Medical Treatments using Lasers

In the last decade the application of lasers in medicine has increased dramatically.With the development of laser technology, lasers from various spectral ranges,characterized by different energies, peak powers, intensities and pulse durations,are being tested in medicine.

An understanding of how the new and traditional sources of laser light interactwith human tissue is an essential prerequisite for choosing suitable methods fortreatment and diagnostics. The development and commercialization of femtosecond lasers has opened up new applications in biomedicine. Particularly in surgery,femtosecond pulses allow for much more precise cutting than do nanosecond lasers .

The biggest advantage of ultrafast lasers in surgical applications is limiting biological tissue damage. The pulse interacts with the tissue faster than thermal energy can diffuse to surrounding tissues. It simply means less, if any, burning and destruction of neighboring tissue. In addition, cuts on the dimensions of microns may result in new applications to repair nerve damage.

Here, we only present the principle of interaction between laser radiation and biological tissue. Before going into detailsone can state that the radiation–biological tissue interaction is determined mainly by the laser irradiance [W/cm2], which depends on the pulse energy, pulse duration, and the spectral range of the laser light. The interaction depends also on thermal properties of tissue – such as heat conduction, heat capacity and the coefficients of reflection, scattering and absorption .

The main components of biological tissue that contribute to the absorption are melanin, hemoglobin, water and proteins.

Figure 1 presents the absorption spectra of the main absorbers in biological tissue. One can see that absorption in the IR region (2000–10000 nm) originates from water, which is the main constituent of most tissues. Proteins absorb in the UV region (mainly 200–300 nm). Pigments such as emoglobin in blood and melanin, the basic chromophore of skin, absorb in the visible

range

Fig. 1 Absorption spectra of main absorbers in biological tissue. Modified from .

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