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W Folberth

Publications and source records attributed to W Folberth.

8 recordsLinked to original sources
PubMed1992

Pressure distribution and energy flow in the focal region of two different electromagnetic shock wave sources.

In extracorporeal shock wave lithotripsy there is still a lack of knowledge about the basic physical terms that are essential for a scientific comparison of lithotripters with different technologies. The main goal of this article is to introduce the relation between pressure distribution, acoustic energy flow and intensity. The procedure of how these data can be achieved quantitatively is described. Technical data of two different commercially available electromagnetic shock wave sources are presented. The results show that acoustic energy flow and intensity depend on the variation of the shock wave parameters and the focal area.

Electromagnetic Phenomena↗
PubMed1992

Experiences with lithotripters: measurements of standardized fragmentation.

A comparison of lithotripters in terms of the fragmentation efficacy was established by using artificial stones. Two hundred pulses were applied to identical calcium sulphate cubes at varied energy levels of different lithotripters. In the cubics the shock waves formed regular craters, which could be analyzed with regard to depth, diameter, and volume. Dimensions of the craters increased with increasing energy. Each shock wave source designed a typical crater form. Different efficacies of fragmentation within different lithotripters could be recognized. High focal peak pressures did not guarantee better fragmentation effects. By using different acoustic lenses in the same electromagnetic lithotripter, the influence of different focus zones of the shock wave on the fragmentation could be investigated without any changes of the energy input. Results clearly emphasize the possibility of an increase of fragmentation efficacy by changing only the focal zones and the distribution of energy within the focal area.

Cholelithiasis↗
PubMed1992

[New trends in extracorporeal shockwave lithotripsy].

Extracorporeal shock wave lithotripsy has become an established and successful treatment modality for urinary and biliary calculi. However, shock wave technology and corresponding device designs are still at an innovative stage. Three trends are discussed in this paper. In shock wave technology the electromagnetic principle seems to win the race. The demands for successful and tissue-protective stone disintegration require shockwave sources with high dynamic range and optimised focal geometry. Electromagnetic shock wave generators meet all these requirements. For stone localisation an isocentric X-ray targeting system combined with integrated shock wave application is accepted as the "gold standard". In ultrasound localisation in-line targeting is superior to out-of-line targeting.

Equipment Design↗
PubMed1991

The mechanisms of stone disintegration by shock waves.

Through interpretation of high-speed films at 10,000 frames per second of shock wave action on kidney stones and gallstones, the mechanism of stone destruction was analyzed in detail. This shows that the interaction of the shock wave with the targets firstly produces fissures in the stone material. Liquid then enters these small cracks. The actual disintegration is caused later by the enormous violence of imploding cavitation bubbles within these small split lines. That cavitation acts inside the stone and causes fragmentation even within the human gallbladder could furthermore be demonstrated by using scanning electron microscopy. These results should lead to a different process in gallstone lithotripsy leaving intervals between the shock wave treatments. This will allow the viscous bile fluids to occupy the fissures of the stones more completely and, therefore, should increase the cavitational activity on the subsequent treatment with shock pulses.

Cholelithiasis↗
PubMed1991

First experience with a modified Siemens Lithostar shock wave system.

A Siemens Lithostar shock wave system was modified and investigated clinically. The modified system yields increased focal pressure and energy density. The first clinical experience in renal calculi shows a significant reduction in shock wave numbers per treatment. Higher energy output enables better treatment results for difficult stones such as staghorn and infections calculi. Despite the higher energy output more than 90% of treatments could be performed without anesthesia or analgesia. No significant side effects could be detected. The service life of the modified shock wave system increased by a factor of two.

Ceramics↗
PubMed1990

Value of in-line and out-of-line ultrasound targeting in extracorporeal shock wave lithotripsy.

Acoustic inhomogeneities of body tissue may deflect diagnostic ultrasound waves as well as therapeutic shock waves. The influence of incorrect ultrasound targeting and shock wave application due to these deflection effects has been examined quantitatively by means of a two-dimensional physical model. The accuracy of in-line and out-of-line targeting has been determined. Calculations on 2 stone patients show that in-line deflection effects remain below 2 mm, while they reach values up to 6 mm for out-of-line systems. These results, confirmed by first clinical observations done by others, indicate that in-line ultrasound targeting is superior to out-of-line targeting.

Acoustics↗
PubMed1990

Pressure-optimized lithotripsy with the Siemens Lithostar: successful and tissue-protecting treatment of urinary stones.

With the Siemens Lithostar all kinds of urinary stones can be successfully treated at significantly lower pressure levels than with other commercially available lithotripters. Experimental and clinical experience indicates that for urinary stones there exists a pressure region between 200 and 400 bar (20-40 MPa) where lithotripsy can be performed successfully and the tissue can be protected. By calculation of isobar zones the pressure distribution of different lithotripters can be compared quantitatively. From this it becomes evident that the dynamic range of the Lithostar is optimized to that 'golden' pressure region.

Humans↗