Medical robots for MRI guided diagnosis and therapy

Magnetic Resonance Imaging (MRI) provides the capability of imaging tissue with fine resolution and superior soft tissue contrast, when compared with conventional ultrasound and CT imaging, which makes it an important tool for clinicians to perform more accurate diagnosis and image guided therapy. Medical robotic devices combining the high resolution anatomical images with real-time navigation, are ideal for precise and repeatable interventions. Despite these advantages, the MR environment imposes constraints on mechatronic devices operating within it. This thesis presents a study on the design and development of robotic systems for particular MR interventions, in which the issue of testing the MR compatibility of mechatronic components, actuation control, kinematics and workspace analysis, and mechanical and electrical design of the robot have been investigated. Two types of robotic systems have therefore been developed and evaluated along the above aspects. (i) A device for MR guided transrectal prostate biopsy: The system was designed from components which are proven to be MR compatible, actuated by pneumatic motors and ultrasonic motors, and tracked by optical position sensors and ducial markers. Clinical trials have been performed with the device on three patients, and the results reported have demonstrated its capability to perform needle positioning under MR guidance, with a procedure time of around 40mins and with no compromised image quality, which achieved our system speci cations. (ii) Limb positioning devices to facilitate the magic angle effect for diagnosis of tendinous injuries: Two systems were designed particularly for lower and upper limb positioning, which are actuated and tracked by the similar methods as the first device. A group of volunteers were recruited to conduct tests to verify the functionality of the systems. The results demonstrate the clear enhancement of the image quality with an increase in signal intensity up to 24 times in the tendon tissue caused by the magic angle effect, showing the feasibility of the proposed devices to be applied in clinical diagnosis

Virtual Reality Based Environment for Orthopedic Surgery (Veos)

The traditional way of teaching surgery involves students observing a �live� surgery and then gradually assisting experienced surgeons. The creation of a Virtual Reality environment for orthopedic surgery (VEOS) can be beneficial in improving the quality of training while decreasing the time needed for training. Developing such virtual environments for educational and training purposes can supplement existing approaches. In this research, the design and development of a virtual reality based environment for orthopedic surgery is described. The scope of the simulation environment is restricted to an orthopedic surgery process known as Less Invasive Stabilization System (LISS) surgery. The primary knowledge source for the LISS surgical process was Miguel A. Pirela-Cruz (Head of Orthopedic Surgery and Rehabilitation, Texas Tech University Health Sciences Center (TTHSC)). The VEOS was designed and developed on a PC based platform. The developed VEOS was validated through interactions with surgical residents at TTHSC. Feedback from residents and our collaborator Miguel A. Pirela-Cruz was used to make necessary modifications to the surgical environment.Industrial Engineering & Managemen

Modeling and design of an electromagnetic actuation system for the manipulation of microrobots in blood vessels

Tese de mestrado integrado em Física, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2015A navegação de nano/microdispositivos apresenta um grande potencial para aplicações biomédicas, oferecendo meios de diagnóstico e procedimentos terapêuticos no interior do corpo humano. Dada a sua capacidade de penetrar quase todos os materiais, os campos magnéticos são naturalmente adequados para controlar nano/microdispositivos magnéticos em espaços inacessíveis. Uma abordagem recente é o uso de um aparelho personalizado, capaz de controlar campos magnéticos. Esta é uma área de pesquisa prometedora, mas mais simulações e experiências são necessárias para avaliar a viabilidade destes sistemas em aplicações clínicas. O objectivo deste projecto foi a simulação e desenho de um sistema de atuação eletromagnética para estudar a locomoção bidimensional de microdispositivos. O primeiro passo foi identificar, através da análise de elementos finitos, usando o software COMSOL, diferentes configurações de bobines que permitiriam o controlo de dispositivos magnéticos em diferentes escalas. Baseado nos resultados das simulações, um protótipo de um sistema de atuação magnética para controlar dispositivos com mais de 100 m foi desenhado e construído de raiz, tendo em conta restrições de custos. O sistema consistiu num par de bobines de Helmholtz e rotacionais e um par de bobines de Maxwell dispostas no mesmo eixo. Além disso, componentes adicionais tiveram de ser desenhados ou selecionados para preencher os requisitos do sistema. Para a avaliação do sistema fabricado, testes preliminares foram realizados. A locomoção do microrobot foi testada em diferentes direções no plano x-y. As simulações e experiências confirmaram que é possível controlar a força magnética e o momento da força que atuam num microdispositivo através do campos produzidos pelas bobines de Maxwell e Helmholtz, respectivamente. Assim, este tipo de atuação magnética parece ser uma forma adequada de transferência de energia para futuros microdispositivos biomédicos.Navigation of nano/microdevices has great potential for biomedical applications, offering a means for diagnosis and therapeutic procedures inside the human body. Due to their ability to penetrate most materials, magnetic fields are naturally suited to control magnetic nano/microdevices in inaccessible spaces. One recent approach is the use of custom-built apparatus capable of controlling magnetic devices. This is a promising area of research, but further simulation studies and experiments are needed to estimate the feasibility of these systems in clinical applications. The goal of this project was the simulation and design of an electromagnetic actuation system to study the two dimensional locomotion of microdevices. The first step was to identify, through finite element analysis using software COMSOL, different coil configurations that would allow the control of magnetic devices at different scales. Based on the simulation results, a prototype of a magnetic actuation system to control devices with more than 100 m was designed and built from the ground up, taking into account cost constraints. The system comprised one pair of rotational Helmholtz coils and one pair of rotational Maxwell coils placed along the same axis. Furthermore, additional components had to be designed or selected to fulfil the requirements of the system. For the evaluation of the fabricated system, preliminary tests were carried out. The locomotion of a microdevice was tested along different directions in the x-y plane. The simulations and experiments confirmed that it is possible to control the magnetic force and torque acting on a microdevice through the fields produced by Maxwell and Helmholtz coils, respectively. Thus, this type of magnetic actuation seems to provide a suitable means of energy transfer for future biomedical microdevices

Enabling technologies for MRI guided interventional procedures

This dissertation addresses topics related to developing interventional assistant devices for Magnetic Resonance Imaging (MRI). MRI can provide high-quality 3D visualization of target anatomy and surrounding tissue, but the benefits can not be readily harnessed for interventional procedures due to difficulties associated with the use of high-field (1.5T or greater) MRI. Discussed are potential solutions to the inability to use conventional mecha- tronics and the confined physical space in the scanner bore. This work describes the development of two apparently dissimilar systems that repre- sent different approaches to the same surgical problem - coupling information and action to perform percutaneous (through the skin) needle placement with MR imaging. The first system addressed takes MR images and projects them along with a surgical plan directly on the interventional site, thus providing in-situ imaging. With anatomical images and a corresponding plan visible in the appropriate pose, the clinician can use this information to perform the surgical action. My primary research effort has focused on a robotic assistant system that overcomes the difficulties inherent to MR-guided procedures, and promises safe and reliable intra-prostatic needle placement inside closed high-field MRI scanners. The robot is a servo pneumatically operated automatic needle guide, and effectively guides needles under real- time MR imaging. This thesis describes development of the robotic system including requirements, workspace analysis, mechanism design and optimization, and evaluation of MR compatibility. Further, a generally applicable MR-compatible robot controller is de- veloped, the pneumatic control system is implemented and evaluated, and the system is deployed in pre-clinical trials. The dissertation concludes with future work and lessons learned from this endeavor

Mixed-reality visualization environments to facilitate ultrasound-guided vascular access

Ultrasound-guided needle insertions at the site of the internal jugular vein (IJV) are routinely performed to access the central venous system. Ultrasound-guided insertions maintain high rates of carotid artery puncture, as clinicians rely on 2D information to perform a 3D procedure. The limitations of 2D ultrasound-guidance motivated the research question: “Do 3D ultrasound-based environments improve IJV needle insertion accuracy”. We addressed this by developing advanced surgical navigation systems based on tracked surgical tools and ultrasound with various visualizations. The point-to-line ultrasound calibration enables the use of tracked ultrasound. We automated the fiducial localization required for this calibration method such that fiducials can be automatically localized within 0.25 mm of the manual equivalent. The point-to-line calibration obtained with both manual and automatic localizations produced average normalized distance errors less than 1.5 mm from point targets. Another calibration method was developed that registers an optical tracking system and the VIVE Pro head-mounted display (HMD) tracking system with sub-millimetre and sub-degree accuracy compared to ground truth values. This co-calibration enabled the development of an HMD needle navigation system, in which the calibrated ultrasound image and tracked models of the needle, needle trajectory, and probe were visualized in the HMD. In a phantom experiment, 31 clinicians had a 96 % success rate using the HMD system compared to 70 % for the ultrasound-only approach (p= 0.018). We developed a machine-learning-based vascular reconstruction pipeline that automatically returns accurate 3D reconstructions of the carotid artery and IJV given sequential tracked ultrasound images. This reconstruction pipeline was used to develop a surgical navigation system, where tracked models of the needle, needle trajectory, and the 3D z-buffered vasculature from a phantom were visualized in a common coordinate system on a screen. This system improved the insertion accuracy and resulted in 100 % success rates compared to 70 % under ultrasound-guidance (p=0.041) across 20 clinicians during the phantom experiment. Overall, accurate calibrations and machine learning algorithms enable the development of advanced 3D ultrasound systems for needle navigation, both in an immersive first-person perspective and on a screen, illustrating that 3D US environments outperformed 2D ultrasound-guidance used clinically

An Image-Based Tool to Examine Joint Congruency at the Elbow

Post-traumatic osteoarthritis commonly occurs as a result of a traumatic event to the articulation. Although the majority of this type of arthritis is preventable, the sequence and mechanism of the interaction between joint injury and the development of osteoarthritis (OA) is not well understood. It is hypothesized that alterations to the joint alignment can cause excessive and damaging wear to the cartilage surfaces resulting in OA. The lack of understanding of both the cause and progression of OA has contributed to the slow development of interventions which can modify the course of the disease. Currently, there have been no reported techniques that have been developed to examine the relationship between joint injury and joint alignment. Therefore, the objective of this thesis was to develop a non-invasive image-based technique that can be used to assess joint congruency and alignment of joints undergoing physiologic motion. An inter-bone distance algorithm was developed and validated to measure joint congruency at the ulnohumeral joint of the elbow. Subsequently, a registration algorithm was created and its accuracy was assessed. This registration algorithm registered 3D reconstructed bone models obtained using x-ray CT to motion capture data of cadaveric upper extremities undergoing simulated elbow flexion. In this way, the relative position and orientation of the 3D bone models could be visualized for any frame of motion. The effect of radial head arthroplasty was used to illustrate the utility of this technique. Once this registration was refined, the inter-bone distance algorithm was integrated to be able to visualize the joint congruency of the ulnohumeral joint undergoing simulated elbow flexion. The effect of collateral ligament repair was examined. This technique proved to be sensitive enough to detect large changes in joint congruency in spite of only small changes in the motion pathways of the ulnohumeral joint following simulated ligament repair. Efforts were also made in this thesis to translate this research into a clinical environment by examining CT scanning protocols that could reduce the amount of radiation exposure required to image patient’s joints. For this study, the glenohumeral joint of the shoulder was examined as this joint is particularly sensitive to potential harmful effects of radiation due to its proximity to highly radiosensitive organs. Using the CT scanning techniques examined in this thesis, the effective dose applied to the shoulder was reduced by almost 90% compared to standard clinical CT imaging. In summary, these studies introduced a technique that can be used to non-invasively and three-dimensionally examine joint congruency. The accuracy of this technique was assessed and its ability to predict regions of joint surface interactions was validated against a gold standard casting approach. Using the techniques developed in this thesis the complex relationship between injury, loading and mal-alignment as contributors to the development and progression of osteoarthritis in the upper extremity can be examined

Design, Development, and Evaluation of a Teleoperated Master-Slave Surgical System for Breast Biopsy under Continuous MRI Guidance

The goal of this project is to design and develop a teleoperated master-slave surgical system that can potentially assist the physician in performing breast biopsy with a magnetic resonance imaging (MRI) compatible robotic system. MRI provides superior soft-tissue contrast compared to other imaging modalities such as computed tomography or ultrasound and is used for both diagnostic and therapeutic procedures. The strong magnetic field and the limited space inside the MRI bore, however, restrict direct means of breast biopsy while performing real-time imaging. Therefore, current breast biopsy procedures employ a blind targeting approach based on magnetic resonance (MR) images obtained a priori. Due to possible patient involuntary motion or inaccurate insertion through the registration grid, such approach could lead to tool tip positioning errors thereby affecting diagnostic accuracy and leading to a long and painful process, if repeated procedures are required. Hence, it is desired to develop the aforementioned teleoperation system to take advantages of real-time MR imaging and avoid multiple biopsy needle insertions, improving the procedure accuracy as well as reducing the sampling errors. The design, implementation, and evaluation of the teleoperation system is presented in this dissertation. A MRI-compatible slave robot is implemented, which consists of a 1 degree of freedom (DOF) needle driver, a 3-DOF parallel mechanism, and a 2-DOF X-Y stage. This slave robot is actuated with pneumatic cylinders through long transmission lines except the 1-DOF needle driver is actuated with a piezo motor. Pneumatic actuation through long transmission lines is then investigated using proportional pressure valves and controllers based on sliding mode control are presented. A dedicated master robot is also developed, and the kinematic map between the master and the slave robot is established. The two robots are integrated into a teleoperation system and a graphical user interface is developed to provide visual feedback to the physician. MRI experiment shows that the slave robot is MRI-compatible, and the ex vivo test shows over 85%success rate in targeting with the MRI-compatible robotic system. The success in performing in vivo animal experiments further confirm the potential of further developing the proposed robotic system for clinical applications

Porcine Spine Finite Element Model of Progressive Experimental Scoliosis and Assessment of a New Dual-Epiphyseal Growth Modulating Implant

RÉSUMÉ La scoliose est une déformation tridimensionnelle de la colonne vertébrale dont l’étiologie reste encore à élucider. Il est généralement admis que la progression de la déformation scoliotique pédiatrique est liée au principe d’Hueter-Volkmann qui stipule une réduction de la croissance suite à des contraintes en compression excessives au niveau de la concavité de la courbure scoliotique vs. sa convexité. Les stratégies de traitement des courbures sont difficiles, surtout chez les jeunes enfants. Typiquement, une intervention chirurgicale avec une instrumentation rachidienne accompagnée d’une arthrodèse segmentaire est nécessaire pour des courbures progressant au-delà de 40° d’angle de Cobb. De nouveaux dispositifs visent à manipuler la croissance vertébrale en exploitant le principe d’Hueter-Volkmann pour contrôler la progression de et corriger la courbure. Ces implants sans fusion exploitent la croissance vertébrale résiduelle en manipulant des gradients de croissance pour localement inverser la cunéiformisation vertébrale et, au fil du temps, réaligner la colonne vertébrale globalement. Des essais cliniques ont démontré une correction prometteuse pour les courbures généralement inférieures à 45°; cependant, les dispositifs actuels chevauchent l’espace du disque intervertébral et le compriment augmentant les risques de dégénérescence du disque à long terme. Par ailleurs, les implants nouvellement conçus sont généralement testés en utilisant des modèles animaux équivalents pour évaluer leur efficacité à corriger des déformations par l'intermédiaire de l’approche inverse (création d'une déformation) ou l’approche à 2- étapes (création d'une déformation suivie d’une correction). Néanmoins, une plate-forme de conception efficace est nécessaire pour évaluer la manipulation de la croissance à court et long termes par de nouveaux implants et de raccourcir le transfert de connaissances vers des applications cliniques. L’objectif général de cette thèse était de développer et de vérifier un modèle par éléments finis porcin (MEFp) unique en tant qu’une plateforme alternative pour la simulation de scolioses expérimentales progressives et des implants sans fusion, et d’évaluer un nouvel implant double-épiphysaire local ne chevauchant pas l’espace du disque sur des porcs immatures. Ainsi, les objectifs spécifiques suivants ont été complétés : 1) développer et----------ABSTRACT Scoliosis is a complex three-dimensional deformity of the spine whose etiology is yet to be elucidated. The pathomechanism of scoliosis progression is believed to be linked to the Hueter-Volkmann principle, by which growth is reduced due to increased growth plate compression, with the inverse also valid. Treatment strategies are challenging, especially in young children. Curves progressing beyond 40° Cobb angle are typically treated via invasive surgical interventions requiring spinal instrumentation accompanied by segmental spinal arthrodesis, impairing spinal mobility. New devices aim at manipulating vertebral growth by exploiting the Hueter-Volkmann principle to control curvature progression. These fusionless implants harness remaining vertebral growth by manipulating growth gradients to reverse vertebral wedging locally and, over time, globally realign the spine. Clinical trials have demonstrated promising deformity correction for curves generally below 45°; however, current devices bridge the intervertebral disc gap and predominantly compress the disc increasing the risks of longterm disc degeneration. Moreover, in a time-consuming manner, newly designed implants are commonly tested using equivalent animal models to assess their efficacy in correcting spinal deformities via the inverse (creation of a deformity) or the 2-step approaches (creation of a deformity followed by its subsequent correction). Nevertheless, a solid design platform is required to evaluate the short- and long-term growth manipulating efficacy of new implant designs and shorten knowledge transfer to clinical applications. The general objective of this thesis was to develop and verify a unique porcine spine finite element model (pFEM) as an alternative testing platform for the simulation of progressive experimental scoliosis and fusionless implants, and assess a new localized dualepiphyseal implant on immature pigs. Thus, specific objectives were devised as follows: 1) develop and verify a distinctive pFEM of the spine and ribcage, 2) develop and test, in vivo, a dual-epiphyseal implant incorporating a custom expansion mechanism, 3) exploit the developed pFEM to investigate differences between the inverse and 2-step fusionless implant testing approaches, and 4) exploit the pFEM to evaluate the biomechanical contribution of the ribcage in fusionless scoliosis surgery