Book of Abstracts 15th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering and 3rd Conference on Imaging and Visualization

In this edition, the two events will run together as a single conference, highlighting the strong connection with the Taylor & Francis journals: Computer Methods in Biomechanics and Biomedical Engineering (John Middleton and Christopher Jacobs, Eds.) and Computer Methods in Biomechanics and Biomedical Engineering: Imaging and Visualization (JoãoManuel R.S. Tavares, Ed.). The conference has become a major international meeting on computational biomechanics, imaging andvisualization. In this edition, the main program includes 212 presentations. In addition, sixteen renowned researchers will give plenary keynotes, addressing current challenges in computational biomechanics and biomedical imaging. In Lisbon, for the first time, a session dedicated to award the winner of the Best Paper in CMBBE Journal will take place. We believe that CMBBE2018 will have a strong impact on the development of computational biomechanics and biomedical imaging and visualization, identifying emerging areas of research and promoting the collaboration and networking between participants. This impact is evidenced through the well-known research groups, commercial companies and scientific organizations, who continue to support and sponsor the CMBBE meeting series. In fact, the conference is enriched with five workshops on specific scientific topics and commercial software.info:eu-repo/semantics/draf

Augmented Reality and Artificial Intelligence in Image-Guided and Robot-Assisted Interventions

In minimally invasive orthopedic procedures, the surgeon places wires, screws, and surgical implants through the muscles and bony structures under image guidance. These interventions require alignment of the pre- and intra-operative patient data, the intra-operative scanner, surgical instruments, and the patient. Suboptimal interaction with patient data and challenges in mastering 3D anatomy based on ill-posed 2D interventional images are essential concerns in image-guided therapies. State of the art approaches often support the surgeon by using external navigation systems or ill-conditioned image-based registration methods that both have certain drawbacks. Augmented reality (AR) has been introduced in the operating rooms in the last decade; however, in image-guided interventions, it has often only been considered as a visualization device improving traditional workflows. Consequently, the technology is gaining minimum maturity that it requires to redefine new procedures, user interfaces, and interactions. This dissertation investigates the applications of AR, artificial intelligence, and robotics in interventional medicine. Our solutions were applied in a broad spectrum of problems for various tasks, namely improving imaging and acquisition, image computing and analytics for registration and image understanding, and enhancing the interventional visualization. The benefits of these approaches were also discovered in robot-assisted interventions. We revealed how exemplary workflows are redefined via AR by taking full advantage of head-mounted displays when entirely co-registered with the imaging systems and the environment at all times. The proposed AR landscape is enabled by co-localizing the users and the imaging devices via the operating room environment and exploiting all involved frustums to move spatial information between different bodies. The system's awareness of the geometric and physical characteristics of X-ray imaging allows the exploration of different human-machine interfaces. We also leveraged the principles governing image formation and combined it with deep learning and RGBD sensing to fuse images and reconstruct interventional data. We hope that our holistic approaches towards improving the interface of surgery and enhancing the usability of interventional imaging, not only augments the surgeon's capabilities but also augments the surgical team's experience in carrying out an effective intervention with reduced complications

Development and Implementation of Mathematical Modeling, Vibration and Acoustic Emission Technique to Correlate \u3cem\u3eIn Vivo\u3c/em\u3e Kinematics, Kinetics and Sound in Total Hip Arthroplasty with Different Bearing Surfaces

The evaluation of Total Hip Arthroplasty (THA) outcome is difficult and invasive methods are often applied. Fluoroscopy has been used as an in vivo diagnostic technique to determine separation which may lead to vibration propagation and audible interactions. The objective of this study was to develop a new, non-invasive technique of digitally capturing vibration and sound emissions at the hip joint interface and to correlate those with the hip kinematics derived from fluoroscopy. Additionally, an examination of the role of hip mechanics on walking performance in THA subjects of various bearings surfaces was performed. In vivo kinematics, kinetics, corresponding vibration and sound measurements of THA were analyzed post-operatively using video-fluoroscopy, mathematical modeling, sound sensors and accelerometers during gait on a treadmill. Twenty-seven subjects (31 hips) with a metal-on-metal, metal-on-polyethylene, ceramic-on-ceramic, ceramicon- polyethylene or metal-on-metal polyethylene-sandwich THA were analyzed. A data acquisition system was used to amplify the signal and filter out associated frequencies attributed to noise. The sound measurements were correlated to in vivo kinematics. A mathematical model of the human extremity was derived to determine in vivo bearing and soft-tissue forces. For all bearings a distinct correlation of a high frequency sound occurring at the time when the femoral head slides back into the acetabular component was observed. Subjects having a hard-on-hard bearing seemed to attenuate a squeaking and/or impacting sound, while those having polyethylene liner only revealed a knocking sound attributed to impact loading conditions. For the first time, audible effects can be derived in vivo and the examined correlation brings valuable insight into the hip joint performance in an inexpensive and non-invasive manner. This research may allow for a further correlation to be derived between sound and different types of failure mechanisms. Results from this study will give surgeons and engineers a better understanding of in vivo mechanics of the hip joint and this way improve the quality of life of THA patients. In addition, the developed technique builds the first milestone in the design and implementation of a cost effective, non-invasive diagnostic technique which has the potential to become a routine diagnosis of joint conditions

Quantification of knee extensor muscle forces: a multimodality approach

Given the growing interest of using musculoskeletal (MSK) models in a large number of clinical applications for quantifying the internal loading of the human MSK system, verification and validation of the model’s predictions, especially at the knee joint, have remained as one of the biggest challenges in the use of the models as clinical tools. This thesis proposes a methodology for more accurate quantification of knee extensor forces by exploring different experimental and modelling techniques that can be used to enhance the process of verification and validation of the knee joint model within the MSK models for transforming the models to a viable clinical tool. In this methodology, an experimental protocol was developed for simultaneous measurement of the knee joint motion, torques, external forces and muscular activation during an isolated knee extension exercise. This experimental protocol was tested on a cohort of 11 male subjects and the measurements were used to quantify knee extensor forces using two different MSK models representing a simplified model of the knee extensor mechanism and a previously-developed three-dimensional MSK model of the lower limb. The quantified knee extensor forces from the MSK models were then compared to evaluate the performance of the models for quantifying knee extensor forces. The MSK models were also used to investigate the sensitivity of the calculated knee extensor forces to key modelling parameters of the knee including the method of quantifying the knee centre of rotation and the effect of joint translation during motion. In addition, the feasibility of an emerging ultrasound-based imaging technique (shear wave elastography) for direct quantification of the physiologically-relevant musculotendon forces was investigated. The results in this thesis showed that a simplified model of the knee can be reliably used during a controlled planar activity as a computationally-fast and effective tool for hierarchical verification of the knee joint model in optimisation-based large-scale MSK models to provide more confidence in the outputs of the models. Furthermore, the calculation of knee extensor muscle forces has been found to be sensitive to knee joint translation (moving centre of rotation of the knee), highlighting the importance of this modelling parameter for quantifying physiologically-realistic knee muscle forces in the MSK models. It was also demonstrated how the movement of the knee axis of rotation during motion can be used as an intuitive tool for understanding the functional anatomy of the knee joint. Moreover, the findings in this thesis indicated that the shear wave elastography technique can be potentially used as a novel method for direct quantification of the physiologically-relevant musculotendon forces for independent validation of the predictions of musculotendon forces from the MSK models.Open Acces

Aligning 3D Curve with Surface Using Tangent and Normal Vectors for Computer-Assisted Orthopedic Surgery

Registration that aligns different views of one interested organ together is an essential technique and outstanding problem in medical robotics and image-guided surgery (IGS). This work introduces a novel rigid point set registration (PSR) approach that aims to accurately map the pre-operative space with the intra-operative space to enable successful image guidance for computer-assisted orthopaedic surgery (CAOS). The normal vectors and tangent vectors are first extracted from the pre-operative and intra-operative point sets (PSs) respectively, and are further utilized to enhance the registration accuracy and robustness. The contributions of this article are three-folds. First, we propose and formulate a novel distribution that describes the error between one normal vector and the corresponding tangent vector based on the von-Mises Fisher (vMF) distribution. Second, by modelling the anisotropic position localization error with the multi-variate Gaussian distribution, we formulate the PSR considering anisotropic localization error as a maximum likelihood estimation (MLE) problem and then solve it under the expectation maximization (EM) framework. Third, to facilitate the optimization process, the gradients of the objective function with respect to the desired parameters are computed and presented. Extensive experimental results on the human femur and pelvis models verify that the proposed approach outperforms the state-of-the-art methods, and demonstrate potential clinical values for relevant surgical navigation applications

Modelling gait abnormalities and bone deformities in children with cerebel palsy

Cerebral palsy (CP) is a neuromuscular disorder that affects the motor control of muscles. CP children exhibit abnormal walking patterns and frequently develop lower limb, long bone deformities. To improve functionality and guide orthopaedic treatments effectively, it is critical to elucidate the relationship existing between bone morphology and movement of the lower limbs CP children. The hypothesis of this study is that gait abnormalities result in bone deformities. The investigation of this complex relationship represents the core of this thesis. The examination of magnetic resonance images and gait analysis of healthy and CP children showed different development in femoral and tibial morphology and varied gait characteristics between them. Similarly, different correlations between bone morphology and gait characteristics resulted in healthy and CP children. Gait characteristics also varied between CP children. An objective and quantitative graphical classification method of CP gait patterns was developed. This classified the CP children in overlapping clusters according to their gait patterns, confirming the presence of multiple gait abnormalities on the same lower limb for CP children. With the intention to define the effect of the walking characteristics on the bone structure, femoral muscle and hip contact forces in healthy and CP children with different walking strategies were estimated by using inverse dynamic analysis. The different gait styles resulted in different loadings on the developing femur bone. These constituted the loading conditions for bone growth analysis. A three-dimensional finite element model for femoral growth was developed and mechanobiological theories applied in order to predict femur changes over time in healthy and CP children. The models predicted higher femoral anteversion and neck3 shaft angle formation in children with CP, emphasizing how different gait characteristics can influence bone morphology. This information has potential to explain and eventually prevent or treat the development of bone deformities in CP children

Development and Experimental Analysis of Wireless High Accuracy Ultra-Wideband Localization Systems for Indoor Medical Applications

This dissertation addresses several interesting and relevant problems in the field of wireless technologies applied to medical applications and specifically problems related to ultra-wideband high accuracy localization for use in the operating room. This research is cross disciplinary in nature and fundamentally builds upon microwave engineering, software engineering, systems engineering, and biomedical engineering. A good portion of this work has been published in peer reviewed microwave engineering and biomedical engineering conferences and journals. Wireless technologies in medicine are discussed with focus on ultra-wideband positioning in orthopedic surgical navigation. Characterization of the operating room as a medium for ultra-wideband signal transmission helps define system design requirements. A discussion of the first generation positioning system provides a context for understanding the overall system architecture of the second generation ultra-wideband positioning system outlined in this dissertation. A system-level simulation framework provides a method for rapid prototyping of ultra-wideband positioning systems which takes into account all facets of the system (analog, digital, channel, experimental setup). This provides a robust framework for optimizing overall system design in realistic propagation environments. A practical approach is taken to outline the development of the second generation ultra-wideband positioning system which includes an integrated tag design and real-time dynamic tracking of multiple tags. The tag and receiver designs are outlined as well as receiver-side digital signal processing, system-level design support for multi-tag tracking, and potential error sources observed in dynamic experiments including phase center error, clock jitter and drift, and geometric position dilution of precision. An experimental analysis of the multi-tag positioning system provides insight into overall system performance including the main sources of error. A five base station experiment shows the potential of redundant base stations in improving overall dynamic accuracy. Finally, the system performance in low signal-to-noise ratio and non-line-of-sight environments is analyzed by focusing on receiver-side digitally-implemented ranging algorithms including leading-edge detection and peak detection. These technologies are aimed at use in next-generation medical systems with many applications including surgical navigation, wireless telemetry, medical asset tracking, and in vivo wireless sensors

Augmented reality for computer assisted orthopaedic surgery

In recent years, computer-assistance and robotics have established their presence in operating theatres and found success in orthopaedic procedures. Benefits of computer assisted orthopaedic surgery (CAOS) have been thoroughly explored in research, finding improvements in clinical outcomes, through increased control and precision over surgical actions. However, human-computer interaction in CAOS remains an evolving field, through emerging display technologies including augmented reality (AR) – a fused view of the real environment with virtual, computer-generated holograms. Interactions between clinicians and patient-specific data generated during CAOS are limited to basic 2D interactions on touchscreen monitors, potentially creating clutter and cognitive challenges in surgery. Work described in this thesis sought to explore the benefits of AR in CAOS through: an integration between commercially available AR and CAOS systems, creating a novel AR-centric surgical workflow to support various tasks of computer-assisted knee arthroplasty, and three pre–clinical studies exploring the impact of the new AR workflow on both existing and newly proposed quantitative and qualitative performance metrics. Early research focused on cloning the (2D) user-interface of an existing CAOS system onto a virtual AR screen and investigating any resulting impacts on usability and performance. An infrared-based registration system is also presented, describing a protocol for calibrating commercial AR headsets with optical trackers, calculating a spatial transformation between surgical and holographic coordinate frames. The main contribution of this thesis is a novel AR workflow designed to support computer-assisted patellofemoral arthroplasty. The reported workflow provided 3D in-situ holographic guidance for CAOS tasks including patient registration, pre-operative planning, and assisted-cutting. Pre-clinical experimental validation on a commercial system (NAVIO®, Smith & Nephew) for these contributions demonstrates encouraging early-stage results showing successful deployment of AR to CAOS systems, and promising indications that AR can enhance the clinician’s interactions in the future. The thesis concludes with a summary of achievements, corresponding limitations and future research opportunities.Open Acces

Clinical investigation of the functional outcome of fixed bearing versus mobile bearing knees

Total Knee Arthroplasty is a high-volume and high-cost procedure, with persisting limitations to patient satisfaction. Prosthesis designs aim to restore function whilst providing stability, without joint constraint. This double-blinded randomised controlled trial is the first of its kind where the functional performance of a low congruent fixed (CR DD), ultra-congruent fixed (UC), and ultra-congruent mobile (UCR) bearing Columbus Total Knee Systems were assessed. The pre- and postoperative function of twenty-four osteoarthritic patients was evaluated against nine control participants whilst carrying out activities of daily living. Spatiotemporal, kinematic, and kinetic gait parameters during walking, stair navigation and sloped walking were extracted using fully instrumented motion capture. Questionnaire responses were also recorded. Across all ADLs, postoperative patient function improved, although not to control levels. The average postoperative increase in range of sagittal knee motion across all tasks came to: 7.3±3.1o (CRDD), 4.9±4.9o (UC), 0.7±7.7o (UCR), and peak knee flexion was mostly reduced at postoperative. Both fixed bearing implants presented larger post-surgery hip and ankle kinetics in magnitude, and improved distinction between knee adduction moment maxima, linked to improved loading to the mobile bearing group. Overall, the CRDD group showed more significant changes to preoperative and any significant inter-implant differences at post-surgery was also to this group. The UC and UCR groups showed less improvements during challenging activities, with the UCR group showing some limits to knee extension. The UCR group also self-reported more difficulty, pain, and tiredness than the fixed bearing groups. Kinematic cross talk error significantly impacted the interpretation of non-sagittal kinematics, and small and unequal sample sizes reduced statistical power. Despite the limitations it was concluded that both fixed bearing implants initially outperformed the mobile bearing joint and the CRDD group showed the most prominent improvements. Clinically relevant thresholds for all parameters, would further determine whether functional advantages exist between implant bearing types.Total Knee Arthroplasty is a high-volume and high-cost procedure, with persisting limitations to patient satisfaction. Prosthesis designs aim to restore function whilst providing stability, without joint constraint. This double-blinded randomised controlled trial is the first of its kind where the functional performance of a low congruent fixed (CR DD), ultra-congruent fixed (UC), and ultra-congruent mobile (UCR) bearing Columbus Total Knee Systems were assessed. The pre- and postoperative function of twenty-four osteoarthritic patients was evaluated against nine control participants whilst carrying out activities of daily living. Spatiotemporal, kinematic, and kinetic gait parameters during walking, stair navigation and sloped walking were extracted using fully instrumented motion capture. Questionnaire responses were also recorded. Across all ADLs, postoperative patient function improved, although not to control levels. The average postoperative increase in range of sagittal knee motion across all tasks came to: 7.3±3.1o (CRDD), 4.9±4.9o (UC), 0.7±7.7o (UCR), and peak knee flexion was mostly reduced at postoperative. Both fixed bearing implants presented larger post-surgery hip and ankle kinetics in magnitude, and improved distinction between knee adduction moment maxima, linked to improved loading to the mobile bearing group. Overall, the CRDD group showed more significant changes to preoperative and any significant inter-implant differences at post-surgery was also to this group. The UC and UCR groups showed less improvements during challenging activities, with the UCR group showing some limits to knee extension. The UCR group also self-reported more difficulty, pain, and tiredness than the fixed bearing groups. Kinematic cross talk error significantly impacted the interpretation of non-sagittal kinematics, and small and unequal sample sizes reduced statistical power. Despite the limitations it was concluded that both fixed bearing implants initially outperformed the mobile bearing joint and the CRDD group showed the most prominent improvements. Clinically relevant thresholds for all parameters, would further determine whether functional advantages exist between implant bearing types