PubMed Health⌕ Search

Biomedical subjects

P Descouts

Publications and source records attributed to P Descouts.

25 records · Page 2Linked to original sources

Spatial reconstruction of coronary arteries from angiographic images.

A method for 3D reconstruction of coronary arteries from two angiographic projection views is presented (cinefilm 35 mm, 50 images/s). The geometric information defining the two projections is secured by filming a cube bearing 15 steel markers in the approximate location of the heart. For 3D reconstruction, a pair of images of the cube and two simultaneous images of the coronary tree are digitized on a computer assisted system. Two matrices describing the two projections are obtained from the 15 x 2 x 2 image coordinates of the cube markers. Next, the operator draws with a mouse the approximate centre lines of the coronary arteries to be 3D reconstructed. The program then determines the centre lines and the edges of the vessels in the two images accurately. The 3D centre lines are reconstructed and the true local vessel diameters determined. Intravascular volumes are obtained by summation of elementary volumes. The reconstructed arteries are visualized on a colour TV monitor. Measurements on various phantoms have shown that lengths of a few centimetres can be measured with typically 2% error. The accuracy of volume determination was somewhat less due to the inaccuracy of lumen determination. For real coronary arteries the volume error is estimated to be about 15% because of the poorer image quality.

Angiography↗

A small scanning tunnelling microscope with large scan range for biological studies.

We have developed a scanning tunnelling microscope specially designed for biological application presenting some new features: the scanner tube is mounted parallel to the surface of the sample which enables a high resolution optical microscope to be brought close to the sample when working in air or liquids. The maximum scan range is 5x20 microm with a vertical range of 20 microm and the total size of the system does not exceed 10x40 mm. The piezo-sensitivity of the scanner tube versus applied voltage was analysed by interferometry measurements and by using scanning tunnelling microscopes. We found a value for the piezoelectric constant d13 of -1.71 A/V at low voltages (under a few volts) going up to -2 A/V for higher voltages. Large-scale images of a carbon grid showed a surprisingly good linearity of the scanner tube.

Microscopy, Electron, Scanning↗

Imaging of DNA by scanning force microscopy.

The scanning probe microscopies applied to the sequencing of DNA is a challenging goal attempted by several groups. But one limitant parameter has been the sample preparation of DNA molecules. Here we report how to hold DNA molecules fixed on mica substrate and we show the three-dimensional configuration of double-stranded DNA obtained with our scanning force microscope. We can image DNA under negative supercoiling, a feature of general importance controlling the activities of DNA. We compared the electron micrographs of a carbon replica of the same DNA specimen with scanning force images which demonstrates well the feasibility and accuracy of our scanning probe measurements.

DNA↗