Navigating in Patient Space Using Camera Pose Estimation Relative to the External Anatomy

Ultrasound probe localization is essential for volumetric imaging with a 2D ultrasound probe, and for establishing a recorded anatomical context for ultrasound-guided surgery and for longitudinal studies. The existing techniques for probe localization, however, require external tracking devices, making them inconvenient for clinical use. In addition, the probe pose is typically measured with respect to a fixed coordinate system independent of the patient’s anatomy, making it difficult to correlate ultrasound studies across time. This dissertation concerns the development and evaluation of a novel self-contained ultrasound probe tracking system, which navigates the probe in patient space using camera pose estimation relative to the anatomical context. As the probe moves in patient space, a video camera on the probe is used to automatically identify natural skin features and subdermal cues, and match them with a pre-acquiring high-resolution 3D surface map that serves as an atlas of the anatomy. We have addressed the problem of distinguishing rotation from translation by including an inertial navigation system (INS) to accurately measure rotation. Experiments on both a phantom containing an image of human skin (palm) as well as actual human upper extremity (fingers, palm, and wrist) validate the effectiveness of our approach. We have also developed a real-time 3D interactive visualization system that superimposes the ultrasound data within the anatomical context of the exterior of the patient, to permit accurate anatomic localization of ultrasound data. The combination of the proposed tracking approach and the visualization system may have broad implications for ultrasound imaging, permitting the compilation of volumetric ultrasound data as the 2D probe is moved, as well as comparison of real-time ultrasound scans registered with previous scans from the same anatomical location. In a broader sense, tools that self-locate by viewing the patient’s exterior could have broad beneficial impact on clinical medicine

Enhanced ultrasound for advanced diagnostics, ultrasound tomography for volume limb imaging and prosthetic fitting

Ultrasound imaging methods hold the potential to deliver low-cost, high-resolution, operator-independent and nonionizing imaging systems-such systems couple appropriate algorithms with imaging devices and techniques. The increasing demands on general practitioners motivate us to develop more usable and productive diagnostic imaging equipment. Ultrasound, specifically freehand ultrasound, is a low cost and safe medical imaging technique. It doesn't expose a patient to ionizing radiation. Its safety and versatility make it very well suited for the increasing demands on general practitioners, or for providing improved medical care in rural regions or the developing world. However it typically suffers from sonographer variability; we will discuss techniques to address user variability. We also discuss our work to combine cylindrical scanning systems with state of the art inversion algorithms to deliver ultrasound systems for imaging and quantifying limbs in 3-D in vivo. Such systems have the potential to track the progression of limb health at a low cost and without radiation exposure, as well as, improve prosthetic socket fitting. Current methods of prosthetic socket fabrication remain subjective and ineffective at creating an interface to the human body that is both comfortable and functional. Though there has been recent success using methods like magnetic resonance imaging and biomechanical modeling, a low-cost, streamlined, and quantitative process for prosthetic cup design and fabrication has not been fully demonstrated. Medical ultrasonography may inform the design process of prosthetic sockets in a more objective manner. This keynote talk presents the results of progress in this area. Keywords: Clinical ultrasound, Force control, 3-D ultrasound, Tomograph

Reliability of Robotic Ultrasound Scanning for Scoliosis Assessment in Comparison with Manual Scanning

Background: Ultrasound (US) imaging for scoliosis assessment is challenging for a non-experienced operator. The robotic scanning was developed to follow a spinal curvature with deep learning and apply consistent forces to the patient' back. Methods: 23 scoliosis patients were scanned with US devices both, robotically and manually. Two human raters measured each subject's spinous process angles (SPA) on robotic and manual coronal images. Results: The robotic method showed high intra- (ICC > 0.85) and inter-rater (ICC > 0.77) reliabilities. Compared with the manual method, the robotic approach showed no significant difference (p < 0.05) when measuring coronal deformity angles. The MAD for intra-rater analysis lies within an acceptable range from 0 deg to 5 deg for a minimum of 86% and a maximum 97% of a total number of the measured angles. Conclusions: This study demonstrated that scoliosis deformity angles measured on ultrasound images obtained with robotic scanning are comparable to those obtained by manual scanning

Building and validation of low-cost breast phantoms for interventional procedures

Breast cancer is one of the types of cancer with the highest incidence in female population. Current treatment for breast cancer is lumpectomy, a breast conserving tumor excision procedure based on localizing the tumor with the help of hook-wire needle placement. Although this constitutes the standard approach in clinical practice, these procedures do not ensure the complete removal of the lesion due to the demonstrated high rate of positive margins. Improvements in these techniques are needed in order to reduce the number of second interventions, which usually involve mastectomy. Here is where ultrasound-guided interventions with real-time position tracking find their place. The problem is that these techniques require a high level of expertise and they present long learning curves. Therefore, training is needed in order to get from these tools their highest potential and have a real impact in the life of patients. For this purpose, breast phantoms were manufactured using liquid vinyl in order to achieve a mammary mimicking tissue. Optimal manufacturing technique was determined based on a gold-standard (commercial phantom). CT and ultrasound imaging were used to assess the identification of lesions. In addition, manufactured breast phantoms were evaluated by an expert clinician and surgical navigation was tested. This was done with the purpose of validating the breast phantom as a training tool useful for improving the outcomes of these procedures. The results indicated that the optimized formula achieved for the manufacturing of low-cost breast phantoms was suitable for training the skillset required in the interventions related with breast cancer treatment.Ingeniería Biomédica (Plan 2010

Intraoperative Navigation Systems for Image-Guided Surgery

Recent technological advancements in medical imaging equipment have resulted in a dramatic improvement of image accuracy, now capable of providing useful information previously not available to clinicians. In the surgical context, intraoperative imaging provides a crucial value for the success of the operation. Many nontrivial scientific and technical problems need to be addressed in order to efficiently exploit the different information sources nowadays available in advanced operating rooms. In particular, it is necessary to provide: (i) accurate tracking of surgical instruments, (ii) real-time matching of images from different modalities, and (iii) reliable guidance toward the surgical target. Satisfying all of these requisites is needed to realize effective intraoperative navigation systems for image-guided surgery. Various solutions have been proposed and successfully tested in the field of image navigation systems in the last ten years; nevertheless several problems still arise in most of the applications regarding precision, usability and capabilities of the existing systems. Identifying and solving these issues represents an urgent scientific challenge. This thesis investigates the current state of the art in the field of intraoperative navigation systems, focusing in particular on the challenges related to efficient and effective usage of ultrasound imaging during surgery. The main contribution of this thesis to the state of the art are related to: Techniques for automatic motion compensation and therapy monitoring applied to a novel ultrasound-guided surgical robotic platform in the context of abdominal tumor thermoablation. Novel image-fusion based navigation systems for ultrasound-guided neurosurgery in the context of brain tumor resection, highlighting their applicability as off-line surgical training instruments. The proposed systems, which were designed and developed in the framework of two international research projects, have been tested in real or simulated surgical scenarios, showing promising results toward their application in clinical practice

Development of a cognitive robotic system for simple surgical tasks

The introduction of robotic surgery within the operating rooms has significantly improved the quality of many surgical procedures. Recently, the research on medical robotic systems focused on increasing the level of autonomy in order to give them the possibility to carry out simple surgical actions autonomously. This paper reports on the development of technologies for introducing automation within the surgical workflow. The results have been obtained during the ongoing FP7 European funded project Intelligent Surgical Robotics (I-SUR). The main goal of the project is to demonstrate that autonomous robotic surgical systems can carry out simple surgical tasks effectively and without major intervention by surgeons. To fulfil this goal, we have developed innovative solutions (both in terms of technologies and algorithms) for the following aspects: fabrication of soft organ models starting from CT images, surgical planning and execution of movement of robot arms in contact with a deformable environment, designing a surgical interface minimizing the cognitive load of the surgeon supervising the actions, intra-operative sensing and reasoning to detect normal transitions and unexpected events. All these technologies have been integrated using a component-based software architecture to control a novel robot designed to perform the surgical actions under study. In this work we provide an overview of our system and report on preliminary results of the automatic execution of needle insertion for the cryoablation of kidney tumours

A hybrid camera- and ultrasound-based approach for needle localization and tracking using a 3D motorized curvilinear ultrasound probe

Three-dimensional (3D) motorized curvilinear ultrasound probes provide an effective, low-cost tool to guide needle interventions, but localizing and tracking the needle in 3D ultrasound volumes is often challenging. In this study, a new method is introduced to localize and track the needle using 3D motorized curvilinear ultrasound probes. In particular, a low-cost camera mounted on the probe is employed to estimate the needle axis. The camera-estimated axis is used to identify a volume of interest (VOI) in the ultrasound volume that enables high needle visibility. This VOI is analyzed using local phase analysis and the random sample consensus algorithm to refine the camera-estimated needle axis. The needle tip is determined by searching the localized needle axis using a probabilistic approach. Dynamic needle tracking in a sequence of 3D ultrasound volumes is enabled by iteratively applying a Kalman filter to estimate the VOI that includes the needle in the successive ultrasound volume and limiting the localization analysis to this VOI. A series of ex vivo animal experiments are conducted to evaluate the accuracy of needle localization and tracking. The results show that the proposed method can localize the needle in individual ultrasound volumes with maximum error rates of 0.7 mm for the needle axis, 1.7° for the needle angle, and 1.2 mm for the needle tip. Moreover, the proposed method can track the needle in a sequence of ultrasound volumes with maximum error rates of 1.0 mm for the needle axis, 2.0° for the needle angle, and 1.7 mm for the needle tip. These results suggest the feasibility of applying the proposed method to localize and track the needle using 3D motorized curvilinear ultrasound probes