Image analysis – Histogram processing – For setting a threshold
Patent
1991-01-25
1993-08-31
Razavi, Michael T.
Image analysis
Histogram processing
For setting a threshold
382 1, 36441315, G06K 900
Patent
active
052416070
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention concerns a process that makes it possible to automate the calculation of deformations that make possible the matching of successive sections of microscopy, electronic transmission microscopy and optical microscopy.
The matching of successive sections is traditionally done by moving images according to the operator's judgment. This method does not make it possible to correct the deformations that the mechanical action of the cutting introduces to the thin sections.
Some deformations are related to the techniques used to make it possible to visualize successive sections in microscopy. These include supporting blades which cannot be reproduced exactly, and ultramicrotome.
Also included is of an electron microscope in transmission mode).
SUMMARY OF THE INVENTION
The process of the invention makes it possible to correct all these deformations by calculating an inverse transformation function and establishing a fixed marker derived from markings previously obtained mechanically or by firing a pulsed laser.
The process according to the invention takes place after the histological preparation stage, prior to observation with the optical microscope or the electron transmission microscope.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a process according to the invention.
FIG. 2 is a perspective view of marking holes in a microscopic preparation (weak magnification).
FIG. 3 is a plan view of an example of an electron microscope grid with a series of sections.
FIGS. 4A-4C are schematic drawings of the acquisition of images and rotation related to the functioning of an electronic transmission microscope between two different magnifications.
FIGS. 5A-5B are schematic drawings of deformations related to sectioning techniques.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The process according to the invention includes several steps: (See FIG. 1)
1. "Marking"
The process according to the invention includes a sample preparation step before a series of sections is cut (see FIG. 2). The microscopic preparation 1 is pierced by at least three holes 2 not in a straight line near area to be studied and made either mechanically or by means of a pulsed laser. The barycenters of these holes 2 will be used as marking points to establish a fixed marker and for final calculation of the inverse transformation function.
2. "Section in Series"
The process according to the invention takes the classic step of making successive sections 4 of the preparation 1 using a microtome for the sections to be viewed by optical microscopy and an ultramicrotome for sections to be viewed with an electron microscope (see FIG. 3).
3. Digitation
The process according to the invention includes observation steps with the optical microscope or with the electron transmission microscope, as well as the acquisition and digitation of images by a computer system. This computerized system includes a camera and an image-digitation system connected to a computer. Three images are acquired for an image to be studied (see FIG. 4): slide 3 making it possible to see at least one of the marking holes 2. at the same magnification as for image B.
4. "Normalization"
A normalization step for digital processing of all the images A of the sections to be studied, making it possible to obtain homogeneous information in terms of contrast and distribution of grey levels.
The distributions of the grey levels of the images are normalized in terms of their average and their variance.
Enhancement is done by dispersion of the diagram distributions.
Specific mathematical functions are used for the work on the distributions (improvement and stabilization).
5. "Calculation of the Inverse Transformation"
The process according to the invention includes a step for calculating the inverse transformation function making it possible to re-establish more closely from an initial section considered a reference a set marker that is fixed for all the sections. This method is as follows:
5.1 Automatic calculation
REFERENCES:
patent: 4404684 (1983-09-01), Takada
patent: 4975973 (1990-12-01), Kasano et al.
Bron et al "Three-Dimensional Electron Microscopy of Entire Cells", Journal of Microscopy, vol. 157, Pt. 1, Jan. 1990, pp. 115-126.
Bron Christophe R.
Launay Didier M.
Couso Yon J.
Razavi Michael T.
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