Catálogo de publicaciones - libros

For quantitative C-arm fluoroscopy, we have developed a unified mathematical framework to tackle the issues of intra-operative calibration, pose estimation, correspondence and reconstruction, without the use of optical/electromagnetic trackers or precision-made fiducial fixtures. Our method uses randomly distributed unknown points in the imaging volume, either naturally present or induced by randomly sticking beads or other simple markers in the image pace. After these points are segmented, a high dimensional non-linear optimization computes all unknown parameters for calibration, C-arm pose, correspondence and reconstruction. Preliminary phantom experiments indicate an average C-arm tracking accuracy of 0.9 and a 3D reconstruction error of 0.8 , with an 8 region of convergence for both the AP and lateral axes. The method appears to be sufficiently accurate for many clinical applications, and appealing since it works without any external instrumentation and does not interfere with the workspace.

The objective of this paper is to develop an outer sheath for flexible endoscopic manipulators. This sheath can switch two states including flexible and rigid, and make a rigid curved path for inserting manipulators. The flexible mode can be curved into a required shape. The rigid mode can hold the shape of the sheath, and then keep the path for instruments. Through the managed path, the flexible manipulators become easy to reach the target. We proposed a serial multi joint model to realize the flexible mechanism. This model is composed of a set of frame units which are connected serially. Each unit can be rotated to a given angle around the center of the joint. We developed a slider-link mechanism and a gear stopper controlled by air pressure for rigid mode. We designed and fabricated the prototype with a diameter of 16mm and length of 290mm. The experiment showed that the device could be switched from the flexible mode to the rigid mode when the air pressure was over 150kPa, and each joint could hold its angle against the maximum 400mNm. The phantom experiment showed that the flexible devices are possible to transmit the wire tension to the endpoint of the manipulator without changing the curving shape with by the developed outer sheath device.

This paper describes the development of a robotic assistance system for image guided operations. To minimize operation time, a multimodal user interface enables freehand robotic manipulation of an extracorporeal stereoscopic digital camera (exoscope) and an endoscope. The surgeon thereby wears a head-mounted unit with a binocular display, a head tracker, a microphone and earphones. Different view positioning and adjustment modes can be selected by voice and controlled by head rotation while pressing a miniature confirmation button with a finger. Initial studies focused on the evaluation and optimization of the intuitiveness, comfort and precision of different modes of operation, including a user test with neurosurgeons in a virtual reality simulation. The first labtype of the system was then implemented and demonstrated in the operating room on a phantom together with the clinical partners.

The excellent soft tissue contrast of Magnetic Resonance Imaging (MRI) has encouraged the development of MRI compatible systems capable of combining the advantages of robotic manipulators with high quality anatomical images. Continuing this development, a new five DOF prostate biopsy manipulator has been designed for use inside a closed 1.5T MRI scanner. Space constraints in the bore and the current trend to restrict field strength exposure for operators indicate that a master-slave configuration is ideal for controlling the robotic system from outside the bore. This system has been designed to work with piezoceramic motors and optical encoders placed inside or near the field of view of the scanner, using real time image guidance for targeting biopsies to specific lesions in the prostate. MRI tests have been performed to prove the feasibility of this concept and a one DOF proof-of-concept test rig implementing closed loop position control has been tested and is presented here. A first prototype of the slave manipulator has been designed and manufactured incorporating this new technology.

In robot-assisted laparoscopic surgery, an endoscopic camera is used to control the motion of surgical instruments. With this minimally invasive surgical (MIS) technique, every instrument has to pass through an insertion point in the abdominal wall and is mounted on the end-effector of a surgical robot which can be controlled by visual feedback. To achieve an accurate vision-based positioning of laparoscopic instruments, we introduce the motion constraint in MIS which is based on the location of out-of-field of view insertion points. The knowledge of the (image of the) insertion point location is helpful for real-time image segmentation issues, particularly to initiate the search for region seeds corresponding to the instruments. Moreover, with this ”eye-to-hand” robot vision system, visual servoing is a very convenient technique to automatically guide an instrument but it requires the velocity screw to be expressed in the appropriate frame. Then, the location of the insertion point is seen as the main part of the larger problem of determining the overall transformation between the camera and the robot end-effector frame. This is achieved thanks to a novel algorithm for the pose determination of cylindrical-shaped instruments. With the proposed method, the location of insertion points can be recovered, on-line, with no marker, without any knowledge of robot kinematics and without an external measurement device.

The use of a robotized camera holder in laparoscopic surgery allows a surgeon to control the endoscope without the intervention of an assistant. Today, the orders that the surgeon can give to robotized camera holders remain limited. In order to provide higher level interactions between the surgeon and a robotized camera holder, we have developed a new method for the automatic tracking of laparoscopic instruments which works in near real-time. The method is based on the measurement of the 3D positions of the insertion points of the instruments in the abdominal cavity and a simple shape model of the laparoscopic instruments. We present the results of our first experimentation on a cadaver.

We developed a combined system of tumor detection by 5-ALA-induced PpIX fluorescence and precise ablation by micro laser for the first time, with an automatic focusing and robotic scanning mechanism for the brain surface. 5-ALA accumulates on tumors to be metabolized to become PpIX that is a fluorescent. Intra-operative detection of 5-ALA induced PpIX fluorescence provides useful information for tumor detection. The wavelength of the micro laser is 2.8 m close to the absorption band of water. This laser is effective only on the surface of brain tissue, enabling precise ablation at the boundary between tumor and normal tissue identified by intra-operative 5-ALA induced fluorescence. Combination tests of the fluorescence measurement and the laser ablation were performed, and it was possible to extract the area with fluores-cence appropriately from the measurement data, and the micro laser with automatically scanning selectively ablated the extracted area.

The problem of positioning mobile C-arms, e.g. for down the beam techniques, as well as repositioning during surgical procedures currently requires time, skill and additional radiation. This paper uses a Camera-Augmented Mobile C-arm (CAMC) to speed up the procedure, simplify its execution and reduce the necessary radiation. For positioning the C-arm in down-the-beam position, the pre-operative diagnostic CT is used for defining the axis. Additional CT visible markers on patient’s skin allow the CAMC’s optical camera to compute the C-arm’s pose and its required displacement for positioning. In the absence of electronically controlled mobile C-arms, the system provides step-by-step guidance to surgical staff until the final position is achieved. At this point, the surgeon can acquire an X-ray to ensure the correct positioning. In the case of intra-operative repositioning, no pre-operative CT is required. X-ray/Optical markers allow the visual servoing algorithm to guide the surgical staff in C-arm repositioning using CAMC’s optical camera. This work paves the path for many possible applications of visual servoing in C-arm positioning and in surgical navigation. Experiments on phantom and a cadaver study demonstrate the advantages of the new methods.

In minimally invasive tumor resection, the desirable goal is to perform a minimal but complete removal of cancerous cells. In the last decades interventional nuclear medicine probes supported the detection of remaining tumor cells. However, scanning the patient with an intraoperative probe and applying the treatment are not done simultaneously. The main contribution of this work is to extend the one dimensional signal of a beta-probe to a four dimensional signal including the spatial information of the distal end of the probe. We generate a color encoded surface map of the scanned activity and guide any tracked surgical instrument back to the regions with measured activity. For navigation, we implement an augmented reality visualization that superimposes the acquired surface on a visual image of the real anatomy. Alternatively, a simulated beta-probe count rate in the tip of a tracked therapeutic instrument is simulated showing the count number and coding it as an acoustic signal. Preliminary tests were performed showing the feasibility of the new designed system and the viability of such a three dimensional intraoperative molecular imaging modality.

This paper introduces a novel mechanism for surgical robotic systems to generate human arm-like compliant motion. The mechanism is based on the idea of the equilibrium point control hypothesis which claims that multi-joint limb movements are achieved by shifting the limbs’ equilibrium positions defined by neuromuscular activity. The equilibrium point control can be implemented on a robot manipulator by installing two actuators at each joint of the manipulator, one to control the joint position, and the other to control the joint stiffness. This double-actuator mechanism allows us to arbitrarily manipulate the stiffness (or impedance) of a robotic manipulator as well as its position. Also, the force at the end-effector can be estimated based on joint stiffness and joint angle changes without using force transducers. A two-link manipulator and a three-link manipulator with the double-actuator units have been developed, and experiments and simulation results show the potential of the proposed approach. By creating the human arm-like behavior, this mechanism can improve the performance of robot manipulators to execute stable and safe movement in surgical environments by using a simple control scheme.