente realizou as mensurações em quatro regiões de interesse para maxila e mandíbula, incluindo dentes e ossos alveolares. As regiões de interesse consistiram em áreas quadrangulares, nas quais foram determinados todos os valores de cinzas expressos em pixels. Os resultados mostraram que tanto a região avaliada quanto os tipos de simuladores testados interferiram diretamente nos valores de pixels obtidos. As caixas de acrílico de 0,5 e 1,5 cm de espessura foram os simuladores que mais se assemelharam ao padrão-ouro, não apresentando diferença significativa. No entanto, essa similaridade apenas foi observada para a maxila, limitada às regiões dos dentes e ossos alveolares anteriores. A simulação dos tecidos moles realizada apenas com o acrílico foi a que mais se aproximou dos tecidos moles humanos nas imagens de TCFC, apenas para maxila / Abstract: The aim of this study was to validate the materials water and acrylic as soft tissue simulators in an in vitro study conducted with cone beam computed tomography (CBCT). For this we used three human heads, with soft tissues intact, to determine the "gold standard". These heads were submitted to CBCT exams, and subsequently stripped and scanned again, this time with different types of soft tissue simulators, following the same acquisition protocol. For soft tissue simulation, three acrylic boxes of differing dimensions and thicknesses were prepared. These boxes were used separately, combined together, and in combination with water, totaling ten different types of simulators. A single experienced evaluator did measurements in four regions of interest for the maxilla and mandible, including teeth and alveolar bone. The regions of interest consisted of quadrangular areas, in which all gray values were determined, expressed in pixels. The results sowed both the region evaluated as well as the types of simulators tested directly affected the pixel values obtained. The acrylic boxes with 0.5 and 1.5 cm thickness were the simulators that more closely resembled the gold standard, presenting no significant difference. However, this similarity was observed only for the maxilla, limited to the anterior tooth and alveolar bone regions. The simulation of soft tissues done solely with acrylic was the one closest to human soft tissues in the CBCT images, only for maxilla / Doutorado / Radiologia Odontologica / Doutora em Radiologia Odontológica

Orientadores: Glaucia Maria Bovi Ambrosano, Paulo Sérgio Flores Campos / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-20T02:59:51Z (GMT). No. of bitstreams: 1 Aguiar_LucianaBarretoVieira_D.pdf: 775343 bytes, checksum: 32297ad518d640437e10e0db97d996fa (MD5) Previous issue date: 2012 / Resumo: O objetivo neste estudo foi avaliar a validade de medidas verticais lineares para fins de inserção de implantes dentários em mandíbula a partir de imagens paracoronais diagonais (tomógrafo k9000 3D) e imagens paracoronais ortogonais (tomógrafo i-CAT). A amostra consistiu de 11 mandíbulas humanas secas e desdentadas na região posterior. Foram realizadas, a partir dos sítios implantares, três linhas de orientação, desde o rebordo alveolar até a base da mandíbula, simulando o ângulo de implantação dos dentes na base óssea. Para que estas linhas pudessem ser visualizadas nas imagens tomográficas, foram colocadas no rebordo três esferas plásticas, para localização do sítio implantar, e cones de guta percha com 01 cm de espaçamento entre eles. A aquisição das imagens foi procedida nos tomógrafos i-CAT e k9000 3D, de acordo com os protocolos estabelecidos para este fim. Após as aquisições, três avaliadores analisaram as imagens nos softwares i-CAT Vision e do KDIS, dos respectivos tomógrafos. Para a análise das imagens do i-CAT, os avaliadores realizaram cortes paracoronais ortogonais mensurando a partir do rebordo ósseo até o teto do canal mandibular o corte com a imagem da esfera mais nítida. Nas imagens do k9000 3D, os avaliadores realizaram cortes paracoronais diagonais usando a ferramenta do próprio software e mensurando também do rebordo ósseo até o teto do canal mandibular, acompanhando a orientação da guta percha. Os avaliadores realizaram uma segunda mensuração após uma semana. As mandíbulas foram cortadas seguindo a localização e a orientação das linhas previamente tracejadas nos três sítios, sendo as alturas mensuradas com um paquímetro digital desde o rebordo ósseo até o teto do canal mandibular. As medidas assim aferidas foram utilizadas como padrão ouro. Após a tabulação, os dados foram avaliados pela análise de correlação intraclasse e a comparação entre as médias obtidas nos dois tomógrafos com o real foi realizada pelo teste t pareado (?=0,05). Observou-se que o coeficiente de correlação intraclasse intra-avaliadores foi excelente (variando de 0,98 a 0,99) para os dois tomógrafos. Para a primeira e a segunda avaliação o ICC interavaliadores para os dois tomógrafos foi de satisfatório a excelente: 0,72 a 0,99 e 0,69 a 0,98 respectivamente. Quando comparados os avaliadores com o padrão ouro, o ICC foi excelente variando de 0,76 a 0,87 e 0,82 a 0,89, para o i-CAT e o k9000 3D, respectivamente. Os resultados do ICC para os tomógrafos comparados com o padrão ouro foram excelentes (0,88 e 0,94). O resultado da estatística descritiva obteve um valor de p= 0,0002 com uma média de 13,5 para o i-Cat havendo diferença estatisticamente significativa em relação ao padrão ouro (média 12,5). O k9000 apresentou uma média de 12,7 (p=0,4454) não havendo diferença estatisticamente significativa em relação ao padrão ouro. Dessa forma, pode-se concluir que as medidas verticais reproduzem a condição anatômica e são válidas para fins de inserção de implantes dentários / Abstract: The aim of this study was to evaluate the validity of vertical linear measurements for the purpose of inserting dental implants in the mandible using diagonal parasagittal images (K9000 3D Tomograph) and orthogonal parasagittal images (i-CAT Tomograph). The sample consisted of 11 dry, human mandibles, edentulous in the posterior region. From the implant sites, three orientation lines were drawn from the alveolar ridge to the base of the mandible, simulating the angle of implantation of teeth in the bony base. So that these lines could be visualized in the tomographic images, three plastic spheres were placed on the ridge to localize the implant site, and gutta percha cones spaced at a distance of 01cm between them. Image acquisition was performed with i-CAT and K9000 3D tomographs, in accordance with the protocols established for this purpose. After acquisition, three evaluators analyzed the images by means of i-CAT Vision and KDIS software of the respective tomographs. For analysis of i-CAT images, the evaluators made parasagittal orthogonal cuts measuring the cut with the most nitid image of the sphere from the bone ridge up to the roof of the mandibular canal. In the images of the K9000, the evaluators made diagonal parasagittal cuts using the tool of the software itself and also measured from the bone ridge up to the roof of the mandibular canal, following the orientation of the gutta percha. The evaluators made a second measurement after one week. The hemi-mandibles were cut following the localization and orientation of the previously traced lines in the three sites, with the heights being measured with a digital pachymeter from the bone ridge up to the roof of the mandibular canal. The measurements thus checked were used as the gold standard. After tabulation, the data were evaluated by the interclass correlation analysis. The results demonstrated that the intraclass intra-evaluator coefficient of correlation was excellent (ranging from 0.98 to 0.99) for the two Tomographs. For the first and second evaluation the inter-evaluator ICC for the two tomographs was from satisfactory to excellent: 0.72 to 0.99 and 0.69 to 0.98 respectively. When the evaluators were compared with the gold standard, the ICC was excellent variation from 0.76 to 0.87 and 0.82 to 0.89, for i-CAT and K9000 3D, respectively. The results of the ICC for the tomographs compared with the gold standard were excellent (0.88 and 0.94). Thus, it could be concluded that the vertical measurements reproduced the anatomic condition and are valid for the purpose of inserting dental implants / Doutorado / Radiologia Odontologica / Mestre em Radiologia Odontológica

Objective: To compare condylar dimensions of young adults with Class II and Class III skeletal patterns using cone-beam computed tomography (CBCT). Materials and methods: 124 CBCTs from 18-30 year-old patients, divided into 2 groups according to skeletal patterns (Class II and Class III) were evaluated. Skeletal patterns were classified by measuring the ANB angle of each patient. The anteroposterior diameter (A and P) of the right and left mandibular condyle was assessed from a sagittal view by a line drawn from point A (anterior) to P (posterior). The coronal plane allowed the evaluation of the medio-lateral diameter by drawing a line from point M (medium) to L (lateral); all distances were measured in mm. Results: In Class II the A-P diameter was 9.06±1.33 and 8.86±1.56 for the right and left condyles respectively, in Class III these values were 8.71±1.2 and 8.84±1.42. In Class II the M-L diameter was 17.94±2.68 and 17.67±2.44 for the right and left condyles respectively, in Class III these values were 19.16±2.75 and 19.16±2.54. Conclusion: Class III M-L dimensions showed higher values than Class II, whereas these differences were minimal in A-P.

This thesis concerns the simulation of locomotion in vertebrates. The state-of-the-art uses genetic algorithms together with solid body kinematics to generate possible solutions for stable gaits. In recent work, this methodology led to a hopping gait in a dinosaur and the researchers wondered if this was realistic. The purpose of the research carried out in this thesis was to examine whether quick and simple finite-element analyses could be added to the simulator, to evaluate a simple ―break or―not break failure criterion. A break would rule out gaits that might damage theowner‘s skeleton. Linear elastic analysis was considered as a possible approach as it would add little overhead to the simulations. The author used X-ray computed tomography and the finite element method to examine the axial loading of a barnacle goose femur. The study considered four levels of detail for a linear elastic simulation, finding that all the analyses carried out overestimated the strength of the bone, when considering safety factors. The conclusion is that to incorporate stress-strain analysis into the gait simulation requires more realistic models of bone behaviour that incorporate the nonlinear response of bone to applied loading. A new study focusing on the use of novel techniques such as model order reduction is recommended for future work. The outputs of this research include chapters written up as journal papers covering a 4D tomography experiment; a level of detail study; an analysis of a purported tendon avulsion injury in Tyrannosaurus rex and a review of the elastic properties of bone.

Pressboard, a high-density cellulose-based product, is used both as load bearing structures and dielectric insulation in oil-filled power transformers. During transformer operation, mechanical forces and vibrations are applied on the material. In particular, this investigation focuses on pressboard sheets placed between the turns of transformer windings, called the spacers, which during short circuit are subjected to high compressive forces of impulse nature. As a result of these forces, remaining deformations are created in the components. One step to reduce the negative consequences that come from the deformations is to understand how the fiber structure of the material changes by these forces, thus finding the week link. Understanding these changes could lead to future modification of the material to better withstand short circuits. To see the fiber structure and its changes in the material, pressboard has been investigated with a micro-CT at the Division of Applied Mechanics at Uppsala University. The scanned images have been reconstructed and analyzed in NRecon, CTAnalyser, and Matlab to investigate the density distribution changes and to identify the densification patterns. The study shows that pressboard initially has an inhomogeneous density distribution through the thickness and after mechanical indentations, the densification tends to begin in the more porous parts of the material. The project also included a prediction of the densification pattern, performed by finite element analysis (FEA) using a simplified material model. The results show that a material model with varying Young’s modulus through the thickness, based on a stiffness and porosity relationship, can produce similar densification patterns as in the experiments.

Abstract Subarachnoid haemorrhage (SAH) is a life-threatened disease with poor outcome. It is usually caused by an intracranial aneurysm (IA) rupture and rapid diagnosis and treatment are of great importance. Computed tomography (CT) is a reliable method to detect the blood in the subarachnoid (SA) spaces. Digital subtraction angiography (DSA) offers dynamic and morphological information of a ruptured IA. The treatment options for excluding an aneurysm from the main circulation are neurosurgical clipping and endovascular procedures. The purpose of the present study was to evaluate the risk factors of acute hydrocephalus (HC) and the reliability to localize the ruptured aneurysm based on non-contrast CT. The aim was also to compare the effect of neurosurgical and endovascular treatment on the development of chronic HC, and evaluate the incidence and the risk factors of early rebleeding (<  30 days) after coiling. The data of 180 operated patients with a ruptured IA were checked. Two neuroradiologists separately located the IAs based on non-contrast CT. The analyses of blood amount and distribution was a reliable method for estimating the location of ruptured middle cerebral artery (MCA) aneurysms and anterior communicate artery (ACoA) aneurysms. Intracerebral haemorrhage (ICH) was a predictor for detecting the precise site. The results confirmed that intraventricular haemorrhage (IVH) was the most consistent single risk factor for the development of acute HC. Haemorrhage in the basal region and the large total blood amount in the SA spaces were strong predictors. The effect of early treatment modality for ruptured IAs on the development of chronic HC with 102 clipped and 107 coiled patients was compared. The treatment method used was not significantly associated with the occurrence of chronic HC or the need for shunt operation. The incidence and risk factors of early rebleeding after coiling were investigated in 194 consecutive acutely (within 3 days) coiled patients with ruptured IAs. The incidence of early rehaemorrhage was 3.6%. The presence of ICH at admission and poor clinical condition were significant predictors for rebleeding. An early rehaemorrhage appeared as an enlargement of the ICH in all of these patients. In conclusion, the non-contrast CT is a reliable method to detect the location of ruptured IA in patients with MCA and ACoA aneurysms. The risk factor for the development of acute HC is IVH. Other predictors are the total SA blood amount and blood in the basal regions. The treatment method used for acutely ruptured IA has no significant effect on the occurrence of chronic HC. The incidence of early rebleeding after coiling is low. The risk factors of rebleeding are the presence of ICH and poor clinical condition. Rehaemorrhage appears often as an enlargement of the ICH.

Abstract Technical improvements in computed tomography (CT) scanners have provided new possibilities to exploit the resources of this imaging modality in the evaluation of patients with multiple injuries or patients being treated in an intensive care unit (ICU). The purpose of this study was to assess the significance of multi-detector computed tomography (MDCT) in diagnostics and treatment decisions concerning multiple trauma and critically ill patients. Findings of MDCT using a dedicated trauma protocol in 133 patients exposed to high-energy blunt trauma were retrospectively evaluated. Diagnostic information about the injuries that would enable planning of treatment was sought. The imaging protocol consisted of axial scanning of the head and helical scanning of the facial bones, cervical spine, thorax, abdomen, and pelvis. Ninety-nine of the patients (74%) had at least one finding consistent with trauma. Nineteen false negative findings and two false positive findings were made. The overall sensitivity of MDCT was 94%, specificity 100%, and accuracy 97%. The reliability of a structured 5-min evaluation of MDCT images from the scanner’s console was prospectively evaluated in 40 high-energy trauma patients. The dedicated trauma protocol covering the thorax, abdomen, and pelvis was used in MDCT scanning. The findings were compared with the final radiological diagnosis of the MDCT data made on a picture archiving and communicating system (PACS) workstation, the operative findings, and the clinical follow-up. The evaluation from the scanner’s console enabled diagnosis of all potentially life-threatening injuries, the sensitivity for all injuries being 60% and specificity 98%. The effects of MDCT on the treatment of patients in a 12-bed medical-surgical ICU were observed prospectively. Sixty-four patients with an ICU stay longer than 48 h had had inconclusive findings with other modalities of radiological imaging. They underwent altogether 82 MDCT examinations. Fifty examinations (61%) resulted in a change in treatment, and 20 (24%) of them otherwise contributed to or supported clinical decision-making. Twelve examinations (15%) failed to provide any additional information relevant to the patient’s treatment. MDCT examination was helpful in general ICU patients, with inconclusive findings with other imaging modalities. CT images of 127 mixed medical-surgical ICU patients were retrospectively reviewed for the previously determined findings. Forty-three of these patients underwent open cholecystectomy, revealing eight cases with a normal gallbladder (GB), 26 with an edematous GB, and nine with necrotic acute acalculous cholecystitis (AAC). Abnormal CT findings were present in 96% of all the ICU patients. Higher bile density in the GB body and subserosal edema were associated with an edematous GB. The most specific findings predicting necrotic AAC were gas in the GB wall or lumen, lack of GB wall enhancement, and edema around the GB. The frequent prevalence of nonspecific abnormal imaging findings in the GB of ICU patients limits the diagnostic value of CT scanning.

In the advanced polymer composites reinforced by 3D woven fibre architectures, tows areinterlaced into through-thickness direction to overcome the problems encountered in theapplications of traditional 2D laminates, such as poor interlaminar toughness anddelamination resistance. The understanding of the influence of fibre architectures on thefatigue performance of 3D woven composites is essential in providing guide for the designof fibre architecture. This PhD project is an in-depth study into the fatigue damagemechanisms of 3D woven composites reinforced by two kinds of fibre architectures,namely, 3D modified layer-to-layer (MLL) and 3D angle-interlocked (AI). 3D X-raycomputed tomography (CT) has been used as the main tool to non-destructively evaluateand quantify the evolution of fatigue damage, with an attempt to link macro behaviour withlocal micro (damage) microstructure. Part I is focused on a post-failure study on both typesof materials to identify their respective failure mechanism, using the combination of 2D(optical surface and SEM cross-sectional) imaging and 3D (X-ray CT) imaging. Somecharacteristic features are found in both materials: firstly, fatigue damage progresses by theinitiation of transverse cracks within weft yarns and subsequent propagation as interfacialdebonding crack until the catastrophic failure occurs in a localised area; secondly, bothmaterials display a high resistance to ultimate failure. However, a distinctive damage modeobserved in MLL composites is the extensive development of debonding cracks, whichresult in larger scale of damage (~10μm) than those in AI composites (1-2 μm). Part IIpresents an investigation of evolution of fatigue damage in 3D woven MLL compositesfollowed by an X-ray time-lapse experiment. An innovative algorithm was developed toenable automatic classification of damage, providing insight into the competition andinteraction of different damage modes. Fatigue damage is regularly distributed throughoutfatigue life, with a geometrical dependency on the repeating unit cells. Damageinteractions have been identified, indicating a high level of damage tolerance. Aquantitative analysis has been carried out to examine and compare the growth of differenttypes of damage as a function of fatigue cycles. Transverse cracks initiate at almost thebeginning the fatigue life (0.1%) and govern the growth of weft/binder debonds, but don’tcompromise fatigue life, whereas interply debonds have a large growth towards the end offatigue life and facilitate the ultimate failure. Other types of damage occurring in the resinhave a trivial effect on the fatigue life. Part III carries out a systematic study to find out thebest approach to detect the fatigue damage in the 3D AI composites. Different strategieshave been employed in each scan, including imaging the cracks with the load applied, withcontrast enhanced by phases contrast and staining. The image contrast was not effectivelyenhanced by applying phase contrast imaging, but significantly improved by staining. Withthe application of in-situ loading, the visibility of transverse cracks is highly improved,while longitudinal debonding cracks still cannot be resolved. Overall, the best approachwas found to be high resolution ROI (region of interest) scanning in combination withstaining, in terms of practical feasibility, scan time and image quality.

Submitted by Haroudo Xavier Filho (haroudo.xavierfo@ufpe.br) on 2016-04-22T18:09:16Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação final Max-FINAL .compressed.pdf: 3341309 bytes, checksum: d495284374075775bce6c91531257a7e (MD5) / Made available in DSpace on 2016-04-22T18:09:16Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação final Max-FINAL .compressed.pdf: 3341309 bytes, checksum: d495284374075775bce6c91531257a7e (MD5) Previous issue date: 2015-08-27 / A tomografia computadorizada (TC) é um dos métodos mais importantes de radiodiagnóstico, porém, pode resultar em altas doses absorvidas pelos pacientes quando comparado com exames radiográficos convencionais. O objetivo deste trabalho é avaliar as doses absorvidas pelos pacientes pediátricos nos procedimentos de tomografia computadorizada de crânio realizados em Recife, Brasil, utilizando o software de simulação computacional CALDose_XCT. Os parâmetros de irradiação para os procedimentos de TC de crânio pediátrico de 108 pacientes foram coletados e divididos nas seguintes faixas etárias: <1; 1 a 5; 5 a 10; e 10 a 15 anos de idade. Os valores de índice volumétrico de kerma ar em TC (CVOL) e produto kerma ar-comprimento para exames completos de TC (PKL,CT) foram estimados para cada exame e comparados com os níveis de referência internacional. Foram estimados os valores das doses absorvidos por órgãos relevantes (cristalino, cérebro, mucosa oral e glândulas salivares) utilizando o CALDose_XCT. Outra simulação foi realizada utilizando um fantoma de cabeça com inclinação de 18º para avaliar a redução da dose absorvida quando se utiliza a inclinação do gantry ou da cabeça do paciente. Os parâmetros de irradiação selecionados na maioria dos exames pediátricos avaliados não estão otimizados, já que foram observados valores maiores ou iguais aos parâmetros recomendados para exames em adultos. A maioria dos valores estimados de CVOL foram menores que os níveis de referência referência internacionais para exames pediátricos de TC. Por outro lado, situação inversa ocorreu com os valores de PKL,CT, devido ao uso de valores elevados de comprimento de varredura, em alguns casos maiores que a cabeça inteira do paciente. A maioria dos exames avaliados resultou em valores estimados de PKL,CT acima dos limites recomendados. A simulação da inclinação da cabeça dos pacientes pediátricos para exames de crânio resultou em redução da dose absorvida pelos olhos, mucosa oral e glândulas salivares, demostrando ser um método eficiente para otimização da proteção radiológica nestes procedimentos. Deste modo, ressalta-se a importância de implementação de um programa de garantia de qualidade no serviço, com o objetivo de otimizar os procedimentos e reduzir o detrimento para os pacientes pediátricos submetidos a exames de tomografia computadorizada. / The computed tomography (CT) is one of the most important methods for radio diagnostics, resulting, however, in high absorbed doses to the patients. The objective of this work is to evaluate the pediatric head CT examinations performed at one hospital in Recife, Brazil, and to estimate the mean absorbed doses to organs using the computational simulation software CALDose_XCT. The irradiation parameters used with 108 pediatric head CT examinations were registered and divided in the following age ranges: <1; 1 to 5; 5 to 10; and 10 to 15 years-old. The volume CT air kerma index (CVOL) and the air kerma-length product for full CT examinations (PKL,CT) were estimated to each examination and compared to international diagnostic reference levels. The mean absorbed doses to relevant organs (eye lens, brain, oral mucosa and salivary glands) were simulated using CALDose_XCT. Another simulation was made using a head phantom tilt of 18º, in order to evaluate the dose reduction to some organs using either the gantry or head tilt. The results showed that the irradiation parameters used in the most of the examinations are not optimized, since it was possible to observe tube potential and current-time product values higher than the recommended values to adult examinations. Most of the CVOL values were lower than the international reference levels for pediatric CT examinations. On the other hand, the contrary was observed with the PKL,CT, due to the use of large scan ranges, in some cases, bigger than the patient’s entire head. The simulation of the patient head tilt resulted in absorbed dose reduction to the eyes, oral mucosa and salivary glands, showing to be an efficient method to optimize the radiological protection of pediatric CT examinations. Thus, it can be highlighted the importance of a quality assurance program in the service, with the objective of optimizing the procedures and reducing the risk to the pediatric patients.