Laser Tissue Interactions - Science topic

It is understood that the increased collagen production occurs through photostimulation mechanisms on which certain frequencies/doses may act, thereby modulating cellular proliferation and increasing the amount of fibroblast growth factors. Another possible explanation for this, according to the authors above, would be the better absorption of such energy by the mitochondria and consequently increased production of ATP and nucleic acid, the result being an increase in collagen production, accelerated epithelial repair and facilitated growth of granulation tissue.

Yes it is possible. It depends on the medium on which the laser beam propagates. Each medium can bear a certain density of power. If this density of power is exceeded, the medium is ionised in a plasma, this is called the "breakdown". In air, the maximal density of power before breadown is about 4 GW/cm². Below, there is a partial breadown. When the plasma appears, it block the coming photons and there is nore more energy deposited in the material. The plasma can even reflect the photons in the laser source and it is a possible crash for the laser. In water, the breakdown threeshold is about 8-9 GW/cm². See :

A. Sollier, L. Berthe, and R. Fabbro, Eur. Phys. J. AP 16, 131-139 (2001).

regards

Hi Justice,

In general, liquid lipid-based optical phantoms exhibit scattering properties (mus and mus') that are quite high and close to those of biological tissues. However, the spectral dependence of these quantities usually differs from the dependencies that are exhibited by biological tissues. Absorption parameters on the other hand are lower than typical absorption of biological tissues. To increase absorption, various absorbers can be added like ICG, Hb, HbO2 etc. Again, one has to be clear about their spectral dependence because absolute values usually don't follow the absorption of typical biological tissues in the entire spectral range.

Usually, people try to match properties of the certain tissue of interest (skin, muscle, prostate etc.) at the selected wavelength combining a lipid phantom with an added absorber and playing with corresponding concentrations. One of the benefits of working with liquid phantoms is an ease of preparations and adjusting the concentrations to meet specs of the certain tissue (again, usually at a fixed wavelength). Such phantoms produce reproducible results and don't have a degree of heterogeneity typical for actual biological tissues.

Bottom line, it depends on what tissue you're trying to mimic and in what spectral range. In principle you can have pretty good match of mus and mua, but it all depends on what is coming next - a final goal of the study. Hope it helps!

Also refer

Management of heat in laser tissue welding using NIR cover window material

Lasers in Surgery and Medicine

Vidyasagar Sriramoju Robert R. Alfano

DOI: 10.1002/lsm.21143