Abstract: In this study, we show the use of three-dimensional printing models for preoperative planning of transcatheter valve replacement in a patient with an extreme porcelain aorta. A 70-year-old man with severe aortic stenosis and a porcelain aorta was referred to our center for transcatheter aortic valve replacement. Unfortunately, the patient died after the procedure because of a potential ischemic event. Therefore, we decided to fabricate three-dimensional models to evaluate the potential effects of these constructs for previous surgical planning and simulation of the transcatheter valve replacement.
Abstract: A robot built specifically for stereotactic cochlear implantation provides equal or better accuracy levels together with a better integration into a clinical environment, when compared with existing approaches based on industrial robots.
Abstract: Image overlay projection is a form of augmented reality that allows surgeons to view underlying anatomical structures directly on the patient surface. It improves intuitiveness of computer-aided surgery by removing the need for sight diversion between the patient and a display screen and has been reported to assist in 3-D understanding of anatomical structures and the identification of target and critical structures. Challenges in the development of image overlay technologies for surgery remain in the projection setup. Calibration, patient registration, view direction, and projection obstruction remain unsolved limitations to image overlay techniques. In this paper, we propose a novel, portable, and handheld-navigated image overlay device based on miniature laser projection technology that allows images of 3-D patient-specific models to be projected directly onto the organ surface intraoperatively without the need for intrusive hardware around the surgical site. The device can be integrated into a navigation system, thereby exploiting existing patient registration and model generation solutions. The position of the device is tracked by the navigation system’s position sensor and used to project geometrically correct images from any position within the workspace of the navigation system. The projector was calibrated using modified camera calibration techniques and images for projection are rendered using a virtual camera defined by the projectors extrinsic parameters. Verification of the device’s projection accuracy concluded a mean projection error of 1.3 mm. Visibility testing of the projection performed on pig liver tissue found the device suitable for the display of anatomical structures on the organ surface. The feasibility of use within the surgical workflow was assessed during open liver surgery. We show that the device could be quickly and unobtrusively deployed within the sterile environment.
Abstract: OBJECTIVE: To present the auditory implant manipulator, a navigation-controlled mechanical and electronic system which enables minimally invasive ('keyhole') transmastoid access to the tympanic cavity.
MATERIALS AND METHODS: The auditory implant manipulator is a miniaturised robotic system with five axes of movement and an integrated drill. It can be mounted on the operating table. We evaluated the surgical work field provided by the system, and the work sequence involved, using an anatomical whole head specimen.
RESULTS: The work field provided by the auditory implant manipulator is considerably greater than required for conventional mastoidectomy. The work sequence for a keyhole procedure included pre-operative planning, arrangement of equipment, the procedure itself and post-operative analysis.
CONCLUSION: Although system improvements are necessary, our preliminary results indicate that the auditory implant manipulator has the potential to perform keyhole insertion of implantable hearing devices.
Abstract: BACKGROUND: The surgical treatment of liver tumours relies on precise localization of the lesions and detailed knowledge of the patient-specific vascular and biliary anatomy. Detailed three-dimensional (3D) anatomical information facilitates complete tumour removal while preserving a sufficient amount of functional liver tissue.
METHODS: We present an easy to use, clinically applicable navigation system for efficient visualization and tool guidance during liver surgery. Accurate instrument guidance within 3D planning models was achieved with a fast registration procedure, assuming a locally rigid and temporarily static scenario. After deformations occurring during the procedure, efficient means for registration updates are provided. Special focus was given to workflow integration and the minimization of overhead time. The navigation system was validated with nine clinical cases.
RESULTS: Navigated surgical interventions were performed with a median time overhead of 16.5 min. The navigation technology had a median accuracy of 6.3 mm, improving anatomical orientation and the detection of structures at risk.
CONCLUSIONS: Successful application of the navigation technology to open liver surgery was achieved by minimizing the procedural complexity and optimizing integration within the existing surgical environment. The assumption of locally rigid patient registration was validated, and clinical evaluation shows clear benefits for the surgeon.
Abstract: We propose a computationally efficient, bio-mechanically relevant soft-tissue simulation method for cranio-maxillofacial (CMF) surgery. Special emphasis is given to comply with the current clinical workflow. A template-based facial muscle prediction was introduced to avoid laborious segmentation from medical images. In addition, transversely isotropic mass-tensor model (MTM) was applied to realize the directional behavior of facial muscles in short computation time. Finally, sliding contact was incorporated to mimic realistic boundary condition in error-sensitive regions. Mechanical simulation result was compared with commercial finite element software. And retrospective validation study with post-operative scan of four CMF cases was performed.
Abstract: Statistical shape analysis techniques have shown to be efficient tools to build population specific models of anatomical variability. Their use is commonplace as prior models for segmentation, in which case the instance from the shape model that best fits the image data is sought. In certain cases, however, it is not just the most likely instance that must be searched, but rather the whole set of shape instances that meet certain criterion. In this paper we develop a method for the assessment of specific anatomical/morphological criteria across the shape variability found in a population. The method is based on a level set segmentation approach, and used on the parametric space of the statistical shape model of the target population, solved via a multi-level narrow-band approach for computational efficiency. Based on this technique, we develop a framework for evidence-based orthopaedic implant design. To date, implants are commonly designed and validated by evaluating implant bone fitting on a limited set of cadaver bones, which not necessarily span the whole variability in the population. Based on our framework, we can virtually fit a proposed implant design to samples drawn from the statistical model, and assess which range of the population is suitable for the implant. The method highlights which patterns of bone variability are more important for implant fitting, allowing and easing implant design improvements, as to fit a maximum of the target population. Results are presented for the optimisation of implant design of proximal human tibia, used for internal fracture fixation.
Abstract: Vertebroplasty is a minimally invasive procedure with many benefits; however, the procedure is not without risks and potential complications, of which leakage of the cement out of the vertebral body and into the surrounding tissues is one of the most serious. Cement can leak into the spinal canal, venous system, soft tissues, lungs and intradiscal space, causing serious neurological complications, tissue necrosis or pulmonary embolism. We present a method for automatic segmentation and tracking of bone cement during vertebroplasty procedures, as a first step towards developing a warning system to avoid cement leakage outside the vertebral body. We show that by using active contours based on level sets the shape of the injected cement can be accurately detected. The model has been improved for segmentation as proposed in our previous work by including a term that restricts the level set function to the vertebral body. The method has been applied to a set of real intra-operative X-ray images and the results show that the algorithm can successfully detect different shapes with blurred and not well-defined boundaries, where the classical active contours segmentation is not applicable. The method has been positively evaluated by physicians.
Abstract: BACKGROUND: The Virtopsy project, a multi-disciplinary project that involves forensic science, diagnostic imaging, computer science, automation technology, telematics and biomechanics, aims to develop new techniques to improve the outcome of forensic investigations. This paper presents a new approach in the field of minimally invasive virtual autopsy for a versatile robotic system that is able to perform three-dimensional (3D) surface scans as well as post mortem image-guided soft tissue biopsies.
METHODS: The system consists of an industrial six-axis robot with additional extensions (i.e. a linear axis to increase working space, a tool-changing system and a dedicated safety system), a multi-slice CT scanner with equipment for angiography, a digital photogrammetry and 3D optical surface-scanning system, a 3D tracking system, and a biopsy end effector for automatic needle placement. A wax phantom was developed for biopsy accuracy tests.
RESULTS: Surface scanning times were significantly reduced (scanning times cut in half, calibration three times faster). The biopsy module worked with an accuracy of 3.2 mm.
DISCUSSION: Using the Virtobot, the surface-scanning procedure could be standardized and accelerated. The biopsy module is accurate enough for use in biopsies in a forensic setting.
CONCLUSION: The Virtobot can be utilized for several independent tasks in the field of forensic medicine, and is sufficiently versatile to be adapted to different tasks in the future.
Abstract: Correct registration between pre-operative high-resolution images and intra-operative data of lower detail is a fundamental requirement in image-guided liver surgery. We propose a multi modality liver model for measuring the accuracy of such registration methods. A freshly explanted porcine liver is artificially perfused by a peristaltic pump and liver motion is simulated by means of inflatable objects positioned around the liver. Co-registered ultrasound and CT data sets are acquired in different deformation scenarios and allow compar-ing registration outcomes with a CT data set serving as ground truth. The pre-sent work describes the experimental setup and summarizes the results from ultrasound and CT imaging.
Abstract: This paper presents an automated solution for precise detection of fiducial screws from three-dimensional (3D) Computerized Tomography (CT)/Digital Volume Tomography (DVT) data for image-guided ENT surgery. Unlike previously published solutions, we regard the detection of the fiducial screws from the CT/DVT volume data as a pose estimation problem. We thus developed a model-based solution. Starting from a user-supplied initialization, our solution detects the fiducial screws by iteratively matching a computer aided design (CAD) model of the fiducial screw to features extracted from the CT/DVT data. We validated our solution on one conventional CT dataset and on five DVT volume datasets, resulting in a total detection of 24 fiducial screws. Our experimental results indicate that the proposed solution achieves much higher reproducibility and precision than the manual detection. Further comparison shows that the proposed solution produces better results on the DVT dataset than on the conventional CT dataset.
Abstract: Navigated ultrasound (US) imaging is used for the intra-operative acquisition of 3D image data during image-guided surgery. The presented approach includes the design of a compact and easy to use US calibration device and its integration into a software application for navigated liver surgery. User interaction during the calibration process is minimized through automatic detection of the calibration process followed by automatic image segmentation, calculation of the calibration transform and validation of the obtained result. This leads to a fast, interaction-free and fully automatic calibration procedure enabling intra-operative US calibration being performed by the surgical user.
Abstract: The delicate anatomy of the ear require surgeons to use great care when operating on its internal structures. One example for such an intervention is the stapedectomy, where a small crook shaped piston is placed in the oval window of the cochlea and connected to the incus through crimping thus bypassing the diseased stapes. Performing the crimp process with the correct force is necessary since loose crimps poorly transmit sound whereas tight crimps will eventually result in necrosis of the incus. Clinically, demand is high to reproducibly conduct the crimp process through a precise force measurement. For this reason, we have developed a fiber Bragg grating (FBG) integrated microforceps for use in such interventions. This device was calibrated, and tested in cadaver preparations. With this instrument we were able to measure for the first time forces involved in crimping a stapes prosthesis to the incus. We also discuss a method of attaching and actuating such forceps in conjunction with a robot currently under development in our group. Each component of this system can be used separately or combined to improve surgical accuracy, confidence and outcome.
Abstract: Cranioplasty is a commonly performed procedure. Outcomes can be improved by the use of patient specific implants, however, high costs limit their accessibility. This paper presents a low cost alternative technique to create patient specific polymethylmethacrylate (PMMA) implants using rapid prototyped mold template. We used available patient's CT-scans, one dataset without craniotomy and one with craniotomy, for computer-assisted design of a 3D mold template, which itself can be brought into the operating room and be used for fast and easy building of a PMMA implant. We applied our solution to three patients with positive outcomes and no complications.
Abstract: In this paper we propose a variational approach for multimodal image registration based on the diffeomorphic demons algorithm. Diffeomorphic demons has proven to be a robust and efficient way for intensity-based image registration. However, the main drawback is that it cannot deal with multiple modalities. We propose to replace the standard demons similarity metric (image intensity differences) by point-wise mutual information (PMI) in the energy function. By comparing the accuracy between our PMI based diffeomorphic demons and the B-Spline based free-form deformation approach (FFD) on simulated deformations, we show the proposed algorithm performs significantly better.
Abstract: Percutaneous nephrolithotomy (PCNL) for the treatment of renal stones and other related renal diseases has proved its efficacy and has stood the test of time compared with open surgical methods and extracorporeal shock wave lithotripsy. However, access to the collecting system of the kidney is not easy because the available intra-operative image modalities only provide a two dimensional view of the surgical scenario. With this lack of visual information, several punctures are often necessary which, increases the risk of renal bleeding, splanchnic, vascular or pulmonary injury, or damage to the collecting system which sometimes makes the continuation of the procedure impossible. In order to address this problem, this paper proposes a workflow for introduction of a stereotactic needle guidance system for PCNL procedures. An analysis of the imposed clinical requirements, and a instrument guidance approach to provide the physician with a more intuitive planning and visual guidance to access the collecting system of the kidney are presented.
Abstract: PET/CT guidance for percutaneous interventions allows biopsy of suspicious metabolically active bone lesions even when no morphological correlation is delineable in the CT images. Clinical use of PET/CT guidance with conventional step-by-step technique is time consuming and complicated especially in cases in which the target lesion is not shown in the CT image. Our recently developed multimodal instrument guidance system (IGS) for PET/CT improved this situation. Nevertheless, bone biopsies even with IGS have a trade-off between precision and intervention duration which is proportional to patient and personnel exposure to radiation. As image acquisition and reconstruction of PET may take up to 10 minutes, preferably only one time consuming combined PET/CT acquisition should be needed during an intervention. In case of required additional control images in order to check for possible patient movements/deformations, or to verify the final needle position in the target, only fast CT acquisitions should be performed. However, for precise instrument guidance accounting for patient movement and/or deformation without having a control PET image, it is essential to be able to transfer the position of the target as identified in the original PET/CT to a changed situation as shown in the control CT. Therefore, we present a pipeline for faster target-position correction by isolating and registering the bone of interest, as shown in the control CT, with the CT dataset of the original PET/CT acquisition. Challenges such as the masking of the bone of interest and registration robustness in the presence of the needle and its associated metal artifacts are also addressed in this work. Our results confirmed the feasibility of clinically using this technique for target correction on PET/CT bone intervention, and motivated us to incorporate it as part of our IGS for multimodal intervention.
