Ultrasound Flashcards
What kind of energy comes from the high frequency sound waves emitted by US?
Acoustical energy
Can be used to heat:
Muscles, tendons, ligaments, joint capsules, scar tissue, etc.
What are the non thermal effects of US classified as?
Mechanical effects
T/F
US is the most common heating modality utlized?
False, it is the most common deep heating modality utilized
What is the most commonly utilized heating modality?
moist hot packs
Electrical current is passed through a __________ causing it to __________
Crystal, vibrate.
How are the sound waves in US generated?
By vibration of the crystal
What is the frequency range for US machines used for muskuloskeletal treatments?
800,000 Hz (.8Mhz) - 3.3 Mhz
How do you calculate the duty cycle?
Dividing time sound (delivered?) by total treatment time.
What are the common pulsed duty cycles of US?
50% and 20%
What is the result of continuous ultrasound?
tissue heating
What effects does pulsed ultrasound have?
Mechanical/non-thermal effects.
What is the piezoelectric effect?
Mechanical deformation of a crystal causes an electrical current to form.
What is a reversed piezoelectric effect?
Alternating current is passed through a crystal resulting in a very fast contraction and expansion of the crystal. The vibration produces high frequency sound waves.
To generate a reversed piezoelectric effect, high voltage must be generated. What is needed to facilitate this?
Well insulated cables.
What is the near field?
the treatment zone. The fresnel zone.
What is spacial peak insensity
Max intensity
What is the effective radiating area?
Area of the sound head that produces sound energy. Always smaller than the US head.
T/F:
US beams are uniform across the US head?
False
What is BNR?
Beam non-uniformity ratio. It is the amount of variability of the beam. It is calculated by dividing the peak intensity of the beam by the average intensity.
What is BNR used for?
To compare quality of the US machines
What is the Ideal BNR?
Ideal BNR is 1, but 2:1 - 8:1 is acceptable.
What does lower BNR mean and what does it allow for?
The intensity of the sound wave will be more uniform.
Allows for higher dosage to be administered without discomfort
Allows for greater comfort and safety.
It eliminates hot spots.
T/F:
BNR always adequately explains performance?
False
What is PAMBNR?
Peak area of maximum beam non uniformity ratio. It describes the area of the sound head covered by peak intensity.
T/F:
Air is a great conductor of US.
False, its poor.
What do you use to prevent the reflection of sound waves by air?
Coupling medium like gel/gel packs.
T/F:
You should combine coupling mediums like gels with analgesic creams for better effectiveness.
False
T/F
Underwater ultrasound is indirect ultrasound?
True
What is an example of an appropriate/non appropriate vessel to use for underwater US?
Plastic basin/bucket. DO NOT USE METAL
What is normal US frequency?
1-3 MHz. Frequency dictates depth of heating.
What is the duty cycle?
Can be pulsed or continuous
What is considered high frequency US and what does it affect?
3 MHz. Absorbed more rapidly therefore it affects superficial tissues
What is considered low frequency and what does it affect?
1 MHz. Absorbed at a slower rate therefore affects deeper tissues.
Greatest tissue heating is observed at what?
Continuous US
Higher protein/density concentration to a tissue =
Higher absorption rate
T/F:
Skin and fat absorb the most US?
False, they absorb the least. Less protein and density.
US energy is reflected at soft tissue-bone interface, leading to what?
Increased heating, especially of tissues close to the bone.
What is the primary effect of US?
Heating, which causes an increase in metabolic activity, which which increases 02 demand which increases blood flow.
What is associated with a 1 degree C increase in Temp?
Increased metabolic activity
What is associated with a 2-3 degrees C increase in Temp?
Reduction in muscle spasm, increase blood flow, and reduction of chronic inflammation.
What is associated with a 4 degree C increase in Temp?
Alters viscoelastic properties of collagen
T/F
Longer times are need when lower intensities are used
True
What are some thereapeutic effects of US?
Increased extensibility of collagen fibers, of tendons, of joint capsules.
Increased blood flow and cell metabolism
Increased collagen synthesis
Decreased joint stiffness and muscle spasm
Enhanced tendon, ligament and muscle healing
T/F
Any manipulation or stretching should be applied BEFORE the usage of US
False. Manipulations or stretching should be applied AFTER US.
T/F
Pulsed ultrasound gives a great amount of tissue heating?
False. It gives very little.
What kind of effect is pulsed US?
Non thermal
What is pulsed US good for?
Shown to be good for stimulation of fibroblast activity, increase blood flow and proteins associated with injury repair.
What does pulsed US work through
Acoustical streaming and stable cavitation
What is acoustical streaming?
Movement of fluids across cell membranes due to mechanical pressure generated by sound waves.
What is it good for?
Increases cell permeability and facilitates fluid movement.
What is unstable cavitation associated with?
low frequency high intensity US. It is non therepeutic.
What areas besides obvious contraindications should you avoid using US on ?
Bony prominences (unless using smaller soundhead). Epiphyseal plates
What is caused by lowering the BNR?
Higher intensity
What is appropriate size of the treatment area?
An area 2-3 times the ERA
What is the general treatment time?
5-8 minutes (can be as little as 1-2 minutes).
Treatment should never exceed how many minutes?
15
What if you have a large treatment area?
Break treatment area into 2 or 3 smaller areas and treat for 5 minutes a piece.
What is phonophoresis?
Similar to iontophoresis. Sound energy used to drive medication through the tissues.
Is phonophoresis a good treatment option?
No. It lacks evidence among other things.
What is low intensity pulsed US good for?
Fracture healing.
What is non-contact low frequency US good for?q
Wound cleaning and debridement, it stimulates healing.
