Question

1. During laser-tissue interaction, heat is generated. Heat produced will increase the temperature of the tissue. Different temperature stages will give different tissue reaction. Typically, the temperature ranges can be grouped into various stages. Describe the reactions of skin tissues for the following stage:

1. 42 - 45 °C,

2. 50 - 60 °C, and

3. Above 100 °C

Answer 1

Laser-tissue interaction is a method that is used for diagnosis and treatment of diseases. However, it is well known that lasers induce heat in the tissues, which increases the temperature of tissues. Hence, it is essential to understand heat distribution in skin tissue. Different temperatures used in these process, will result in varying effects on the tissue. These include hyperthermia, coagulation, etc.

a. 42-45⁰C: At this temperature, primary effect on the tissues is hyperthermia, which is increased temperature of the tissue. Hyperthermia will break bond between the molecules (protein, carbohydrates, lipids etc) within the tissues. Membrane of the cells is also damaged due to presence of proteins. Enzymes present within the tissues will have reduced enzymatic activity as kinetic energy of the reactants becomes reduced. Further, breakage of bonds will alter the active site of the enzyme, resulting in reduced activity. However, all these effects on the tissues are completely reversible when the tissue is brought back to its ideal body temperature.

b. 50-60⁰C: At this temperature, proteins will undergo denaturation. The secondary, tertiary and quaternary structure of protein is converted to primary structure, which is the amino acid sequence. This leads to loss of 3D shape and function. Enzymes will denature and hence, completely lose enzymatic activity. This is irreversible change. Collagen in skin tissues will also denature causing the tissue to be coagulated. There is also necrosis of the cells due to this extensive damage.

c: 100⁰C:At 80⁰C, Permeability of cell increases at this high temperature due to destruction of equilibrium of chemical concentration. Water present in tissue undergoes vaporization at this boiling temperature. This phase of vaporization does not cause tissue temperature to alter. However, there is formation of gas which bubbles. As a result, there are changes in volume of the tissue. This altered volume causes the tissue fragments to decompose. Excess vaporization leads to blackening of tissues as carbon atoms are released. This process is called carbon vaporization. Ultimately, necrosis causes cell death and destruction of tissue.