Laser And Ultraviolet Flashcards
Physics behind LASER
Photon- energy packet that light contains, contains certain amount of energy depending on wavelength of light emitted by the laser.
Photon hits electron and is absorbed. yields and excited electron state.
THROUGH SPONTANEOUS EMISSION- the electron will release a photon of equal energy to one absorbed.
Stimulated emission is when an external power source causes population inversion (environment of excited electrons). Excited electrons release photons and chain reaction occurs.
3 properties distinguish Laser from incandescent light
- Coherence- all photons of emitted light are in phase with one another
- Monochromaticity- only one wavelength of light is produced
- Collimation- photons move in parallel fashion with minimal divergence in a concentrated beam of light
Types of laser
classified by material generating the light, will produce light of a different wavelength and therefore a different amount of energy
- High Power
- Low power
High power laser
- High power/hot lasers generate thermal response
- used in surgical procedures
- output is greater than 500 Watts
Low power laser
- Low power/cold lasers are used for wound and tissue healing, and for pain management.
- Helium neon (HeNe) and Gallium arsenide (GaAs) are two types of low power lasers used.
- Output is in mWatt
Low power laser techniques
Gridding is most common technique
Size of grid depends on size of symptomatic area.
Treatment areas within the grid depend on the size of the laser
Dosage of laser
Energy density of laser is described in J/cm2.
Dosage depends on:
1. Laser output in mWatt
2. Time of exposure
3. Surface area of beam in cm2
the more chronic the injury the greater the energy
the deeper the tissue the greater the energy
Depth of penetration
- Direct response- the superficial response that occurs from the absorption of light
- Indirect response- the catalyzed metabolic response in deeper tissues
- Helium has more superficial direct and indirect response compared to Gallium
How laser works
light penetrates skin and tissues, absorbed by cell and converted into energy. cell membrane permeability is altered and triggers cascade of cellular events including:
- stimulation of ATP
- Increase DNA and RNA
- Increased levels beta endorphins and serotonin
- Enhanced collagen production
Clinical application of laser
- Wound healing
- Increase tensile strength of healing tissue
- Reduce edema
- Decrease pain
Contraindications to laser
- over growth plates
- over malignancies
- over eyes
- in 1st trimester of pregnancy
Physics of UV rays
form of electromagnetic radiation with short wavelengths.
energy from UV is absorbed by the skin and causes changes in the cells. alter biochemistry and metabolism, promote DNA/RNA synthesis leading to alteration in protein and enzymes
3 forms of UV
- UV-C - bactericidal and formation of Vit D
- UV-B - formation of Vit D
- UV-A - little known on therapuetic effects
Effects of UV on the epidermis and dermis
- Erythema- sunburn- acute inflammation of skin
- Edema- associated with vasodilation to dermis
- Hyperplasia- thickening of epidermis
- tanning- increase in melanin
- Photokeratitis- inflammation of eye from UV
- Increase in release of Vit D from kidneys and liver, affects absorption of Ca and Phosphorus
- Long term effects- premature aging of skin, skin cancer
UV treatment technique
- Sensitivity to UV is determined by minimal erythemal dose (MED)
- MED amount time exposed to UV to produce faint sunburn 24 hours later.
- Question the patient about photosensitizing drugs
- Eye protection worn by patient
- Distance from lamp to patient ~ 30 inches.
