Ultrasound

Question 1

What parameters are there for US?(5)

Answer 1

Intensity
Frequency
Duty cycle
Effective radiating area (ERA)
Beam uniformity ratio (BMR)

Question 2

How is intensity measured?

Answer 2

W/cm2 (cm2=the size of the sound head)
for 1 MHz Frequency 1.5-2 W/cm2
For 3MHz o.5 W/cm2
> if no heat is felt after 2-3 mins

Question 3

What is frequency measured in?

Answer 3

MHz or amplitude this is soundwaves per sec. equivalent to pps in Estim

Question 4

What is duty cycle?

Answer 4

The % of on/off time for sound waves
Continuous is 100% and used for thermal US
50% is on half the time and is non-thermal, anything below 100% is non thermal
20% is the lowest used often.

Question 5

What is ERA? (effective radiating area)

Answer 5

The area of sound that eminates from the sound head (slightly smaller than the head)
,The Tx time depends on this.

The Tx should be 5-10mins per 2 treatment head areas.
Higher=closer to 10 mins for lower intensity=closer to 5 mins

Question 6

Attenuation?

Answer 6

< in US as it travels through tissues

Question 7

Which is a deeper Tx 1MHz or 3MHz?

Answer 7

1MHz it goes about 5cm

3MHz goes 1cm

Question 8

What is the difference between continuous and 20% duty cycle? 50% duty cycle?

Answer 8

Continuous has no off time
20% has 2ms on and 8ms
50% has 5ms on and 5ms off

Question 9

Effects of US?(2) Think basic effects

Answer 9

Thermal

Non-thermal

Question 10

What does thermal US do?

Answer 10

> temp by absorption into tissues by type.

Use 0.5-1.5 Wcm2/intensity

Question 11

What does non-thermal US do?(3 and A-E)

Answer 11

1Tissue healing
2modifies inflammation
3Enhances transdermal drug delivery

a> intercellular CA+ which makes cell membrane action potentials easier to affect by increasing membranes more permiable

bPromotes cell Fx by doing so and makes them easier to clean for macrophages

c>macrophages in the area
d>Mast cell degranulation
e>histamine(dilates BV)

Question 12

Clincal applications of US?(6)

Answer 12

1. < soft tissue shortening
2. P control
3. Dermal ulcer/incision healing
4. Tendon/lig healing
5. Bone Fx (with <intensity)
6. Carpal tunnel

Question 13

Contraindications of US?(9)

Answer 13

1. Malignancy
2. Pregnancy (area of uterus)
3. 0 over CNS
4. 0 jt cement
5. 0 plastic
6. pacemaker (shoulder chest area)
7. Thrombosis/phlebitis
8. Eyes
9. Reproductive organs

Question 14

Precautions?(4)

Answer 14

1. Acute inflammation
2. Epiphysieal plates
3. Fractures
4. Breast implants (use non-thermal)

Question 15

Adverse effects?(3)

Answer 15

1. Burns
2. Standing waves (cause cavitation)
3. Cross contamination

Question 16

Cavitation?

Answer 16

Formation, growth and pulsation of gas filled bubbles (occurs during non-thermal)

Question 17

Standing wave?

Answer 17

Causes sound waves to reflect back and superimpose on existing waves, and causes burns. Avoid by moving the sound head.

Question 18

Acoustic streaming?

Answer 18

The steady, circular flow of cellular fluids introduced by US. Larger than micro, Xports material from one side of the US field to another.

Question 19

Microstreaming?

Answer 19

Eddying that takes place near any small, vibrating object. Around gas bubbles from cavitation.

Question 20

What do acoustic/micro streaming and cavitation do?

Answer 20

Disperse heat caused by US sound waves.

Question 21

Absorption coefficient?

Answer 21

The tendency of US to heat collagen rich tissues more effectively since they absorb sound waves.
Low absorption coefficient tissues usually have high water content, adipose is one of the lowest.

US is good for breaking down scar tissue.

Higher fq also has an effect on collagen rich tissues.

Question 22

What distance should ultrasound be from the surface under water?

Answer 22

1-3 inches