Ultrasound & Lasers

Question 1

Ultrasound

Answer 1

• Electrical energy is converted into sound energy

Question 2

What is the sound head?

Answer 2

• Size ranges from 2cm2 to 10 cm2 (5cm2 is most common)

- Sound head contains a crystal

Question 3

What is ERA?

Answer 3

• Effective radiating area

- Indicates size of transducer that is producing the vibration

Question 4

What does the sound head crystal do?

Answer 4

• Expands and contracts as electrical energy passes through it to create mechanical sound energy.
• Expansion/contraction of the crystal results in compression/decompression of the tissue

Question 5

Beam Non-Uniformity Ratio

Answer 5

• Phenomenon where some parts of the crystal may release more energy then other areas.
• Causes sound head to have areas of hot spots and cold spots

Question 6

What is frequency?

Answer 6

• Measured as number of cycles/second; unit is Hz
• 1 HZ = 1 cycle/second
  Therapeutic ultrasound frequency = 0.75-3 MHz

Question 7

Is frequency directly or inversely related to the shape of the wave?

Answer 7

Directly related

Question 8

Is the frequency directly or inversely related to the depth of penetration into the tissue?

Answer 8

• Inversely related.

- Means as frequency goes up, tissue depth decreases.

Question 9

What is propagation?

Answer 9

• How long it takes for energy to move from one place to another

Question 10

T/F: Ultrasound propagates faster through less dense tissues than dense tissues.

Answer 10

False - the denser the tissue the faster the energy propagates.
- Occurs because the molecules are closer together in denser tissues and are therefore transmitted quicker.

Question 11

Is ultrasound energy absorbed more in less dense or highly dense tissues?

Answer 11

• More energy is absorbed in more dense tissues because the molecules are tightly packed
• Results in decreased penetration in denser tissues

Question 12

When frequency is higher what happens to the tissue penetration?

Answer 12

• As frequency increases penetration decreases because high frequency molecules have to vibrate faster to overcome friction.
• High frequency = short wavelengths = less penetration

Question 13

When frequency is lower what happens to the tissue penetration?

Answer 13

• Lower frequencies result in larger wavelengths. Larger wavelengths require less energy or vibration to overcome friction. Therefore tissue penetration increases.

Question 14

What frequency treats superficial tissues?

Answer 14

• 3 MHz

Question 15

What frequency treats tissues up to 2-5cm deep?

Answer 15

• 1 MHz

Question 16

What is attenuation?

Answer 16

• Concept where the beam losses energy as it passes through the tissue.

Question 17

What occurs when ultrasound energy reflects off of bone?

Answer 17

• Causes the energy to be redirected to surrounding tissues like the muscle, ligaments, tendons, joint capsules
• Results in pain
  Too much of this can results in bone burning/damage

Question 18

T/F: Ultrasound beams are more likely to be reflected when the surface skin is dry, thick and callused.

Answer 18

True

Question 19

What is intensity?

Answer 19

• How much energy is contained in the ultrasound beam

- Measured in W/cm2

Question 20

Spatial Power Equation

Answer 20

SP = Intensity (Watts)/Sound head ERA (cm2)
SP= W/cm2

Question 21

Describe Spatial Average Temporal Peak Intensity

Answer 21

• the highest amount of intensity delivered within the ERA during one pulse.

Question 22

Pulsed intensity

Answer 22

• Intensity is periodically interrupted (not on all the time)
• Can be 25%, 50%, 75%, etc.
• % indicates how much time the intensity is ON

Question 23

Spatial Average Intensity Equation

Answer 23

SAI = Spatial Power (W/cm2) x Time (%)

Question 24

Calculate the spatial average intensity if the spatial power is 2 W/cm2 and the time is 50%

Answer 24

SAI = 2W/cm2 x 0.50 = 1W/cm2

Question 25

T/F: If the pulsed time is 75% that means the pulse is on 25% of time.

Answer 25

False - pulse is on 75% of the time and off 25%

Question 26

What changes does thermal ultrasound cause in the body?

Answer 26

- Reduce muscle spasms/guarding - Change perception of pain - Increase nerve conduction velocity - Increase blood flow - Increase enzymatic activity

Question 27

What needs to occur during ultrasound for scar treatment to be effective?

Answer 27

- 4 degree temperature change

Question 28

What physiological changes in the body does non-thermal ultrasound cause?

Answer 28

- Increase cell membrane permeability - Increase histamine release (results in increased blood vessel permeability and inflammatory response) - Increase macrophage activity - Enhance wound contraction (closing)

Question 29

Ultrasound Contraindications

Answer 29

- Not to eyes, genitals, or heart - Do not do over low back or abdomen during pregnancy - Not over pacemaker - Not over tumors or other abnormal growths - Not over infection/abscess - Not over ischemic (low blood flow) areas - Not over areas with reduced sensation - Not on someone w/ current DVT or PE - Not over growth plates in children

Question 30

Ultrasound Precautions

Answer 30

- Careful over fracture or joint replacement hardware | - Careful if person has infection (concern of transmission to other patients)

Question 31

What should ultrasound be used for?

Answer 31

- Pain relief - Muscle relaxation - Increase muscle's ability to stretch - Break up scar tissue - Increase blood flow (not in acute stages) - Possible wound healing

Question 32

Why does ultrasound head have to be in contact with liquid medium at all times once the ultrasound begins?

Answer 32

- Sound head crystal cannot transmit energy waves through the air; energy therefore becomes trapped and increases within the crystal causing it to break

Question 33

How quickly should the sound head be moved on the skin?

Answer 33

- 4cm/sec

Question 34

Ultrasound Application Types

Answer 34

- Traditional w/ gel - Immersion - sound head and tissue underwater - Bladder - balloon/glove used; gel applied to both sides - Phonophoresis - ultrasound enhances delivery of medication that is applied on the skin into the tissue

Question 35

How deep does 1 MHz ultrasound heat penetrate?

Answer 35

3-5 cm | Heats deeper tissues

Question 36

How deep does 3 MHz ultrasound heat penetrate?

Answer 36

1-2 cm | Heats superficial tissues

Question 37

What is the desired temperature change of the tissue when using ultrasound?

Answer 37

- 2 degrees F | - 4 degrees F for scar tissue

Question 38

Why is it important to have ultrasound applied at a 90 degree angle to the tissue being treated?

Answer 38

Increases chance of greatest amount of ABSORPTION and least amount of reflection

Question 39

``` How fast should the sound head be moved during an ultrasound session? A. 2 cm/sec B. 3 cm/sec C. 4 cm/sec D. > 4 cm/sec ```

Answer 39

C. 4cm/sec

Question 40

Should pulsed or continuous ultrasound be used on acute stage injuries?

Answer 40

- Pulsed only

Question 41

Should 1 MHz or 3 MHz ultrasound be used to treat patellar tendonitis and why?

Answer 41

- 3 MHz because the patellar tendon is a more superficial tissue

Question 42

Is ultrasound created through the piezoelectric or reverse piezoelectric effect?

Answer 42

- Reverse piezoelectric effect | - States electrical energy is converted into mechanical energy (sound in the case of ultrasound).

Question 43

Which BNR ratio for ultrasound would be the least likely to create "hot spots"? A. 2:1 B. 4:1 C. 6:1

Answer 43

A. 2:1 - the lower the ratio, the more uniform the heat output is across the ultrasound sound head. A high ratio indicates some areas of the sound head will put out more heat than other areas creating "hot spots".

Question 44

``` If an ultrasound head has a BNR ratio of 7:1, how fast do you need to move the sound head to prevent hot spots in the tissue? A. 2cm/sec B. 3cm/sec C. 4cm/sec D. >4cm/sec ```

Answer 44

D. >4cm/sec to reduce chance of some tissue areas developing hot spots.

Question 45

For a patient w/ patellar tendonitis what would be the goal of using pulsed ultrasound?

Answer 45

- Increase healing of the tissue

Question 46

What is ultrasound cavitation?

Answer 46

- Expansion and compression of gas filled bubbles due to pressure changes - Used in non-thermal ultrasound

Question 47

T/F: Ultrasound cavitation cannot potentially damage the tissues.

Answer 47

False, it can cause damage.