Ultrasound and Laser Therapy Flashcards
What is Ultrasound?
Sound wave with frequencies above the range of human hearing
Ultrasound uses:
- Diagnostic test (fetal)
- Anti-cancer treatment to eradicate cancer tumors
- Heating and healing soft tissues, reducing pain, and restoring function (therapeutic)
Ultrasound Variables
- Size of sound head
- Frequency
- Intensity
Sound Head characteristics
- Head size: 2cm2, 5 (most common), 10
- Effective Radiating Area (ERA) - size of transducer that is producing the vibration
- Crystal will be slightly smaller than circumference of surface area
Sound Head - Beam Non-Uniformity Ratio
- Some parts of crystal may emit more energy than others
- Move sound head at all times
Frequency
- Frequency and shape of the wave are directly related
- Frequency and depth of penetration are inversely related
- Measured in Hz (Hertz) = 1 cycle/sec
What is the Frequency for therapeutic ultrasound?
0.75-3 MHz
What are the high frequency sound waves created with?
Piezoelectric crystals
Piezoelectric effect
Transforms mechanical energy to electrical energy (cigarette lighter)
Crystals and materials that have piezo properties? (8)
- Quartz
- Sucrose
- Topaz
- Bone
- Tendon
- Silk
- Enamel
- Synthetic crystals
The more dense the tissue the ________
closer together the molecules are and faster the energy will be transmitted
More dense tissues absorb more energy therefore ________ the penetration
decreasing
Why do higher frequencies decrease penetration?
Molecules vibrate faster, requiring more energy to overcome friction
What type of frequency will allow for deeper penetration?
Low - due to less friction
What frequency treats superficial tissue?
3MHz
What frequency penetrates to tissues b/w 2-5cm deep?
1MHz
What is Attenuation?
As beam passes through tissue, loses energy
What is Intensity in Ultrasound?
The amount of energy contained in the ultrasound beam - in Watts
Example problem - Intensity: Power = 2 W and sound head is 2cm2
Intensity = 1W/cm2
Spatial Average Temporal Peak Intensity
Highest intensity delivered w/n the ERA during a pulse
Intensity - Pulsed
- Interrupted periodically
- If on for 2 ms, then off for 2ms = 50% duty cycle
What is Duty Cycle?
% time that it is on
Intensity - definition
To provide the lowest intensity of ultrasound energy at the highest frequency that will transmit the energy to a specific tissue and achieve the desired therapeutic effect
General Thermal Effects (6)
- Reduce muscle spasm and guarding
- Modulate perception of pain
- Increase nerve conduction velocity
- Increase blood flow
- Increase enzyme activity
- Increase extensibility of collagen fibers
Thermal Mechanisms - Muscle @ 3 MHz
Intensity: 0.5-1.5
Time: 5-10 minutes
Thermal Mechanisms - Muscle @ 1 MHz
Intensity: 1.0-2.0
Time: 5-10
Thermal Mechanisms - Connective Tissue @ 3 MHz
Intensity: 0.5-1.0
Time: 2-10
Thermal Mechanisms - Connective Tissue @ 1 MHz
Intensity: 0.5-1.5
Time: 2-10
Non-Thermal? Effects (4)
- Increase cell membrane permeability
- Increase histamine release
- Increase macrophage activity
- Enhance wound contraction
Contraindications for Ultrasound
**Do NOT go over growth plates in children
How fast should you move the sound head?
4cm/sec
What does LASER stand for?
Light Amplification of Stimulated Emissions of Radiation
What is Coherence?
same wavelength and in phase
What is monochromacity?
Same color (same as wavelength)
What is Collimation?
In parallel (minimal divergence)
How does a Laser work?
- Activate electrons
- Inversion to an excited state
- Emission of a photon
- Stimulated emission - the striking of an electron by a photon
- Amplification - repeated stimulated emission
- Maximum capacity is reached, then photons are released for a light beam
4 Types of Lasers
- Crystal lasers
- Gas lasers
- Diode lasers
- Liquid lasers
High Power Laser
Surgical laser produces heat and can cut tissue
-Tissue destruction
Low Power Laser
Tissue healing
Class 1 Laser
Cannot emit laser radiation at known hazard levels invisible
Class 1A Laser
Lasers that are “not intended for viewing”, such as a supermarket laser scanner
Class 2 Laser
Low-power visible lasers that emit above Class 1 levels but not above 1 mW. The concept is that the human aversion reaction to bright light will protect a person
Class 3A Laser
- Intermediate -power lasers (1-5 mW)
- hazardous only for intrabeam viewing
- pen-like lasers
Class 3B Laser
- Moderate-power lasers
- 5-500 mW
- Can damage the retina
- Protective eyewear needed for clinician and client
Class 4 Laser
- High-power lasers - hazardous to view under any condition
- Potential fire and skin hazard
What does the depth of penetration depend on?
Types of Laser (wavelength)
-Longer wavelengths have greater penetration
How deep can Infrared lasers penetrate?
Up to 13 cm
What is a Joule?
- 1W/sec
- Energy density J/cm2 (average power)
Will you have more energy with pulsed or continuous?
Continuous
Dosage depends on:
- Power - output of the laser
- Exposure time
- Power Density
- Energy Density
- Dose Tissue
Dose Tissue equation
Dose Tissue = Sum of Dose per Diode X number of applications (Joules)
Treatment time equation
TA = (Energy/Power) x Area
Laser dosage for acute conditions?
0.05 to 0.5 J/cm2
Laser dosage for chronic conditions?
0.5 to 3.0 J/cm2
Laser: Clinical Applications
- Largely unknown
- Pain
- Wound Healing/Scar
- Immunological response
- Connective tissue stimulation (bone)
What happens to light when it hits an object? (4)
- Absorbed
- Reflected
- Transmitted
- Refracted
