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Biomedical subjects

M Walter

Publications and source records attributed to M Walter.

268 records · Page 15Linked to original sources
PubMedDate not supplied

CT-guided lumbar sympathectomy: results and analysis of factors influencing the outcome.

PURPOSE: To prospectively analyze the effectiveness of computed tomography-guided percutaneous lumbar sympathectomy (CTLS) in patients with peripheral arterial occlusive disease in relation to angiographic findings and vascular risk factors. METHODS: Eighty-three patients were treated by CTLS. After clinical evaluation of the risk profile and diagnostic intraarterial digital subtraction arteriography, 14 patients underwent unilateral, and 69 bilateral one-level treatment. Follow-up studies took place on the day following the intervention, after 3 weeks, and after 3 months. RESULTS: A total of 152 interventions were performed in 83 patients. After 3 months, clinical examination of 54 patients (5 patients had died, 24 were lost to follow-up) revealed improvement in 46% (25/54), no change in 39% (21/54), and worsening (amputation) in 15% (8/54). There was no significant statistical correlation among any of the analyzed factors (diabetes mellitus, arterial hypertension, smoking, hyperlipidemia, obesity, hyperuricemia, number of risk factors, ankle-arm index, and angiography score) and the outcome after CTLS. Three major complications occurred: one diabetic patient developed a retroperitoneal abscess 2 weeks after CTLS, and in two other patients ureteral strictures were detected 3 months and 2 years after CTLS, respectively. CONCLUSION: As no predictive criteria for clinical improvement in an individual patient could be identified, CTLS, as a safe procedure, should be employed on a large scale in patients who are unsuitable for treatment by angioplasty or revascularization.

Adult↗
PubMedDate not supplied

The correlation grid: analysis of synchronous spiking in multi-dimensional spike train data and identification of feasible connection architectures.

This paper presents a visualization technique specifically designed to support the analysis of synchronous firings in multiple, simultaneously recorded, spike trains. This technique, called the correlation grid, enables investigators to identify groups of spike trains, where each pair of spike trains has a high probability of generating spikes approximately simultaneously or within a constant time shift. Moreover, the correlation grid was developed to help solve the following reverse problem: identification of the connection architecture between spike train generating units, which may produce a spike train dataset similar to the one under analysis. To demonstrate the efficacy of this approach, results are presented from a study of three simulated, noisy, spike train datasets. The parameters of the simulated neurons were chosen to reflect the typical characteristics of cortical pyramidal neurons. The schemes of neuronal connections were not known to the analysts. Nevertheless, the correlation grid enabled the analysts to find the correct connection architecture for each of these three data sets.

Action Potentials↗
PubMedDate not supplied

Visualisation of synchronous firing in multi-dimensional spike trains.

The gravity transform algorithm is used to study the dependencies in firing of multi-dimensional spike trains. The pros and cons of this algorithm are discussed and the necessity for improved representation of output data is demonstrated. Parallel coordinates are introduced to visualise the results of the gravity transform and principal component analysis (PCA) is used to reduce the quantity of data represented whilst minimising loss of information.

Action Potentials↗
PubMedDate not supplied

Injuries in soccer.

The injury profile of a professional soccer team from the 1976 to 1977 season is compiled in this report. Injuries are spread across all of the playing positions, with midfielders and forwards being most prone to injury. During the entire season of this report, 60 injuries were encountered, 35 during game situations and 25 in practice. The most common injuries noted were foot and ankle sprains, but muscle strains were also frequent. Most injuries were of a minor variety. Seventeen injuries resulted in missed games while 46 injuries resulted in no games being missed. Only one player had an injury which did not allow him to return to play during the season. Although little is written in the American literature concerning soccer injuries, it does appear that the injury potential is much less when compared with that of football. The rapid increase in interest in this sport will require physicians and trainers to become familiar with its specific needs in order to render adequate care and participate in injury prevention programs.

Ankle Injuries↗
PubMedDate not supplied

[Possibilities and limits of automatic detection of pathologic intracranial pressure waves with FFT].

Owing to the existence of "reserve spaces" varying individually in extent and expressed by the term compliance, space-consumption intracranial processes do not raise the intracranial pressure (ICP) primarily. Only when this compliance has been exhausted may ICP rise dramatically and may rapidly reach dangerously high levels. It has been shown in the past that "anticipatory" initiation of ICP-reducing measures--i.e. very early in the development of increasing mean ICP--may greatly benefit patient outcome. To recognize an imminent ICP crisis, the available compliance needs to be known. The classical method for determining this latter is the bolus test, which, however, has the disadvantage of being discontinuous and associated with the risk of infection. Another, less invasive and continuous, option is the recognition of pathological intracranial pressure waves. However, recognition of such patterns requires specialized knowledge, that is not widely available. Since, however, knowledge of the compliance is of general importance for intensive care, the idea of developing a PC-based automated system for the identification of pathological waves was followed up. During the course of our basic research effort, we investigated the suitability of the fast Fourier transformation (FFT) algorithm for this purpose. We were able to show that while the FFT is theoretically useful for the detection of pathological intracranial waves, its shortcomings in terms of its sensitivity to extraneous signals (noise) (of considerable importance for biological data handling) and errors in correctly estimating the amplitudes of pathological waves (of great importance for clinical evaluation) make FFT appear less than optimally suitable for this purpose.

Fourier Analysis↗
PubMedDate not supplied

Design and production of dental prosthetic restorations: basic research on dental CAD/CAM technology.

Dental prosthetic restorations (crowns and FPDs) are currently produced mainly by conventional dental technology methods. The automation of the production process can be achieved by the use of CAD/CAM techniques. In addition, it has become possible to use materials that previously could not be processed for technical reasons or could not be processed economically, especially high-performance ceramics. Although CAD/CAM methods for producing fixed restorations are of increasing interest, little information has been published about their mode of operation and functionality. To date, studies have focused mostly on special systems. However, basic studies are lacking. Basic research on the most important aspects of CAD/CAM fixed dental restorations from the viewpoint of production, information technology, and dentistry/dental technology are the subject of a current research project. The aim of this study is the presentation of preliminary results. The CAD/CAM process for fixed restorations was analyzed and broken down into single steps. In order to examine the influence of the single steps in the process chain, a computer test model with the teeth of the maxilla and mandible in static occlusion was developed and reverse engineered. While producing the test model, fundamental knowledge regarding the manufacturing of dental restorations with functional occlusal surfaces was gained. The intersection of the maxillary and mandibulary occlusal surfaces allows the qualitative analysis of occlusal contacts analogous to the conventional technique. Furthermore, a quantitative assessment of the size of the occlusal contacts and the measurement of intersection is possible.

Analog-Digital Conversion↗
PubMedDate not supplied

[Surgical treatment of lung cancer: therapy or palliative?].

In spite of the revolutionary innovations concerning diagnostic and intensive care techniques as well as better understanding of tumor biology during the last decade, rates of resection and long-term survival in bronchogenic carcinoma could not be improved. All efforts are to be done in investigation on practicable, suitable, and supportable screening programs for early recognition of tumors in the first stages.

Carcinoma, Non-Small-Cell Lung↗