Catálogo de publicaciones - libros

A novel manipulator is described for stabilizing fetus and preventing it from free-floating during the endoscopic intrauterine surgery. Minimally invasive endoscopic fetal surgery enables intrauterine intervention with reduced risk to the mother and fetus. We designed and fabricated a prototype of a fetus supporting manipulator equipped with a flexible bending/curving mechanisms and a soft balloon-based stabilizer. The flexible bending and curving mechanisms enable the stabilizer to reach the target sites within the uterus under an ultrasound-guidance. The balloon-based stabilizer could be inserted into the uterus with a small incision for entry. The accuracy evaluation showed that the maximum error of the curving mechanism was as small as 7 mm and the standard deviation of the bending mechanism was just 1.6°. In the experiments using a fetus model, the manipulator could be well controlled under ultrasound guidance and its curving mechanism with the balloon-based stabilizer could be clearly visualized during the implementation of fetus model supporting. The manipulator has the potential to be used in minimally invasive intrauterine surgery, though further improvements and experiments remain to be carried out.

Workflow recovery is crucial for designing context-sensitive service systems in future operating rooms. Abstract knowledge about actions which are being performed is particularly valuable in the OR. This knowledge can be used for many applications such as optimizing the workflow, recovering average workflows for guiding and evaluating training surgeons, automatic report generation and ultimately for monitoring in a context aware operating room.

This paper describes a novel way for automatic recovery of the surgical workflow. Our algorithms perform this task without an implicit or explicit model of the surgery. This is achieved by the synchronization of multidimensional state vectors of signals recorded in different operations of the same type. We use an enhanced version of the dynamic time warp algorithm to calculate the temporal registration. The algorithms have been tested on 17 signals of six different surgeries of the same type. The results on this dataset are very promising because the algorithms register the steps in the surgery correctly up to seconds, which is our sampling rate. Our software visualizes the temporal registration by displaying the videos of different surgeries of the same type with varying duration precisely synchronized to each other. The synchronized videos of one surgery are either slowed down or speeded up in order to show the same steps as the ones presented in the videos of the other surgery.

Teleoperated robots for minimally invasive surgery make surgeons loose direct contact with the patient. We are developing a hand-held, dexterous surgical robot that can be controlled with one hand only, while standing at the operating table. The instrument is composed of a master part (the handle) and a slave part (the tip). This work compares the performance of different control modes, i.e. different ways to map the degrees of freedom of the handle to those of the tip. We ask users to drive the tip along complex trajectories in a virtual environment, using the real master to drive a simulated slave, and assess their performance. Results show that, concerning time, users with no training in laparoscopy prefer a direct mapping of position and orientation, like in free hand motion. However, users trained in laparoscopy perform equally fast with our hand-held robot and, concerning precision, make a smaller number of errors.

In this paper, we present a left atrium registration system which utilizes a 3D intra-cardiac ultrasound catheter for (more than 700 times) and higher quality surface registration point collection than current systems and eventually improves the registration and . With better registration our system can greatly improve the ablation catheter navigation system which is being used in many hospitals to guide left atrium endocardium ablation procedure.

Scarless surgery is a new and very promising technique that can mark a new era in surgical procedures. We have created and validated a navigation system for endoscopic and transgastric access interventions in pilot studies. The system provides augmented visual feedback and additional contextual information by establishing a correspondence between the real time endoscopic ultrasound image and a preoperative CT volume using rigid registration. The system enhances the operator’s ability to interpret the ultrasound image reducing the mental burden used in probe placement. Our analysis shows that rigid registration is accurate enough to help physicians in endoscopic abdominal surgery where, by using preoperative data for context and real-time imaging for targeting, distortions that limit the use of only preoperative data can be overcome.

Aiming at real-time 3-D visualization of organ motion to navigate surgical procedures in MRI-guided surgery, a new 4-D MR imaging technique called “Adaptive 4-D Scan” has been proposed. The technique is designed to acquire a time series of volumetric 3-D images (4-D image) of cyclically moving organ, even in a low-field open-configuration MR scanner. A pre-operative 4-D image is acquired with respiratory phase parameter, which is monitored by using navigator-echo-based real-time tracking of the liver and diaphragm. During operation, the respiratory phase is again monitored in real-time, and a 3-D image, reflecting the current state of the target organ, is extracted from the pre-operative 4-D image and provided to physicians as a pseudo real-time 3-D image. We implemented Adaptive 4-D Scan into a 0.5 Tesla open-configuration clinical MRI system for intervention. Phantom and volunteer studies were performed to assess feasibility of this technique, in terms of image quality, imaging time and position accuracy of the imaged subject. A 4-D image (matrix: 256×128×10×8) of cyclically moving phantom was acquired in 719 s, and RMS position error between the imaged subject and the real subject was 2.3 mm, where the range of motion was 50 mm. 4-D image of the moving liver was also successfully acquired under near clinical condition. In conclusion, the study shows that the proposed method is feasible and has capability to provide real-time dynamic 3-D atlas for surgical navigation.

In minimally invasive surgery, a small field-of-view is often required for achieving a large magnification factor during micro-scale tasks such as coronary anastomosis. Constant change of the orientation and focal length of the laparoscope camera, however, is cumbersome and can impose extra visual and cognitive load to the operating surgeon in realigning the visual pathways and anatomical landmarks. The purpose of this paper is to investigate the use of fixational movements for robotic assisted minimal invasive surgery such that the perceived resolution of the foveal field-of-view is greater than the intrinsic resolution of the laparoscope camera. The proposed technique is based on super resolution imaging using projection onto convex sets. Validation with both phantom and data from totally endoscopic coronary artery bypass surgery is provided.

As interventional magnetic resonance imaging (iMRI) is getting closer to clinical practice, new means of visualization and navigation are required. We present an approach to create a virtual endoscopic view inside the human aorta in real-time. In our approach, defined cross-sectional slices are acquired and segmented in a highly optimized fashion. A geometric shape model is fit to the segmentation points and continuously updated during the intervention. The physician can then view and navigate inside the structure to plan the intervention and get immediate feedback about the procedure. As a component of this system, this work focuses on the segmentation of the cross-sectional images and the fitting of the shape model. We present a real-time 2D segmentation implementation for this application domain and a model fitting scheme for a generalized cylinder (GC) model. For the latter we employ a new scheme for choosing the local reference frame.

We describe scripting facilities to create medical animations for intervention planning based on medical volume data and derived segmentation information. A data independent scripting language has been developed to separate animation scripts from imaging data. The scripting facilities are adaptive and allow to reuse one script to create animations for many different patients. With expressive animations, we support the individual planning process, the preoperative documentation as well as discussions between medical doctors, for example in a tumor board. We also discuss the enhancement of interactive explorations with animations generated on the fly.

We present a model for the optimal placement of mono- and bipolar probes in radio-frequency (RF) ablation. The model is based on a numerical computation of the probe’s electric potential and of the steady state of the heat distribution during RF ablation. The optimization is performed by minimizing a temperature based objective functional under these constraining equations. The paper discusses the discretization and implementation of the approach. Finally, applications of the optimization to artificial data and a comparison to a real RF ablation are presented.