Biomedical subjects

M Kaschke

Publications and source records attributed to M Kaschke.

3 recordsLinked to original sources

PubMed1997

Frequency-domain techniques enhance optical mammography: initial clinical results.

We present a novel approach to optical mammography and initial clinical results. We have designed and developed a frequency-domain (110-MHz) optical scanner that performs a transillumination raster scan of the female breast in approximately 3 min. The probing light is a dual-wavelength (690 and 810 nm, 10-mW average power), 2-mm-diameter laser beam, and the detection optical fiber is 5 mm in diameter. The ac amplitude and phase data are processed with use of an algorithm that performs edge effect corrections, thereby enhancing image contrast. This contrast enhancement results in a greater tumor detectability compared with simple light intensity images. The optical mammograms are displayed on a computer screen in real time. We present x-ray and optical mammograms from two patients with breast tumors. Our initial clinical results show that the frequency-domain scanner, even at the present stage of development, has the potential to be a useful tool in mammography.

Algorithms↗

PubMed1996

Frequency-domain optical mammography: edge effect corrections.

We have investigated the problem of edge effects in laser-beam transillumination scanning of the human breast. Edge effects arise from tissue thickness variability along the scanned area, and from lateral photon losses through the sides of the breast. Edge effects can be effectively corrected in frequency-domain measurements by employing a two-step procedure: (1) use of the phase information to calculate an effective tissue thickness for each pixel location; (2) application of the knowledge of tissue thickness to calculate an edge-corrected optical image from the ac signal image. The measurements were conducted with a light mammography apparatus (LIMA) designed for feasibility tests in the clinical environment. Operating in the frequency-domain (110 MHz), this instrument performs a transillumination optical scan at two wavelengths (685 and 825 nm). We applied the proposed two-step procedure to data from breast phantoms and from human breasts. The processed images provide higher contrast and detectability in optical mammography with respect to raw data breast images.

Biophysical Phenomena↗

PubMed1994

[FeS/FeS2], a redox system for the origin of life (some experiments on the pyrite-hypothesis).

The FeS/FeS, redox system, whose importance is stressed in recent theories on the origin of life, has been tested experimentally. In this paper it is demonstrated by thermodynamical calculations as well as by experiments, that cyclohexanone, which served as model compound, can be reduced by the aforementioned redox system. Reactions were carried out in methanol and DMF at 25 degrees C and at 100 degrees C. Besides products that were synthesised in both solvents, like cyclohexanethiol and dicyclohexydisulphide, special compounds were obtained in methanol and in DMF, because of the involvement of the respective solvent in the reaction. Yields of reduced compounds were lower in methanol owing to compound that hindered the reduction (cyclohexylketal). With increasing temperature and duration the amount of reduced compounds increased. Further experiments have shown that 1,1-cyclohexanedithiol is likely to be a necessary intermediate for the reduced products. The experiments give evidence to the 'pyrite hypothesis', which postulates that the FeS/FeS2, redox system was of importance for the origin of life.

Cyclohexanones↗