How to optimise treatment parameters for coagulation of visible sub-dermal blood vessels

The most frequent use of lasers in medicine is to heat tissue, as performed in, for instance, laser surgery. One specific application under development is to destroy non-flattering sub-dermal blood vessels by laser coagulation. The aim of this application is that the absorption of laser light by the haemoglobin in the blood will heat and thereby coagulate it. For this purpose, several different types of lasers can be used. Often laser light around the last major absorption peak of haemoglobin at 577 nm is used. In this project you will look into the possibilities to coagulate deeply lying vessels using a wavelength in the NIR region.

The aim of the project is to identify how to best perform such a treatment specifically heating the blood vessel, while avoiding heating the epidermis and the melanin in skin.

In order to optimise such a treatment, you should especially consider the following parameters:

• The laser wavelength
• The laser pulse energy
• The laser pulse length
• The laser spot size
• How to best apply cooling on the tissue surface to minimize the heating of the epidermis

The intention is that the project should include the following:

• You are supposed to briefly study the field of destruction of vessel lesion in the skin using laser light. Compare the suggested technique with other therapeutic laser procedures of skin lesions using laser light. This background should be included in the introduction of the report.
• You should obtain optical properties of chromophores and wavelengths of interest for the project from literature. 
• You should calculate the light distribution for the wavelength of interest (during the computer exercises and by yourself).
• You should calculate the temperature distribution following such a treatment (during the exercise and by yourself).
• Discuss the influences of the parameters mentioned above.
• Discuss whether the absorption properties are known to depend on the tissue temperature, i.e. if they are constant during the treatment.

Suggested key-words: vascular dermatology, thermotherapy, laser, blood vessels, laser dermatology, tissue optics, teleangiectasia