![second harmonic generation second harmonic generation](https://svi.nl/wikiimg/FvsSHG.jpg)
SHG microscopy is a natural choice for in vivo imaging and pathologies of cornea infected by collagenous stroma. For that they compared the distribution of elastin/collagen in normal tissue to those in tissue in lesion. have used SHG imaging in association with CARS and TPEF imaging on the same platform to study a tissue from Ossabaw swine suffering from metabolic syndrome–induced cardiovascular plagues, the disease responsible for heart attack and stroke in human. In fact, SHG microscopy is proving itself as a medically relevant technique because many types of spatially ordered structures within an organ tissue, for example, muscle myosin lattices within muscle cells, are able to generate sufficient amount of SHG without the use of any fluorescent marker. The majority of work done in SHG microscopy is focused on visualization of collagen fibers in different kinds of organs and connecting tissues. Forward- and epi-detection second harmonic generation signal from different tissue thicknesses. In medium tissue thickness, the dominancy shifts toward epi-direction ( Fig. 5.16), whereas in very thick tissues, it gives only epi-detection SHG signal ( Fig. 5.16C).įigure 5.16. Fig. 5.16A represents the fact that for very thin tissue, forward SHG signal is dominant over the epi-SHG signal. Therefore, SHG microscopes usually have the arrangements for both detections.
#Second harmonic generation full
As we have seen that the SHG signal from tissue is quasi-coherent and emission directions depend on spatial distribution of the targeted species, it is required to have both the forward detection and the epi-detection schemes to gather the full information of the SHG mechanism. Tunable wavelength range (700–1000 nm) of Ti:S provides penetration depths up to few hundreds of microns in a tissue environment, making it capable of deep-tissue imaging. In most cases, they contain a tunable titanium sapphire (Ti:S) oscillator pumped by a Nd:YAG laser as an SHG excitation source.
![second harmonic generation second harmonic generation](https://www.researchgate.net/profile/Chi-Kuang-Sun-2/publication/44589034/figure/fig1/AS:394183799001088@1470992149155/Energy-level-diagrams-describing-a-second-harmonic-generation-and-b-third-harmonic_Q640.jpg)
SHG microscopes are, in general, a laser scanning microscope ( Fig. 5.3).