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

A Low-Cost Camera-based Transducer Tracking System for Freehand Three-Dimensional Ultrasound Imaging

Freehand three-dimensional ultrasound (3D US) imaging is commonly used for clinical diagnosis and therapy monitoring. In this technique, accurate tracking of the US transducer is a crucial requirement to develop high-quality 3D US volumes. However, current methods for transducer tracking are generally expensive and inconvenient. This thesis presents a low-cost camera-based system for tracking the US transducer with six degrees of freedom (DoF). In this system, two orthogonal cameras with non-overlapped views are mounted on the US transducer. During US scanning, the two cameras are employed to track artificial features attached to the skin of the patient. A 3D surface map is constructed based on the tracked features and the 3D poses of each camera with respect to the skin are extracted separately. The estimated poses of the two cameras are spatially combined to provide accurate and robust pose estimation of the US transducer. In particular, the fusion of the estimated poses by the two cameras is performed using Kalman filtering based technique, which is a popular optimization technique in motion guidance and tracking. The camera-based tracking of the US transducer has been applied to synthesize freehand 3D US volumes. The performance of the proposed system is evaluated by performing in-vitro 3D US imaging experiments and quantifying the synthesized US volumes. The results demonstrate that two points in the 3D US volume separated by a distance of 10 mm can be reconstructed with an average error of 0.35 mm and a 3D volume of a cylinder can be estimated within an error of 3.8%

Freehand 2D Ultrasound Probe Calibration for Image Fusion with 3D MRI/CT

The aim of this work is to implement a simple freehand ultrasound (US) probe calibration technique. This will enable us to visualize US image data during surgical procedures using augmented reality. The performance of the system was evaluated with different experiments using two different pose estimation techniques. A near-millimeter accuracy can be achieved with the proposed approach. The developed system is cost-effective, simple and rapid with low calibration erro

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

Three-dimensional ultrasound image-guided robotic system for accurate microwave coagulation of malignant liver tumours

Background The further application of conventional ultrasound (US) image-guided microwave (MW) ablation of liver cancer is often limited by two-dimensional (2D) imaging, inaccurate needle placement and the resulting skill requirement. The three-dimensional (3D) image-guided robotic-assisted system provides an appealing alternative option, enabling the physician to perform consistent, accurate therapy with improved treatment effectiveness. Methods Our robotic system is constructed by integrating an imaging module, a needle-driven robot, a MW thermal field simulation module, and surgical navigation software in a practical and user-friendly manner. The robot executes precise needle placement based on the 3D model reconstructed from freehand-tracked 2D B-scans. A qualitative slice guidance method for fine registration is introduced to reduce the placement error caused by target motion. By incorporating the 3D MW specific absorption rate (SAR) model into the heat transfer equation, the MW thermal field simulation module determines the MW power level and the coagulation time for improved ablation therapy. Two types of wrists are developed for the robot: a ‘remote centre of motion’ (RCM) wrist and a non-RCM wrist, which is preferred in real applications. Results The needle placement accuracies were < 3 mm for both wrists in the mechanical phantom experiment. The target accuracy for the robot with the RCM wrist was improved to 1.6 ± 1.0 mm when real-time 2D US feedback was used in the artificial-tissue phantom experiment. By using the slice guidance method, the robot with the non-RCM wrist achieved accuracy of 1.8 ± 0.9 mm in the ex vivo experiment; even target motion was introduced. In the thermal field experiment, a 5.6% relative mean error was observed between the experimental coagulated neurosis volume and the simulation result. Conclusion The proposed robotic system holds promise to enhance the clinical performance of percutaneous MW ablation of malignant liver tumours. Copyright © 2010 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78054/1/313_ftp.pd

Medical image computing and computer-aided medical interventions applied to soft tissues. Work in progress in urology

Until recently, Computer-Aided Medical Interventions (CAMI) and Medical Robotics have focused on rigid and non deformable anatomical structures. Nowadays, special attention is paid to soft tissues, raising complex issues due to their mobility and deformation. Mini-invasive digestive surgery was probably one of the first fields where soft tissues were handled through the development of simulators, tracking of anatomical structures and specific assistance robots. However, other clinical domains, for instance urology, are concerned. Indeed, laparoscopic surgery, new tumour destruction techniques (e.g. HIFU, radiofrequency, or cryoablation), increasingly early detection of cancer, and use of interventional and diagnostic imaging modalities, recently opened new challenges to the urologist and scientists involved in CAMI. This resulted in the last five years in a very significant increase of research and developments of computer-aided urology systems. In this paper, we propose a description of the main problems related to computer-aided diagnostic and therapy of soft tissues and give a survey of the different types of assistance offered to the urologist: robotization, image fusion, surgical navigation. Both research projects and operational industrial systems are discussed

Engineering precision surgery: Design and implementation of surgical guidance technologies

In the quest for precision surgery, this thesis introduces several novel detection and navigation modalities for the localization of cancer-related tissues in the operating room. The engineering efforts have focused on image-guided surgery modalities that use the complementary tracer signatures of nuclear and fluorescence radiation. The first part of the thesis covers the use of “GPS-like” navigation concepts to navigate fluorescence cameras during surgery, based on SPECT images of the patient. The second part of the thesis introduces several new imaging modalities such as a hybrid 3D freehand Fluorescence and freehand SPECT imaging and navigation device. Furthermore, to improve the detection of radioactive tracer-emissions during robot-assisted laparoscopic surgery, a tethered DROP-IN gamma probe is introduced. The clinical indications that are used to evaluate the new technologies were all focused on sentinel lymph node procedures in urology (i.e. prostate and penile cancer). Nevertheless, all presented techniques are of such a nature, that they can be applied to different surgical indications, including sentinel lymph node and tumor-receptor-targeted procedures, localization the primary tumor and metastatic spread. This will hopefully contribute towards more precise, less invasive and more effective surgical procedures in the field of oncology. Crystal Photonics GmbH Eurorad S.A. Intuitive Surgical Inc. KARL STORZ Endoscopie Nederland B.V. MILabs B.V. PI Medical Diagnostic Equipment B.V. SurgicEye GmbH Verb Surgical Inc.LUMC / Geneeskund

New Mechatronic Systems for the Diagnosis and Treatment of Cancer

Both two dimensional (2D) and three dimensional (3D) imaging modalities are useful tools for viewing the internal anatomy. Three dimensional imaging techniques are required for accurate targeting of needles. This improves the efficiency and control over the intervention as the high temporal resolution of medical images can be used to validate the location of needle and target in real time. Relying on imaging alone, however, means the intervention is still operator dependent because of the difficulty of controlling the location of the needle within the image. The objective of this thesis is to improve the accuracy and repeatability of needle-based interventions over conventional techniques: both manual and automated techniques. This includes increasing the accuracy and repeatability of these procedures in order to minimize the invasiveness of the procedure. In this thesis, I propose that by combining the remote center of motion concept using spherical linkage components into a passive or semi-automated device, the physician will have a useful tracking and guidance system at their disposal in a package, which is less threatening than a robot to both the patient and physician. This design concept offers both the manipulative transparency of a freehand system, and tremor reduction through scaling currently offered in automated systems. In addressing each objective of this thesis, a number of novel mechanical designs incorporating an remote center of motion architecture with varying degrees of freedom have been presented. Each of these designs can be deployed in a variety of imaging modalities and clinical applications, ranging from preclinical to human interventions, with an accuracy of control in the millimeter to sub-millimeter range