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Biomedical subjects

K Radermacher

Publications and source records attributed to K Radermacher.

27 records · Page 2Linked to original sources
PubMed1998

Computer assisted orthopaedic surgery with image based individual templates.

Recent developments in computer assisted surgery offer promising solutions for the translation of the high accuracy of the preoperative imaging and planning into precise intraoperative surgery. Broad clinical application is hindered by high costs, additional time during intervention, problems of intraoperative man and machine interaction, and the spatially constrained arrangement of additional equipment within the operating theater. An alternative technique for computerized tomographic image based preoperative three-dimensional planning and precise surgery on bone structures using individual templates has been developed. For the preoperative customization of these mechanical tool guides, a desktop computer controlled milling device is used as a three-dimensional printer to mold the shape of small reference areas of the bone surface automatically into the body of the template. Thus, the planned position and orientation of the tool guide in spatial relation to bone is stored in a structural way and can be reproduced intraoperatively by adjusting the position of the customized contact faces of the template until the location of exact fit to the bone is found. No additional computerized equipment or time is needed during surgery. The feasibility of this approach has been shown in spine, hip, and knee surgery, and it has been applied clinically for pelvic repositioning osteotomies in acetabular dysplasia therapy.

Acetabulum↗
PubMed1996

A desktop image processing system for computer-assisted orthopedic surgery (DISOS).

Within the framework of our research activities in orthopedic surgery a PC-based imageprocessing system for the processing of x-ray computer-tomographic data has been developed. The system is used as a work platform for the investigations concerning interaction modalities, strategies and techniques for an efficient planning and execution of surgical interventions in orthopedic surgery by means of individual templates. The method of individual templates has been presented in /1,2/ and will not be subject of this paper.

Computer Peripherals↗
PubMed1996

The influence of LCD shutter glasses on spatial perception in stereoscopic visualization.

For a general establishment of stereoscopic visualisation systems in clinical routine a fundamental analysis of the influence of technical, optical and physiological parameters onto visual spatial perception seems to be necessary to achieve an optimisation of the existing devices. As one important component of these systems we perform studies on the influence of LCD Shutter glasses on the individual binocular perception. The developed shutter system, the initial experiments and their results are presented.

Computer Simulation↗
PubMed1996

Using human factor analysis and VR simulation techniques for the optimization of the surgical worksystem.

The introduction of minimal invasive operating techniques into the conventional surgical worksystem, requires a fundamental analysis of the resulting problems. Based on ergonomic investigations, concerning working postures, static holding work and task sequence analysis, bottlenecks of workplace design can be demonstrated. As a contribution to the optimization of workplace design, the development of a CAD-based VR simulation environment with an integrated anthropometric man-model, as a very useful tool for anthropometric system design is presented.

Computer Simulation↗
PubMed1996

Three-dimensional versus two-dimensional video endoscopy. A clinical field study in laparoscopic application.

Stereoscopic visualisation systems are available for the medical application in clinical routine, especially in the field of endoscopic or minimal invasive surgery. As we have shown in laboratory studies in 1991 the use of stereoscopic visualisation systems leads to a significant improvement of endoscopic manipulation. A broader diffusion of these systems in clinical routine will be based on quantitative evaluation of the influence of stereoscopic visualisation systems on the intervention. As a first approach we performed a clinical field study to compare 2D and 3D video endoscopy in laparoscopic interventions in urological surgery.

Computer Simulation↗
PubMedDate not supplied

[Intraoperative 3D reconstruction of the PMMA plug for computer-assisted revision of total hip arthroplasty based on 2D X-ray images].

AIM: Computer-assisted cement removal out of the femoral medullary canal requires the exact definition of the plug's shape within a 3D coordination system. Aiming at a sufficiently precise reconstruction based on segmentation of just a few 2D X-ray images a special mathematic procedure is needed for automatic surface interpolation. The geometric specification of the resulting virtual model should take into account the characteristic geometry of the navigated tools in order to achieve the best possible removal. METHOD: Studies were performed on anatomic specimens of entire human femora, that underwent cemented THA before being cut every 5 mm. The cross-sections were scanned at the high resolution of 600 dpi. Segmentation of the cement was performed with the help of a virtual deformable template and was both used for simulation of X-ray projections from various points of view and for validation of the reconstructed 3D model. By this means systematic errors such as those possible during X-ray acquisition, tracking or segmentation could be avoided and the precision of the procedure could be measured exclusively. RESULTS: With increasing number of X-rays the distance from the reconstructed 3D model to the original could continuously be reduced. Using only two x-rays a maximum error was measured with 6.5 mm, whereas 5 pictures taken from different angles showed to be enough to ensure an error below 1 mm in the distal part of the femur. By the use of 6 or more pictures no significant improvement could be attained. CONCLUSION: The innovative procedure is essential for future 2D image-based fluoroscopic navigation of PMMA removal and bears the options of computer-controlled and robotic material working, respectively.

Algorithms↗