Untersuchung und Reduzierung der Gefaehrdung durch Emissionen beim Abtrag von PMMA-Knochenzement mittels Laserstrahlung Abschlussbericht

Abstract

Within the framework of removal investigations, parameters for the optimal removal of PMMA bone cement were set. These describe the correlation between the laser and process parameters and the removal rate and quality. CO2 and excimer lasers have proved to be suitable laser sources, wheras the excimer laser could achieve the best removal quality. However, the achievable removal rates were too low to be relevant for medicinal applications. Holmium and Nd:YAG lasers are not suitable for the removal of PMMA cement. Following this, emission measurements were made at various points. These show that methylmethacrylate, formaldehyd, ozone and dust were the main components of the removed material. For both PMMA and PMMA bone cement, nearly the same emission components are released; however, the concentrations differ. Methylmethacrylate and formaldehyde concentrations exceed the threshold levels. Due to manual beam guidance in medicine, during which the focal point, feed rate and working angle of the laser can differ reatly, the removal of PMMA bone cement could, up to now, only be carried out as an uncontrolled thermal process. For this reason, further investigations concerning the development of guidance and control strategies during the removal of bone cement were carried out, in order to make a controlled process with reduced emissions possible, despite manual guidance. The results show that process controls can be used to achieve laser output regulation, to avoid overheating the material, causing smoke and soot. The plasma radiation is used as a process signal, which can be measured using a foto diode, and subsequently evaluated via computer technology. (orig.)SIGLEAvailable from TIB Hannover: F96B973+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany); European Union (Euro), Brussels (Belgium)DEGerman