A Virtual Imaging Platform for Multi-Modality Medical Image Simulation

IntroductionA simple and accurate technique to determine the Burgers vector of a dislocation has become feasible with the advent of HVEM. The conventional image vanishing technique(1) using Bragg conditions with the diffraction vector perpendicular to the Burgers vector suffers from various drawbacks; The dislocation image appears even when the g.b = 0 criterion is satisfied, if the edge component of the dislocation is large. On the other hand, the image disappears for certain high order diffractions even when g.b ≠ 0. Furthermore, the determination of the magnitude of the Burgers vector is not easy with the criterion. Recent image simulation technique is free from the ambiguities but require too many parameters for the computation. The weak-beam “fringe counting” technique investigated in the present study is immune from the problems. Even the magnitude of the Burgers vector is determined from the number of the terminating thickness fringes at the exit of the dislocation in wedge shaped foil surfaces.

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Simulation of high-resolution annular dark field STEM images

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010013657x ◽

1995 ◽

Vol 53 ◽

pp. 40-41

Author(s):

E. J. Kirkland

Keyword(s):

Electron Beam ◽

Atomic Layer ◽

Fresnel Diffraction ◽

Dark Field ◽

Objective Lens ◽

Image Simulation ◽

Small Probe ◽

Annular Dark Field ◽

Stem Image ◽

Uniform Plane

In a STEM an electron beam is focused into a small probe on the specimen. This probe is raster scanned across the specimen to form an image from the electrons transmitted through the specimen. The objective lens is positioned before the specimen instead of after the specimen as in a CTEM. Because the probe is focused and scanned before the specimen, accurate annular dark field (ADF) STEM image simulation is more difficult than CTEM simulation. Instead of an incident uniform plane wave, ADF-STEM simulation starts with a probe wavefunction focused at a specified position on the specimen. The wavefunction is then propagated through the specimen one atomic layer (or slice) at a time with Fresnel diffraction between slices using the multislice method. After passing through the specimen the wavefunction is diffracted onto the detector. The ADF signal for one position of the probe is formed by integrating all electrons scattered outside of an inner angle large compared with the objective aperture.

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The quantitative comparison of experimental and simulated diffraction contrast images

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010013688x ◽

1995 ◽

Vol 53 ◽

pp. 102-103

Author(s):

Stuart McKernan

Keyword(s):

Image Processing ◽

Personal Computer ◽

Close Agreement ◽

Quantitative Comparison ◽

Image Simulation ◽

Computing Power ◽

Diffraction Contrast ◽

Simulated Images ◽

Made In

For many years the concept of quantitative diffraction contrast experiments might have consisted of the determination of dislocation Burgers vectors using a g.b = 0 criterion from several different 2-beam images. Since the advent of the personal computer revolution, the available computing power for performing image-processing and image-simulation calculations is enormous and ubiquitous. Several programs now exist to perform simulations of diffraction contrast images using various approximations. The most common approximations are the use of only 2-beams or a single systematic row to calculate the image contrast, or calculating the image using a column approximation. The increasing amount of literature showing comparisons of experimental and simulated images shows that it is possible to obtain very close agreement between the two images; although the choice of parameters used, and the assumptions made, in performing the calculation must be properly dealt with. The simulation of the images of defects in materials has, in many cases, therefore become a tractable problem.

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Computers and diffraction analysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100152197 ◽

1989 ◽

Vol 47 ◽

pp. 44-45

Author(s):

J. A. Eades

Keyword(s):

Electron Microscopy ◽

High Resolution ◽

Electron Diffraction ◽

Diffraction Analysis ◽

Electron Diffraction Analysis ◽

Image Simulation ◽

Correct Interpretation ◽

High Profile ◽

High Resolution Images ◽

Image Simulations

For well over two decades computers have played an important role in electron microscopy; they now pervade the whole field - as indeed they do in so many other aspects of our lives. The initial use of computers was mainly for large (as it seemed then) off-line calculations for image simulations; for example, of dislocation images.Image simulation has continued to be one of the most notable uses of computers particularly since it is essential to the correct interpretation of high resolution images. In microanalysis, too, the computer has had a rather high profile. In this case because it has been a necessary part of the equipment delivered by manufacturers. By contrast the use of computers for electron diffraction analysis has been slow to prominence. This is not to say that there has been no activity, quite the contrary; however it has not had such a great impact on the field.

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