9 research outputs found
Development of procedures for the design, optimization and manufacturing of customized orthopaedic and trauma implants: Geometrical/anatomical modelling from 3D medical imaging
Tese de Doutoramento (Programa Doutoral em Engenharia Biomédica)The introduction of imaging techniques in 1970 is one of the most relevant historical
milestones in modern medicine. Medical imaging techniques have dramatically changed
our understanding of the Human anatomy and physiology. The ability to non-invasively
extract visual information allowed, not only the three-dimensional representation of the
internal organs and musculo-skeletal system, but also the simulation of surgical procedures,
the execution of computer aided surgeries, the development of more accurate biomechanical
models, the development of custom-made implants, among others.
The combination of the most advanced medical imaging systems with the most
advanced CAD and CAM techniques, may allow the development of custom-made implants
that meet patient-speci c traits. The geometrical and functional optimization of these
devices may increase implant life-expectancy, especially in patients with marked deviations
from the anatomical standards. In the implant customization protocol from medical
image data, there are several steps that need to be followed in a sequential way, namely:
Medical Image Processing and Recovering; Accurate Image Segmentation and 3D Surface
Model Generation; Geometrical Customization based on CAD and CAE techniques;
FEA Optimization of the Implant Geometry; and Manufacturing using CAD-CAM
Technologies.
This work aims to develop the necessary procedures for custom implant development
from medical image data. This includes the extraction of highly accurate three-dimensional
representation of the musculo-skeletal system from the Computed Tomography imaging,
and the development of customized implants, given the speci c requirements of the target
anatomy, and the applicable best practices found in the literature.
A two-step segmentation protocol is proposed. In the rst step the region of interest
is pre-segmented in order to obtain a good approximation to the desired geometry. Next, a fully automatic segmentation re nement is applied to obtain a more accurate
representation of the target domain. The re nement step is composed by several sub-steps,
more precisely, the recovery of the original image, considering the limiting resolution of
the imaging system; image cropping; image interpolation; and segmentation re nement
over the up-sampled domain. Highly accurate segmentations of the target domain were
obtained with the proposed pipeline. The limiting factor to the accurate description of the
domain accuracy is the image acquisition process, rather the following image processing,
segmentation and surface meshing steps.
The new segmentation pipeline was used in the development of three tailor-made
implants, namely, a tibial nailing system, a mandibular implant, and a Total Hip
Replacement system. Implants optimization is carried with Finite Element Analysis,
considering the critical loading conditions that may be applied to each implant in working
conditions. The new tibial nailing system is able of sustaining critical loads without
implant failure; the new mandibular endoprosthesis that allows the recovery of the natural
stress and strain elds observed in intact mandibles; and the Total Hip Replacement system
that showed comparable strain shielding levels as commercially available stems.
In summary, in the present thesis the necessary procedures for custom implant design
are investigated, and new algorithms proposed. The guidelines for the characterization of
the image acquisition, image processing, image segmentation and 3D reconstruction are
presented and discussed. This new image processing pipeline is applied and validated in
the development of the three abovementioned customized implants, for di erent medical
applications and that satisfy speci c anatomical needs.Um dos principais marcos da história moderna da medicina e a introdução da imagem médica, em meados da década de 1970. As tecnologias de imagem permitiram aumentar e potenciar o nosso conhecimento acerca da anatomia e fisiologia do corpo Humano. A capacidade de obter informação imagiológica de forma não invasiva permitiu, não são a representação tridimensional de órgãos e do sistema músculo-esquelético, mas também a simulação de procedimentos cirúrgicos, a realização de cirurgias assistidas por computador, a criação de modelos biomecânicos mais realistas, a criação de implantes personalizados, entre outros.
A conjugação dos sistemas mais avançados de imagem medica com as técnicas mais avançadas de modelação e maquinagem, pode permitir o desenvolvimento de implantes personalizados mais otimizados, que vão de encontro as especificidades de cada paciente.
Por sua vez, a otimização geométrica e biomecânica destes dispositivos pode permitir, quer o aumento da sua longevidade, quer o tratamento de pessoas com estruturas anatómicas que se afastam dos padrões normais. O processo de modelação de implantes a partir da imagem medica passa por um conjunto de procedimentos a adotar, sequencialmente, ate ao produto final, a saber: Processamento e Recuperação de Imagem; Segmentação de Imagem e Reconstrução tridimensional da Região de Interesse; Modelação Geométrica do Implante; Simulação Numérica para a Otimização da Geometria; a Maquinagem do Implante.
Este trabalho visa o desenvolvimento dos procedimentos necessários para a criação de implantes personalizados a partir da imagem medica, englobando a extração de modelos ósseos geométricos rigorosos a partir de imagens de Tomografia Computorizada e, a partir desses modelos, desenvolver implantes personalizados baseados nas melhores praticas existentes na literatura e que satisfaçam as especificidades da anatomia do paciente. Assim, apresenta-se e discute-se um novo procedimento de segmentação em dois passos.
No primeiro e feita uma pre-segmentação que visa obter uma aproximação iniciala região de interesse. De seguida, um procedimento de refinamento da segmentação totalmente automático e aplicada a segmentação inicial para obter uma descrição mais precisa do domínio de interesse. O processo de refinamento da segmentação e constituído por vários procedimentos, designadamente: recuperação da imagem original, tendo em consideração a resolução limitante do sistema de imagem; o recorte da imagem na vizinhança da região pre-segmentada; a interpolação da região de interesse; e o refinamento da segmentação aplicando a técnica de segmentação Level-Sets sobre o domínio interpolado.
O procedimento de segmentação permitiu extrair modelos extremamente precisos a partir da informação imagiológica. Os resultados revelam que o fator limitante a descrição do domínio e o processo de aquisição de imagem, em detrimento dos diversos passos de processamento subsequentes.
O novo protocolo de segmentação foi utilizado no desenvolvimento de três implantes personalizados, a saber: um sistema de fixação interna para a tíbia; um implante mandibular; e um sistema para a Reconstrução Total da articulação da Anca. A otimização do comportamento mecânico dos implantes foi feita utilizado o Método dos Elementos
Finitos, tendo em conta os carregamentos críticos a que estes podem estar sujeitos durante a sua vida útil. O sistema de fixação interna para a tíbia e capaz de suportar os carregamentos críticos, sem que a sua integridade mecânica seja comprometida; o implante mandibular permite recuperar os campos de tensão e deformação observados em mandíbulas intactas; e a Prótese Total da Anca apresenta níveis de strain shielding ao longo do fémur proximal comparáveis com os níveis observados em dispositivos comercialmente disponíveis.
Em suma, nesta tese de Doutoramento são investigados e propostos novos procedimentos para o projeto de implantes feitos por medida. São apresentadas e discutidas as linhas orientadoras para a caracterização precisa do sistema de aquisição de imagem, para o processamento de imagem, para a segmentação, e para a reconstrução 3D das estruturas anatómicas a partir da imagem medica. Este conjunto de linhas orientadoras é aplicado e validado no desenvolvimento de três implantes personalizados, citados anteriormente, para aplicações médicas distintas e que satisfazem as necessidades anatómicas específicas de cada paciente.Fundação para a Ciência e Tecnologia (FCT
Spine Surgery
We are very excited to introduce this new book on spinal surgery, which follows the curriculum of the EUROSPINE basic and advanced diploma courses.
The approach we take is a purely case-based one, in which each case illustrates the concepts surrounding the treatment of a given pathology, including
the uncertainties and problems in decision-making. The readers will notice
that in many instances a lack of evidence for a given treatment exists. So decisions taken are usually not a clearcut matter of black or white, but merely
different shades of gray. Probably in a lot of cases, there is often more than
one option to treat the patient. The authors were asked to convey this message
to the reader, giving him a guidance as what would be accepted within the
mainstream. In addition, the reader is provided with the most updated literature and evidence on the topic.
Most of the authors are teachers in the courses of EUROSPINE or other
national societies with often vast clinical experience and have given their own
perspective and reasoning.
We believe that the readers will profit very much from this variety and
bandwidth of knowledge provided for them in the individual chapters. We
have given the authors extensive liberty as to what they consider the best
solution for their case. It is thus a representative picture of what is considered
standard of care for spine pathologies in Europe.
We hope that this book will be an ideal complement for trainees to the
courses they take.
Munich, Germany Bernhard Meyer
Offenbach, Germany Michael Rauschman
Characterization of alar ligament on 3.0T MRI: a cross-sectional study in IIUM Medical Centre, Kuantan
INTRODUCTION: The main purpose of the study is to compare the normal anatomy of alar
ligament on MRI between male and female. The specific objectives are to assess the prevalence
of alar ligament visualized on MRI, to describe its characteristics in term of its course, shape and
signal homogeneity and to find differences in alar ligament signal intensity between male and
female. This study also aims to determine the association between the heights of respondents
with alar ligament signal intensity and dimensions.
MATERIALS & METHODS: 50 healthy volunteers were studied on 3.0T MR scanner
Siemens Magnetom Spectra using 2-mm proton density, T2 and fat-suppression sequences. Alar
ligament is depicted in 3 planes and the visualization and variability of the ligament courses,
shapes and signal intensity characteristics were determined. The alar ligament dimensions were
also measured.
RESULTS: Alar ligament was best depicted in coronal plane, followed by sagittal and axial
planes. The orientations were laterally ascending in most of the subjects (60%), predominantly
oval in shaped (54%) and 67% showed inhomogenous signal. No significant difference of alar
ligament signal intensity between male and female respondents. No significant association was
found between the heights of the respondents with alar ligament signal intensity and dimensions.
CONCLUSION: Employing a 3.0T MR scanner, the alar ligament is best portrayed on coronal
plane, followed by sagittal and axial planes. However, tremendous variability of alar ligament as
depicted in our data shows that caution needs to be exercised when evaluating alar ligament,
especially during circumstances of injury
Case series of breast fillers and how things may go wrong: radiology point of view
INTRODUCTION: Breast augmentation is a procedure opted by women to overcome sagging
breast due to breastfeeding or aging as well as small breast size. Recent years have shown the
emergence of a variety of injectable materials on market as breast fillers. These injectable
breast fillers have swiftly gained popularity among women, considering the minimal
invasiveness of the procedure, nullifying the need for terrifying surgery. Little do they know
that the procedure may pose detrimental complications, while visualization of breast
parenchyma infiltrated by these fillers is also deemed substandard; posing diagnostic
challenges. We present a case series of three patients with prior history of hyaluronic acid and
collagen breast injections.
REPORT: The first patient is a 37-year-old lady who presented to casualty with worsening
shortness of breath, non-productive cough, central chest pain; associated with fever and chills
for 2-weeks duration. The second patient is a 34-year-old lady who complained of cough, fever
and haemoptysis; associated with shortness of breath for 1-week duration. CT in these cases
revealed non thrombotic wedge-shaped peripheral air-space densities.
The third patient is a 37‐year‐old female with right breast pain, swelling and redness for 2-
weeks duration. Previous collagen breast injection performed 1 year ago had impeded
sonographic visualization of the breast parenchyma. MRI breasts showed multiple non-
enhancing round and oval shaped lesions exhibiting fat intensity.
CONCLUSION: Radiologists should be familiar with the potential risks and hazards as well
as limitations of imaging posed by breast fillers such that MRI is required as problem-solving
tool
Textbook of Plastic and Reconstructive Surgery
Written by experts from London’s renowned Royal Free hospital, Textbook of Plastic and Reconstructive Surgery offers a comprehensive overview of the vast topic of reconstructive plastic surgery and its various subspecialties for introductory plastic surgery and surgical science courses. The book comprises five sections covering the fundamental principles of plastic surgery, cancer, burns and trauma, paediatric plastic surgery and aesthetic surgery, and covers the breadth of knowledge that students need to further their career in this exciting field. Additional coverage of areas in which reconstructive surgery techniques are called upon includes abdominal wall reconstruction, ear reconstruction and genital reconstruction. A section on aesthetic surgery includes facial aesthetic surgery and blepharoplasty, aesthetic breast surgery, body contouring and the evolution of hair transplantation. The broad scope of this volume makes this a unique contribution to the field.Heavily illustrated throughout, Textbook of Plastic and Reconstructive Surgery is essential reading for anyone interested in furthering their knowledge of this exciting field