Lasers Flashcards
Electromagnetic radiation is composed of what 2 types of fields?
electric and magnetic that are perpendicular to one another
Electromagnetic radiation with a lower frequency has a ____ wavelength
longer
Electromagnetic radiation with a higher frequency has a ____ wavelength
shorter
What is low frequency EM radiation used for?
therapeutic medical applications
What is high frequency EM radiation used for?
imaging or tissue destruction
Which type of EM radiation is ionizing and which is not?
high frequency EM radiation is ionizing therefore it can break molecular bonds to form ions
low frequency EM radiation is not ionizing therefore it cannot break molecular bonds or produce ions
What does the intensity of the EM radiation directly proportional to?
The energy of the output from the source
the greater the energy output from the source the greater the intensity
When is the intensity of the EM radiation greatest?
When the…
- energy output is high
- radiation source is close to the patient
- beam is perpendicular to the surface of the skin
What 3 things determine the effect of the EM radiation?
- Frequency
- Wavelength range of the radiation
- Intensity of the radiation
What is the effect of IR radiation?
it produces superficial heating
What are the effects of UV radiation?
it produces erythema, tanning, and epidermal hyperplasia
What are the effects of shortwave and microwave radiation?
They heat deep tissues, decrease pain, decrease edema, and facilitate tissue healing
What are the effects of low-intensity laser therapy?
promotes tissue healing, controls pain and inflammation
What are the non-thermal effects of EM radiation?
It cause changes at the cellular level by:
- Altering cell membrane function and permeability - Altering intracellular organelle function - Binding of chemical to the cell membrane to trigger complex sequences of cellular reactions - Causing proteins to undergo conformational changes to promote active transport and ATP use
LASER stands for what?
Light Amplification by Stimulated Emission of Radiation
When are hot and cold lasers used?
Hot lasers heat and destroy tissue
Cold laser is used clinically
Lasers produce ____ light of a ____ wavelength
coherent
single
3 types of diodes
- Light-emitting diode (LEDs)
- Supraluminous diode (SLDs)
- Laser diodes
2 sources of light
Which is the most commonly used for therapeutic reasons?
Light can be produced by emission from a gas-filled glass tube or a photodiode
Today, therapeutic light sources generally use photodiodes instead of glass tubes
A laser (photo)diode produces light that has what 3 characteristics?
- Monochromatic
- Coherent
- Directional
Are LEDs and SLDs Monochromatic, Coherent, and Directional?
LEDs
- Not coherent
- Not monochromatic
- Not directional, spreads widely
SLDs
- Not coherent
- Almost monochromatic
- Deliver energy to a wider area than laser but a smaller area than LEDsWhich wave characteristic affects the depth of penetration?
wavelength
What is the optimal depth of penetration of a wave?
600-1300 nm
Longer wavelength, lower frequency penetrates _____ than shorter wavelength, higher frequency waves
deeper
How deep does IR penetrate into soft tissue?
2-4 cm
How deep does red light penetrate into soft tissue?
only a few millimeters
*better for treating superficial tissues
What is power?
the rate of energy flow
Most laser diodes used for therapy have a power between _-__ mW
5-500
What does energy equal?
= Power (W) x Time (s)
The energy density is aka what?
the treatment dose
How do laser and light effect a target cell?
They directly effect of photons on intracellular chromophores (the light-absorbing part of a molecule)
What are high power (hot) lasers used for?
Surgical cutting and coagulation Ophthalmologic (LASIK) Dermatologic Oncologic Vascular
What are low-level (cold) lasers used for?
Therapy
- Treatment of tendon or ligament injury - Arthritis - Lymphedema - Soft-tissue healing - Bone healing - Neurological conditions - Pain management
Contraindications for Lasers
Malignancy Direct irradiation of the eyes Within 4-6 months of radiotherapy Hemorrhaging regions Over thyroid or other endocrine glands
Precautions for Lasers
Low back or abdomen during pregnancy Epiphyseal plates in children Impaired sensation Impaired mentation Photophobia Abnormally high sensitivity to light Pretreatment with one or more photosensitizers
Adverse effects of lasers and light
Transient tingling Mild erythema Skin rash Burning sensation Adverse effects from irradiation of the eyes
Laser wavelength
500-1100 nm
Near-IR wavelength
700-1100 nm
Clinically what power class is used?
3B (5-500 mW)
3 Laser Treatment Techniques
Gridding – imaginary grid with 1 cm squares
Scanning – no contact between laser tip and the skin
Wanding – uses oscillatory technique over a grid area
