Safety in computer assisted surgery.

Today, surgeons accept computer assisted technologies as important tools to enhance the treatment of a patient. The positive impact and acceptance of computer assisted technologies could be increased to a great extent, if all methods and devices used for diagnosis and treatment of a patient are better co-ordinated and more finely tuned. Often computer assisted treatments cannot be performed due to a lack of communication between hospital departments, useless patient data, deficient interfaces, etc. Risks for the patient and potential errors within the treatment are often unrecognised, as up to now the safety of computer integrated surgery is only product-, device and security oriented. We have developed a new approach for a safety architecture, which includes safety aspects considering patients, users, interdependencies and interactions of computer assisted methods and apparatuses.

Clinical evaluation of a highly accurate algorithm for CT bone contour segmentation.

Planning, visualisation and intraoperative navigation in a robot assisted environment for craniofacial surgery require highly accurate methods for the segmentation of bone structures in CT data. Clinical systems are still based on time consuming interactive methods like the seed-point segmentation. Faster methods with no need for interactivity lacks in precision. In the following we will present an automatic and highly accurate algorithm for the segmentation of bone contours in CT data. It is based on an algorithm for the automatic calculation of a grey-value tissue relation model for CT and MRI data.

A real-time CORBA based system architecture for robot assisted craniofacial surgery.

We present the concept of a system architecture for the computer aided craniofacial surgery. The architecture is based on CORBA, an industrial standard specification for the development of distributed applications. Our concept includes a fundamental behaviour oriented communication model and some fundamental software safety considerations. We've developed a standard library for the integration of new services and devices into our system architecture. It decreases development time noticeably. We tested the performance and usability of our concept on an evaluation set up consisting of a surgery robot system, an infrared navigation system, a force-torque sensor and a visualisation software, obtaining excellent results. Future work will consist in the integration of further devices and the extension of our safety concept. An accurate clinical evaluation will take place continuously.

Computer aided planning device for preoperative bending of osteosynthesis plates.

In craniofacial surgery bone fractures and repositioned bone segments often have to be fixed by titanium miniplates. In clinical routines the surgeon has to fit each miniplate t be used to the individual bone structure of the patient: bending and fitting of a miniplate must frequently be repeated several times. Often up to twenty minutes are required to achieve the best fit of a single osteosynthesis plate. As a patient usually receive several miniplates for bone fixture, he will be exposed to long anaesthesia. In co-operation with the surgeons of the Clinic of Maxillofacial surgery at the University of Heidelberg we have conceived a planning system for the preoperative positioning of miniplates on a model of the patient's skull. The appropriate bending is computed and the bending data are stored for later use by a bending device and an intraoperative positioning aid. The principles of our computer-aided tool are presented in this paper.

A system for robot assisted maxillofacial surgery.

In maxillofacial surgery the quality of the surgical outcome mainly depends on the experience of the operating surgeon. Thus we intend to support the surgeon before and during surgery in order to enhance the surgical results. On the one hand this implies the use of image processing, three dimensional modelling techniques and visualization techniques of medical image data, on the other hand planning systems, intraoperative navigation devices and surgical robots are needed. In this paper a complex expert system is presented, which uses a planner for generating treatment plans, an infrared navigation for monitoring both patient, robot, and surgical tool, and a surgical robotic system in order to work on bone. Special stress is laid on the architecture of the planning system, the structure of the treatment plans, and the intraoperative communication protocols.

Planning and simulation of medical robot tasks.

Complex techniques for planning and performing surgery revolutionize medical interventions. In former times preoperative planning of interventions usually took place in the surgeons mind. Today's new computer techniques allow the surgeon to discuss various operation methods for a patient and to visualize them three-dimensionally. The use of computer assisted surgical planning helps to get better results of a treatment and supports the surgeon before and during the surgical intervention. In this paper we are presenting our planning and simulation system for operations in maxillo-facial surgery. All phases of a surgical intervention are supported. Chapter 1 gives a description of the medical motivation for our planning system and its environment. In Chapter 2 the basic components are presented. The planning system is depicted in Chapter 3 and a simulation of a robot assisted surgery can be found in Chapter 4. Chapter 5 concludes the paper and gives a survey about our future work.

Knowledgebased segmentation.

The segmentation of medical images like CT or MRI scans represents a great challenge to researchers in computer vision, due to the variability of the individual anatomy and the different characteristics of the scanning systems. As an anatomical knowledge base improves the recognition of structures in CT or MRI scans, we chose a knowledge based segmentation in our approach, which will be explained in the following.

Resistance to occlusion: sensitivity to induced blur in 6- to 12-month-old infants.

BACKGROUND: Resistance to occlusion and fix and follow are often used to make inferences about the acuity of young children. In this study, the acuity of 6- to 12-month-old infants was degraded monocularly to elicit resistance to occlusion or loss of fixation. METHODS: Occlusion foils and optical blur were used to simulate monocular acuity reduction. Two different targets, a mechanical rabbit and a "flickering" light were used for fixation. RESULTS: More infants resisted occlusion when viewing the rabbit than the light. Resistance to occlusion was observed in the majority of infants when acuity was degraded to the level expected for 6 to 12-month-old infants (20/80-20/300). CONCLUSIONS: The sensitivity of resistance to occlusion is influenced by the test target and if an interesting target is used, resistance to occlusion may be a useful tool for detecting interocular acuity differences in 6- to 12-month-old infants.