Catálogo de publicaciones - libros

The performance of robotic assisted minimally invasive beating heart surgery is a challenging task due to the rhythmic motion of the heart, which hampers delicate tasks such as small vessel anastomosis. In this paper, a virtual motion compensation scheme is proposed for stabilizing images from the surgical site. The method uses vision based 3D tracking to accurately infer cardiac surface deformation and augmented reality for rendering a motion stabilized view for improved surgical performance. The method forgoes the need of fiducial markers and can be integrated with the existing master-slave robotic consoles. The proposed technique is validated with both simulated surgical scenes with known ground truth and data acquired from a TECAB procedure. The experimental results demonstrate the potential of the proposed technique in performing microscale tasks in a moving frame of reference with improved precision and repeatability.

Numerous studies have demonstrated the efficacy of image-guided needle-based therapy and biopsy in the management of prostate cancer. The accuracy of traditional prostate interventions performed using transrectal ultrasound (TRUS) is limited by image fidelity, needle template guides, needle deflection and tissue deformation. Magnetic Resonance Imaging (MRI) is an ideal modality for guiding and monitoring such interventions due to its excellent visualization of the prostate, its sub-structure and surrounding tissues. We have designed a comprehensive robotic assistant system that allows prostate biopsy and brachytherapy procedures to be performed entirely inside a 3T closed MRI scanner. We present a detailed design of the robotic manipulator and an evaluation of its usability and MR compatibility.

This paper introduces a new method for navigated spine surgery using a stereoscopic video see-through head-mounted display (HMD) and an optical tracking system. Vertebrae are segmented from volumetric CT data and visualized in-situ. A surgical drilling device is virtually extended with a mirror for intuitive planning of the drill canal, control of drill direction and insertion depth. The first designated application for the virtually extended drilling device is the preparation of canals for pedicle screw implantation in spine surgery. The objective of surgery is to install an internal fixateur for stabilization of injured vertebrae. We invited five surgeons of our partner clinic to test the system with realistic replica of lumbar vertebrae and compared the new approach with the classical, monitor-based navigation system providing three orthogonal slice views on the operation site. We measured time of procedure and scanned the drilled vertebrae with CT to verify accuracy of drilling.

Target registration error (TRE) refers to the uncertainty in localizing a point of interest after a point-based registration is performed. Common in medical image registration, the metric is typically represented as a root-mean-square statistic. In the late 1990s, a statistical model was developed based on the rigid body definition of the fiducial markers and the localization error associated in measuring the fiducials. The statistical model assumed that the fiducial localizer error was isotropic, but recently the model was reworked to handle anisotropic fiducial localizer error (FLE).

In image guided surgery, the statistical model is used to predict the surgical tool tip tracking accuracy associated with optical spatial measurement systems for which anisotropic FLE models are required. However, optical tracking systems often track the surgical tools relative to a patient based reference tool. Here the formulation for modeling the TRE of a surgical probe relative to a reference frame is developed mathematically and evaluated using a Monte Carlo simulation. The effectiveness of the statistical model is directly related to the FLE model, the fiducial marker design and the distance from centroid to target.

An important part of image-guided radiation therapy or surgery is registration of a three-dimensional (3D) preoperative image to two-dimensional (2D) images of the patient. It is expected that the accuracy and robustness of a 3D/2D image registration method do not depend solely on the registration method itself but also on the number and projections (views) of intraoperative images. In this study, we systematically investigate these factors by using registered image data, comprising of CT and X-ray images of a cadaveric lumbar spine phantom and the recently proposed 3D/2D registration method [1], [2]. The results indicate that the proportion of successful registrations (robustness) significantly increases when more X-ray images are used for registration.

In abdominal surgery, a laparoscopic ultrasound transducer is commonly used to detect lesions such as metastases. The determination and visualization of position and orientation of its flexible tip in relation to the patient or other surgical instruments can be of much help to (novice) surgeons utilizing the transducer intraoperatively. This difficult subject has recently been paid attention to by the scientific community [1,2,3,4,5,6]. Electromagnetic tracking systems can be applied to track the flexible tip. However, the magnetic field can be distorted by ferromagnetic material. This paper presents a new method based on optical tracking of the laparoscope and magneto-optic tracking of the transducer, which is able to automatically detect field distortions. This is used for a smooth augmentation of the B-scan images of the transducer directly on the camera images in real time.

This paper proposes an evaluation of a novel calibration method for an optically tracked oblique laparoscope. We present the necessary tools to track an oblique scope and a camera model which includes changes to the intrinsic camera parameters thereby extending previously proposed methods. Because oblique scopes offer a wide ‘virtual’ view on the surgical field, the method is of great interest for augmented reality guidance of laparoscopic interventions using an oblique scope.

The model and an approximated version are evaluated in an extensive validation study. Using 5 sets of 40 calibration images, we compare both camera models (i.e. model and approximation) and 2 interpolation schemes. The selected model and interpolation scheme reaches an average accuracy of 2.60 pixel and an equivalent 3D error of 0.60 mm.

Finally, we present initial experience of the presented approach with an oblique scope and optical tracking in a clinical setup. During a laparoscopic rectum resection surgery the setup was used to augment the scene with a model of the pelvis. The method worked properly and the attached probes did not interfere with normal procedure.

Navigated bronchoscopy has been developed by various groups within the last decades. Systems based on CT data and electromagnetic tracking enable the visualization of the position and orientation of the bronchoscope, forceps, and biopsy tools within CT data. Therefore registration between the tracking space and the CT volume is required. Standard procedures are based on point-based registration methods that require selecting corresponding natural landmarks in both coordinate systems by the examiner. We developed a novel algorithm for a fully automatic registration procedure in navigated bronchoscopy based on the trajectory recorded during routine examination of the airways at the beginning of an intervention. The proposed system provides advantages in terms of an unchanged medical workflow and high accuracy. We compared the novel method with point-based and ICP-based registration. Experiments demonstrate that the novel method transforms up to 97% of tracking points inside the segmented airways, which was the best performance compared to the other methods.

This paper presents an automatic surgical target and trajectory identification technique for planning deep brain stimulation (DBS) procedures. The probabilistic functional maps, constructed from population-based actual stimulating field information and intra-operative electrophysiological activities, were integrated into a neurosurgical visualization and navigation system to facilitate the surgical planning and guidance. In our preliminary studies, we compared the actual surgical target locations and trajectories established by an experienced stereotactic neurosurgeon with those automatically planned using our probabilistic functional maps on 10 subthalamic nucleus (STN) DBS procedures. The average displacement between the surgical target locations in both groups was 1.82mm with a standard deviation of 0.77mm. The difference between the surgical trajectories was 3.1 º and 2.3 º in the lateral-to-medial and anterior-to-posterior orientations respectively.

We present software engineering methods to provide free open-source software for MR-guided therapy. We report that graphical representation of the surgical tools, interconnectively with the tracking device, patient-to-image registration, and MRI-based thermal mapping are crucial components of MR-guided therapy in sharing such software. Software process includes a network-based distribution mechanism by multi-platform compiling tool CMake, CVS, quality assurance software DART. We developed six procedures in four separate clinical sites using proposed software engineering and process, and found the proposed method is feasible to facilitate multicenter clinical trial of MR-guided therapies. Our future studies include use of the software in non-MR-guided therapies.