Biomedical subjects

Gert von Bally

Publications and source records attributed to Gert von Bally.

5 recordsLinked to original sources

PubMed2005

Dynamic holographic endoscopy--ex vivo investigations of malignant tumors in the human stomach.

Laser holographic interferometry is based on the superimposition of the holograms of different motional states of an object on a single holographic storing medium. Using a combination of holographic interferometry and endoscopic imaging, we tried to detect areas of focally disturbed tissue elasticity in gastric cancer preparations. By connecting a mobile electronic speckle pattern interferometry (ESPI) camera system (light source: double frequency Nd:YAG laser, lambda = 532 nm) to different types of endoscopes, ex vivo experiments were performed on ten formalin fixed human stomachs, nine containing adenocarcinomas and one with a gastric lymphoma. Linking the endoscopic ESPI camera complex to a fast image processing system, the method of double pulse exposure image subtraction was applied at a video frame rate of 12.5 Hz. Speckle correlation patterns and corresponding phase difference distributions resulting from gastric wall deformation by gentle touch with a guide wire were analyzed. Tumor-free gastric areas showed high-contrast concentric fringes around the point of stimulation. In contrast, fringe patterns and filtered phase difference distributions corresponding to the areas of malignancy in all the cases were characterized by largely parallel lines, indicating that stimulation of rigid tumor tissue primarily led to tilting. Our ex vivo investigations of malignant gastric tumors show that the application of dynamic holographic endoscopy makes it possible to distinguish areas of malignancy from surrounding healthy tissue based on the differences in tissue elasticity.

Adenocarcinoma↗

PubMed2004

Parameter-optimized digital holographic microscope for high-resolution living-cell analysis.

A parameter-optimized off-axis setup for digital holographic microscopy is presented for simultaneous, high-resolution, full-field quantitative amplitude and quantitative phase-contrast microscopy and the detection of changes in optical path length in transparent objects, such as undyed living cells. Numerical reconstruction with the described nondiffractive reconstruction method, which suppresses the zero order and the twin image, requires a mathematical model of the phase-difference distribution between the object wave and the reference wave in the hologram plane. Therefore an automated algorithm is explained that determines the parameters of the mathematical model by carrying out the discrete Fresnel transform. Furthermore the relationship between the axial position of the object and the reconstruction distance, which is required for optimization of the lateral resolution of the holographic images, is derived. The lateral and the axial resolutions of the system are discussed and quantified by application to technical objects and to living cells.

Algorithms↗

PubMed2004

Two-wavelength method for endoscopic shape measurement by spatial phase-shifting speckle-interferometry.

A two-wavelength method for endoscopic topography reconstruction is introduced that can be applied to out-of-plane sensitive electronic-speckle-pattern interferometry systems based on rigid endoscope imaging systems. The surface measurement is performed by detection of the phase-difference distribution affected by a change in the applied laser wavelength. Furthermore, the off-axis endoscopic illumination geometry is taken into account by an approximation. Experimental results of the characterization of the endoscopic surface reconstruction technique and the measurement accuracy obtained are described and discussed. Finally, the applicability of the method is demonstrated with results from the topographic reconstruction of a free-form surface.

Journal Article↗

PubMedDate not supplied

Investigation of living pancreas tumor cells by digital holographic microscopy.

Digital holographic microscopy provides new facilities for contactless and marker-free quantitative phase contrast imaging. In this work, a digital holographic microscopy method for the integral refractive index determination of living single cells in cell culture medium is presented. Further, the obtained refractive index information is applied to full field thickness and shape determination of adherent pancreas tumor cells, as well as for analysis of drug-induced dynamic changes of a single cell's cytoskeleton. The results demonstrate that digital holographic microscopy is a quantitative phase contrast technique for living cells under conventional laboratory conditions.

Cell Line, Tumor↗

PubMedDate not supplied

Optical data acquisition for computer-assisted design of facial prostheses.

PURPOSE: The conventional impression technique for manufacturing facial prostheses has the disadvantage of deforming the soft tissues because of the tension caused by the impression material, as well as causing discomfort to the patient. The purpose of this study was to establish a system that allows contact-free reproduction of the facial surface combined with computer-assisted design and fabrication of facial prostheses. MATERIALS AND METHODS: Three-dimensional data of the facial surface were obtained using an optical acquisition system based on the method of phase-measuring profilometry. A sensor head with a fringe projector and two CCD cameras for photogrammetric triangulation were used in connection with a PC for measurement control and data evaluation. Software for computer-assisted design of the facial surface to be reconstructed was developed. A prototype facial prosthesis was fabricated using stereolithography. The system was tested using a modified puppet head. First clinical tests were performed with a patient who had undergone maxillofacial surgery including the resection of one eye. RESULTS: Three-dimensional data acquisition and imaging allow visualization of a whole face without causing tension or neuromuscular reaction. As surface brightness is also part of the digital model, it is even more realistic than a plaster cast. The stereolithographic object showed good marginal fit and satisfactory shape. CONCLUSION: The presented technique allows three-dimensional data reproduction of the facial surface, computer-assisted design of a facial prosthesis, and transfer to a rapid prototyping unit. The system has obvious advantages over conventional impression techniques. Further clinical trials are planned to evaluate the clinical success of the technique.

Computer-Aided Design↗