Ultrasound

Question 1

What is US?

Answer 1

mechanical energy consisting of high frequency vibrations

Question 2

An increase in frequency leads to a higher rate of absorption, therefore _ the depth of penetration.

Answer 2

Decreasing

Question 3

How does US work?

Answer 3

reverse piezoelectric effect

Question 4

What is the basis of the piezoelectric effect?

Answer 4

electrical energy (AC current) applied to lead zirconate titanate crystal in sound head which is converted to mechanical energy

Question 5

What are the parameters of US?

Answer 5

frequency, intensity, duty cycle, ERA, BMR

Question 6

What can happen with the US beam as its applied?

Answer 6

absorption, refraction, reflection

Question 7

How do you minimize reflection of the sound energy?

Answer 7

deliver perpendicular to treatment surface

Question 8

How does refraction occur?

Answer 8

as the beam travels from one medium to the other

Question 9

What is spatial peak?

Answer 9

the maximum amplitude of the beam

Question 10

What is spatial average?

Answer 10

the avg amplitude of the beam

Question 11

What is BNR?

Answer 11

ratio of highest intensity in the field relative to the avg

Question 12

What determines BNR?

Answer 12

Material used for piezoelectric transducer

Question 13

What ratios do most machines have? and what is the best?

Answer 13

2:1 and 8:1, lower the better

Question 14

What is attenuation?

Answer 14

the decrease in energy due to absorption, reflection, or refraction

Question 15

Tissues with more attenuation will show what?

Answer 15

greater temperature rise

Question 16

Attenuation values are higher for tissues with a higher what?

Answer 16

collagen content

Question 17

What increase also increases attenuation?

Answer 17

frequency

Question 18

How are attenuation and penetration related?

Answer 18

inversely

Question 19

What are the highest attenuations at 1 MHz?

Answer 19

bone, cartilage, tendon

Question 20

What are the types of effects US has?

Answer 20

mechanical and thermal

Question 21

What are the mechanical benefits of US?

Answer 21

1. cavitation, microstreaming, acoustic streaming - movement of tissues at the cellular level
2. increased intracellular Ca2+
3. Promotes cell function

Question 22

What are the ways mechanical effects of US promote cell function?

Answer 22

a. mast cell degranulation
b. increased macrophage responsiveness
c. synthesis of fibroblasts
d. proteoglycan synthesis in chondrocytes
e. some evidence in fracture healing

Question 23

What are the thermal effects of US?

Answer 23

at 100% duty cycle:
@1C - increases metabolism and healing (13% for every 1 deg increase)
@2-3C - decreases pain and muscle spasm
@4+ - increases extensibility of collagen and scars, decreases joint stiffness

Question 24

What is the required for the effects at 4C to occur?

Answer 24

a 40-45C temp for at least 5 minutes

Question 25

What is the duty cycle?

Answer 25

time on/total time - reduced thermal effects as the time off allows heat to dissipate

Question 26

What is continuous duty cycle?

Answer 26

100%

Question 27

What effects occur at 100% duty cycle?

Answer 27

mechanical and thermal

Question 28

What are pulsed duty cycle?

Answer 28

anything under 100%

Question 29

What are the common options on US machines for pulsed duty cycle?

Answer 29

20 and 50%

Question 30

What effects occur at 50%?

Answer 30

Mostly mechical but some thermal

Question 31

What effects occur at 20%?

Answer 31

Mechanical only

Question 32

What are the frequency options and what are their MOAs?

Answer 32

1MHz for up to 5 cm, 3MHz for 1-2 cm

Question 33

What intensity should you use to increase temperature at a 1MHz frequency?

Answer 33

1.5 to 2.0 W/cm^2

Question 34

What intensity should you use to increase temperature at a 3MHz frequency?

Answer 34

0.5 W/cm^2

Question 35

What intensity should be selected for mechanical effects?

Answer 35

0.5 to 1.0 W/cm^2

Question 36

How soon should warmth be felt?

Answer 36

2-3 minutes

Question 37

What is the speed and shape of the motions of an US?

Answer 37

slow circles in a 1 cm/sec

Question 38

What is the size of the treatment area for US?

Answer 38

2-3x ERA (size of US head)

Question 39

What is the common duration of US?

Answer 39

5-10 minutes

Question 40

How soon should improvements be recognized?

Answer 40

2-3 treatments

Question 41

What are indications of US?

Answer 41

soft tissue shortening, pain control, dermal ulcers, tendon and ligament injuries, resorption of calcium deposits, bone Fx, CTS, Phonophoresis

Question 42

What are the precautions for US?

Answer 42

acute inflammation, epiphyseal plates, Fxs, breast implants

Question 43

What are the contraindications for US?

Answer 43

malignancy, pregnancy, CNS tissue, joint cement, plastic, pacemaker, thrombophlebitis, eyes and reproductive organs