THG Microscopy of Cells and Tissues: Contrast Mechanisms and Applications

2016 ◽  
pp. 71-100
Keyword(s):  
Contrast Mechanisms

Various technic for the measurement of step thickness on crystal surfaces

1978 ◽  
Vol 36 (1) ◽  
pp. 438-439
Author(s):  
C. Boulesteix ◽  
C. Colliex ◽  
C. Mory ◽  
B. Pardo ◽  
D. Renard
Keyword(s):  
Critical Thickness ◽  
Symmetric Case ◽  
Transmitted Intensity ◽  
Crystal Surfaces ◽  
Bright Field ◽  
Excited Wave ◽  
Highly Sensitive ◽  
Contrast Mechanisms ◽  
Step Thickness ◽  
Thickness Variations

Contrast mechanisms, which are responsible of the various types of image formation, are generally thickness dependant. In the following, two imaging modes in the 100 kV CTEM are described : they are highly sensitive to thickness variations and can be used for quantitative estimations of step heights.Detailed calculations (1) of the bright-field intensity have been carried out in the 3 (or 2N+l)-beam symmetric case. They show that in given conditions, the two important symmetric Bloch waves interfere most strongly at a critical thickness for which they have equal emergent amplitudes (the more excited wave at the entrance surface is also the more absorbed). The transmitted intensity I for a Nd2O3 specimen has been calculated as a function of thickness t. The capacity of the method to detect a step and measure its height can be more clearly deduced from a plot of dl/Idt as shown in fig. 1.

Basic MR physics

2018 ◽  
pp. 6-10
Author(s):  
Sebastian Kozerke ◽  
Redha Boubertakh ◽  
Marc Miquel
Keyword(s):  
Magnetic Field ◽  
Chemical Shift ◽  
Magnetic Moments ◽  
Image Contrast ◽  
Specific Time ◽  
Time Constants ◽  
Contrast Mechanisms ◽  
Transverse And Longitudinal Components ◽  
Mr Physics ◽  
Additional Image

In magnetic resonance, the properties of protons in tissue giving rise to so-called magnetic moments are exploited. The sum of many magnetic moments yields what is referred to as net magnetization, which can be seen as similar to the magnetization a bar magnet produces. The relation and interaction between magnetic moments, net magnetization, the static magnetic field, and radiofrequency fields are discussed. It is shown that radiofrequency excitation can be used to manipulate the net magnetization, such that it can be detected using radiofrequency antennae or coils. Upon excitation, the net magnetization will recover back to its equilibrium orientation with tissue-specific time constants for the transverse and longitudinal components, which, in turn, are important sources of image contrast in cardiac imaging. The discussion concludes with a foray into susceptibility and chemical shift effects resulting from different molecular environments in which protons can reside and which provide additional image contrast mechanisms.

Raman Imaging of Small Biomolecules

2019 ◽  
Vol 48 (1) ◽  
pp. 347-369 ◽  
Author(s):  
Yihui Shen ◽  
Fanghao Hu ◽  
Wei Min
Keyword(s):  
Imaging Techniques ◽  
Living Cells ◽  
Raman Imaging ◽  
Biological Processes ◽  
Comprehensive Knowledge ◽  
Contrast Mechanisms ◽  
Recent Developments ◽  
Imaging Methodology ◽  
Small Biomolecules ◽  
Microscopic Techniques

Imaging techniques greatly facilitate the comprehensive knowledge of biological systems. Although imaging methodology for biomacromolecules such as protein and nucleic acids has been long established, microscopic techniques and contrast mechanisms are relatively limited for small biomolecules, which are equally important participants in biological processes. Recent developments in Raman imaging, including both microscopy and tailored vibrational tags, have created exciting opportunities for noninvasive imaging of small biomolecules in living cells, tissues, and organisms. Here, we summarize the principle and workflow of small-biomolecule imaging by Raman microscopy. Then, we review recent efforts in imaging, for example, lipids, metabolites, and drugs. The unique advantage of Raman imaging has been manifested in a variety of applications that have provided novel biological insights.

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