Biomedical subjects

Pavel Novak

Publications and source records attributed to Pavel Novak.

3 recordsLinked to original sources

PubMed2006

Colorimetric method for phase evaluation.

Measurements of very small phase changes in optical measurement techniques are usually performed with interferometric methods that are based on evaluation of interference patterns, which correspond to a phase change of the investigated wave field. If values of the phase change are small, it is difficult to determine accurately the phase values, and one needs very expensive measurement systems. We present a simple method for evaluation of small phase variations that uses the interference of polychromatic light. The phase change affects the color of the interference pattern, and the color of the interference pattern corresponds to a specific phase change that can be evaluated using colorimetric analysis. We describe and analyze our colorimetric phase evaluation method. The proposed method offers accurate results, and it may be suitable for practical utilization in the optical industry.

Journal Article↗

PubMed2005

Influence of total reflection on the imaging quality of optical systems.

In the case of total reflection at a boundary surface between two different optical media, the ray reflected at the boundary is spatially shifted with respect to the point where the incident ray intersects the boundary. The light penetrates into the second medium, and the evanescent electromagnetic wave propagates along the boundary. The described effect is called the Goos-Hänchen effect. Our work describes the influence of the Goos-Hänchen effect on the imaging properties of planar optical systems, and a differential equation of a wave-front meridian that corresponds to a reflected bundle of rays is derived. It is shown that the wave front can be described by the d'Alambert differential equation. This equation makes it possible to determine the coordinates of individual points on the wave-front meridian. The influence of total reflection on the value of the Strehl definition of the reflected ray bundle, is also investigated.

Journal Article↗

PubMed2002

Ex vivo testing of a temperature- and pressure-controlled amnio-irrigator for fetoscopic surgery.

BACKGROUND: Currently, amnioinfusion fluids used in operative fetoscopy usually are preheated to body temperature. As the complexity of procedures increases, purposed designed devices should be designed that allow control of pressure and temperature during amnioinfusion or amnioexchange. In the current study, a prototype amnio-irrigator and fluid heater were evaluated. METHODS: The medical fluid heater heats fluid by conduction up to 37 degrees C. The maximum irrigation pressure and flow rates can be preset. Actual irrigation pressure (0 to 30 mm Hg) and flow rate (0 to 300 mL/min) can be read on the front panel. A series of ex vivo experiments were set up to determine the relationship between the flow rate (FR) and lumen of the instruments as well as the maximum flow rate (MFR) with and without the pressure control. Further, the relationship between FR and the irrigation pressure (IP) was determined. In an artificial pseudoamniotic sac the relationship between FR and change in temperature was measured, with and without the use of the medical fluid heater. RESULTS: When the IP was limited to 24 mm Hg, FR and pressure were correlated (r = 0.34; P <.001). The larger the functional lumen of the fetoscopic instrumentation, the higher the flow (r = 0.43; P <.001) and the lower the increase in IP (r = -0.47; P <.001). A quadratic relation between flow and temperature was observed both for preheated fluid as when using the fluid heater (r(2) = 0.71 and r(2) = 0.88; P <.001). However, at low flow rates, a thermal decrease of over 3 degrees C was observed when the fluid heater was not used. CONCLUSIONS: The current study quantifies an expected relationship between the diameter of the irrigation channel and achievable flow rates. It also shows that a medical fluid heater is needed when strict control of temperature would be desired.

Equipment Design↗