Imaging of knee injuries with special focus on tibial plateau fractures

Acute knee injury is a common event throughout life, and it is usually the result of a traffic accident, simple fall, or twisting injury. Over 90% of patients with acute knee injury undergo radiography. An overlooked fracture or delayed diagnosis can lead to poor patient outcome. The major aim of this thesis was retrospectively to study imaging of knee injury with a special focus on tibial plateau fractures in patients referred to a level-one trauma center. Multi-detector computed tomography (MDCT) findings of acute knee trauma were studied and compared to radiography, as well as whether non-contrast MDCT can detect cruciate ligaments with reasonable accuracy. The prevalence, type, and location of meniscal injuries in magnetic resonance imaging (MRI) were evaluated, particularly in order to assess the prevalence of unstable meniscal tears in acute knee trauma with tibial plateau fractures. The possibility to analyze with conventional MRI the signal appearance of menisci repaired with bioabsorbable arrows was also studied. The postoperative use of MDCT was studied in surgically treated tibial plateau fractures: to establish the frequency and indications of MDCT and to assess the common findings and their clinical impact in a level-one trauma hospital. This thesis focused on MDCT and MRI of knee injuries, and radiographs were analyzed when applica-ble. Radiography constitutes the basis for imaging acute knee injury, but MDCT can yield information beyond the capabilities of radiography. Especially in severely injured patients , sufficient radiographs are often difficult to obtain, and in those patients, radiography is unreliable to rule out fractures. MDCT detected intact cruciate ligaments with good specificity, accuracy, and negative predictive value, but the assessment of torn ligaments was unreliable. A total of 36% (14/39) patients with tibial plateau fracture had an unstable meniscal tear in MRI. When a meniscal tear is properly detected preoperatively, treatment can be combined with primary fracture fixation, thus avoiding another operation. The number of meniscal contusions was high. Awareness of the imaging features of this meniscal abnormality can help radiologists increase specificity by avoiding false-positive findings in meniscal tears. Postoperative menisci treated with bioabsorbable arrows showed no difference, among different signal intensities in MRI, among menisci between patients with operated or intact ACL. The highest incidence of menisci with an increased signal intensity extending to the meniscal surface was in patients whose surgery was within the previous 18 months. The results may indicate that a rather long time is necessary for menisci to heal completely after arrow repair. Whether the menisci with an increased signal intensity extending to the meniscal surface represent improper healing or re-tear, or whether this is just the earlier healing feature in the natural process remains unclear, and further prospective studies are needed to clarify this. Postoperative use of MDCT in tibial plateau fractures was rather infrequent even in this large trauma center, but when performed, it revealed clinically significant information, thus benefitting patients in regard to treatment.

A MatLAB Based Virtual Phantom for 2D Electrical Impedance Tomography (MatVP2DEIT): Studying the Medical Electrical Impedance Tomography Reconstruction in Computer

Electrical Impedance Tomography (EIT) is a computerized medical imaging technique which reconstructs the electrical impedance images of a domain under test from the boundary voltage-current data measured by an EIT electronic instrumentation using an image reconstruction algorithm. Being a computed tomography technique, EIT injects a constant current to the patient's body through the surface electrodes surrounding the domain to be imaged (Omega) and tries to calculate the spatial distribution of electrical conductivity or resistivity of the closed conducting domain using the potentials developed at the domain boundary (partial derivative Omega). Practical phantoms are essentially required to study, test and calibrate a medical EIT system for certifying the system before applying it on patients for diagnostic imaging. Therefore, the EIT phantoms are essentially required to generate boundary data for studying and assessing the instrumentation and inverse solvers a in EIT. For proper assessment of an inverse solver of a 2D EIT system, a perfect 2D practical phantom is required. As the practical phantoms are the assemblies of the objects with 3D geometries, the developing of a practical 2D-phantom is a great challenge and therefore, the boundary data generated from the practical phantoms with 3D geometry are found inappropriate for assessing a 2D inverse solver. Furthermore, the boundary data errors contributed by the instrumentation are also difficult to separate from the errors developed by the 3D phantoms. Hence, the errorless boundary data are found essential to assess the inverse solver in 2D EIT. In this direction, a MatLAB-based Virtual Phantom for 2D EIT (MatVP2DEIT) is developed to generate accurate boundary data for assessing the 2D-EIT inverse solvers and the image reconstruction accuracy. MatVP2DEIT is a MatLAB-based computer program which simulates a phantom in computer and generates the boundary potential data as the outputs by using the combinations of different phantom parameters as the inputs to the program. Phantom diameter, inhomogeneity geometry (shape, size and position), number of inhomogeneities, applied current magnitude, background resistivity, inhomogeneity resistivity all are set as the phantom variables which are provided as the input parameters to the MatVP2DEIT for simulating different phantom configurations. A constant current injection is simulated at the phantom boundary with different current injection protocols and boundary potential data are calculated. Boundary data sets are generated with different phantom configurations obtained with the different combinations of the phantom variables and the resistivity images are reconstructed using EIDORS. Boundary data of the virtual phantoms, containing inhomogeneities with complex geometries, are also generated for different current injection patterns using MatVP2DEIT and the resistivity imaging is studied. The effect of regularization method on the image reconstruction is also studied with the data generated by MatVP2DEIT. Resistivity images are evaluated by studying the resistivity parameters and contrast parameters estimated from the elemental resistivity profiles of the reconstructed phantom domain. Results show that the MatVP2DEIT generates accurate boundary data for different types of single or multiple objects which are efficient and accurate enough to reconstruct the resistivity images in EIDORS. The spatial resolution studies show that, the resistivity imaging conducted with the boundary data generated by MatVP2DEIT with 2048 elements, can reconstruct two circular inhomogeneities placed with a minimum distance (boundary to boundary) of 2 mm. It is also observed that, in MatVP2DEIT with 2048 elements, the boundary data generated for a phantom with a circular inhomogeneity of a diameter less than 7% of that of the phantom domain can produce resistivity images in EIDORS with a 1968 element mesh. Results also show that the MatVP2DEIT accurately generates the boundary data for neighbouring, opposite reference and trigonometric current patterns which are very suitable for resistivity reconstruction studies. MatVP2DEIT generated data are also found suitable for studying the effect of the different regularization methods on reconstruction process. Comparing the reconstructed image with an original geometry made in MatVP2DEIT, it would be easier to study the resistivity imaging procedures as well as the inverse solver performance. Using the proposed MatVP2DEIT software with modified domains, the cross sectional anatomy of a number of body parts can be simulated in PC and the impedance image reconstruction of human anatomy can be studied.

O acesso aos exames de alta complexidade nos planos de saúde privados na perspectiva dos usuários

A dissertação trata do acesso aos serviços de alta complexidade, particularmente os exames diagnósticos e complementares, estudado entre usuários de planos de saúde privados que buscam atendimento e diagnóstico especializado. Desde a década de 80 o usuário do sistema público de saúde vem procurando a saúde suplementar. Contudo, afirmar que o acesso é garantido no domínio privado, através da contratação dos planos de saúde, é uma incerteza que rodeia a inspiração para esta pesquisa, que se justifica pela relevância de ações que possibilitem a melhora da qualidade regulatória dos planos de saúde, a partir do controle social de seus usuários. O objetivo geral é analisar as percepções do acesso aos exames de alta complexidade nos serviços de saúde privados entre usuários de planos de saúde. Os objetivos específicos são descrever as percepções dos usuários de planos de saúde acerca do acesso aos exames de alta complexidade; analisar as motivações dos usuários de planos de saúde privados para a realização de exames de alta complexidade através da rede privada de assistência; e analisar o nível de satisfação dos usuários de planos de saúde quanto ao acesso aos exames de alta complexidade. A metodologia é qualitativa-descritiva, onde a amostra foi de trinta usuários de planos de saúde, acima de 18 anos, selecionados no campo de estudo no ano de 2010. O cenário de estudo foi um laboratório privado de medicina diagnóstica no Rio de Janeiro. As técnicas de coleta de dados utilizadas foram formulário e entrevista individual estruturada. A análise do formulário foi realizada através de estatística descritiva, e as entrevistas através da análise de conteúdo temática-categorial. Os usuários de plano de saúde declararam que o acesso é garantido com facilidade para os exames de alta complexidade. Suas principais motivações para a realização desses exames na rede privada de assistência foram caracterizadas pela rapidez de atendimento, flexibilidade e facilidade de marcação pela internet, telefone ou pessoalmente no laboratório estudado, pronta entrega dos resultados, dificuldade e morosidade do atendimento do SUS, localização do prestador credenciado próxima de bairros residenciais ou do trabalho, resolutividade diagnóstica de imagem de excelência, possibilidade de escolha pelo usuário entre as modalidades aberta e fechada de ressonância magnética e tomografia computadorizada, além da densitometria óssea que foram facilmente acessíveis a todos os sujeitos da pesquisa. O nível de satisfação foi correspondido com a rapidez na realização dos exames em caráter eletivo e de urgência quase equiparados na escala de tempo de acordo com os usuários. Contudo, embora as notas de avaliação dos usuários quanto aos seus planos de saúde tenham sido altas, foram abordadas algumas dificuldades, tais como: prazos de validade dos pedidos médicos com datação prévia; solicitações de senhas de autorização pela operadora; burocracia nos procedimentos de agendamento; dificuldades de acesso para tratamentos como implantes, fisioterapia, RPG, pilates, home care, consultas de check up; negação de reembolsos; restrição de materiais cirúrgicos, em especial as próteses e órteses; e restrições específicas de grau para cirurgias de miopia. Conclui-se que o atendimento rápido dos exames de imagem de alto custo na amostra foi descrito como satisfatório, embora a percepção de rapidez possa variar em função do tipo de produto do plano de saúde privado contratado, com necessidade de melhoria regulatória em alguns aspectos pontuais da saúde suplementar.

Avaliação da estabilidade da cirurgia de avanço mandibular através da superposição de modelos tridimensionais

Embora a cirurgia de avanço mandibular seja considerada um procedimento altamente estável, existem algumas preocupações clínicas em relação a mudanças nos côndilos e nos segmentos proximais, que podem levar a recidiva sagital e abertura de mordida. A avaliação dos resultados da cirurgia através de ferramentas de geração e superposição de modelos virtuais tridimensionais (3D) permite a identificação e quantificação dos deslocamentos e remodelação óssea que podem ajudar a explicar as interações entre os componentes dentários, esqueléticos e de tecido mole que estão relacionados a resposta ao tratamento. Este estudo observacional prospectivo avaliou, através de tomografia computadorizada de feixe cônico (CBCT), mudanças na posição/remodelação 3D dos ramos mandibulares, côndilos e mento. Assim, exames CBCT de 27 pacientes foram adquiridos antes da cirurgia (T1), imediatamente após a cirurgia(T2), e 1 ano após a cirurgia(T3). Uma técnica automática de superposição na base do crânio foi utilizada para permitir a avaliação das mudanças ocorridas nas regiões anatômicas de interesse (RAI). Os deslocamentos foram visualizados e quantificados em mapas coloridos 3D através da ferramenta de linha de contorno (ISOLINE). Pelo teste t pareado compararam-se as mudanças entre T1-T2 e T2-T3. O coeficiente de correlação de Pearson verificou se os deslocamentos ocorridos nas RAI foram correlacionados entre si e entre os tempos de avaliação. O nível de significância foi determinado em 0,05. O avanço mandibular médio foi de 6,813,2mm em T2 e 6,363,41mm em T3 (p=0,13). Entre T2 e T3, a posição do mento variou positivamente (≥2mm) em 5 pacientes negativamente em 7. 12% dos pacientes sofreram recidivas ≥4mm. Para todas as outras RAI avaliadas, apenas a porção inferior dos ramos (lado direito - 2,342,35mm e lado esquerdo 2,972,71mm) sofreram deslocamentos médios >2mm com a cirurgia. No acompanhamento em longo prazo, esse deslocamento lateral da porção inferior dos ramos foi mantido (lado direito - 2,102,15mm, p=0,26; e lado esquerdo -2,762,80, p=0,46), bem como todos os outros deslocamentos observados (p>0,05). As mudanças na posição do mento foram correlacionadas a adaptações pós-cirúrgicas nos bordos posteriores dos ramos (esquerdo r=-0,73 e direito r=-0,68) e côndilos (esquerdo r=-0,53 e direito r=-0,46). Os deslocamentos médios sofridos pelas estruturas do lado esquerdo foram suavemente maiores do que no direito. Correlações dos deslocamentos ocorridos entre T1-T2 e T2-T3 mostraram que: os deslocamentos dos côndilos esquerdos com a cirurgia foram negativamente correlacionados às adaptações pós-cirúrgicas destes (r=-0,51); e que o deslocamento da porção superior do ramo esquerdo com a cirurgia foi correlacionado à adaptação pós-cirúrgica ocorrida nos bordos posteriores (r=0,39) e côndilos do mesmo lado (r=0,39). Pode-se concluir que: (1) os deslocamentos causados pela cirurgia foram de modo geral estáveis no acompanhamento de 1 ano, mas identificou-se uma considerável variação individual; (2) as mudanças pós-cirúrgicas na posição do mento foram correlacionadas a adaptações sofridas pelos côndilos e bordos posteriores dos ramos; e que (3) deslocamentos suavemente maiores causados pela cirurgia nas estruturas do lado esquerdo levaram a maiores adaptações pós-cirúrgicas no segmento proximal deste lado.

Resultados da expansão de maxila cirurgicamente assistida sem disjunção ptérigomaxilar: uma avaliação tridimensional

A expansão rápida da maxila cirurgicamente assistida tornou-se amplamente utilizada e muito aceitável no tratamento da deficiência maxilar de pacientes adolescentes e adultos. Diversas técnicas cirúrgicas foram propostas ao longo dos anos com o objetivo de solucionar este problema de forma eficiente, com estabilidade dos resultados e baixa morbidade. Controvérsias em relação ao procedimento cirúrgico persistem, principalmente relacionadas a quais osteotomias devem ser realizadas para se obter bons resultados. O objetivo deste trabalho foi avaliar os resultados da expansão ortocirúrgica da maxila realizando osteotomias nas paredes laterais da maxila e na sutura palatina mediana. Foram selecionados dezessete pacientes adultos portadores de deficiência transversa maxilar, com média de idade de 24 anos e 8 meses; todos foram submetidos a exames de tomografia computadorizada convencional e moldagens maxilares previamente ao procedimento cirúrgico e após três meses, no mínimo, do término de ativação e estabilização do aparelho expansor. As medidas do pós-cirúrgico foram confrontadas com as do pré-cirúrgico e os resultados foram comparados e analisados estatisticamente. Foi obtida a expansão desejada clinicamente em todos os pacientes. No entanto, a quantidade de expansão na região de molares foi estatisticamente maior nas áreas referentes aos dentes, enquanto que os resultados obtidos referentes aos caninos se mostraram similares nas três regiões maxilares avaliadas. Quando comparadas às regiões de caninos e molares entre si, a expansão intercaninos foi maior na altura dos forames palatinos e o inverso ocorreu nas regiões de processo alveolar e dentária, nas quais a expansão intermolar foi maior.

Perfil das pacientes submetidas a gluteoplastia

Durante nossas frequentes apresentações em cursos, congressos e jornadas e mesmo em nossas publicações, existiam constantes perguntas sobre o perfil dessas pacientes. O crescente interesse da mídia e das pacientes a este respeito e também a crescente procura pela cirurgia nos estimulou a realizar este trabalho. Segundo dados da Sociedade Brasileira de Cirurgia Plástica (SBPC) e da American Society of Plastic Surgery (ASPS), referem que 20.000 pacientes foram submetidas a esta cirurgia. Em 2012, 40.000 pares de implantes glúteos foram produzidos. Existe um crescimento da cirurgia de 20% nos últimos três anos e no Brasil houve aumento de 42% em 2011. Esta tese tem como objetivo estabelecer o perfil epidermiologico das pacientes que se submetem a gluteoplastia de aumento utilizando implantes de silicone, avaliar o grau de satisfação com resultado e a correlação deste com o volume dos implantes utilizados. Cinquenta pacientes responderam a um questionário e foram examinadas pelo cirurgião e outro médico. Outras 37 pacientes foram avaliadas prospectivamente com tomografia computadorizada e volumetria, avaliação de resultado por oito cirurgiões plásticos, medidas antropométricas e correlação destas variáveis. A análise destes dados evidenciou tratar-se de cirurgia com baixo índice de complicação e alto índice de satisfação com resultado (96%). A maior procura foi por pacientes brancas (62%) e pardas (34%). Não percebemos relação de profissão ou nível socioeconômico com a procura pela cirurgia. Observou-se um alto número de pacientes que referiram naturalidade do resultado, sendo que em 94% dos casos, ninguém notou que a paciente havia se submetido à cirurgia, sem que a própria desse esta informação. As queixas, quando existiram, 4% foram referentes a terem achado as próteses pequenas. O tempo de recuperação da maioria (60%) para atividades normais foi de até 45 dias. Houve grande influência positiva na vida sexual e afetiva das pacientes que se submeteram a esta cirurgia. A correlação entre o volume dos implantes utilizados e das medidas antropométricas com o resultado estético da operação não demonstrou significância estatística. Conclui-se que as pacientes que desejam a gluteoplastia são predominantemente brancas e na quarta década de vida. A operação alcança altos índices de satisfação e o volume dos implantes apresenta correlação positiva com a renda mensal, a idade e a satisfação das pacientes, porém com maior tempo de recuperação. Quando o resultado é avaliado por cirurgiões plásticos, este não apresenta correlação com o volume dos implantes ou com as medidas antropométricas das pacientes.

Extraction of fibre network architecture by X-ray tomography and prediction of elastic properties using an affine analytical model

This paper proposes a method for extracting reliable architectural characteristics from complex porous structures using micro-computed tomography (μCT) images. The work focuses on a highly porous material composed of a network of fibres bonded together. The segmentation process, allowing separation of the fibres from the remainder of the image, is the most critical step in constructing an accurate representation of the network architecture. Segmentation methods, based on local and global thresholding, were investigated and evaluated by a quantitative comparison of the architectural parameters they yielded, such as the fibre orientation and segment length (sections between joints) distributions and the number of inter-fibre crossings. To improve segmentation accuracy, a deconvolution algorithm was proposed to restore the original images. The efficacy of the proposed method was verified by comparing μCT network architectural characteristics with those obtained using high resolution CT scans (nanoCT). The results indicate that this approach resolves the architecture of these complex networks and produces results approaching the quality of nanoCT scans. The extracted architectural parameters were used in conjunction with an affine analytical model to predict the axial and transverse stiffnesses of the fibre network. Transverse stiffness predictions were compared with experimentally measured values obtained by vibration testing. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The geometry and the number of contacts of monodisperse sphere packs using X-ray tomography

The three-dimensional structure of very large samples of monodisperse bead packs is studied by means of X-Ray Computed Tomography. We retrieve the coordinatesofeach bead inthe pack and wecalculate the average coordination number by using the tomographic images to single out the neighbors in contact. The results are compared with the average coordination number obtained in Aste et al. (2005) by using a deconvolution technique. We show that the coordination number increases with the packing fraction, varying between 6.9 and 8.2 for packing fractions between 0.59 and 0.64. © 2005 Taylor & Francis Group.

Nasopharyngeal Masses Arising from Embryologic Remnants of the Clivus: A Case Series.

Objectives This study aims to (1) discuss rare nasopharyngeal masses originating from embryologic remnants of the clivus, and (2) discuss the embryology of the clivus and understand its importance in the diagnosis and treatment of these masses. Design and Participants This is a case series of three patients. We discuss the clinical and imaging characteristics of infrasellar craniopharyngioma, intranasal extraosseous chordoma, and canalis basilaris medianus. Results Case 1: A 16-year-old male patient with a history of craniopharyngioma resection, who presented with nasal obstruction. A nasopharyngeal cystic mass was noted to be communicating with a patent craniopharyngeal canal. Histology revealed adamantinomatous craniopharyngioma. Case 2: A 43-year-old male patient who presented with nasal obstruction and headache. Computed tomography (CT) and magnetic resonance imaging revealed an enhancing polypoid mass in the posterior nasal cavity abutting the clivus. Histopathology revealed chondroid chordoma. Case 3: A 4-year-old female patient with a recurrent nasopharyngeal polyp. CT cisternogram showed that this mass may have risen from a bony defect of the middle clivus suggestive of canalis basilaris medianus. Conclusions Understanding the embryology of the clivus is crucial when considering the differential diagnosis of a nasopharyngeal mass. Identification of characteristic findings on imaging is critical in the diagnosis and treatment of these lesions.

Microcomputed tomography imaging in a rat model of delayed union/non-union fracture

We aimed to develop a clinically relevant delayed union/non-union fracture model to evaluate a cell therapy intervention repair strategy. Histology, three-dimensional (3D) micro-computed tomography (micro-CT) imaging and mechanical testing were utilized to develop an analytical protocol for qualitative and quantitative assessment of fracture repair. An open femoral diaphyseal osteotomy, combined with periosteal diathermy and endosteal excision, was held in compression by a four pin unilateral external fixator. Three delayed union/non-union fracture groups established at 6 weeks-(a) a control group, (b) a cell therapy group, and (c) a group receiving phosphate-buffered saline (PBS) injection alone-were examined subsequently at 8 and 14 weeks. The histological response was combined fibrous and cartilaginous non-unions in groups A and B with fibrous non-unions in group C. Mineralized callus volume/total volume percentage showed no statistically significant differences between groups. Endosteal calcified tissue volume/endosteal tissue volume, at the center of the fracture site, displayed statistically significant differences between 8 and 14 weeks for cell and PBS intervention groups but not for the control group. The percentage load to failure was significantly lower in the control and cell treatment groups than in the PBS alone group. High-resolution micro-CT imaging provides a powerful tool to augment characterization of repair in delayed union/non-union fractures together with outcomes such as histology and mechanical strength measurement. Accurate, nondestructive, 3D identification of mineralization progression in repairing fractures is enabled in the presence or absence of intervention strategies. (c) 2007 Orthopaedic Research Society.

Single vocal cord irradiation:a competitive treatment strategy in early glottic cancer

INTRODUCTION: The treatment of choice for early glottic cancer is still being debated; ultimately it relies on the functional outcome. This paper reports on a novel sparing 4D conformal technique for single vocal cord irradiation (SVCI).

MATERIAL AND METHODS: The records of 164 T1a patients with SCC of the vocal cord, irradiated in the Erasmus MC between 2000 and 2008, were analyzed for local control and overall survival. The quality of life was determined by EORTC H&N35 questionnaires. Also the VHI (voice handicap index), and the TSH (thyroid stimulating hormone) blood levels, were established. On-line image guided SVCI, using cone beam CT or stereotactic radiation therapy (SRT) techniques, were developed.

RESULTS: A LC rate at five-years of 93% and a VHI of 12.7 (0-63) was determined. It appeared feasible to irradiate one vocal cord within 1-2mm accuracy. This way sparing of the contralateral (CL) vocal cord and CL normal tissues, could be achieved.

CONCLUSIONS: Given the accuracy (1-2mm) and small volume disease (CTV limited to one vocal cord), for the use of stereotactic RT techniques SVCI with large fraction sizes is currently being investigated in clinic. It is argued that hypofractionated SVCI can be a competitive alternative to laser surgery.

Acute Upper Limb Ischemia, a Rare Presentation of Giant Cell Arteritis

Giant cell arteritis (GCA) is a systemic large vessel vasculitis, with extracranial arterial involvement described in 10-15% of cases, usually affecting the aorta and its branches. Patients with GCA are more likely to develop aortic aneurysms, but these are rarely present at the time of the diagnosis. We report the case of an 80-year-old Caucasian woman, who reported proximal muscle pain in the arms with morning stiffness of the shoulders for eight months. In the previous two months, she had developed worsening bilateral arm claudication, severe pain, cold extremities and digital necrosis. She had no palpable radial pulses and no measurable blood pressure. The patient had normochromic anemia, erythrocyte sedimentation rate of 120 mm/h, and a negative infectious and autoimmune workup. Computed tomography angiography revealed concentric wall thickening of the aorta extending to the aortic arch branches, particularly the subclavian and axillary arteries, which were severely stenotic, with areas of bilateral occlusion and an aneurysm of the ascending aorta (47 mm). Despite corticosteroid therapy there was progression to acute critical ischemia. She accordingly underwent surgical revascularization using a bilateral carotid-humeral bypass. After surgery, corticosteroid therapy was maintained and at six-month follow-up she was clinically stable with reduced inflammatory markers. GCA, usually a chronic benign vasculitis, presented exceptionally in this case as acute critical upper limb ischemia, resulting from a massive inflammatory process of the subclavian and axillary arteries, treated with salvage surgical revascularization.

Portal vein embolization before right hepatectomy: prospective clinical trial.

OBJECTIVE: To assess the impact of liver hypertrophy of the future liver remnant volume (FLR) induced by preoperative portal vein embolization (PVE) on the immediate postoperative complications after a standardized major liver resection. SUMMARY BACKGROUND DATA: PVE is usually indicated when FLR is estimated to be too small for major liver resection. However, few data exist regarding the exact quantification of sufficient minimal functional hepatic volume required to avoid postoperative complications in both patients with or without chronic liver disease. METHODS: All consecutive patients in whom an elective right hepatectomy was feasible and who fulfilled the inclusion and exclusion criteria between 1998 and 2000 were assigned to have alternatively either immediate surgery or surgery after PVE. Among 55 patients (25 liver metastases, 2 cholangiocarcinoma, and 28 hepatocellular carcinoma), 28 underwent right hepatectomy after PVE and 27 underwent immediate surgery. Twenty-eight patients had chronic liver disease. FLR and estimated rate of functional future liver remnant (%FFLR) volumes were assessed by computed tomography. RESULTS: The mean increase of FLR and %FFLR 4 to 8 weeks after PVE were respectively 44 +/- 19% and 16 +/- 7% for patients with normal liver and 35 +/- 28% and 9 +/- 3% for those with chronic liver disease. All patients with normal liver and 86% with chronic liver disease experienced hypertrophy after PVE. The postoperative course of patients with normal liver who underwent PVE before right hepatectomy was similar to those with immediate surgery. In contrast, PVE in patients with chronic liver disease significantly decreased the incidence of postoperative complications as well as the intensive care unit stay and total hospital stay after right hepatectomy. CONCLUSIONS: Before elective right hepatectomy, the hypertrophy of FLR induced by PVE had no beneficial effect on the postoperative course in patients with normal liver. In contrast, in patients with chronic liver disease, the hypertrophy of the FLR induced by PVE decreased significantly the rate of postoperative complications.

A fully echo-guided trans-apical aortic valve implantation.

The trans-apical aortic valve implantation (TA-AVI) is an established technique for high-risk patients requiring aortic valve replacement. Traditionally, preoperative (computed tomography (CT) scan, coronary angiogram) and intra-operative imaging (fluoroscopy) for stent-valve positioning and implantation require contrast medium injections. To preserve the renal function in elderly patients suffering from chronic renal insufficiency, a fully echo-guided trans-catheter valve implantation seems to be a reasonable alternative. We report the first successful TA-AVI procedure performed solely under trans-oesophageal echocardiogram control, in the absence of contrast medium injections.

Optimization and validation of a new 3D-US imaging robot to detect, localize and quantify lower limb arterial stenoses

L’athérosclérose est une maladie qui cause, par l’accumulation de plaques lipidiques, le durcissement de la paroi des artères et le rétrécissement de la lumière. Ces lésions sont généralement localisées sur les segments artériels coronariens, carotidiens, aortiques, rénaux, digestifs et périphériques. En ce qui concerne l’atteinte périphérique, celle des membres inférieurs est particulièrement fréquente. En effet, la sévérité de ces lésions artérielles est souvent évaluée par le degré d’une sténose (réduction >50 % du diamètre de la lumière) en angiographie, imagerie par résonnance magnétique (IRM), tomodensitométrie ou échographie. Cependant, pour planifier une intervention chirurgicale, une représentation géométrique artérielle 3D est notamment préférable. Les méthodes d’imagerie par coupe (IRM et tomodensitométrie) sont très performantes pour générer une imagerie tridimensionnelle de bonne qualité mais leurs utilisations sont dispendieuses et invasives pour les patients. L’échographie 3D peut constituer une avenue très prometteuse en imagerie pour la localisation et la quantification des sténoses. Cette modalité d’imagerie offre des avantages distincts tels la commodité, des coûts peu élevés pour un diagnostic non invasif (sans irradiation ni agent de contraste néphrotoxique) et aussi l’option d’analyse en Doppler pour quantifier le flux sanguin. Étant donné que les robots médicaux ont déjà été utilisés avec succès en chirurgie et en orthopédie, notre équipe a conçu un nouveau système robotique d’échographie 3D pour détecter et quantifier les sténoses des membres inférieurs. Avec cette nouvelle technologie, un radiologue fait l’apprentissage manuel au robot d’un balayage échographique du vaisseau concerné. Par la suite, le robot répète à très haute précision la trajectoire apprise, contrôle simultanément le processus d’acquisition d’images échographiques à un pas d’échantillonnage constant et conserve de façon sécuritaire la force appliquée par la sonde sur la peau du patient. Par conséquent, la reconstruction d’une géométrie artérielle 3D des membres inférieurs à partir de ce système pourrait permettre une localisation et une quantification des sténoses à très grande fiabilité. L’objectif de ce projet de recherche consistait donc à valider et optimiser ce système robotisé d’imagerie échographique 3D. La fiabilité d’une géométrie reconstruite en 3D à partir d’un système référentiel robotique dépend beaucoup de la précision du positionnement et de la procédure de calibration. De ce fait, la précision pour le positionnement du bras robotique fut évaluée à travers son espace de travail avec un fantôme spécialement conçu pour simuler la configuration des artères des membres inférieurs (article 1 - chapitre 3). De plus, un fantôme de fils croisés en forme de Z a été conçu pour assurer une calibration précise du système robotique (article 2 - chapitre 4). Ces méthodes optimales ont été utilisées pour valider le système pour l’application clinique et trouver la transformation qui convertit les coordonnées de l’image échographique 2D dans le référentiel cartésien du bras robotisé. À partir de ces résultats, tout objet balayé par le système robotique peut être caractérisé pour une reconstruction 3D adéquate. Des fantômes vasculaires compatibles avec plusieurs modalités d’imagerie ont été utilisés pour simuler différentes représentations artérielles des membres inférieurs (article 2 - chapitre 4, article 3 - chapitre 5). La validation des géométries reconstruites a été effectuée à l`aide d`analyses comparatives. La précision pour localiser et quantifier les sténoses avec ce système robotisé d’imagerie échographique 3D a aussi été déterminée. Ces évaluations ont été réalisées in vivo pour percevoir le potentiel de l’utilisation d’un tel système en clinique (article 3- chapitre 5).