Flashcards in Ultrasound and Laser Therapy Deck (56)
What is Ultrasound?
Sound wave with frequencies above the range of human hearing
-Diagnostic test (fetal)
-Anti-cancer treatment to eradicate cancer tumors
-Heating and healing soft tissues, reducing pain, and restoring function (therapeutic)
-Size of sound head
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 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?
What are the high frequency sound waves created with?
Transforms mechanical energy to electrical energy (cigarette lighter)
Crystals and materials that have piezo properties? (8)
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
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?
What frequency penetrates to tissues b/w 2-5cm deep?
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
-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
Time: 5-10 minutes
Thermal Mechanisms - Muscle @ 1 MHz
Thermal Mechanisms - Connective Tissue @ 3 MHz
Thermal Mechanisms - Connective Tissue @ 1 MHz
Non-Thermal? Effects (4)
-Increase cell membrane permeability
-Increase histamine release
-Increase macrophage activity
-Enhance wound contraction