Biomedical subjects

S E Rosenow

Publications and source records attributed to S E Rosenow.

3 recordsLinked to original sources

PubMed1999

Cyclophotocoagulation: experimental investigations of dosage problems.

BACKGROUND: During cyclophotocoagulation, transsclerally applied laser light reduces the aqueous-producing structures of the eye. One problem using this therapy is patient-specific dosage of the applied laser energy. The aim of our investigations was to obtain information about intensity and distribution of tissue destruction in the coagulation area. This may provide a basis for further on-line control of cyclophotocoagulation by ultrasound-controlled engineering of the diode laser. METHODS: To visualize the process of cyclophotocoagulation, a multifunctional measurement set-up was developed. It allowed the visualization of structural changes in the coagulation area using a common light microscope and comparison in the first set-up to the results detected by high-resolution ultrasound, applied in different working modes (B-mode, M-mode and RF signal analyses). In a second set-up an infrared thermography system showing temperature distribution on the scleral surface at the contact point of the laser probe was used. RESULTS: High resolution working in B- and M-mode was unsuitable to visualize structural changes within the therapeutic width. By analyzing RF ultrasound date, structural changes within the therapeutic width could be detected. Surface temperatures measured by infrared thermography correlated with visible structural changes when long exposure times and low laser power were applied. CONCLUSIONS: In certain cases the visualization of coagulation effects was possible with the help of either high-resolution ultrasound or infrared thermography. Spectrum analysis of RF ultrasound signals seems to be a potential method for successful control of cyclophotocoagulation.

Animals↗

PubMed1994

Flow visualization in the Baylor total artificial heart.

To analyze the flow patterns of the left and right blood chambers of the total artificial heart (TAH), flow visualization studies were performed. Two setup levels were used for the flow visualization studies. For estimating the global flow patterns, the pumps were illuminated using incandescent light, and the patterns were recorded by either videotape or photography. To evaluate sectional flow patterns, a laser light was applied, and the pump could be scanned segmentally. The flow patterns were recorded by a high-speed camera. A signal was also used that synchronized the timing of the camera shutter to the pusher-plate movement signal. In the left pump chamber, major stagnations were observed in the middle area of the inflow site. To solve this problem, a modification was made that changed the inflow direction appropriately. After evaluation of the inflow port direction, a proper flow pattern was obtained, which was validated by a global flow visualization study. Furthermore, both pump chambers indicated excellent flow patterns as obtained by a segmental flow visualization study method utilizing a laser light. The Baylor TAH demonstrated excellent flow patterns in flow visualization studies, with antithrombogenicity expected. These flow visualization studies are very useful not only for validations of global flow patterns but also for validations of local areas of stagnation in various blood pumps.

Equipment Design↗

PubMed1993

A fluid dynamic analysis of a rotary blood pump for design improvement.

The proper design of a left ventricular assist device (LVAD) requires an understanding of the pump's fluid dynamic and biocompatible properties. A hydraulically efficient system minimizes the power required for pumping. Biocompatibility refers to the ability to pump blood with minimal hemolysis and thrombus formation. Typically, shear stresses below a threshold level will not damage blood significantly. A fluid dynamic analysis of a prototype centrifugal pump designed for use as an LVAD was performed to establish flow characteristics. A flow visualization technique using Amberlite particles suspended in a glycerin/water blood analogue was used. The system was illuminated with a 1 mm planar beam strobed helium-neon laser, and the results were recorded photographically. An analysis of photographs revealed laminar and turbulent flows with vortices within an illuminated plane in both the inlet and outlet port areas. From these data, velocity and shear stress profiles were generated that showed possible areas of improvement. It was concluded that the outlet port design could be improved by changing its angle and the continuity of its expansion. The inlet port could also be improved by smoothing the transition area between the inlet tube and the pump body to allow for gradual acceleration of the entering fluid.

Blood Flow Velocity↗