Ultrasound/ Ionto Flashcards
(54 cards)
What is ultrasound?
is the application of high frequency sound waves beyond human audibility
arguably most effective deep heating tissue modality
Why is ultrasound effective?
provides heat to soft tissues with minimal increase in superficial temperature
How is ultrasound wave produced?
an alternating current passes through the crystal which causes crystal to vibrate which then creates high frequency sound waves
What is this process called?
reverse piezoelectric effect, expanding and compression of crystal produces heat
What does ERA stand for?
effective radiating area, area of US head that actually produces soundwaves, smaller than US head
described in cm2
What is the intensity formula for US?
watts/ERA= x w/cm2
What is size of treatment area in relation to ERA?
2-3 times the size of ERA
What is the beam profile?
describes the idea that multiple waves emerge from the head and the spatial peak intensity is farthest away from head
What is BNR?
beam non-uniformity ratio, measures consistency and quality of the crystal
Is a 6:1 or 4:1 ratio better for BNR?
4:1 as it will produce less high intensity areas and reduce risk of burn
What are two types of modes of application for ultrasound?
continuous and pulsed
What is continuous ultrasound?
outflow is 100%, can produce thermal effects based on intensity and tx duration
How deep can continuous go?
3-6 cm maybe deeper
What is pulsed?
produces non thermal effects
What is duty cycle equation?
pulse length/ (pulse length+ pulse interval) x 100
What are the two output frequencies most commonly used with US?
1 and 3 MHz
Which frequency goes deeper?
1mHz- goes 3-6 cm deep, thermal effects last longer
3 mhZ- 1-2 cm, heats 3 times faster than 1 mhZ
What are biophysical effects of US?
non thermal- changes within tissue resulting from mechanical energy
thermal- changes in tissue direct result of US elevation of tissue
Why would we want non thermal effects?
acute injury, wound healing
times when we don’t need inflammation
What are two ways non thermal can be achieved?
1) using pulsed output, duty cycle at 20–50%
2) continuous output with very low intensity (less than0.3 w/cm2
What are thermal effects of US?
1 degree- increase metabolism
2-3- decrease pain/spasm, increase blood flow, reduces chronic inflammation
4- increase collagen elasticity and extensibility
How does US directly reduce pain?
- increased nerve cell sodium permeability
- alters nerve function
- increases pain thresholds
How does US indirectly reduce pain?
- increase blood flow
- increase capillary permeability
- increase oxygen delivery
- decreased muscle spasm
How does US reduce muscle spasm?
- decreased pain
- altered nerve conduction velocity
- increased temp.
- muscle relaxation
