Biomedical subjects

J Raczkowsky

Publications and source records attributed to J Raczkowsky.

14 recordsLinked to original sources

PubMed2001

Statistical analysis of the morphology of three-dimensional objects and pathologic structures using spherical harmonics.

To support diagnosis and therapy, it is a fundamental aim of medical image processing to describe morphological characteristics of pathological structures or image objects in general. Different authors propose quantitative methods of description like bounding boxes[1], fourier descriptors[2] or contour moments[3]. Unfortunately, these methods either don't supply a complete, respectively precise description of the object or only operate on two-dimensional images. Among the range of application are systems to classify lung nodules [4] or to help the diagnosis of brain tumors [5]. In this paper we present a method to analyze the morphology or shape of any three-dimensional object in order to describe it mathematically well-defined. We show how the description can be used to perform statistical operations on morphologies. The method presented in this paper was developed to assist the planning of craniofacial surgery. We analyze the shape of a given set of skull CT-data and use the mathematical description to statistically calculate the average shape of the skulls.

Cephalometry↗

PubMed2001

Virtual simulation system for collision avoidance for medical robot.

For the collision avoidance with a medical robot with 6 DOF a virtual simulation system is presented. Manipulator and obstacles are modelled by geometric primitives. Collisions are detected in the Cartesian workspace by hierarchical distance computation based on the given CAD model. The application initially being addressed is maxillofacial surgery, where the safety of the patient is the main requirement,because of the closeness to vital parts. The simulation system allows the surgeon to check up the trajectory of the robot before the current operation begins.

Computer Graphics↗

PubMed2001

Intraoperative visualization of surgical planning data using video projectors.

The Institute for Process Control and Robotics has developed a new system using projector based augmented reality for the intraoperative visualization of preoperatively defined surgical planning data. Projector based augmented reality in medical applications represents a new field of research and gives an alternative solution to the commonly used Head Mounted Display technology. Moreover, the projector is not only used for visualization, but also for registration of the patient without the usage of invasive fiducial techniques as e.g. screw markers or frames. Recent results showed an achieved accuracy of +/- 1.5 mm which roughly meets clinical demands.

Data Display↗

PubMed2001

An endoscopic navigation system.

Endoscopy is an important procedure for the diagnostic and therapy of various pathologies. We develop extensive and automated systems for this field. Due to application of these new systems, a patient is subject to considerably less strains, as opposed to prevailing commercial systems. The capability of such instruments, unlike the presently used systems, to independently follow anatomical peculiarities of the body means also a reduced risk of complications for a patient. A further advantage is that difficult to access regions deep inside the body, like the small intestine or peripheral parts of the bronchial tubes, can thus be reached. We use a complex navigation system for our new endoscopic system.

Computer Simulation↗

PubMed2000

3D norm data: the first step towards semiautomatic virtual craniofacial surgery.

When planning craniofacial surgical interventions, the ideal appearance of the patient is very important. The final appearance should be as close as possible to that which the patient would have if he/she were without defects. Our first step towards achieving this is to build a database containing sets of three-dimensional CT images that allows for comparison of the shape of a patient with defects to the typical shape of an age- and sex-matched "average" person without defects. We started to collect CT data from patients without pathologies and, in co-operation with two radiology institutes (in Mannheim and Heidelberg), over 100 CT data sets have now been collected and classified according to age and sex. It is necessary to choose an appropriate statistical method to calculate the norm data from the different data sets. Based on the statistical method, an age- and sex-matched "average" model of the anatomy will be created.

Adolescent↗

PubMed2000

[Computer-assisted oral, maxillary and facial surgery].

BACKGROUND: Methods from the area of virtual reality are used in oral and maxillofacial surgery for the planning and three-dimensional individual simulation of surgeries. SIMULATION: In order to simulate complex surgeries with the aid of a computer, the diagnostic image data and especially various imaging modalities (CT, MRT, US) must be arranged in relation to each other, thus enabling rapid switching between the various modalities as well as the viewing of mixed images. Segmenting techniques for the reconstruction of three-dimensional representations of soft-tissue and osseous areas are required. We must develop ergonomic and intuitively useable interaction methods for the surgeon, thus allowing for precise and fast entry of the planned surgical intervention in the planning and simulation phase. SURGERY: During the surgical phase, instrument navigation tools offer the surgeon interactive support through operation guidance and control of potential dangers. This feature is already available today. Future intraoperative assistance will take the form of such passive tools for the support of intraoperative orientation as well as so-called tracking systems (semi-active systems) which accompany and support the surgeons' work. The final form are robots which execute specific steps completely autonomously. DISCUSSION: The techniques of virtual reality keep gaining in importance for medical applications. Many applications are still being developed or are still in the form of a prototype. However, it is already clear that developments in this area will have a considerable effect on the surgeon's routine work.

Computer Simulation↗

PubMed2000

Intuitive operation planning based on force feedback.

In the craniofacial surgery image-slices obtained from tomographies are used for planning and simulation of surgical interventions. Using these image-slices three-dimensional geometric models can be reconstructed, representing bones and soft tissue. However, for planning complex surgical interventions simulation methods are needed additionally to the pure visualisation. Exemplary, planning a Frontal Orbital Advancement (FOA) operation the cutting trajectories, their depth and orientation in each point, the drill hole, the position, orientation and deformation of bones, etc. are the point of interest. Especially for intraoperative execution supported by navigation systems or robots. In order to be able to plan such complex interventions with the help of computers, geometrical and haptical models must be generated from the image-slices. On the one hand these models represent the anatomical structures exactly, on the other hand they are needed for the simulation of the different activities, which have to be performed during the surgical intervention like drilling, milling, deforming, positioning, etc. Beside the geometrical and haptical models methods for interactions must be supplied to the physician for an accurate and intuitive planning of the surgical intervention. We developed such an operation planning system which is already used in clinical practise in Heidelberg.

Artificial Intelligence↗

PubMed2000

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.

Algorithms↗

PubMed2000

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 Graphics↗

PubMed2000

Texture mapping based visualisation methods for the manipulation of CT data: interaction and ergonomics.

The manipulation of large CT datasets needs fast visualisation methods for a comfortable user interaction. Modern visualisation techniques make use texture hardware in graphics workstations extensively. In the following we will present an interactive tool for the positioning of anatomical landmarks in CT datasets of non-pathological children. The tool includes a fast visualisation of CT cross sections based on a texture mapping technique and an interactive three-dimensional view of the segmented CT dataset.

Cephalometry↗

PubMed2000

Synthesis of CAD/CAM, robotics and biomaterial implant fabrication: single-step reconstruction in computer-aided frontotemporal bone resection.

The preoperative manufacturing of individual skull implants, developed by an interdisciplinary research group at Ruhr-University Bochum, is based on the use of titanium as the most common material for implants at present. Using the existing technology for materials that can be milled or moulded, customized implants may be manufactured as well. The goal of the study was to examine biodegradable materials and to evaluate the practicability of intraoperative instrument navigation and robotics. Data acquisition of an adult sheep's head was performed with helical computer tomography (CT). The data were transferred onto a computer aided design/computer aided manufacturing system (CAD/CAM system), and two complex defects in the frontotemporal skull were designed. Standard individual titanium implants were milled for both of the defects. Additionally, for one of the defects a resection template, as well as a mould for the biodegradable poly(D,L-lactide) (PDLLA) implant, were fabricated by the CAD/CAM system. A surgeon carried out the first bone resection (#1) for the prefabricated titanium implant using the resection template and an oscillating saw. The robot system Stäubli RX90CR, modified for clinical use, carried out the other resection (#2). Both titanium implants and the PDLLA implant were inserted in their respective defects to compare the precision of their fit. A critical comparison of both implant materials and both resection types shows that fabrication of a PDLLA implant and robot resection are already possible. At present, the titanium implant and resection using a template are more convincing due to the higher precision and practicability.

Absorbable Implants↗

PubMed1998

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.

Algorithms↗

PubMed1997

[Robotics in oral and maxillofacial surgery. Possibilities, chances, risks].

Robot systems are being tested in stereotactic neurosurgical interventions, orthopedic surgery of the hip or knee and advancal endoscopic systems for minimally invasive surgery. In contrast to most industrially manufactured products, objects for medical treatment are characterized by plasticity as well as by complex and individual forms. Thus, features of robots in this field have to be further developed in terms of advanced sensory and specific micromotoric systems. Safety and cooperation between surgeon and robot on the patient in the operating room have to be guaranteed. Extensive three-dimensional diagnosis, computer-aided planning and simulation of the intervention as well as sensory systems that monitor the actual performance of the operation are mandatory parts of this concept. In our interdisciplinary study, we aim to examine whether a robot-given a complete preoperative planning and simulation procedure-is able to perform certain surgical operations more precisely than the surgeon. Examples are drilling with depth control, shaping of bone surface by milling, sawing with defined depth in cranial osteotomies, defined preparation of implant sites and the positioning and insertion of dental and other surgical implants, whereby autonomous employment of the robot is not that which is aspired to in these interventions but rather the interactive support of the surgeon.

Humans↗

PubMed1996

A communication system supporting simultaneous planning and execution in cranio-maxillo-facial surgery.

This paper describes the development of a system for simultaneous planning and execution of surgical operations in the cranio-maxillo-facial area. Simultaneous planning and execution is the process of taking an implicit task description, planning a sequence of explicit execution commands (e.g. for robots) and monitoring their execution. As the execution planning process is run completely on-line, during the execution of the assembly task, the planning process is highly reactive, based on sensor information about the robot's present environment. In order to meet the problem that medical data are usually complex and need time-consuming preprocessing, an appropriate architecture for evaluating sensor data has been developed. In this paper, a detailed presentation of the phases of execution planning and sensor data evaluation is given. As an example, the execution of a LeFort I osteotomy is presented.

Computer Communication Networks↗